An experiment was conducted during the summer of 1983/84 in a clay textured allic, dark red Latosol at Mococa Experimental Station, State of São Paulo, Brazil. Sorghum Contigrão 111 was planted in plots that had received the equivalent to 1, 4, 7 and 10 t/ ha of dolomitic limestone in 1980. These plots were cultivated continuously with soybeans during the three previous years. In the subplots, 0, 40, 80 and 120 of N were applied as side dressing 35 days after germination. The results showed that liming increased the yield of grain sorghum despite the drought at the seed filling stage. It also decreased the toxic effect of aluminum and increased the availability of N from the residues of previous soybean crops. At all the liming rates a linear increase was observed in the leaf N concentration as a function of the rates of nitrogen applied as side dressing. The quantity of N fertilizer required to attain adequate leaf N concentration was substancially reduced at the higher rates of lime applied.
soybeans; sorghum; nitrogen fertilization; Al toxicity; liming