Calibration and validation of UPLB soil test kit (STK) for vegetable fertilization in CALABARZON [Cavite, Laguna, Batangas, Rizal, Quezon province, Philippines]
2008
Soriano, J.D.C. | Salazar, J.T. | Manguiat, I.J.
Calibration experiments were conducted to quantify the results of STK[soil test kit] analysis for available N,P, and K. N calibration results indicate the following: low (0-30ppm), medium (30-60ppm), and high (60ppm). These values correspond to 0-60, 60-120, and 120 kg available N/ha, respectively. For the P calibration curve, the results indicate the following: low (0-13ppm), medium (13-40ppm), and high (40ppm). On the other hand, the K calibration curve reflects the following ranges: deficient (0-0.2cmol(p supt)/Kg soil) and sufficient (0.2cmol(p supt)/kg soil). In terms of costs of analysis per sample, ASL[analytical services laboratory] was about 97% more expensive than STK in analyzing either pH, available P, or exchangeable K. Additionally, ASL was 100% more costly than STK in analyzing either available N or lime requirement. For the costs of fertilizer recommendations, STK was less expensive (10-53%) than ASL for fruit vegetables such as eggplant and okra but more expensive (15.183%) for leafy vegetable,e.g. pechay and viny vegetable,e.g. ampalaya. For the screenhouse experiments designed to validate STK fertilizer recommendations, the results revealed that the effect of STK was not significantly different from that of ASL in improving dry biomass production of four vegetables. For ampalaya, the N and P uptakes due to ASL and STK were about the same. Correlation analysis among the uptakes of N, P, and K for STK and ASL revealed that for eggplant and pechay only the N uptake obtained with ASL. However, for okra, highly significant and positive correlation between P uptake based on STK and P uptake based on ASL was obtained. Generally, the requirements for the validation of STK in comparison with ASL standard had been satisfied.
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