Plant Demand Adapted Fertilization in Organic and Precision …
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organic certification of which half was cultivated and half was wild harvest collection. Conventional agriculture relies on readily soluble forms of nutrients for nutrient
supply while organic systems use a long-term strategy relying upon crop rotations,
nitrogen fixing cover crops, and manures, compost and biofertilizers to derive nutrients through biological cycles to optimize crop production. The present review aims
to present the most important lessons learnt in precision chemical fertilization and
organic fertilization with a focus on developing countries and also discusses environmental influences including effects on soil health in the context of the current
concerns.
2 Organic Farming Approaches
In organic systems, farmers manage the whole farm like a living organism with a
balanced growth of crops and livestock holding to ensure that nutrient cycles are
closed as far as possible. Only the nutrients in the form of food are exported out of
the farm. Plant nutrition depends on “biologically derived” nutrients from organic
materials; the challenge is to economically meet crop nutrient needs and address
soil nutrient depletion. The benefits include lesser leaching losses of nitrogen due to
extended mineralization period of organic matter and soil structure improvement and
replenishment of the nutrient-holding capacity of the soil by building up microbial
biomass.
2.1 Strategies to Meet Nutrient Demand
Manures contain nitrogen both in organic and ammonium forms; N mineralization
from manures with a C:N ratio < 20:1 occurs readily; but only 15% of the organic
N in the compost may be available during that season if ratio is high. Application
of compost with C:N ratio > 30:1 will result in net immobilization of soil nitrogen
with reduced nitrogen availability to the first crop. Some estimates of organic N
availability for some of the manures through years 2 through year 4 are 15, 7 and 4%
per year ([104]; Table 1). Succulent plant residues are mineralized faster than more
lignified ones, so the type and timing of incorporation must be tailored to needs of
the crop in question to create synchrony with crop demand. Incorporation of nutrient
poor wide C:N ratio plant material such as cereal straw can serve to prevent leaching
by immobilizing the nitrate N, thus ensuring also a build-up of microbial biomass
which will be re-mineralized later to meet crop demand.
Cover crops improve soil physical properties and soil biological activity. They
improve nutrient cycling by scavenging residual nitrogen mineralized from soil
and organic amendments (before it is lost to volatilization, runoff, or leaching) and
139
organic certification of which half was cultivated and half was wild harvest collection. Conventional agriculture relies on readily soluble forms of nutrients for nutrient
supply while organic systems use a long-term strategy relying upon crop rotations,
nitrogen fixing cover crops, and manures, compost and biofertilizers to derive nutrients through biological cycles to optimize crop production. The present review aims
to present the most important lessons learnt in precision chemical fertilization and
organic fertilization with a focus on developing countries and also discusses environmental influences including effects on soil health in the context of the current
concerns.
2 Organic Farming Approaches
In organic systems, farmers manage the whole farm like a living organism with a
balanced growth of crops and livestock holding to ensure that nutrient cycles are
closed as far as possible. Only the nutrients in the form of food are exported out of
the farm. Plant nutrition depends on “biologically derived” nutrients from organic
materials; the challenge is to economically meet crop nutrient needs and address
soil nutrient depletion. The benefits include lesser leaching losses of nitrogen due to
extended mineralization period of organic matter and soil structure improvement and
replenishment of the nutrient-holding capacity of the soil by building up microbial
biomass.
2.1 Strategies to Meet Nutrient Demand
Manures contain nitrogen both in organic and ammonium forms; N mineralization
from manures with a C:N ratio < 20:1 occurs readily; but only 15% of the organic
N in the compost may be available during that season if ratio is high. Application
of compost with C:N ratio > 30:1 will result in net immobilization of soil nitrogen
with reduced nitrogen availability to the first crop. Some estimates of organic N
availability for some of the manures through years 2 through year 4 are 15, 7 and 4%
per year ([104]; Table 1). Succulent plant residues are mineralized faster than more
lignified ones, so the type and timing of incorporation must be tailored to needs of
the crop in question to create synchrony with crop demand. Incorporation of nutrient
poor wide C:N ratio plant material such as cereal straw can serve to prevent leaching
by immobilizing the nitrate N, thus ensuring also a build-up of microbial biomass
which will be re-mineralized later to meet crop demand.
Cover crops improve soil physical properties and soil biological activity. They
improve nutrient cycling by scavenging residual nitrogen mineralized from soil
and organic amendments (before it is lost to volatilization, runoff, or leaching) and