142
D. L. N. Rao et al.
of Sesbania cannabina was 21.5 and 9.4 Mg ha
−1 ; Biofertilizer value in leaf and
upper tender stems was 125, 5, 81 and 12 kg ha
−1 of N, P, K and S ha
−1 respectively
[75]. Crops like Pigeonpea (Cajanus cajan) produce significant amounts of litter;
Rao and Gill [74] recorded 1.9 Mg ha
−1 of litter fall in a season that contains 39.5,
2.1, 7.3 and 2.1 kg of N, P, K and S ha
−1 respectively, that improves yields of wheat
grown in rotation. The rotational benefit of legumes and N credit for succeeding
cereal crops are widely known. Long term experiments over 8 years in a Vertisol
showed a fertilizer nitrogen credit of soybean of 30 kg ha
−1 in wheat [76].
Natural minerals or materials rated very slow (rock phosphate, granite meal, sand)
to medium (kaolinite) in nutrient availability may be used to maintain a given level
and nutrient balance in the soil. Where a rapid change in nutrient levels or balance is
necessary, materials having medium to rapid nutrient availability such as gypsum and
pyrites should be used. It is beneficial to add raw rock phosphate to manures when
making composts rather than as a soil application. Microbial activity and localized
acidity in manures and composts can increase the availability of the phosphate from
rock phosphate. Generally, farmyard manure produced by farmers in India contains
very low P and S. And P deficiency is very common in majority of the Indian soils
and most of the soils of oilseed growing areas are also deficient in S. Therefore, the
deficiency of P and S are expected in organic farms and rock phosphate is a good
source of P for such soils. Naturally occurring gypsum is a good source of S in
organic farming.
2.2 Nutrient Budgets and Management
2.2.1 Nutrient Budgeting
Nutrient budgeting is a useful balancing approach that helps to ensure that organic
farmers do not unsustainably mine inherent soil nutrient reserves and at the same time
do not also build them up to levels that pose risk of environmental contamination.
Critical levels for soil nutrient availability can be used to make annual decisions
about nutrient source and application rates; however, developing a long-term nutrient
management plan and proactive management of soil fertility is advised for organic
farms. Soil sampling every four years is advised to test for soil organic matter, pH, and
availabilities of P, K and Zn as well as other properties of interest. Plant tissue analysis
for every three to five years to diagnose potential nutrient deficiencies of perennial
crops, such as fruit tree crops, is advised. A long-term accounting of phosphorus
addition via manure (or other fertilizer source) and removal via harvested crops in
Vertisols of Central India is shown in Table 3 [77].
Nutrient management plan describes the amount, source, placement, form and
timing of the application of nutrients and soil amendments, to meet crop nutrient
demand while protecting water quality and improving soil health. This takes into
account the crop’s nutrient needs as well as all credits in the system such as N
contribution of cover crops, the mineralization of N from previous additions of
D. L. N. Rao et al.
of Sesbania cannabina was 21.5 and 9.4 Mg ha
−1 ; Biofertilizer value in leaf and
upper tender stems was 125, 5, 81 and 12 kg ha
−1 of N, P, K and S ha
−1 respectively
[75]. Crops like Pigeonpea (Cajanus cajan) produce significant amounts of litter;
Rao and Gill [74] recorded 1.9 Mg ha
−1 of litter fall in a season that contains 39.5,
2.1, 7.3 and 2.1 kg of N, P, K and S ha
−1 respectively, that improves yields of wheat
grown in rotation. The rotational benefit of legumes and N credit for succeeding
cereal crops are widely known. Long term experiments over 8 years in a Vertisol
showed a fertilizer nitrogen credit of soybean of 30 kg ha
−1 in wheat [76].
Natural minerals or materials rated very slow (rock phosphate, granite meal, sand)
to medium (kaolinite) in nutrient availability may be used to maintain a given level
and nutrient balance in the soil. Where a rapid change in nutrient levels or balance is
necessary, materials having medium to rapid nutrient availability such as gypsum and
pyrites should be used. It is beneficial to add raw rock phosphate to manures when
making composts rather than as a soil application. Microbial activity and localized
acidity in manures and composts can increase the availability of the phosphate from
rock phosphate. Generally, farmyard manure produced by farmers in India contains
very low P and S. And P deficiency is very common in majority of the Indian soils
and most of the soils of oilseed growing areas are also deficient in S. Therefore, the
deficiency of P and S are expected in organic farms and rock phosphate is a good
source of P for such soils. Naturally occurring gypsum is a good source of S in
organic farming.
2.2 Nutrient Budgets and Management
2.2.1 Nutrient Budgeting
Nutrient budgeting is a useful balancing approach that helps to ensure that organic
farmers do not unsustainably mine inherent soil nutrient reserves and at the same time
do not also build them up to levels that pose risk of environmental contamination.
Critical levels for soil nutrient availability can be used to make annual decisions
about nutrient source and application rates; however, developing a long-term nutrient
management plan and proactive management of soil fertility is advised for organic
farms. Soil sampling every four years is advised to test for soil organic matter, pH, and
availabilities of P, K and Zn as well as other properties of interest. Plant tissue analysis
for every three to five years to diagnose potential nutrient deficiencies of perennial
crops, such as fruit tree crops, is advised. A long-term accounting of phosphorus
addition via manure (or other fertilizer source) and removal via harvested crops in
Vertisols of Central India is shown in Table 3 [77].
Nutrient management plan describes the amount, source, placement, form and
timing of the application of nutrients and soil amendments, to meet crop nutrient
demand while protecting water quality and improving soil health. This takes into
account the crop’s nutrient needs as well as all credits in the system such as N
contribution of cover crops, the mineralization of N from previous additions of