The deterioration is not due to the material itself but is due to improper use of chemical fertilizers. The harmful consequences of applying fertilizers can be eliminated or minimized if only we follow this cardinal rule: application has to be based mainly on the need of the crop and on the capacity of the soils to store and provide the essential nutrients.
Despite its benefits, organic fertilizers have inherent characteristics that show that it may not be the best option for rice farming.
The Truth About Organic Fertilizers
Despite its benefits, organic fertilizers have inherent characteristics that show that it may not be the best option for rice farming. These characteristics are cited below:
Organic materials after undergoing decomposition especially when applied in large quantities could cause groundwater pollution.
High nitrate levels in groundwater from organic matter have been reported in the US, the Netherlands, and other developed countries where animal populations are large and concentrated in limited areas. Unless in a stable state or humified (resulting from the decomposition), organic fertilizers applied under conditions in which oxygen is at a minimum level (like in flooded rice soils) may produce toxins harmful to the plant.
Plants do not directly use the nutrients found in organic material.
The organic compounds that contain the essential nutrients needed by plants have to be subjected to a process called “mineralization” to be absorbed. For example, plants cannot absorb organic N. The organic N has to
be transformed into its ammonium nitrate forms (NH4-N or NO3-N) before it can be absorbed by plants. In a case such as this, the remedy is to apply the micronutrients in organic materials (in inorganic form) through common chemical fertilizers. To do this, one needs to identify which essential nutrients are limiting so that they can be applied with the common inorganic fertilizers.
The amounts of essential plant nutrients in organic materials including commercial organic fertilizers are very low.
To supply the amount of nutrients required for high yields, a tremendous volume of organic material is required. To illustrate, there is hardly any organic material that will contain more than three percent nitrogen. Consequently, when one encounters commercial organic fertilizer containing nitrogen higher than three percent, it is likely that such material has been fortified with inorganic fertilizer N.
Organic materials are claimed to be important in improving the physical properties of soils such as water- holding capacity, aggregated soil structure, and nutrient-holding capacity. But this could only be true under aerobic soil conditions where upland or dryland crops are grown.
In humid tropical conditions like in the Philippines, it would take continuous and high rates of organic material application before the benefits may be realized. This is because under humid tropical condition organic matter decomposition is relatively rapid thus organic accumulation in soils is minimal.
Soil organic matter will not increase significantly (by as much as one percent or higher) in just one or two years of applying organic materials.