Nutrients Required for Sorghum Production | Agronomy

The following points highlight the four nutrients required for sorghum production and which were considered as the major plant nutrients for enhancing the crop productivity: 1. Nitrogen 2. Phosphorus 3. Potassium 4. Micronutrients.

1. Nitrogen:

Nitrogen is the most commonly deficient nutrient and sorghum readily respondents to its application. The amount of nitrogen fertiliser needed depends upon the nitrogen available from the soil and the yielding potential of the cultivar under different environments.

Response to Nitrogen:

All India Coordinated Sorghum Improve Project (AICSIP) studied response of improved and local cultivars to nitrogen in different sorghum growing tracts. Hybrids are most responsive to nitrogen (Table 4.8) followed by Swarna variety. Grain yield for the three cultivars increased up to 150 kg N ha^-1. Average yield of locals was only 2029 kg ha^-1 with was less than half for CHS 1 due to no nitrogen.

TABLE 5.7: Response of kharif sorghums (kg ha^-1) to nitrogen.

Relative efficiency of nitrogen utilisation indicated that the locals were less than half as efficient as other cultivars. In 0-50 kg N ha^-1, grain yield increased by 21.2, 16.6, 18.2 and 7.1 kg grain kg^-1 of applied nitrogen for CSH 1, CSH 2, Swarna and locals, respectively. The improved cultivars were not only more responsive to nitrogen than locals but also resulted in 53-81 per cent higher yields than the locals without fertiliser nitrogen. There results suggested necessity for nitrogen between 50 and 100 kg ha^-1.

Further trials with CSH 5, CSH 6, CSV 2 and CSV 3 indicated that the response was 26 kg grain kg^-1 nitrogen at 40 kg N ha^-1 and the CSH 6 produced 22 kg grain kg^-1 nitrogen at 80 kg N ha^-1. Several such trials conclusively proved that the improved cultivars should be fertilised with 40-100 kg N ha^-1, depending on rainfall during kharif for economics returns.

The ICAR (2006), based on large number of trials, concluded that for kharif sorghum, optimum recommended dose is 40 kg N ha^-1 in addition to the application of farm yard manure at regular intervals. For irrigated or rainfed sorghum with assured rainfall, nitrogen application should be 80-100 kg ha^-1 depending on native soil fertility.

As already indicated, optimum rate of nitrogen for improved kharif sorghums ranges from a minimum of 40 to 100 kg ha^-1, depending on rainfall distribution and initial soil fertility. Minimum recommended dose of 40 kg N ha^-1 should be applied at sowing. However, if adequate rainfall in received when the crop is around knee-height stage, another 40 kg N ha^-1 by drilling between rows of the crop considerably improve the yield leading to economic returns.

For sorghum on stored soil moisture, 80 kg N ha^-1 appears to be profitable if the soil profile is fully saturated with water up to 2.0 m depth. If the soil is not fully saturated, 40 kg N ha^-1 appear to be an economic optimum dose. Recommended fertiliser schedule for improved rainfed sorghums in Andhra Pradesh is 60 N (in two equal splits), 40 P₂O₅ and 30 K₂O kg ha^-1 in addition to FYM at 10 t ha^-1.

Time and Method of Application:

Results of field experiments under AICSIP indicated that at most of the locations there was no significant difference due to single and split application at any of the nine locations at 80 kg N ha^-1. Also, there was no difference at any location between foliar applications at knee-height stage compared to soil application at the same stage.

Results suggested a trend in favour of single application. Placement of nitrogen improves the fertiliser use efficiency. Drilling the fertiliser before sowing the seed appears to be the best method if ferti-seed drills are not used for placement of the fertiliser.

2. Phosphorus:

Response of kharif sorghum to phosphorus was studied at 12 locations in AICSIP. Significant response was obtained in two out of seven locations on research stations and four out of five locations in cultivator’s fields. At locations where significant response was obtained, the economic optimum levels were around 50 kg P₂O₅ ha^-1.

In most locations, the magnitude of response was in the range of 7-9 kg grain kg^-1 of P₂O₅ applied. Based on several other trials (ICAR 2006), a dose of 40 kg P₂O₅ ha^-1 is recommended to kharif sorghums. Entire recommended rate should be applied by placement at sowing.

3. Potassium:

Potassium fertiliser experiments were conducted at the same 12 locations as phosphorus experiments. In 6 locations, there was no significant response or trends in favor of potassium application. In the other 6 locations, there was significant response in only two locations (Pantnagar and Hyderabad). Even at these locations, the magnitude of yield response was low, around 500 kg ha^-1. However, soil test based potassium application may result in economic response to added potassium fertilisers.

4. Micronutrients:

Iron and zinc are the commonly deficient micronutrients in sorghum. Iron deficiency is commonly found in calcareous soils. There was no beneficial response to iron application at any of the nine locations. At Nandyal (AP), sorghum yield on receding soil moisture increased from 1660 to 2150 kg ha^-1 due to 0.2 per cent zinc sulphate foliar application.

Recent studies, however, indicated increasing response of improved sorghums to zinc application, especially under intensive cropping systems. Application of 25-50 kg ha^-1 of zinc sulphate to any one of the crops in the system can take care of the needs of sorghum crop. If not, deficiency of zinc in the standing crop can be corrected by 2.0 per cent foliar application of zinc sulphate.