INTEGRATED NUTRIENT MANAGEMENT
• The gap between fertilizer application to nutrient removal is estimated to be 8-10 million tonnes of N + P2O5 + K2O each year in the country.
• Legumes can fix 50-500 kg N/ha depending upon the crop and its growth period.
• Green manuring along with recommended level of fertilizers increases the total productivity of the system to the tune of 10-20%.
• French bean has poor root nodulation, particularly when it is grown in Indo-gangetic plains.
• Loppings of perennial multi-purpose woody legumes, such as Gliricidia sepium, Cassia siamea and Leucaena leucocephala (Subabool) can be used for green leaf manuring.
• Green manures can add 60-120 kg N/ha and in many situations can meet the entire N demand of a crop to which they are supplied.
• Biogas slurry is the residue left in biogas units after the fermentation and liberation of biogas.
• Pressmud cake is a waste product of sugar industry.
• About 52.8 million tonnes rice residue is produced from about 10 million ha under rice-wheat cropping system belt.
WATER AND NUTRIENT INTERACTIONS
• Nutrient availability is at a minimum as the soil water content approaches the permanent wilting point.
• Mobile nutrients like calcium, magnesium, nitrate-N and sulphate are transported to the root by mass flow.
• Excessive water use reduces N recovery by the means of nitrate – N leaching.
• Organic N – mineralization is proportionately related to increase in soil water content.
• Fe and Zn deficiencies are frequently associated with high soil moisture availability.
• Application of water and nutrients together is known as fertigation.
• Solubility of urea fertilizer is 1100 g/litre at 20oC
• The lower the soil-moisture content, the greater the response to P.
• Phosphatic and calcium water-soluble fertilizers are compatible for mixing the solutions.
• Cultivation of undulating soil is possible with fertigation.
• Deeper placement of fertilizer in water limiting areas gives better response than surface application.
• For maximum use efficiency on sandy-loam soil, urea-N top dressing should be made 2-3 days after irrigation.
• Plant requirements for P and K are mostly met by the process of diffusion.
• Application of K reduces water loss in plants through stomatal movement and osmoregulation.
• Fertigation improves water-use efficiency and Nutrient-use efficiency.
• Maximum water and nitrogen use efficiency in rice can be achieved by irrigation after 2-3 days of disappearance of standing water.