Fertilizer experiments with soybeans and dry beans in «arentto botucatu» soil

In this paper are reported the results of two factorial experiments on poor soil derived from the Botucatu sandstone, to study the effects of three levels of nitrogen, phosphorus, and potassium on the yields of soybeans. The experiments were located in neighboring areas, one of which was previously limed with dolomitic lime. The plots of the latter were sown with dry beans in the following year, to study the residual effect of the fertilizers applied to the soybeans. The responses to nitrogen and potassium, as well as the interactions, were insignificant. The effect of phosphorus, however, was significant and linear with both crops. Although high in the two areas, this effect was much higher in the limed one. Comparing the results of the two experiments, it was concluded that the response to lime was negligible in absence of phosphorus but increased considerably in its presence. On the limed area the yield of soybeans, as an average of the treatments with the higher level of phosphorus, reached about 1,800 kilograms to the hectare and was similar to those obtained in fertile soils of the State of São Paulo.