Introduction to major field crops (1+1)

Nutrient Management

Responses to fertilizer application are higher in dry season as compared to wet season. This is mainly due to higher solar radiation and lack of rains and better possibility of irrigation water management.

Incorporation of well decomposed farm yard manure @ 10 t/ha or green manure @ 5 t/ha 2-3 weeks in advance is essential. Nitrogen @ 60-100 kg/ha, phosphorus and potassium 50 kg/ha may be considered desirable for wet season; for the dry season, a rate of 80-120 kg N/ha, 60 kg P2O5 and K2O/ha may be considered.







Fig: Green manure crop. Fig: Well decomposed F.Y.M. Fig: Vermicompost.

Regarding the form of nitrogenous fertilizers, ammonical forms are better than nitrates. However, urea, which is the cheapest fertilizer, is widely used in the country. Nitrogen recovery in low land rice is less (30-40%). Nitrogen use efficiency can be increased by effective water control, use of slow releasing nitrogen fertilizers,split application and method of application.

A better return can be obtained from a given amount of nitrogen when it is applied in splits and the application is suitably synchronized with active growth of the crop. Application of nitrogen in three splits viz., 50 per cent at planting, 25 per cent each at active tillering and at panicle initiation stages have been found to be appropriate for increasing nitrogen use efficiency and yield of rice. The entire dose ofphosphorus and potassiumpreferably applied as basal dose at the time of planting.

Nitrogen has to be applied to reduced zone and incorporated at the time of puddling or manually placed to avoid conversion of ammonia to nitrate and subsequent loss by leaching.
Use of biofertilizers like Azolla, blue green alga, Azatobacter, Azospirillum saves about one-third of the recommended N fertilizer without sacrificing the yield.

Fig: Azolla.

Among micronutrients, zinc has been found to be a limiting nutrient in realizing normal yield of rice. The practice of applying zinc sulphate @ 25 kg/ha or foliar spay of zinc sulphate @ 0.5 per cent and 0.25 per cent of lime in zinc deficient soils has been found profitable and bringing synergistic effect with nitrogen and phosphorus. Deficiency of zinc leads to khaira disease.