The influence of nitrogen and potassium on plant growth and on yield of soybeans planted in winter

Abstract

An experiment was installed at three Experimental Stations, namely Mococa, Ribeirão Preto and Votuporanga, SP, Brazil, in three different types of soil to study the effect of doses of N and K on soybeans planted in winter. The doses of N used were 0, 50 and 100 kg of N/ha in the form of urea and those of K were 0, 30 and 60 kg of K₂O/ha in the form of potassium chloride. The two cultivars of soybeans utilized were IAC-8 and IAC-14. The statistical design was factorial with three replications. The seeds of all treatments were inoculated with the recommended strains of Bradyrhizobium japonicum. At full bloom, the dry matter weight of the roots and the above ground parts were determined as well as the concentration of N and K. Growth of roots and of the above-ground parts was facilitated by the use of nitrogen at Mococa and Votuporanga. Nitrogen increased the soybean yield at the three localities. Potassium did not affect the parameters studied, but there was a preferencial absorption of K by IAC-14 which is very demanding in this element.