The study has clearly shown that there is an avenue to improve the current nutrient management by considering the crop nutrient utilization dynamics to identify the best timing and amount of fertilizer application.
The use of elemental tracer techniques allows direct quantitative measurement of the influence of various environmental factors on production. It distinguishes between different sources of nutrients and allows direct determination of fertilizer nutrient recovery. In the study site in Floridablanca, Pampanga, the Isotope tracer data showed that more than half of N in the plant came from the indigenous soil N, especially during initial phase and at crop maturity; Also revealed was the high losses of applied N to the environment especially with the application of higher doses. Findings indicate that there is very short residence time of applied nitrogenous fertilizer (~3months), especially during wet season. There was a considerable amount of inherent soil nutrients in the studied soils, which contradicts the initial soil analyses results.
