02059nam a2200253 a 450000100080000000500110000800800410001910000160006024501050007626000510018130000110023250000200024352014060026365000110166965000150168065000150169565000120171065000130172265000110173565300110174665300190175765300190177665300100179515652572002-09-04       1977    bl uuuu  m   00u1 u    #d1 aYOST, R. S.  aEffect of rate and placement on availability and residual value of P in an Oxisol of Central Brazil.  aRaleigh: North Carolina State Universityc1977  a160 p.  aTese Doutorado.  aThe effects of P rate and placent on the yield of corn were studied on na Oxisol in Central Brazil. Residual effects of P applications were measured by corn growth and soil analyses. With five crops of corn grow in two and-half years about 20% of the applied P was utilized in grain and stover where grain yield appeared to be a maximum ( assuming no contribution from soil). Maximum yields of corn grain were obtained wich na initial broadscast application of 560 Kg P/há which gave a soil solution concentration of obout 0.05 ug P/ml as measured by sorption curves. The highest combination of yield and utilization occurred with an inicial broadcast application of 140 Kg P/Há and consecutive band aplications of 35 Kg P/há. The band application of P provided for rapid initial growth and also provided effective residual effects due to localized zones of high P concentration. Both double acid and .5N NaHCO3 methods of extracting soil P provided reliable estimates of critical levels, 10-15, 6-10 ug P/g, respectively, which were similar to values obtained min other areas in Brazil. Basing P requirements on field calibration of these soil test extractants should provide for 80 to 85% maximum yields using only one half the amounts of fertilizer P as that estimated by the requirement for maximum yield based on amounts of adsorbed P required to provide . 05 ug P/ml in the soil solution.   .  aBrazil  aFerralsols  aphosphorus  aCerrado  aFósforo  aOxisol  aBrasil  aCentral region  aRegiao Central  aSolos