of composts thus requires applying the composts at proper rates and frequency, as
well as balancing the rest of nutrients with inorganic fertilizers. Proper application of
rates is crucial in reducing adverse effects such as build-up of toxic elements. The
optimal amount of organic fertilizer to be applied in a field is dependent on the
composition, available soil nutrients, the crop to be produced and environmental
conditions. Efficient, economic, and environmentally sustainable organic fertilizer
application should aim to achieve a balance between nutrient application and crop
nutrient demand. The first step in determining application rates for the organic
fertilizers is establishing target yields.
Organic fertilizer application software packages have been developed by commercial testing laboratories for calculating application rates. The computer-based
software simplifies application rate calculations, allows record keeping and provides
applicator calibration information. They also allow users to keep records for each
field on nutrient application rates, soil test values, crop yield and nutrient removal.
Such records are useful for longer term nutrient budgeting. The use of global
positioning systems, site-specific soil and yield capability information within a
field can further enhance the ability to match nutrient applications to crop. Lastly,
proper calibration of a spreader will help insure correct rate and uniform application.
All organic fertilizers continue to decompose during storage. This results in
nutrient transformations and losses, especially N. Aeration, higher temperatures
and higher N concentration increase the risk for N loss before collection and during
storage. Turning has a similar stimulating effect on decomposition. Nutrient and
carbon losses during storage tend to be lower for more compact and anaerobic
storage systems and for organic fertilizers with higher C/N ratios. There will be
higher nutrient losses if the organic fertilizer is not handled properly in transition
from production to field.
18.5.2 Application Methods for Organic Fertilizers
Organic fertilizers should be placed in soil, rather than surface-applied, to increase
crop root access to nutrients and to reduce potential losses by runoff and volatilization. Under dry conditions, surface-applied organic fertilizer nutrients may be
isolated from crop roots by remaining in the dry surface layer. With heavy rain
and high runoff, surface-applied organic fertilizers are subject to loss by runoff and
erosion. Surface applications of organic fertilizers are accompanied by inevitable
losses of N in the form of ammonia gas. Applying organic fertilizers close to the time
the crop will need the nutrients will help to reduce losses. Timing and method of
organic fertilizer application determines the efficiency of nutrient recycling. It must
be spread uniformly to achieve consistent results. Applying and incorporating
compost too early for the crop, as in the autumn on saturated soils in high rainfall
areas, could result in significant N leaching and groundwater contamination.
When using organic fertilizers, knowledge of the mineralization rate under field
conditions is needed. Since mineralization is microbe driven, it is influenced by
18 Some Perspectives on Vermicompost Utilization in Organic Agriculture
313
well as balancing the rest of nutrients with inorganic fertilizers. Proper application of
rates is crucial in reducing adverse effects such as build-up of toxic elements. The
optimal amount of organic fertilizer to be applied in a field is dependent on the
composition, available soil nutrients, the crop to be produced and environmental
conditions. Efficient, economic, and environmentally sustainable organic fertilizer
application should aim to achieve a balance between nutrient application and crop
nutrient demand. The first step in determining application rates for the organic
fertilizers is establishing target yields.
Organic fertilizer application software packages have been developed by commercial testing laboratories for calculating application rates. The computer-based
software simplifies application rate calculations, allows record keeping and provides
applicator calibration information. They also allow users to keep records for each
field on nutrient application rates, soil test values, crop yield and nutrient removal.
Such records are useful for longer term nutrient budgeting. The use of global
positioning systems, site-specific soil and yield capability information within a
field can further enhance the ability to match nutrient applications to crop. Lastly,
proper calibration of a spreader will help insure correct rate and uniform application.
All organic fertilizers continue to decompose during storage. This results in
nutrient transformations and losses, especially N. Aeration, higher temperatures
and higher N concentration increase the risk for N loss before collection and during
storage. Turning has a similar stimulating effect on decomposition. Nutrient and
carbon losses during storage tend to be lower for more compact and anaerobic
storage systems and for organic fertilizers with higher C/N ratios. There will be
higher nutrient losses if the organic fertilizer is not handled properly in transition
from production to field.
18.5.2 Application Methods for Organic Fertilizers
Organic fertilizers should be placed in soil, rather than surface-applied, to increase
crop root access to nutrients and to reduce potential losses by runoff and volatilization. Under dry conditions, surface-applied organic fertilizer nutrients may be
isolated from crop roots by remaining in the dry surface layer. With heavy rain
and high runoff, surface-applied organic fertilizers are subject to loss by runoff and
erosion. Surface applications of organic fertilizers are accompanied by inevitable
losses of N in the form of ammonia gas. Applying organic fertilizers close to the time
the crop will need the nutrients will help to reduce losses. Timing and method of
organic fertilizer application determines the efficiency of nutrient recycling. It must
be spread uniformly to achieve consistent results. Applying and incorporating
compost too early for the crop, as in the autumn on saturated soils in high rainfall
areas, could result in significant N leaching and groundwater contamination.
When using organic fertilizers, knowledge of the mineralization rate under field
conditions is needed. Since mineralization is microbe driven, it is influenced by
18 Some Perspectives on Vermicompost Utilization in Organic Agriculture
313