Open Academy for Philippine Agriculture - Use organic fertilizer to save on fertilizer costs

Use organic fertilizer to save on fertilizer costs

Written by Written by the Web Team
Wednesday, 06 August 2008
With the prices of inorganic fertilizers skyrocketing, should farmers be using organic fertilizers instead? According to Ms. Evelyn Javier, Philippine Rice Research Institute soil scientist, using only organic fertilizers is actually more expensive. Farmers would need to spend much more to achieve high yields if they only use organic fertilizer. “To achieve a yield of 1 t/ha, the rice plants need 17 kg elemental Nitrogen (N), 3 kg elemental Phosphorus (P), and 17 kg elemental Potassium (K).” explained Javier. “Thus, to yield 7 t/ha, the plants need to take in 119 kg N, 21kg P, and 119 kg K.” “However, 50% of the applied N is lost through different processes. N is leached or carried away by water down the soil and will no longer be reached by the roots of plants,” Javier explained. “N is highly volatile, meaning, it is easily converted into gas when exposed to air. This process is called volatilization. Also, nitrate can be converted into gas by certain species of bacteria in anaerobic conditions.” Javier said that to compensate for the N losses, farmers need to apply twice the amount of N. Thus, to provide the required 119 kg N/ha, farmers need to apply 238 kg N/ha. Because commercial organic fertilizer (COF) only contains one to three percent NPK, farmers would need to apply 7,966.6 kg COF or 159 bags COF to provide the required 238 kg N/ha, according to Javier’s computations. “At P175/bag, farmers need to spend almost PhP28,000/ha to target a yield of 7 t/ha. In contrast, farmers only need at most 4 bags of urea for the wet season, spending only PhP4800.” This, however, does not mean that farmers should not apply organic matter to their fields. In fact, PhilRice soil experts recommend applying farm wastes, i.e. rice straw, animal manure, and kitchen wastes as organic fertilizer. “Re-incorporating these farm wastes into the soils will eventually restore and increase the indigenous nutrient supplying (INS) capacity of the soils. If the INS capacity of the soil is high, basal fertilizer application will no longer be needed. Farmers will just apply nutrients that are lacking. In the long term, they will be using less fertilizer, and thus more savings,” Javier explained. She also stressed that rice straw, if incorporated in the soil, provides the elements K and sulfur (S). Farmers should not burn rice straw because about 40-60% of S contained in straw is lost during burning. Chicken manure, on the other hand, can supply P when used as fertilizer. “In short, while organic fertilizer contains less amount of nutrients, it improves the soils condition and would decrease the fertilizer need in the future,” she ended.