Effects of different times and methods of ammonium sulphate-15N application and nitrogen-phosphorus 32P interaction on quantities and contents of N, P, K, in plant and leaf of maize, on yield,quantity of protein and efficiency of the nitrogen of the fertilizer and its conversion into protein

Abstract

The experiment herein described was carried on a podzolic soil, in the State of São Paulo, Brazil with the double hybrid corn HD-6999B. The following conclusions were drawn: 1 - In respect of placement and times of application of superphosphate-32P and ammonium sulfate-15N the data showed that: a) greater yield and fair quantity of protein were obtained when the nitrogen and phosphorus were mixed and applied in banding at seeding time; b) lower yield and lower quantity of protein were obtained when phosphorus and applied in banding and nitrogen applied at side-dressing, 83 days after seeding; c) phosphorus application in banding and nitrogen application in side-dressing, 63 days afeter seeding, gave a fair yield and a higher quantity of protein and a higher efficiency of nitrogen of the fertilizer in its conversion into protein. 2 - In respect of % FPPF, it seemed there was an effect of NHΪ on phosphorus uptake, but this effect disapeared at 63 days after seeding. Regarding the % NPPF, there was also an effect of phosphorus on nitrogen uptake, but of short duration. 3 - The corn plants still continue to take up the nitrogen of the fertilizer even at 73 and 83 days after seeding, not to increase yield, but to increase the contents and quantity of protein. 4 - The maize leaf +2 can be taken for analisys at 73 days after seeding as an indicator of the nutritional status of maize plant in nitrogen and phosphorus. In the case of potassium, the leaf will be taken for analisys at 117 days after seeding. 5 - The superphosphate at the level applied constituted a limiting factor for better yield.