“Dry land soils are not only thirsty, but also hungry.” Uncertainty of return from the investment on fertilizer use and the poor resource base are the reasons for not using fertilizer by the dry land farmers. The fertilizer use in dry land crops might vary between 5 and 40 kg/ha (N+P2O5+K2O). Soils are low in N and P, and Zn is the most limiting factor among micronutrient. The response for Ca, Mg and S has also been recorded. The reasons for poor soil fertility are slow weathering of minerals, low organic matter content, reduced microbial activity, erosion, very low addition of manures and fertilizers, soil salinity and alkalinity, and reduced mobility of nutrients and nutrient fixation. The following Tables 81 and 82 gives the quantity of nutrient removed by dry land crops and nutrient requirement by dry land crops.
The beneficial effects of nutrient supply in dry lands are given below:
• Deficiency in soil supply of nutrients required by crops is corrected.
• Nutrient supply promotes root development, which enables higher uptake of soil moisture and high water use efficiency. This positive relationship between nutrients and moisture is mutual.
• Increased vigour of a fertilized crop enables it to survive drought better than an unfertilized crop.
Farmers in dry lands however do not apply sufficient quantity of nutrients since nutrient sources like manures and fertilizers are costly and risks to dependable crop production. The average consumption of inorganic fertilizers is less than 10 kg per ha in dry lands. Even this is confined to a few commercial crops like cotton, groundnut and chillies only. The reasons attributed by farmers for poor adoption of nutrient supply to rainfed crops include:
• High cost, inadequate availability of fertilizers and inadequate availability plus high cost of transport of organic manures, fear of scorching due to inorganic fertilizer addition.
• Low and uncertain yield, and income due to undependable rainfall behaviour.
• Apprehension that a well fertilized crop growing vigorously would exhaust soil moisture supply early and subject to moisture stress at later stages.
• Adoption of fertilizer non responsive varieties in large.
Due to the above reasons, nutrient supply in dry lands is at a slow pace. In order to ensure adequate nutrient supply, care must be taken to understand the factors that influence nutrient use efficiency in dry crops and to evolve an integrated nutrient management system that will be efficient, economical and environmentally sustainable.
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