Spatial and temporal distribution of cattle dung, nutrient cycling and soybean yield inIntegrated Crop–Livestock Systems

Abstract

The aim of the present study was to (i) mapping the distribution of cattle dung in two ICLS, i.e., with and without trees, CLT and CL, respectively (ii) quantify nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) releases from cattle dung in two integrated crop-livestock systems (ICLS), either with pasture (black oats + ryegrass) and beef cattle during winter and soy or corn in summer (iii) evaluate the influence of the presence of cattle dung and trees on soybean nutrition and yield in ICLS. The experiment was divided into two periods: grazing period and soybean crop season. Grazing period: The experimental design was subplots were different times, comprising two ICLS (presence and absence of trees) and different times (0, 7, 14, 21, 28, 56 and 84 days after animal entry) with six replications. No differences were observed between systems for initial contents: 18.8 g kg−1 N and 7.3 g kg−1 S. However, significant differences were observed over time for N (9.7 g kg−1), at the 84th assessment day. The ICLS did not affect N and S decomposition and release dynamics. However, total N and S released from the cattle dung and potentially available for the crops varied according to the ICLS, depending on the number of animals present during the grazing period and the amount of cattle dung. The CL system revealed a higher concentration of faeces at locations near the water points, gate and fences. The CLT affects the spatial distribution of the dung, causing uniformity. Soybean crop season: 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 the tree rows (nested in the systems). In the CL system the plant height (+18.1%), the number of pods per plant (+51.2%) and grains per pod (+7.2%), pods per area (+50.6%), dry mass in V8 (+59%) and R2 (+60%), and grain yield of the soybean crop (+52.9%) were increased compared to the CLT system. 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%) as well as the grain yield (+22%). The light restriction, the competition for nutrients in the trees and drought periods were factors to be considered, to explain the difference in productivity between the CL and CLT systems.