Controlled-release fertilizer (CRF) for lahar affected and coarse-textured agricultural soils

Pyroclastic deposits emitted by Mt. Pinatubo [Philippines] in 1991 are currently being utilized as a medium for crop production, however, since lahar deposits are considered marginal due to poor physicochemical properties, low yield, high input requirement and high nutrient losses became a consequence. In this less favorable soil condition, production and testing of a new fertilizer material suitable in lahar and coarse textured soils with controlled release property is deemed necessary. Lysimeter studies revealed that CRFs (Coated urea, muriate of potash, di-ammonium phosphate and complete fertilizers) released their nutrient contents at an incubation period of 45 to 85 days under submerged condition while a much slower release when the fertilizers were incubated under upland condition. Efficacy test of CRF in onion showed that the amount of NPK (190-70-70 kg NPK/ha) application using conventional fertilizer (COF) can be reduced to only half of the rate using CRF as nutrient source. At this level, height, dry matter yield, bulb diameter and bulb yield were significantly increased. Full substitution by CRF have tremendously increased the performance of onion, out yielding those plants with either full COF, partially substituted COF or those applied in combination with organic fertilizer. Similar trend were observed when the CRFs were used in tomato and lowland rice. Nutrient uptakes of the test crops increased by 40 to 496% when CRF were used as compared to the conventional fertilizer materials. This can be attributed to the gradual release of fertilizer nutrients thereby minimizing losses through leaching or volatilization. It can be deduced from the study that the use of CRF in rehabilitating lahar laden agricultural soil is very promising. Applying the fertilizer normally a weak after planting is all it takes to realize greater efficiency and yield because the CRFs are able to release their nutrient content within a longer period