Qualidade nutricional do grão e parâmetros de produção de soja em sistema orgânico e convencional

Abstract

Soybean (Glycine max L.) is an important source of protein and fatty acids, to human food as well as an animal feed component. Growing interest in sustainably produced food has boosted the organic cultivation of a variety of products, considered healthier, including soybean for human consumption and as to alternative to producing animal protein. However, little is known about how the cultivation system improves the quality of the final product, and in soybean case, how it affects aspects related to nodulation and biological nitrogen fixation. Therefore, the present study aimed to evaluate the effect of organic cultivation system on nodulation and quality of soybean grains. The field experiment was carried out in the experimental area of the Departamento de Fitotecnia of Universidade Federal de Santa Maria (UFSM) in the agricultural years 2016/17 and 2017/18. The experimental design was in a factorial 2 x 2 with subplot in randomized blocks with four replications. The two systems were separated by an eight-meters interval without cultivation, in which the development of spontaneous plants was allowed. At stage R4 the number of nodules per plant, nodules diameter, nodule dry mass, nodule activity and plant nutritional status were evaluated. At harvest, grain yield was verified and samples were taken for analysis of pesticide residues, macro and micronutrient, protein and oil contents and fatty acid profile. The number of nodules was not affected by the organic or conventional system. Node diameter and percentage of active nodules were smaller in the organic system compared to the conventional one. There is a positive correlation between number of nodules and leaf nitrogen content. Yield is similar between organic and conventional cropping systems. There was no effect of the cropping system on the macronutrient content or protein content in soybeans. Oil content in grains was lower in the organic system in the first year of experiment. The fatty acid profile was modified by the cultivation system employed in soybean.