Phosphorus availability from natural and soluble phosphate sources for irrigated corn production

This research’s aims were to evaluate the mixture ratios of P fertilizers in irrigated corn yield in two seasons as well as evaluate the capacity of Resin and Mehlich 1 extractors to predict the P availability under field conditions in two soils: Hapludults and Oxisol. In the first crop, the experimental design was randomized block with four replications where two P sources, Triple Superphosphate (TSP) and Daoui Natural Phosphate (DNP), were tested in four rations (100%:0%; 67%:33%; 33%:67%; 0%:100%). The second planting was carried out in a similar manner, with some modifications to verify the residual effect of the fertilizers. DNP provided lower productivity and leaf P levels when compared to TSP in the first year but the DNP contributed with a higher residual effect through the test conditions. DNP fertilization provided higher residual effect in Hapludults than in Oxisol. Only Resin extractor, in Oxisol without TSP application in the second cultivation, was efficient in estimating the availability of P to the corn plants in the experiment conditions. In the experiment conditions, DNP provided productivity and leaf P levels similar to Triple Superphosphate in the first year and its residual effect is highly dependent on the soil type.   Key words: Zea mays, fertilizing, phosphorus, extractors.