Phosphorus is the macronutrient that most often contributes to increasing the productivity of crops in Brazil. It has been shown that certain Rhizobium-plants symbiosis require higher levels of phosphorus, as compared to the nitrogen- fertilized plants. Several different ways of placing soluble phosphate were tested for both common beans and chickpea crops, with the objective of increasing the efficiency of using phosphorus available in the soil without increasing fertilizer amount. The common bean crop set up in Jaguapitã (PR), was sown in October, 1986 in an Oxisol with 113 g kg-1 of clay and 2.2 mg dm-3 of P. The fertilizer was distributed at 7 cm depth and the seeds at 3 cm depth, both being placed in the row. Row fertilization was compared to pit fertilization using 50 and 100 kg ha-1 of P2O5, as triple superphosphate. In addition to the control, without phosphate fertilization, an extra treatment using 25 kg ha-1 was also included. The common bean was seeded in pits. The chickpea trial was set up in Londrina (PR) in June 1987, in an Oxisol with 760 g kg-1 of clay and 3,6 mg dm-3 of P. The fertilizer was placed at the depth of 7 cm and the seeds at 3 cm. The treatments Rhizobium-free control, inoculation with Rhizobium, and without inoculation + 30 kg N.ha-1, were tested in the plots, while in the subplots the tests involved phosphate fertilization in rows or in pits. The chickpea was seeded in the row. The contents of N, P, Zn and Mn in the common bean leaves, as well as the productivity and nodulation of common bean and chickpea, were assessed. There was no root nodulation in the common beans, and a tendency to greater nodulation in the chickpea when using pit fertilization was not statistically significant. There was an increase of about 40% in the common bean yield and of 31% in chickpea as a result of pit fertilization, as compared to row fertilization. The efficiency of using P in pits in the common bean was of 15,5, 10.4 and 7,4 kg of grain for kg of P2O5 for 25, 50, and 100 kg ha-1 P2O5, respectively. In contrast, row fertilization showed an index close to 4. Pit application of soluble phosphate may be an alternative choice to help increase the efficiency of phosphorus fertilization.
efficiency in P utilization; fertilizer placement; biological nitrogen fixation; nodulation