Effect of trees and cattle dung input on soybean yield and nutrition in Integrated Crop-Livestock Systems

In integrated crop-livestock systems (ICLS), grazing cattle influence the distribution of nutrients in the soil. When trees are present, they may affect the cattle dung distribution, as well as the nutrient cycling and crop yield. The objective of this experiment is to evaluate the influence of the presence of cattle dung and trees on soybean nutrition and yield in ICLS during 2018-2019. Two areas were used in this study, that is, with trees (CLT, 1.1 ha) and without trees (CL, 1.2 ha). Both areas have been considered as ICLS (soy-beef cattle), since 2009. The experimental design was in a split-split-plot, the main plots followed the CL and CLT systems, the subplots were the cattle dung input (presence and absence), and the sub-subplots were three positions between two tree rows (i.e., sampling points). In the CL system the plant height (+18.1%), the number of pods per plant (+51.2%), grains per pod (+7.2%), shoot biomass (+60%) and grain yield (+52.9%) were increased compared to the CLT system. The highest values for plant height, shoot biomass, grain yield, grain weight, pods per plant, grains per pod, and phosphorus (P) concentrations in soybean, were observed in the central position among the tree rows, when comparing the positions nearest to the trees. However, in the position adjacent to the rows, an increased content of P in the soil was found and an increased content of sulfur (S) in the plant. The presence of cattle dung increased the availability of soil P (+30%) and potassium (K, + 52.3%), as also the content of P (+ 4.3%), K (+ 5.2%), and S (+ 5.1%) in plant, and the grain yield (+ 22%). The great effect on soybean yield was due the trees presence (3.6 Mg ha(-1) in the CL system vs. 1.7 Mg ha(-1) in the CLT). The light restriction, the competition for nutrients with trees and drought periods were factors to be considered, to explain the difference in productivity between the CL and CLT systems.