In this essay we will discuss about the components of sustainable agriculture.
Components of Sustainable Agriculture
Essay Contents:
- Essay on the Sustainable Utilisation of Land Resources
- Essay on the Sustainable Utilisation of Water Resources
- Essay on the Sustainable Utilisation of Biodiversity
- Essay on Integrated Nutrient Management
- Essay on Integrated Plant Protection
- Essay on the Enhancing Sustainability of Dryland and Irrigated Agriculture
Essay # 1. Sustainable Utilisation of Land Resources:
Land is a finite non-renewable natural resource comprising of three vital components namely soil, water and vegetation. India share in land resources of the world is only 2 per cent on which 18 per cent of the world population and 15 per cent of world’s livestock survive.
Reported geographical area of India (328.7 M ha) can be broadly grouped into three sectors:
i. Agricultural sector (59.27%) consisting of net cultivated area, current fallows, other fallows and cultivable wastes.
ii. Ecological sector (33.56%) comprising forests, miscellaneous, barren and uncultivable wastes.
iii. Non-agricultural sector (7.17%) includes lands under non-agricultural uses.
Soil degradation is posing a potential threat to ecological balance and sustainability of livelihood systems of people due to indiscriminate use of land, water and other natural resources.
Essay # 2. Sustainable Utilisation of Water Resources:
Information on sustainable water resources of India is lacking as it largely depends on the amount of rainfall. However, much of the present practices of utilisation are not sustainable because they largely depend upon luxurious use of water. At the present water use, as much as 3000 t of water is used to produce 1.0 t of husked rice.
Similarly, 1000 t of water is used to produce 1.0 t of wheat. As much as 0.9 ha-m of water is being used for growing 1.0 ha when surface water is used, while it is 0.65 ha-m for ground water. Assuming that with increasing concerns of sustainability, 0.7 ha-m water of use would result in an irrigation potential of 110 M ha against sown area of 210 M ha.
A. Groundwater use Consistent With Aquifer Recharge:
There has been a steady increase in irrigation potential from groundwater, which has gone up from 6.5 M ha in 1950s to 40 M ha in 2000s. Although, the present rate of annual gross withdrawal is less than 50 per cent of the available groundwater for irrigation, the signs of excess withdrawal are clearly visible in many districts in different states.
In these districts, the present rate of development exceeds the annual replenish-able groundwater recharge. The number of districts where water table has declined more than 4.0 m constitutes 137 spread over various states (Table 10.3).
The decline in groundwater levels has resulted in decrease in well yield, failure of wells/tube- wells, increased pumping costs and higher consumption of energy and ingress of seawater in coastal areas.
Thus, depletion of groundwater needs to be arrested by maintaining hydrological equilibrium between annual replenish able recharge and groundwater recharge. An integrated approach to control the decline in water table has been suggested by Khepar et al (1996).
a. Integrated Approach for Control of Declining Water Table:
Reduced Groundwater Draft through:
i. Enhancing Surface Water Supply by:
1. Developing new projects.
2. Interzonal transfer of water.
3. Storage of surplus water.
4. Renovation of wastewater.
ii. Crop diversification.
iii. Optimising water use in rice fields.
iv. Minimising the gap between demand and supply.
v. On farm water management.
vi. Rationalising ground water exploitation policies.
vii. Feasibility of exploiting deep aquifers.
Increased groundwater potential by artificial groundwater recharge through:
1. Existing network of surface drainage system.
2. Percolation tanks, water harvesting structures and watershed management in upper catchments.
3. Diverting surplus water from rivers and streams to declining water table areas.
4. Spreading basins, wells, pits etc.
b. Artificial Groundwater Recharge:
Groundwater resources can be augmented through artificial recharge. The success of ground water recharge depends on the availability of good quality water, suitability of site and appropriate recharge technique. Water resources, which can be used for artificial groundwater recharge, include surplus monsoon runoff, canal water during rainy season and treated sewage water.
i. Surplus Monsoon Runoff:
Out of 400 M ha-m average annual rainfall of the country, 115 M ha-m flows as surface runoff. Including stream regeneration, the annual surface runoff is 187.9 M ha-m. As per the current estimate, ultimate surface water resource likely to be developed has been computed as 69 M ha-m.
Therefore, available surplus water is 116 M ha-m. The monsoon surplus water for groundwater recharge is estimated as 87 M ha-m (assuming 75 per cent of surplus water is available for groundwater recharge). The basic requirement in planning and utilisation of surplus monsoon runoff for recharge is availability of surface storage space in different zones of the country.
The Central Groundwater Board has estimated the surface storage potential at 59 M ha-m for 20 major river basins. However, because of vide variation in the basin wise availability of monsoon runoff and surface storage potential, the feasible groundwater storage has been estimated as 23.39 M ha-m.
ii. Surplus Canal Water:
During rainy days, water may not be required for irrigation but will have to be released for other requirements (hydropower, flood protection etc.). Canal water during this period, therefore, may be utilised for groundwater recharge. Surplus canal water available for groundwater recharge can be estimated, if the number of rainy days when irrigation is not required and daily canal water release during that period are known.
Assuming that 30 m ha-m water is released in a canal during the year and average number of rainy days as 40, the surplus canal water available for artificial groundwater recharge works out to be 30 x 40 / 365 = 3.5 m ha-m. However, the availability of surplus canal water in each zone can be estimated depending on actual canal water release and number of rainy days during which canal water is not required.
iii. Sewage Water:
Treated sewage water is used for groundwater recharge in several countries. In India, the sewage is collected in temporary pumping stations and pumped either on to land for irrigation or into inland surface water or in some cases it is left to find its way into depressions where it stagnates. For augmenting the water resources, the treated sewage water may be used for ground water recharge wherever feasible.
Assuming that 300 M people live in cities/towns having supply of water and water consumption of 200 I capita-1 day-1, the annual estimate of sewage comes to 2.19 M ha-m. If 50 per cent of the sewage water is retrievable, about 1.0 M ha-m will be available for possible recharge.
B. Water Conservation:
Water conservation in irrigated agriculture can be achieved by reducing conveyance losses, efficient canal water management, efficient on farm water management, rainfall conservation, reducing water demand and reuse of waste water.
a. Reducing Conveyance Losses:
Conveyance losses account for 40 to 50 per cent of the water delivered into a canal and almost half of these losses occur in field channels. While seepage is a net loss of water in areas with poor quality groundwater, it can be retrieved for irrigation in areas having good quality groundwater.
This water may be withdrawn by farmers at their conveniences and when needed. In order to reduce these losses, lining of canal network should be done with due importance to economic considerations. However, water courses, which contribute very little to ground water should be lined for efficient conveyance and distribution of water.
b. Canal Water Management:
Canal irrigation systems were scientifically planned. The water allowance, the capacity factors and the irrigation intensities were designed keeping in view the availability of irrigation water and irrigation demands of the cropping systems prevalent at that time. Since then, a major shift has taken place in cropping pattern, groundwater development, cropping intensity, irrigation intensity etc.
This has resulted in a mismatch between demand and supply during the crop period. This gap can be minimised by revising the water allowance and the capacity factor, keeping in view the irrigation requirements of existing crops, quality and availability of ground water.
c. On-Farm Water Management:
On-farm water management including improving the conveyance efficiency of irrigation channels/ canal water courses, application efficiency, scheduling of irrigation and precision land leveling increases the water use efficiency and crop production.
i. Reducing Application Losses:
Application efficiency of surface methods of irrigation is only 30 to 50 per cent as compared to attainable level of 60 to 80 per cent due to the fact that these methods are not designed to match the stream size, soil type, slope etc.
By growing row crops such as cotton, sugarcane, soybean, sunflower etc. under ridge and furrow irrigation, about 30 to 40 per cent of irrigation water can be saved as compared to border irrigation. Around 30 to 40 per cent of irrigation water can be saved by adopting sprinkler or drip irrigation in water scarcity areas, having conditions conducive to their application.
ii. Irrigation Scheduling:
Irrigation scheduling in relation to water availability is an important aspect of on-farm water management for optimising production. Where irrigation water supplies are plentiful, irrigation must be repeated before a yield or quality reducing water stress develops in the field. In the case of rice, intermittent submergence, which includes rotational and occasional submergence, can save irrigation water up to 50 per cent depending on soil type.
Irrigation scheduling for optimising production with limited water supplies is a bigger challenge. The first step for irrigation scheduling with limited water is to assess the relative sensitivity of different growth periods to water stress. Irrigation with limited water should be so managed that the inevitable stress synchronises with the least sensitive stages.
iii. Precision Land Levelling:
Precision land leveling/grading is essential for efficient utilisation, uniform distribution of irrigation water, quick removal of excess rain water in humid and sub-humid areas and conservation of rain water in arid and semiarid areas. In surface method of irrigation, land levelling is essential for high application efficiency. The topography index (TI), the difference between average cut and average fill (cm) should be zero for ideally graded field.
C. Water Harvesting:
Rain water harvesting and management consists of in-situ and ex-situ harvesting.
a. In-Situ Rain Water Harvesting:
In-situ rain water harvesting can be achieved by increasing infiltration rate with deep ploughing, profile modification, vertical mulching and by keeping soil surface relatively rough. The harvesting techniques are location specific and depend on rainfall intensity, slope and soil texture.
On lands having slopes up to 1 to 2 per cent, water conservation could be by bunding, land levelling and contour cultivation. On lands having 2 to 6 per vent slope, graded contour bunds are ideal and on slopes from 6 to 33 per cent, bench terraces could be ideal.
b. Ex-Situ Rain Water Harvesting:
In arid and semiarid areas, low and erratic rainfall with high intensity of short duration results in high runoff with little moisture storage. Harvesting and storage of runoff provides life-saving irrigation to the standing crops during dry spells and for a second crop during rabi.
Ex-situ water harvesting structures include roof top collection, dug out ponds/storage tanks, gully control structures/check dams/barriers etc. The ex-situ harvesting technology is highly location specific. The design procedures of rain water harvesting structures are described by Samra et al (1996) and Dhruva Narayana (1993).
D. Conjunctive use of Surface and Groundwater:
Conjunctive use management of multisource/multi-quality waters can be defined as the management of multiple water resources in a coordinated operation such that the total water yield of the system over the period of time exceeds the sum of water yields of the individual components of the system resulting from uncoordinated operation.
As a result of conjunctive use of surface and groundwater resources, it is possible to have optimum utilisation of water resources as ground water could act and function as a storage reservoir, regularisation agent and conveyance medium. The separate use of surface and groundwater in itself may not always constitute a conjunctive use.
Conjunctive use is planned and practiced with the following objectives:
i. Mitigating the effect of storage in canal water surplus often subject to steep variations in river flow during different periods in the year.
ii. Increasing the dependability of existing water supplies.
iii. Alleviating the problems of high water table and salinity resulting from introduction of canal irrigation.
iv. Facilitating the use of high salinity ground water, which cannot otherwise be used without appropriate dilution.
v. Storing water in groundwater basins closer to the users to ensure water supply in case of interruption of surface water supply.
E. Safe use of Saline and Alkali Water:
Management practices for optimum crop production with saline irrigation must aim at preventing build-up of salinity, sodicity and toxic ions in the root zone to levels that limit the productivity of soils, control salt balance in salt-water system as well as minimise the damage effects of salinity on crop growth.
a. Crop Management:
i. Selection of Crops:
Crops differ considerably in their ability to tolerate salinity/sodicity. The values of salinity for obtaining specific crop yields were computed by Manhas and Gupta (1990) as per response equation: RY = 100 – S (ECe – ECt), where, ECt is threshold salinity. Oilseed crops requiring less water can tolerate higher levels of ECiw, whereas most pulse crops are very sensitive to salts.
Thus, for successful irrigation with saline water in a specific zone, selection of crops should be such as to suit salinity of water, as it may not be possible to change the quality of irrigation water. High water requiring crops like sugarcane and rice should be avoided with brackish water as these aggravate the salinity problems.
ii. Growth Stages:
During initial stages, plant roots are limited to surface few cm, where most salts concentrate on the evaporating surface. Hence, in most crops, germination and early seedling establishment are the most critical stages requiring strategies for minimising salinity in the root zone. Other critical periods are phase changes from vegetative to reproductive (heading and flowering). Otherwise, tolerance to salinity increases with the age.
iii. Crop Varieties:
There is wide variation in inherent salt tolerance of crop varieties. Usually there is a negative correlation between tolerance and their yield potential. Varieties like Damodar in rice and Kharchia in wheat are tolerant to salinity but have low yield potential. Varieties showing stable yield under saline conditions should be preferred.
b. Irrigation Management:
i. Leaching Requirement for Salt Balance:
Areas where highly saline water are used are usually mono-cropped. Only salt tolerant crops are grown during winter. In such areas, rainfall received during monsoon is utilised for meeting the leaching requirements and thus maintaining the salt balance.
A leaching strategy that can work well is to apply saline water for boosting the antecedent moisture contents and reducing salinity levels before the onset of monsoon. The refill of the surface soil with water just before the onset of monsoon will enhance salt leaching during kharif rains.
In addition to amount and frequency of rains, salt leaching with rains depends on soil texture. Removal of 80 per cent of the salts accumulated during the period preceding monsoon would require 1.85, 0.95 and 0.76 cm of rain water cm-1 soil depth in fine, medium and coarse textured soils, respectively. Clay soils irrigated with high SAR – saline/sodic waters become vulnerable to dispersion and movement upon leaching, especially with low electrolytic rainwater.
Thus, salts are held back and such soils have been shown to require almost double the quantity of water (0.7 to 1.2 cm cm-1 soil) compared with the structurally stable saline soils (0.4 to 0.5 cm cm-1 soil). Therefore, addition of gypsum to prevent surface sealing and enhancing infiltration of rain water is advocated for such situations.
ii. Irrigation Interval:
Under saline conditions, irrigation should meet both crop water requirements and leaching requirements to maintain a favourable salt balance. Therefore, it is usually opined that irrigation in saline soils should be more frequent because it reduces the cumulative water deficits between the irrigation cycles.
However, such option is still controversial as small irrigation intervals subsequently induce water uptake from shallow soil layers, increases unproductive evaporative losses from soil surface and with saline irrigations increase the salt load of soils.
Experimental results also indicate no advantage of more frequent irrigations than those recommended for normal soils. Depth of applied water should be simultaneously reduced if higher benefits from small intervals of irrigations are to be accrued.
As the infiltration rate controls the application depths, it is difficult to apply less than 25 mm water with surface methods and too frequent irrigations may infect aggravate the aeration problem. A shift to sprinkler or drip irrigation is desired for applying small quantities of water at frequent intervals.
iii. Water Table Management:
The salts are usually leached down and waterlogging problems alleviated through subsurface drainage for minimising the salinity hazards under high water table conditions. Safer disposal of drainage water is a major problem. Substantial contributions to seasonal water requirements can come from shallow water table.
Crops such as wheat require only one irrigation under shallow water table conditions around 1.0 m. Hence, shallow water table is desirable even if the water is saline. Such a practice simultaneously leads to salt accumulation in rooting zone, which levels out following leaching with monsoon rains.
F. Integrated use of Poor and Good Quality Waters:
When canal water supplies are un-assured or in short supply, farmers are forced to use saline ground or drainage waters to meet the crop water needs. Waters from these two sources can be applied either separately or mixed.
Mixing of waters to acceptable quality for crops also results in improving the stream size and thus the uniformity in irrigation, especially for the surface method on sandy soils. Allocation of two waters, if available on demand, can be done either to different fields, seasons or crop growth stages such that higher salinity water is not applied to sensitive crops or growth stages.
a. Pre-Irrigation:
Pre-sowing irrigation is usually given to facilitate tillage, seedbed preparation and recharge the root zone with water for germination and stand establishment. In saline soils, it also aids in leaching of soluble salts below the seeding zone to mimimise the salt injury to germinating seed and subsequent stand establishment. Crops like sorghum and mustard can tolerate higher salinity once the non-saline water is substituted for pre-sowing irrigation to leach out the salts of seeding zone.
In saline areas prone to water-logging, kharif crops fail to establish owing to high salinity and temperatures if sown before onset of monsoon and due to excess water after the establishment of monsoon. Crops like sorghum can be successfully raised if they could be established in pre- monsoon season after leaching the accumulated salts even with saline water (ECe > ECiw) followed by small additions of non-saline waters as the crop can withstand the excess water from later rains.
b. Cyclic use of Multi-quality Water:
The strategy involves substitution of canal water for saline water at most sensitive growth stages/crops grown in sequence and use of saline water at other stages such that the effects of resultant soil salinity build up can be minimised.
In general, crop yields will be high with cyclic use of canal and saline waters when the cropping intensities are less than 200 per cent. Yields can be maintained close to those obtained with good water by delayed substitution of saline water (after two initial irrigations with good quality water).
Alternate irrigations with good and saline water can also be followed if circumstances demand. Irrigation with saline water should not be at critical stages, especially at seeding phase.
Results of experiments are in favour of cyclic use over mixing. The advantage due to cyclic use followed the order; (2C: IS) > (IC: IS) >IC: 2S); canal: saline water use. Multi-salinity water should be used cyclically and the use of canal water at early stages and of saline water should be delayed to later stages.
c. Rain Water and Saline Irrigation:
In India, water penetrating into soil during monsoon usually exceeds ET demands. This induces leaching of salts added during monsoon to achieve necessary salt balance. Hence, emphasis during monsoon should be to maximise infiltration of rainwater into the soil and minimise its losses due to runoff and erosion. In general, performance of crops on conserved soil moisture is better than normal practice of seeding after a pre-sowing irrigation with saline water.
G. Amendments Needed:
Continuous use of high RSC water increases soil pH and ESP, which in turn decrease the soil permeability to water. High sodium in the absence of adequate calcium can also cause nutritional imbalance within the plants.
Adverse effect of long term use of alkali/sodic water on physical and chemical properties of soils can be mitigated by the use of amendments. Application of gypsum is required in soils irrigated with alkali water (RSC > 5 meq 1-1) especially when rice is grown and rainfall is less than 500 mm.
Application of gypsum before onset of monsoon is better than its application before pre-sowing irrigation to rabi crops. Since amendments use with irrigation is better, the alternative innovation to reduce alkalinity is by passing alkali water through designed gypsum beds. It has been found that kharif crops respond better to gypsum application through beds than soil application at similar doses.
H. Planting Procedure:
Failure to achieve satisfactory germination and thus the required plant population is the major factor limiting crop production with saline waters. Wherever possible, a heavy pre-sowing irrigation with non-saline water should be given to leach out the salts out of seeding zone.
The other technique that seems safe to establish crop is to give a post sowing irrigation. Sowing on northeastern side of ridges or at the side of furrows can also reduce salt accumulation near the seed zone. Relatively higher plant population than the normal appears to be ideal to compensate for poor tillering with saline water.
I. Water Quality Guidelines for Irrigation:
It is evident from the above that apart from its composition, determination of suitability of specific water requires specification of conditions (soil, climate, crop etc.) of its use and the irrigation and other management practices followed.
Therefore, the following broad guidelines, for assessing suitability of irrigation waters, have been suggested from time to time for average use conditions:
i. Growing relatively tolerant crops and varieties.
ii. Sowing on north-eastern side of ridges.
iii. Using around 20 per cent higher seed rate and quick post-sowing irrigation (within 2-3 days) for better germination.
iv. Use of gypsum for saline water having SAR > 20 and/or Mg: CA > 3 and rich in silica.
v. Fallow during rainy season when SAR > 20 and higher saline waters are used in low rainfall areas.
vi. Additional phosphorus application when CI: SO4 ratio is > 2.
vii. Canal water preferably at early growth stages including pre-sowing irrigation for conjunctive use with saline water.
viii. When ECiw < ECe (0-45 cm soil depth at harvest of rabi crops), saline water irrigation just before onset of monsoon.
Essay # 3. Sustainable Utilisation of Biodiversity:
Humans depend on biodiversity for diverse uses: economic, aesthetic, ethical and/or cultural. They depend on biological diversity as a source of food, fibre, fuel, shelter, medicines and several other day-to-day necessities. Sustainable agro-biodiversity management is necessary for progress in agriculture. Only a few biodiversity management options are briefly presented since the topic is beyond the scope of principles of agronomy.
A. Panacea of Agro-Biodiversity:
Genetic diversity is the basis of future improvement to meet the diversified and ever chasing needs of the mankind. Agro-biodiversity includes genetic diversity of plants, livestock, fisheries, microbes, insects, fungi and viruses. Agro-biodiversity is basic to farming systems in which farmers can exploit biological diversity to produce and manage crop, land, water, insects and other biota.
Both experience and research have shown that agro-biodiversity may account for or influence the following:
i. Increased productivity, food security and economic returns through diversified products and income opportunities.
ii. Providing sources of human nutrition and medicines.
iii. Reduced pressure of agriculture on fragile areas, forests and endangered species.
iv. Reduced dependence on external inputs.
v. Ecofriendly management of insects, pests, diseases and weeds.
vi. Making farming systems more stable and sustainable.
vii. Soil conservation and productivity.
viii. Conserving ecosystem structure and stability of species diversity.
Agricultural growth has eroded biodiversity in agro-ecosystems including plant genetic resources, jeopardizing productivity and food security leading to broader social costs. Hence, scientific management of these invaluable resources has assumed greater importance over time.
B. Plant Genetic Resources Conservation:
Conservation of plant genetic resources (PGR) includes their protection including sustainable utilisation of germplasm. Two basic approaches, the ex-situ and in-situ have been advocated for conserving the PGR.
a. Ex-Situ Conservation:
When germplasm conservation is attempted outside the natural habitat, it is known as ex-situ conservation. This can be achieved by perpetuating sample populations in genetic resource centers, botanical gardens, tissue culture repositories, gene banks for seed propagated species and conservation of pollen, embryo and other plant parts/organelle etc.
Conservation of seed propagated plants is relatively easy for seeds with orthodox type of storage behaviour i.e., drying the seed and storing at low temperature can maintain the viability. Most agrihorticultural crop plants, which have orthodox seeds, can tolerate desiccation. The ex-situ preservation of orthodox seeds in gene banks has been the most effective strategy for PGR conservation.
b. In-Situ Conservation:
In-situ conservation is the continued maintenance of a plant population within its ecosystem to which it is adapted. This term is usually applied to naturally occurring plant species, progenitors, forest trees and other species (also wild fauna). It also includes on-farm conservation of weedy/ wild relatives of crops and land races of crops as well as artificial regeneration of obsolete cultivars in there original habitats without conscious selection.
Wild populations of crop plant species and there close relatives are found in two broad categories of in-situ reserves in India : those designed to maintain optimum (natural) conditions and those that permit extraction and even clearing of land for other purposes.
National parks, nature reserves and specialised field gene banks falls in the first category, whereas national forests, indigenous peoples’ reserves and extractive reserves, all of which permit a range of economic activities such as harvesting of forest products, fall into the second category.
C. Conservation in Traditional Farming Systems:
Traditional farming systems sustain the domesticated varieties in interaction with their wild relatives. Such cycles of natural hybridization and introgression have, over time, enhanced the genetic diversity, which is so important for sustainability.
The importance of introgression in promoting genetic diversity in traditional forming systems calls for measures that promote synergy between the in-situ and ex-situ conservation of genetic resources. Yet more important is to view the traditional farming practices as part of an open system that promotes diversity in agro- ecosystems.
To achieve this, the following mechanisms have been visualised:
i. Community seed banks for retention/replacement of traditional germplasm.
ii. Cultivars registry system to ensure intellectual property protection to the concerned.
iii. Agroforestry/natural gardens to perpetuate diversity of species under cultivation.
iv. On-farm conservation of traditional indigenous cultivars along with their cultivation practices.
D. The Global Plan of Action (GPA):
Adopted at the Fourth International Technical Conference on Plant Genetic Resources at Leipzig in June 1996, the GPA constitutes an important element of the Global System on Plant Genetic Resources for Food and Agriculture (PGRFA) aiming to facilitate the implementation of the Agenda 21 and the Convention on Biological Diversity (CBDE).
Broad areas and activities under GPA are:
a. In-Situ Conservation and Development:
i. Surveying and inventorying plant genetic resources for food and agriculture.
ii. Supporting on-farm management and improvement of plant genetic resources for food and agriculture.
iii. Assisting farmers in disaster to restore agricultural systems.
iv. Promoting in-situ conservation of wild crop relatives and wild plants for food production.
b. Ex-Situ Conservation:
i. Sustaining existing ex-situ collections.
ii. Regenerating threatened ex-situ accessions.
iii. Supporting planned and targeted collection of plant genetic resources for food and agriculture.
iv. Expanding ex-situ conservation activities.
Integrated nutrient management is a must for sustaining microbial population and its activity in nutrient transformations. Similarly, integrated post and weed management minimises the use of agrochemicals and aids in buildup of natural enemies in minimising the pest incidences.
c. Utilisation of Plant Genetic Resources:
i. Expanding the characterisation and evaluation and number of core collections to facilitate use.
ii. Increasing genetic enhancement and base broadening efforts.
iii. Promoting sustainable agriculture through diversification of crop production and broader diversity in crops.
iv. Promoting development and commercialisation of under-utilised crops and species. Supporting seed production and distribution.
v. Developing new markets for local varieties.
d. Institutions and Capacity Building:
i. Building strong national programmes.
ii. Promoting network for plant genetic resources for food and agriculture.
iii. Constructing comprehensive information system for plant genetic resources for food and agriculture.
iv. Developing, monitoring and early warning systems for loss of plant genetic resources for food and agriculture.
v. Expanding and improving education and training.
vi. Promoting public awareness of the value of plant genetic resources for food and agriculture.
Essay # 4. Integrated Nutrient Management:
Integrated nutrient management (INM) as defined by Harmsen (1995) differs from the conventional nutrient management by more explicitly considering nutrients from different sources, notably organic sources, nutrients carried over from previous cropping seasons, the dynamics, transformations and interaction of nutrients in soils, interaction between nutrients, their availability in the rooting zone and during growing season in relation to the nutrient demand by the crop.
Integrated plant nutrient system (IPNS), developed by the FAO, is the maintenance or adjustment of soil fertility and of plant nutrient supply to an optimum level for sustaining the desired productivity through optimisation of benefits from all possible sources in an integrated manner. The INM is a prescription for developing a durable IPNS.
The INM is soil fertility sustaining practice because:
i. It enhances the availability of both applied and native soil nutrients during the crop season.
ii. It synchronises the nutrient demand set by the plants both in time and space with supply of nutrients from soil and applied nutrient pool.
iii. It sustains and enhances chemical, biological and physical soil health.
iv. It arrests degradation of soil, water and environmental quality by promoting or minimising the avoidable leakages of fertiliser nutrients to water bodies and atmosphere.
Essay # 5. Integrated Plant Protection:
Plant protection (against pests, diseases and weeds) determines the effectiveness of other inputs in crop production. Exclusive reliance on pesticides, fungicides and herbicides resulted in pesticide and herbicide resistance, pest resurgence, residues and environmental pollution. This led to the development of integrated plant protection strategies, which are components of sustainable agriculture with a sound ecological foundation.
Integrated plant protection should be understood as an ideal combination of agronomical, biological, chemical, physical and other methods of plant protection against entire complex of pests, diseases and weeds in a specified farming ecosystem, with the object of bringing down their infestation to economically insignificant levels with minimum interference on the activity of natural beneficial organisms.
The essence of integrated plant protection concept lies in the harmonious integration of compatible multiple methods used singly or in combination against insect pests, pathogens and weeds.
Masonobu Fkuoka of Japan, considered as the father of organic farming, has been consistently recording yields of many crops that are comparable to the best yields obtained in Japan by not using HYVs, insecticides, fungicides, herbicides or chemical fertilisers. Use of these agrochemicals, according to him, does not necessarily lead to better farming than using integrated plant protection methods.
A. Integrated Pest Management:
Integrated pest management (IPM), which by definition is a pest management system that, in the context of associated environment and population dynamics, utilises all the appropriate techniques to minimise the pest population at levels below those causing economic injury.
Though, several parasitoids, predators and pathogens of pests and antagonistic microorganisms were known to be effective for several decades, they were not commercially exploited because of quick knock down effect and easy availability of chemical pesticides instead of bio-pesticides and IPM. Slowly but steadily, there has been growing appreciation about the role of cultural and biological methods in pest control. Cultural and biological methods are the two major components in integrated plant protection.
B. Integrated Disease Management:
For mitigating the losses due to diseases, several methods such as fungicides, organomercurials, chemotherapy, thremotherapy, cultural methods and host resistance are employed. However, no single method is effective in controlling a disease. Therefore, integrated disease management (IDM) became imperative for effective diseases control.
Broad based tentative IDM components are being adopted for disease control. However, all these components are not feasible for any specific ecosystem or any specific disease. For many diseases the role of host resistance, cultural methods and chemical methods are integrated.
C. Integrated Weed Management:
Integrated weed management (IWM) involves the concept of multiple tactics of weed management for weed population below economic injury level and conservation of environmental quality. A successful IWM strategy has the principle of enhancing farmer’s profitability, environmental protection and responsiveness to consumer preference.
Weeds vary so much in their growth habit and life cycle under different ecosystems and growing seasons that no single method of weed management can provide effective weed control. Continuous use one method of weed control creates problems of buildup of weeds that are tolerant to that particular method of weed control.
Similarly, shift in weed flora from annual grasses to sedges and appearance of resistant biotypes due to continuous use of some herbicides has been reported. Long term strategy to minimise weed problem is through IWM than with weed control.
Major components of IWM include:
i. Monitoring weeds, shifts in weed flora, appearance of resistant weeds and introduction of new weeds
ii. Emphasis on ecological, biological and biotechnological methods for environmental safety
iii. Low Cost Agronomic Strategy for Weed Management in IWM Systems:
a. Stale seedbed.
b. Balanced fertiliser use.
c. Higher plant populartion.
d. Intercropping/relay cropping.
e. Use of competitive cultivars.
f. Supplemental herbicide use at minimum possible rate.
i. Monitoring of Weeds:
Systematic monitoring of weeds would help to devise effective ways to tackle current emerging problems of shift of grassy weed flora like Echinochloa sp to annual sedges like Cyperus iria, Fimbristylis miliacea and broad leaf weeds Spheneriocleci zeylanica. Similarly, appearance of propanil herbicide resistant biotypes of Echinochloa sp in rice has become a problem.
ii. Ecological Management:
Ecological management (cultural management) aims at attacking ecological weak points of weeds during field operations such as ploughing, water management, crop season, crop rotation, intercropping etc.
Ploughing is usually done at optimum soil moisture content by which time the weed seeds start emerging. Hence, emerging weed seedlings are buried or exposed to hot sun for drying. In perennial weeds, ploughing is effective to control emergence whose propaguls are formed at relatively shallow position within soil. Intensive puddling is very effective for weed control in lowland rice.
Water management practices are very effective for weed control especially in lowland rice. Continuous land submergence beyond 5 cm depth for rice is very effective against several weeds and can substitute for weed control.
Lowland rice crop rotation with an upland crop is effective against moisture loving weeds. The population of Scirpus maritimus and Echinochloa increases with continuous cropping of lowland rice but decline when rice is rotated with an upland crop.
Similarly, population of Celosia argentea increases due to continuous growing of short statured crops such as groundnut but decreases considerably when rotated with tall crops such as sorghum, maize, pearl-millet etc.
iii. Biological Management:
Biological weed control using insects, pathogens, fish and snails (bioagents) appears to be ideal for reducing the input of herbicides.
Some promising examples include:
iv. Bio-Herbicides:
Although herbicides are effective for weed control, there has been increasing concern about their safety for food products, their adverse effect on environment and widespread weed resistance to herbicides.
These factors along with rising prohibitive cons have provided the impetus to develop alternative weed management strategies. In this contest, biological control as an alternative or supplemental weed management appears to play a major role in crop production.
Biological approach includes bio-control agents such as insects, nematodes, fungi and bacteria as well as plant based chemicals that exhibit herbicidal properties. A bio-herbicide is a plant pathogen used for weed control through application of its inoculum.
A list of bio-pesticides is given below in Table 10.5:
The present system of plant protection, which relies heavily on agrochemicals, is no more viable from ecological and economical viewpoints. It is time to look at traditional plant protection practices as they hold greater promise in the contest of sustainable agriculture. Necessity of their integration with chemical control methods is strongly felt, as the traditional methods are simple and economical with least fear of environmental pollution.
Essay # 6. Enhancing Sustainability of Dryland Agriculture:
Rainfed production systems are characterised by instability in production due to aberrant weather. However, there is immense scope for enhanced sustainability of these production systems in view of standerdisation of technologies in the recent past.
A. Soil and Moisture Conservation:
Conservation of rainwater is most important for successful dryland crop production systems. A number of land treatment technologies besides contour and graded bunds have been identified for soil and moisture conservation.
These techniques are location specific and highly variable depending on rainfall intensity, slope and texture of the soil and cropping systems.
Summary recommendations on inter-terrace land treatments for different zones are given below in Table 10.6:
From the results it is evident that there is significant yield improvement in crops due to soil and moisture conservation. Farmers are not widely adopting mechanical measures like contour bunding, grassing waterways and construction of farm ponds without Government support due to cost constraint.
Yield advantage due to adoption of conservation measures, at farmers level, usually vary between 10 and 20 per cent, which are not convincing enough to the farmers. However, cumulative effects are significantly visible at some locations. Such measures contribute to long term conservation of natural resources. Hence, they are implemented through Government of India/state sponsored watershed management programme.
B. Improved Crops and Cultivars:
A large number of improved cultivars in different crops have been developed to match the growing period in different agro-ecosystems. Specific cultivars have also been identified for intercropping and sequence cropping.
Yield advantages due to improved cultivars ranges from 20 to 40 per cent depending on the crop and season. Farmers are gaining benefits ranging from Rs. 2,000 to 4,000 by adoption of improved cultivars in crops like sorghum, castor and sunflower.
C. Efficient Cropping Systems:
Efficient crops and cropping systems for different regions to replace traditional ones have been identified. Improved short duration cultivars are replacing long duration varieties to avoid terminal soil moisture stress. Stability in production can be achieved through appropriate inter-cropping and double cropping systems.
i. Intercropping:
Intercropping is usually recommended for areas receiving rainfall up to 800 mm with the objective of obtaining optimum yield at least in one of the component crops. In good rainfall areas, there are greater chances for success of both the crops.
Most of the intercropping systems are additive series, where the population of component crops is maintained equal to the sole crop. To site a few, promising intercropping systems for Vertisols and Alfisols are given in Table 10.7.
ii. Double Cropping:
In areas receiving more than 800 mm annual rainfall with a soil moisture storage of 200 mm m-1 depth, double cropping is a distinct possibility. Early planting of kharif crop enables sowing rabi crop on stored soil moisture in optimum time. Table 10.8 gives ideal double cropping systems for different areas in the country.
In black soil areas of Andhra Pradesh, especially Rayalaseema, a large number of crop sequences are followed:
Recommended crop sequences are:
Adoption of recommended inter and double cropping systems has been low to moderate across the country. One of the major constraints in adoption is the dependence for fodder on the cereal crops. In southern part of the country, especially Andhra Pradesh, farmers grow more rows of sorghum than recommended to obtain more fodder for livestock.
In spite of high yield potential of sorghum hybrids, they are not becoming popular in Rayalaseema (AP) area due to relatively low straw yield compared to traditional varieties. Late onset of monsoon and consequent delay in planting kharif crop is the major constraint in wider adoption of recommended double cropping systems.
Fluctuating prices of the component crops and the overall profitability of the system in terms of additional cost and benefits also play crucial role in farmer’s decision on cropping systems.
D. Cultural Practices:
Agronomic and soil management practices like tillage, time of sowing, mulching, weed management and contingent crop planning have been stadardised for enhancing the sustainability of rain production systems.
i. Tillage:
Tillage increases conservation of soil moisture by making the soil more permeable to rain water. Deep tillage (25 to 30 cm) breaks open hard soil layers for faster penetration of rain water. Off season or pre-monsoon tillage has marked impact on rain water intake and weed management. Improvement in yield due to off season tillage ranges from 150 to 250 kg ha-l under different situations.
However, excessive tillage in light soils accelerates erosion besides creating unfavourable conditions for soil organic matter buildup. In general, no tillage systems are not ideal under rainfed situations in India.
ii. Time of Sowing:
Sowing of dryland crops with the onset of monsoon can significantly improve crop yields across the country. Yield advantages due to early sowing can be as high as 100 per cent.
Timely sowings help in optimum utilisation of seasonal rainfall, minimising the incidence of pests and diseases and in escaping terminal soil moisture stress. Yield losses due to delayed sowing ranges from 50 to 70 per cent depending upon seasonal conditions. Hence, there is no substitute to timely sowing.
iii. Inter-Cultivation:
Timely inter-cultivation aids in weed control and creating soil mulch for minimising soil moisture loss through evaporation. Organic mulches on soil surface are more effective for crops grown on receding soil moisture. Straw mulches around 5 t ha-1 appear to be effective for minimising soil moisture loss.
Limited availability of straw, after meeting the needs of livestock, limits its use as mulch for moisture conservation. Repeated inter-cultivation using local blade harrows aids in creation of soil mulch bedsides weed control.
iv. Contingent Crop Planning:
Drought occurrence is a common phenomenon in dryland agriculture due to late onset or early withdrawal of monsoon and dry spells during crop season. Accordingly, a large number of recommendations have been made for different zones on crop substitution and cultivar replacement in case of delayed onset of monsoon. In this approach, short duration crops and cultivars replace the long ones. A number of options are available for early, mid and late season droughts.
In the case of early season drought (seedling emergence and early growth), implementable suggestions are:
(1) Re-sowing with crop and variety suitable for late sowing and transplanting by raising seedling or
(2) With seedlings from fields in nearby areas with the subsequent rain as in the case of finger-millet, pearl-millet, setaria etc.
In the case of midseason drought, viable options are : forming dead furrows at convenient intervals (3 – 4 m) well in advance of anticipated drought (within a month after seeding or immediately after inter-cultivation) for minimising runoff and storing rain water, thinning the plant population either within the row or by removing alternate rows in a sole crop or removing more sensitive crop in intercropping and harvesting the crops for fodder and allowing the stubbles to grow for grain (ratooning) as in the case of sorghum and pearl-millet. For late season drought, the options are limited.
A crop on relatively deep soils, may be removed and a short duration rabi pulse crop sown on stored soil moisture with subsequent rain. In the case of sorghum and pearl-millet, ratooning appears to be ideal even at times of late season drought, especially in deep black soils.
E. Water Harvesting and Recycling:
Despite the adoption of soil conservation measures, some degree of runoff is inevitable during high intensity rains. Such runoff can be collected in dug out ponds and used for supplemental irrigation to standing kharif crops during drought spells or for rabi crops to the extent possible.
Technologies have been developed for collecting and storing runoff water in different structures. However, its adoption under field conditions is not encouraging due to cost factor associated with storage structures and their maintenance.
It is often argued that the storage structures may not contain much water by the time it is required for irrigation or if it contains some quantity, the area that can be irrigated with that water is negligible. Under these circumstances, it is desirable to follow an integrated approach for soil moisture storage than depending on any one recommendation.
F. Watershed Management:
Rainwater conservation and utilisation is the corner stone for successful dryland agriculture. Watershed management programmes are aimed at soil and water conservation, improved crop production technology and appropriate alternate land use systems based on land capability classes.
Data generated from a number of model watersheds indicated measurable impact on water resources generation and crop productivity. Irrespective of whether the soil and moisture conservation measures improved the productivity of crops in a watershed area, their significant impact on improvement in ground water recharge is an accepted fact. Such an improvement in ground water recharge largely improved the cropping intensity, productivity and economic gains in several watershed areas.
Despite the clear benefits of the watershed approach to development of rainfed areas, there have been some failures, which stressed the need for organising participatory farmers into groups (watershed panchayt, watershed corporation) for the success of watershed development programme.
A village community welded into a water users association endowed by local wisdom with the assured rights and liabilities of individual farmers can play a crucial role in watershed based resource development, conservation and efficient utilisation.
Development of rainfed areas on watershed basis has become an accepted strategy in India. Its success cannot be evaluated in terms of adoption by individual farmers, as it is basically a community targeted strategy. Though, it has remained as a state run programme so far, with the entry of NGOs and new guidelines of the Government of India, involvement and participation of individual farmers is set to accelerate in due course.
G. Nutrient Management:
Fertiliser recommendations in dryland agriculture remained as theoretical recommendations in several situations largely due to undependable rainfall leading to frequent crop failure. It is an established fact that bulky organic manures such as FYM and compost and recycling of other organic wastes greatly contribute to improvement in water retentive capacity of silos, which is the key factor for success of dryland agriculture.
Results of experiments have conclusively proved the need for conjunctive use of bulky organic manures, bio-fertilisers and fertilisers besides crop rotation involving legumes for reducing the investment on fertilisers and increasing the fertiliser use efficiency.
H. Alternate Land Use Systems:
Despite the improved production technology, arable dryads continue to suffer from instability due to aberrant weather. In order to provide stability to farm income and to utilise marginal lands for producing fodder, fuel-wood and fibre, a number of alternate land use systems have been developed to suit location specific needs.
i. Agrisilviculture:
This system is recommended for land capability Class IV with annual rainfall up to 750 mm. A large number of tree crop combinations involving nitrogen fixing trees (NFTs) with sorghum, groundnut, castor and pulses have been identified for income generation.
Faidherbia albida and Hardwickia binata are compatible with arable crops. Short duration green-gram and black-gram combine well with widely spaced (8 x 8 m) Faidherbia albida trees. Hardewickia binata being erect and slow growing will not compete with arable crops during the initial 8 to 10 years. These two species, therefore, hold promise for agrisilvicultural system.
ii. Silvipasture:
This system is recommended for marginal lands (Class V and higher). It involves integrating a tree component with a perennial legume or grass species as pasture. Cenchrus ciliaris and Stylosanthes hamata combination is well suited to marginal lands. Stylo can be independently established as a sole pasture on degraded marginal lands.
iii. Agrihorticulture:
In medium deep soils (Class II to IV) receiving annual rainfall more than 750 mm, this system consisting of fruit trees intercropped with annual arable crops is recommended. Ber, custard apple, anona and pomegranate suits well for drylands both as sole and intercrops. Clusterbean, cowpea, horsegram and other grain legumes are useful for this system in south India.
iv. Alley Cropping:
This system is recommended for Class II and III with annual rainfall between 500 and 750 mm. Arable crops are grown in allies formed by trees or shrubs established, generally, on contour. The trees or shrubs will act as live bunds to control runoff.
Hedge rows are to be cut to height of 15 cm from the ground during the season to avoid competition with crop. However, arable crops suffer yield reduction owing to competition for limited soil moisture under rainfed conditions. This technology, therefore, is not largely acceptable to farmers under different situations.
I. Key Options for Specific Regions:
Key options for enhancing sustainability of dryland production systems in specific regions are summarisrd below:
a. Options for areas with rainfall less than 500 mm:
1. Linking arable farming with animal husbandry.
2. Limiting arable farming to millets and pulses and adopting alternate land use systems.
3. Adopting arid horticulture to augment farm income.
4. Soil and moisture conservation to mitigate occasional dry spells during crop season.
5. Efficient management of grazing lands with improved grasses.
b. Options for areas with rainfall between 500 and 750 mm:
1. Emphasis on oilseed and pulse based inter-cropping systems in not so unfavourable tracts.
2. Encouraging watershed approach with emphasis on offseason tillage, in-situ moisture conservation and runoff water harvesting for recycling.
3. Efficient utilisation of marginal and shallow lands through alternate land use systems.
4. Importance to high value crops (fruits, medical and aromatic plants, dyes etc.,).
5. Increasing afforestation in highly degraded undulating lands.
c. Options for areas with rainfall between 750 and 1,150 mm:
1. Developing aquaculture in high rainfall double cropped areas with rationalisation of area under rice.
2. Emphasis on intercropping systems with improved cultivars of maize, soybean, groundnut and double cropping in deeper soils.
3. Improved cultivars of sorghum, pigeon-pea and cotton in areas up to 1,000 mm rainfall.
4. Encouraging rain water harvesting and ground water recharge.
d. Options for areas with rainfall more than 1,150 mm:
i. Intensive rice cultivation with improved production technology.
ii. Adoption of double cropping in relay cropped areas.
iii. Emphasis on plantation crops, post-harvest processing and export oriented products.
iv. Rain water harvesting and development of water resources for post rainy season crops with supplemental irrigation.
v. Rehabilitating degraded lands with alternate agriculture involving perennial vegetation.
Essay # 7. Enhancing Sustainability of Irrigated Agriculture:
The productivity of irrigated systems, unlike rainfed systems, is assured due to less dependence, on direct rainfall during the crop season. The intensity of cropping varies from around 200 to 300 per cent or even more depending on the duration of irrigation water availability. However, faulty management of surface and groundwater resources has led to serious implications on soil health and crop production.
A. Water Quality Deterioration in Coastal Areas:
Decline in water table owing to excessive pumping in coastal areas leads to ingress of sea water into ground aquifers. Along the Saurashtra coast, 160 km long and 5 to 10 km wide ground water belt has been salinised due over draft of fresh water floating over saline aquifers.
Thousands of wells in this area have gone out of commission or the lands have been salinised, where water from such wells was continuously used for irrigation. Sea water intrusion has also been observed along the east coast in Orissa and Andhra Pradesh.
B. Nitrate Pollution of Groundwater:
Nitrate pollution of groundwater, owing to leaching of nitrates, is relatively new concern in India. In general, at low rates of N fertiliser application in the country, it is not likely to pose a serious problem in most of the farming situations.
An increase in NO3-N content of well waters has been recognised only in intensive irrigated cropping systems. In Ludhiana district of Punjab, average NO3-N content of shallow wells increased from 0.42 to 2.29 mg during 1975- 1988.
C. Efficient Irrigation Water Management and Drainage:
Development of location specific irrigation technologies on farmer’s fields and canal command areas has been considered to be vital for efficient water management and drainage to minimise the impact of poor water management on environment.
i. On-Farm Water Management:
All India Coordinated Research Project on Water Management initiated on-farm water management through operational research projects in selected command areas of the country to demonstrate viable irrigation water management technology.
The package interventions consisted of land preparation, border and furrow irrigation with proper irrigation scheduling, suitable cropping patterns and conjunctive use of brackish groundwater with good quality canal water during scarcity period. Adoption of improved technology increased yields of major crops from 15 to 40 per cent.
ii. Conjunctive use of Water:
Conjunctive use management is management of multiple water resources in a coordinated operation such that the total water uses of the system over a period of time exceed the sum of water use of the individual components of the system resulting from uncoordinated operation.
1. Conjunctive use of Saline and Canal Water:
Under the short supply of canal water, water from the two sources (canal and saline water) can be applied either separately or mixed. Mixing of water to acceptable quality for crops also results in improving the stream size and thus the uniformity of irrigation, especially the surface methods on sandy soils.
Allocation of two waters separately, if available on demand, can be done either to different fields, seasons or crop growth stages such that higher salinity water is not applied to sensitive crops or at sensitive growth stages.
Crops like green-gram, sorghum and mustard can tolerate higher salinity once the non-saline water is substituted for pre-sowing irrigation to leach out salts of seed zone. In saline soils prone to waterlogging, kharif crops fail to establish owing to high salinity and temperatures if sown before onset of monsoon and due to excess water if sown after onset of monsoon.
There is immense scope for successful kharif crops like sorghum if they can be established in the pre monsoon after leaching the salts even with saline water (ECe > ECiw) followed by small addition of non-saline water.
2. Cyclic use of Multi-Quality Waters:
The strategy involves substitution of canal water for saline water at most sensitive growth stages/crops grown in succession.
iii. Groundwater Management:
Artificial recharge of groundwater resources becomes necessary when the annual depletion of groundwater in a given area exceeds the annual replenishment.
The two methods of groundwater recharge are:
(i) Surface and
(ii) Subsurface techniques.
In the surface techniques, the runoff is conserved through gully plugging, bench terracing, contour bunds, percolation tanks, spreading basins and individual well recharge. Subsurface techniques include subsurface dykes and recharge tube-wells.
1. Individual Well Recharge:
Individual farm wells can be recharged after it is passed through a filter bed to prevent silting of well in operation. The flood water is then directed into the open well filled with sand. The suspended material gets settled on top of the sand and the filtered water enters into borehole. The NGOs in Mehsana district of Gujarat, facing acute water shortage, is adopting this method of recharge to meet the needs.
2. Subsurface Dyke:
These are constructed in riverbeds with imperious walls on the downward side. The dyke is dug along the entire width of the river and may have a depth of 15 m or up to water level. A check dam is constructed on the downstream side at an appropriate distance for intercepting the flow. Excavated portion of the dyke section is filled with good pervious sand for facilitating maximum recharge.
3. Recharging Tube-Well:
These are constructed to augment fresh water supplies in deep aquifers. Generally, the recharge tube-well consists of a drilled borehole with a large diameter (30 to 50 cm) and sufficiently below the existing water table. A PVC or mild steel tube with a diameter smaller than the borehole is placed in the borehole and the inter space is packed with gravel.
An artificial filter is constructed at the top of the recharge tube-well for filtration of suspended material. Slotted sections in the pipe provided against the aquifers are generally wrapped with coir and surrounded by gravel pack and sand. An air vent is provided for release of air during recharge.
iv. Management of Waterlogging and Soil Salinity:
Most common techniques to prevent waterlogging and soil salinity are land grading, surface and subsurface drainage. Crop management practices include leaching, selection of crops/varieties, pre-sowing irrigation, sowing/planting time, plant population, sowing/planting technique, plant nutrient supply, methods of irrigation and irrigation scheduling.