The following points highlight the five nutrients required for pearlmillet production and which were considered as the major plant nutrients for enhancing the crop productivity: 1. Organic Manuring 2. Nitrogen 3. Biofertilisers 4. Phosphorus and Potassium 5. Micronutrients.
1. Organic Manuring:
Generally, pearlmillet is grown without application of manures, except on rotational basis once in 3 – 4 years. However, the available information shows that the crop responds to FYM, compost and oil cakes. In southern parts of the country, around 10 t ha-1 of FYM, compost, sheep or goat penning is usual practice for rainfed pearlmillet, especially when the crop is grown to meet the domestic needs of fanners.
Response of pearlmillet to application of bulky organic manure is linear in almost all the pearlmillet growing areas since the amount added is very small. Bulky organic manures supply not only macronutrients but also micronutrients.
Besides nutrients supply, bulky organic manure are very effective in improving the moisture holding capacity of soil. Experimental evidence indicate the necessarily for 10-15 t ha-1 of bulky organic manures for improving the yield of pearlmillet besides improving the soil productivity.
2. Nitrogen:
As most of the soils are deficient in nitrogen, its addition through fertilisers is essential for realising potential yield of pearlmillet. Lot of work has been done on nitrogen needs of pearlmillet at different locations.
Its response to applied nitrogen largely depends on initial soil fertility and rainfall/ irrigation during the crop season. From the results of experiments, it is evident that the hybrids require 40 to 150 kg N ha-1 for optimum grain yield depending on soil moisture availability.
In general, the following recommendations holds good for all the pearlmillet growing regions for economic pearlmillet production:
Low rainfall (<750 mm): 40 kg N ha-1
Limited to adequate rainfall (750-1150 mm): 80 kg N ha-1
Adequate rainfall (>1150 mm): 100 kgN ha-1
Summer irrigated crop: 120 kg N ha-1.
Recommended fertiliser schedule for pearlmillet in different states of the country is given in Table 6.2.
Split application of nitrogen is better than one time application at sowing. For a rainfed crop, recommended dose may be applied in two equal splits at seeding and around 45 days after seeding (DAS). If there is no rain around 45 days after seeding, the second split (20 kg N ha-1) need not be application in regions of low rainfall.
In regions of adequate rainfall, half of the recommended done may be applied as basal dose by placement at seeding and the second half around 45 days after sowing, however, depending on the receipt of rain.
For an irrigated crop on light soils, the recommended rate may be applied in three equal splits at planting, three weeks after planting and six weeks after planting. For medium to deep soils, recommended nitrogen fertiliser may be applied in two equal splits at planting and 6 weeks after planting.
3. Biofertilisers:
Azotobacter and Azospirillum have been reported to play beneficial role in improving the pearlmillet productively through nitrogen fixation. Seed inoculation with Azotobacter significantly increased the grain yield of pearlmillet by 10 to 12 per cent. Reviewing the work done on Azospirillum, Gautam (1984) reported that the amount of nitrogen fixed by Azospirillum was equivalent to 20 kg N ha-1.
In spite of several reports on the efficiency of microbes in improving the grain yield of pearlmillet, their use under field conditions is not as expected because of undependable soil moisture regime during the crop season. Prolonged soil moisture stress is not conducive for the multiplication of microbes fixing the atmospheric nitrogen for crop use.
4. Phosphorus and Potassium:
Response of rainfed pearlmillet to phosphorus and potassium is inconsistent over years and locations, largely due to difference in rainfall and initial fertility status of soils. In general, application of phosphorus and potassium is uneconomical in regions of low rainfall (arid zones). In semiarid regions, pearlmillet responds to low levels of phosphorus when applied with recommended rates of nitrogen.
When the soils are deficient in phosphorus, its application at 40 kg P2O5 ha-1 along with 80 kg N ha-1 appears to be economical. Potassium at 20 kg K2O ha-1 along with 30 kg P2O5 and 80 kg N ha-1 appears to the economical in regions of adequate rainfall. Summer irrigated pearlmillet with grain yield target around 3-4 t ha-1 needs 120 N, 60 P2O5 and 40 K2O kg ha-1 Fertiliser schedule recommended for improved rainfed pearlmillet cultivars in Andhra Pradesh is 60 N (two splits- basal and 30 DAS), 30 P2O5 and 20 K2O kg-1 in addition to 10 t ha-1 of FYM.
5. Micronutrients:
Response of pearlmillet to micronutrients has been studied under laboratory and field conditions. The results indicate increase in grain yield with micronutrient application when rainfall is adequate and well distributed during the season. Therefore, micronutrients use in pearlmillet still remains as recommendations only.
Irrigated pearlmillet responds to zinc application up to 25 kg Zn SO4 ha-1. Since, the crop is grown in intensive cropping systems involving rice or wheat, the residual zinc after these crops can meet the needs of pearlmillet. If deficiency symptoms are observed in standing crop, it can be corrected by foliar application of 0.5 per cent zinc sulphate with 0.25 per cent lime solution.
Sekhawat et al (1972) reported that application of micronutrients increased grain yield of pearlmillet over NPK and control. The percentage increase due to application of Mn, Zn, B, Mo, Fe and all combined was 5.47.16.48, 4.55, 7.70 and 19.35 over NPK alone, respectively. Similar increase in grain yield due to micronutrient application has been reported from different pearlmillet growing regions both under rainfed and irrigated conditions.