Organic fertilizers are good because they improve soil fertility by retaining it in its natural form and crop yields. They are also cost effective.
According to Sambi Reddy, the senior marketing manager of JN Agritech International, a company that distributes organic fertilizers; a kilogram of packed organic fertilizers is sold between Frw.1500 and Frw2,000—depending on the quantity and content while inorganic fertilizers cost twice as much ranging from Frw3,500 a kilogram to Frw5,000.
Organic fertilizers are relatively cheaper because they are not bulky hence are easy to transport.
It is a biological fact that plants require 1 kilogram of nitrogen to produce 10 to 15 kg of grain. Our atmosphere is about 80% nitrogen.
Most tropical soils “fix,” or draw from the atmosphere, enough nitrogen to produce about 1 tonne of grain per hectare.
To produce more grain, the plants must have more nitrogen, whether as organic or mineral fertilizer. Plants must also have phosphorus, potassium, and “trace” minerals.
If the soil lacks or has insufficient amounts of these minerals, they must be added as fertilizers, or production will stagnate.
As plants grow, they absorb and deplete or “mine” nutrients from the soil. Farmers harvest those same nutrients when they harvest crops.
According to agricultural experts, African soils are losing an estimated $4 billion worth of soil nutrients yearly. Three-fourth of the farmland in sub-Saharan Africa is plagued by severe nutrient depletion and 46 percent of the African continent suffers from desertification.
This means African farmers desperately need to use fertilizers to bring life back to the depleted soils, and to feed the continent.
Fertilizers, whether mineral or organic, nourish the soil by returning essential mineral nutrients. But the use of chemical fertilizers has raised mixed feelings among environmentalists and consumers.
“Excessive and continuous use of chemical and inorganic fertilizers has a harmful effect on soil health. It produces an imbalance in plant nutrients of the soil, which affects the acidity or alkalinity of soils and reduces its fertility gradually,” says Reddy.
Inorganic or chemical fertilizers include sodium nitrate, mined rock phosphate and limestone while organic fertilizers include manure, slurry, worm castings, bone meal, compost and seaweed extracts.
Application of organic fertilizers depends on the type of crop because different dosages in turn depend on the climatic conditions and soil type.
Organic products also require the activity of soil microorganisms before nutrients are available for plant uptake. Microorganism activity is dependant on soil temperatures greater than 500 F in the presence of sufficient soil moisture.
“Some organic fertilizers are high in one of the three major nutrients (nitrogen, phosphorus, or potash,) but low or zero in the other two. Some are low in all three macronutrients.
The ingredients used to fortify organic fertilizers are organic materials, for example, rock phosphate to increase phosphorus, or greensand to increase potash,” Reddy explains.
Organic fertilizers depend on soil organisms to break them down to release nutrients, therefore, most are effective only when soil is moist and warm enough for the microorganisms to be active.
Compared to synthetic fertilizer formulations, organic fertilizers contain relatively low concentrations of actual nutrients, but they perform important functions which the synthetic formulations do not.
They increase the organic content and consequently the water-holding capacity of the soil. They improve the physical structure of the soil which allows more air to get to plant roots.
Where organic sources are used for fertilizer, bacterial and fungal activity increases in the soil.
“The use of organic fertilizers as means of improvement of the fertility and productivity of land for farming is feasible and desirable. Whether we like it or not we are getting into a situation in agriculture where we shall intensify the use of agro chemicals to solve the problem of food insecurity but our farmers are poor and can not afford inorganic fertilizers. Organic fertilizers provide short and long term means of maintaining the land fertile,” says Dr.Festus Bagoora, a specialist for soils and land use, at National Environment Management Authority (NEMA, Uganda).
Organically derived plant nutrients are slow to leach from the soil making them less likely to contribute to water pollution than synthetic fertilizers.
Apart from improving the soil structure, organic fertilizers reduce the problem of over fertilization that is associated with use of artificial fertilizers. The high solubility of chemical fertilizers also exacerbates their tendency to degrade ecosystems.
In the recent past organic products have become highly rated on the global market and fetch high prices. These include fruits like pineapples, passion fruits, avocado, and vegetables like carrots and cabbages, animal and poultry products.
“Organic products fetch high prices in international markets and this should encourage the farmers to intensify generation, utilization and application of organic fertilizers.
The world has increasingly realized that excessive use of chemicals may lead to poor health of the people that eat the food” says Bagoora.
The more chemicals you use on crops the more chemicals go into the crops and the more chemicals people who consume the crops will take in.
The affluent society in the developed world has started moving away from heavily dozed products in the developed nations to products from developing nations.