Yield of the soybean crop submitted to different sources of nitrogen

Abstract

 Experiments were carried out in order to compare the effects of N sources on the development and yield of soybean (Glycine max (L.) Merrill), cv. IAC-8, under field conditions. They were located in Piracicaba, SP, Brazil, on a fertile tropudalf soil classified as 'Terra Roxa Estruturada'. They differed on their history of cultivation. One was previously cultivated with sugarcane during two years and the other one received soybeans (Glycine max L.) for three consecutive years. The N sources were mineral (ammonium sulfate and urea) and biological, by the use of the following inoculants carriers: peat, a mineral oil, a plant oil and a water emulsion. On the control treatment, no N sources were applied. A randomized complete block experimental design was used consisting of eight treatments, and five replications in each experiment. The results obtained during the crop life cycle showed that among the N sources used, the peat carriers resulted in highest plant nodulation and yield in the experiment with no inoculation history. In the area with inoculation history, the yield was similar among all of the sources due to the advantageous symbiosis between the bacteria and the host.