Leaching Losses: Conclusion

[addw2p name=”leachingLosses”]
The downward movement of N fertilizer was mainly in the form of NH_4-N with very little NO_3-N because the source of fertilizer was NH₄Cl. This study also indicated that the rate of nitrification was probably slow during the monsoon period. The concentration of N and K in the soil solution decreased with soil depth being highest at 30 cm from the soil surface followed by 60 and 120 cm. The N leaching losses of the applied N fertilizer during the monsoon period in Sabah, North Borneo were 1.0 and 1.6% for treatments, N1P2K0 and N1P2K1, respectively. Higher K leaching losses were obtained at 5.3 and 2.4% for N0P2K1 and N1P2K1, respectively. The groundwater quality under mature oil palms did not exceed the contamination level set by WHO when N and K fertilizers were applied at their optimum rates for oil palm. However, there was a possibility of pollution of groundwater quality when excessive N fertilizer was applied which was mainly in the form of NH₄ ⁺ ion. The concentration of NO₃ ^– ion in the groundwater was below 0.5 mg L^-1 even when excessive N fertilizer was applied due to low nitrification rate.