Plant residue fertilizers

Nitrate is one of the facts of life. It is essential for the growth of many plant species, including most of those we eat, but it becomes a problem if it gets into water in which it is not wanted. It is perceived mainly as a chemical fertilizer used by farmers, but much of the nitrate found in soil is produced by the microbes that break down plant residues and other nitrogen-containing residues in the soil. There is no difference between nitrate from fertilizer and that produced by microbes, but, whatever its origin, this rather commonplace chemical entity has now become a major environmental problem and is also treated as a health hazard. 

High biological activity within the soil promotes metabolism between soil and plants and is an essential part of sustainable plant production and fertiliser management. The role of soil organisms is central to soil processes and fertility since they render available the elements in plant residues and organic debris entering the soil (Alfoldi ef al. 2002). 

Breland T. A. and Hansen S. (1998) Comparison of the difference method and 15N technique for studying the fate of nitrogen from plant residues in soil. Biol. Fertility Soils 26(3), 164-168. 

After balancing all of the nutrient element amounts, it is necessary to choose suitable fertilizers. In every case the contents of all applied organic fertilizers and incorporated plant residues are to be taken into account, after which the gaps in the balance may be closed by use of manufactured fertilizers. 

Radiolabelled phosphorus studies provide information about subsequent remineralization and the crop availability of phosphorus added in organic material. Under field conditions, between 22% and 28% of the P applied in plant residues was recovered in the microbial biomass, compared with <5% of P in banded P-labelled fertilizer (McLaughlin et al., 1988). The amount of microbial phosphorus and the proportion of microbial phosphorus derived from plant residues remained constant between 7 and 95 days after residue incorporation. The microbial biomass therefore appeared to compete successfully for phosphorus from plant residues, leading to only 5% recovery of P in plants, compared with 12% from banded fertilizer. Phosphorus applied with plant residues may continue to be re-mineralized after longer periods. 

McLaughlin, M.J. and Alston, A.M. (1986) The relative contribution of plant residues and fertilizer to the P nutrition of wheat in a pasture/cereal system. Australian Journal of Soil Research 24, 517-526. 

A fertilizer is a material that furnishes one or more of the chemical elements necessary for the proper development and growth of plants. The most important fertilizers are fertilizer products (also called chemical or mineral fertilizers), manures, and plant residues. A fertilizer product is a material produced by industrial processes with the specific purpose of being used as a fertilizer. Fertilizers are essential in today s agricultural system to replace the elements extracted from the soil in the form of food and other agricultural products. 

In fortunate contrast to N, the formation of P com-pounds-oUirnitecLsolubilities in.soils allowre P fertility to increase through P additions, and P ap[ ied in one year can furnish P to succeeding crops. This is called a residual fertilizer effect. The P not used by the crop remains mainly in the nonlabile or plant-unavailable pool, but it still contributes to the P nutrition of crops for many years. From solely an agronomic perspective, it is most beneficial to build P fertility rapidly by fairly large additions, then apply only the amounts needed to mainteun the P status, which can be dme every other year or every third year. 

Inkas from the Amazon area disposed animal and human excrements, charcoal and plant residues from cooking, and potsherds besides their villages. Today, 2000years later, these places transformed into very fertile soils—Terra Preta. ... 

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