Organic fruit crop management is not just exclusion of synthetic inputs and substitution by organically acceptable inputs. Simple input substitution may fulfill the requirement of certification standards, but it will not guarantee the sustainability and long term productivity with intact resource pool.
Organic orchard management begins with right selection of site, selection of high quality cultivars, planting of healthy saplings, and good soil management for nutrient cycling, productivity, and tilth. It also involves an integrated approach to pest management to minimize losses from insect pests, diseases and weeds.
Although fundamental steps of organic orchard management are not very different from conventional systems, but some issues need special attention, as due to prohibition on use of chemicals there may be some limitations in respect of soil fertility maintenance, weed control and disease management. For setting up of new plantations in depth assessment of physical and environmental factors is essential to determine whether the particular crop can be grown easily, marginally, or not at all.
Fruit trees, like any other crops, although respond to good soil with vigour and productivity but can also be grown successfully with optimum commercial yields even on hill sides, rocky soils, and other sites not suitable for other crops requiring tillage.
Management planning begins with selection of suitable site, climate suited crop, and planting material of suitable variety having resistance to prevailing insect pests and diseases. Next step is land preparation and orchard layout (pattern of planting, row and plant to plant spaces, water conservation strategies etc.). Appropriate consideration of all these issues determines the productivity, health, and efficiency of operations in the orchard, and they cannot easily be changed once the orchard is established.
In case of an existing orchard, there is a need to assess strengths and weaknesses of the site, availability of resources and facilities for irrigation, mechanization and post-harvest handling. Generally conversion to organic is linked to the market demand and accessibility to marketing networks, therefore, it also needs to be ascertained that how the produce will be handled within the facilities and how quickly the produce can be processed for marketing.
Selection of Variety and Planting Material:
As fruit trees are perennial and require significant investment both in terms of money and time, it is extremely important to select location suited variety, having resistance to prevailing insect pests and diseases and has market acceptability.
Planting material procured from certified nurseries with known traits should be preferred. Organic certification standards require the use of planting material also from organic origin, but in case if the same is not available, then conventionally grown planting material without any chemical treatment can also be used.
Important considerations in site preparation include alleviating soil compaction, enhancing fertility, adjusting soil pH, and managing weeds, pests, and diseases. Before establishing an orchard, it is important to adjust the soil pH. This can be ascertained through routine soil testing. In case if pH correction is required then the same can be done through use of lime or dolomite for acidic soils and by use of gypsum or sulphur for alkaline soils.
Soil testing laboratories generally provide recommendations on the quantity of soil amendment required for specific crops. Most fruit plants perform best around pH 6.5, although they can tolerate a pH range between 5.5 and 7.2. Generally, fruit crops do not require highly fertile soils for good production, though this varies with the species. Highly fertile soils, rich in nitrogen, can promote too much vegetative growth at the expense of fruiting in trees such as apples.
A nutritionally balanced soil, proper soil pH, and plentiful organic matter are the fundamentals of an organic fertility management plan for fruits. Pre-plant soil improvement for organic fruit planting usually involves some combination of cover and legume cropping and applications of compost, natural minerals, or other organic manures.
Orchard Floor Management/Cover Crops:
The orchard floor, the tree rows and alleyways can be managed in a variety of ways, using tillage or mowing with cover crops, grazing, or mulching. An orchard providing full ground cover with cover crops/mulches etc. ensures best protection against erosion. Clean cultivation (keeping orchard floor free from weeds/crops/mulches) is prone to erosion, gradual depletion of organic matter, increased soil compaction, and reduced water infiltration.
In an organic orchard, crop rotation does not mean changing the economic crop itself, but diversifying the vegetation that grows around the fruit crop. Growing of shallow rooted cover crops, fodder grasses and shade loving crops such as turmeric are few examples. Using alley cropping, intercropping, and hedgerows to enhance biological diversity is also an ideal option.
In organic management as majority of the nitrogen comes from organic sources, accompanied with other minerals such as P, K and micronutrients, generally, nitrogen is considered as the index element for calculation. Organic materials with a C: N ratio of less than 20:1 (such as FYM, enriched compost, vermicompost or concentrated manures from oil cakes etc.), nitrogen is released fairly rapidly into the soil, from which it can be taken up by plants.
Organic materials with a C:N ratio in the range of 25:1 to 30:1 release N slowly while decomposing, whereas materials with C:N ratios above 35:1 (such as crop residue, tree leaves, or wheat/rice straw) can immobilize soil N for several weeks or months. Therefore we need to ensure that only the material having C:N ratio below 25 be incorporated with the soil and the material having C:N ratio above 25 to 35 is used as surface mulch.
In cases where tree leaves, forest litter or crop residue is to be used as surface mulch having wider C:N ratio then it needs to be mixed with either legume residue or be sprayed with dung-urine based liquid manures (such as Jivamrit or Amrit Pani) for faster decomposition.
Based upon long term studies it is understood that, the percent of total nitrogen that is available during the current season can be estimated at 70% for concentrated manures (having C:N ratio below 10:1), 50% for manure and cover crops (having C:N ratio below 25), and just 10-25% for other material having C:N ratio above 30:1. Remaining N, gets incorporated into the soil organic N pool, which is a vital long-term source of N.
Some manure-N may leach or volatilize, and some may enter the organic N pool, depending on the C:N ratio of the manure-mulch mix. While the “available” portion of compost, manure, and mulch N fulfills the needs of the current crop, the “unavailable” portion of manure, compost and mulch N, goes toward replenishing soil organic N and helps to manage the soil’s aeration and water holding capacity.
For calculating nutrient supplementation requirement under organic management one can proceed as follows:
1. As under organic management entire nutrient source is in the organic form and all organic manures contain NPK in the ratio of 2:1:1.5 to 0.5:0.5:1.0, only N is taken into consideration for all nutrient calculation points of view.
2. Only in cases where there is proven deficiency through soil test reports, other deficient nutrients (such as P, K or secondary or micro nutrients) need to be integrated. Micronutrient deficiencies are usually overcome within 3-4 years; thereafter micronutrient application will not be necessary. P and K supplementation through rock phosphate and sulphate of potash can be used in exceptional cases as per crop demand and soil test report.
3. In micronutrients generally it is boron, zinc and in some cases iron and molybdenum which have been noted as deficient in Indian soils. In such cases these micronutrient elements need to be added through composting. Recommended dose of micronutrient is integrated with the biomass during composting process or mixed with mature compost prior to application.
4. In intensively cultivated areas, although sulphur has also been found to be deficient in about 35-40% of soils, but under organic management where nutrients are managed through biomass and organic manures, sulphur deficiency is not common and can be overcome in just 2-3 years without any correction. In highly deficient soils gypsum can be used as sulphur source.
5. Depending upon the crop, nutrients need to be provided in single basal dose or in multiple doses at different stages of growth.
6. To keep the biological activity of the soil at high level and to ensure quick degradation of biomass applied as mulch, liquid manures (such as Jivamrit) also need to be applied 2-3 times without any reference to the quantity of inputs being used.
7. For foliar spray, bio-stimulants/growth promoters should be mixed with plant protection prophylactics for multiple effects.
8. In tune with the spirit of organic farming all out efforts must be made to meet the nutrient requirements from on-farm or on-farm made inputs. Only in case of non-availability, off-farm organically acceptable inputs should be used as supplementary source.
9. Developing an organic management purely on off-farm inputs is not advisable as it will neither be environment friendly nor sustainable and profitable.
10. Combination of multiple inputs should be preferred over single or two inputs.