Abstract
Good to excellent soyabean grain yields averaging 1502-2235 kg ba-1 in the wet season and 2 lOS-3163 kg ba-1 in the dry season were obtained with applications of P, K and lime on the thixotrophic, Isothermic, Hydric Dystrandepts of the Benchmark Solis Project In Segunung, Lembang and Cisarua in West Java. Response to applied P was generally small or non-existent, because of the high levels of residual P resulting from years of application of organic manures; this was especially true of experiments conducted in Cisarua. A significant response to P was obtained with the first P increment at Segunung and Lembang, but there was no consistent response to the higher P levels over the lowest P treatment. It seems that 0.02 ppm P In the soil solution ls adequate for normal growth of soyabean. Experiments on three successive, soyabean crops initially supplied with P and lime averaged accumulated yields of 6000 kg ba-1 over the three crops. An increasing response to P became significant with the third crop. Deceasing availability of P was perhaps due to P sorption on the soil complex; a significant increase in yield with lime occured for the third crop at Cisarua, but not at Segunung. Both experiments showed that K was limiting for soyabean production.
