Residue decomposition from cattle dung is crucial in the nutrient cycling process in Integrated Crop–Livestock Systems (ICLS). It also involves the impact of the presence of trees exerted on excreta distribution, as well as nutrient cycling. The objectives of this research included (i) mapping the distribution of cattle dung in two ICLS, i.e., with and without trees, CLT and CL, respectively, and (ii) quantification of dry matter decomposition and nutrient release (nitrogen—N, phosphorus—P, potassium—K, and sulphur—S) from cattle dung in both systems. The cattle dung excluded boxes were set out from July 2018 to October 2018 (pasture phase), and retrieved after 1, 7, 14, 21, 28, 56 and 84 days (during the grazing period). The initial concentrations of N (~19 g kg−1), P (~9 g kg−1), K (~16 g kg−1), and S (~8 g kg−1) in the cattle dung showed no differences. The total N, P, K and S released from the cattle dung residues were less in the CLT system (2.2 kg ha−1 of N; 0.7 kg ha−1 of P; 2.2 kg ha−1 of K and 0.6 kg ha−1 of S), compared to the CL (4.2 kg ha−1 of N; 1.4 kg ha−1 of P; 3.6 kg ha−1 of K and 1.1 kg ha−1 of S). Lesser quantities of cattle dung were observed in the CLT (1810) compared to the CL (2652), caused by the lower stocking rate, on average, in this system (721 in the CL vs. 393 kg ha−1 in the CLT) because of the reduced amount of pasture in the CLT systems (−41%), probably due to light reduction (−42%). The density of the excreta was determined using the Thiessen polygon area. 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. Therefore, these results strengthen the need to understand the nutrient release patterns from cattle dung to progress fertilisation management.
Sward height (SH) is an important management variable for both continuous and intermittent stocking, since it is easily measured and highly correlated to herbage mass (HM). However, in systems with trees, tree shading can alter the relationship between SH and HM by changes in the sward structure. Understanding these relationships under shading could help identify and design management practices for swards in association with trees. The aim of this study was to investigate the SH and HM relationship for a continuously stocked mixed black oat (Avena strigosa Schreb.) + annual ryegrass (Lolium multiflorum Lam.) pasture in two systems, i.e. with and without trees, with two levels of nitrogen (N) (90 vs. 180 kg N ha−1), three replicates and over 2 years (2014/2015). Comparison of regression lines was performed between SH (x‐variable) and HM (y‐variable), showing mainly a system effect. Shading altered the relationship between SH and HM in order of magnitude (i.e. different intercepts), but not in the rate of change (i.e. equal slopes). Regardless the SH, oat + ryegrass mixture under trees produced 698 kg of dry matter (DM) ha−1 less than those without trees. Therefore, a target SH used at full sun systems as an index for management (e.g. 20 cm) might not apply under trees with >50% shade, since HM may be limiting to ensure intake of grazing animals (e.g. <1200 kg DM ha−1). The shade level must be controlled to optimize the yield of these forage species and to maintain the necessary HM to ensure the sustainability of no‐till silvopastoral systems.
Residue decomposition from pastures and crops plays an important role in nutrient cycling in integrated crop-livestock systems (ICLS). The objective of this research was to quantify dry matter decomposition and nutrient release-nitrogen, phosphorus, and potassium (N, P, and K, respectively), the most commonly required nutrients in tropical and subtropical agriculture-from pasture and soybean (Glycine max) residues of stocking and crop seasons in two ICLS (with and without trees, CLT and CL, respectively) and two N fertilization levels (90 vs. 180 kg N ha −1 , N90 and N180, respectively, applied during the pasture phase). Litter bag incubations were set out in the December 2014 (soybean phase) and May 2015 (pasture phase), and retrieved after 7, 15, 30, 60, 90, and 120 d in each season. The total N, P, and K released from the pasture or soybean residues were related to the initial quantity of plant residues, which was reduced in the CLT systems, mostly for pasture residue (−60%), probably due to light reduction (−55%), rather than changes in litter quality and dynamics. Significant amounts of N (∼57 kg ha −1 ), P (∼11 kg ha −1 ), and K (∼58 kg ha −1 ) were cycled, particularly in CL and N180 treatments. The quantities of K released from pasture residues were enough to restore the quantity of K exported by soybean grains. Therefore, results reinforce the need to understand nutrient release patterns from residues to improve fertilization management.Abbreviations: CL, crop-livestock systems; CLT, crop-livestock systems with trees; DBH, diameter at breast height; DM, dry matter; Gha, animal gain per hectare; Ht, total height; ICLS, integrated crop-livestock systems; LW, live weight; N180, 180 kg N ha −1 ; N90, 90 kg N ha −1 .
The soil tillage practiced over a long period of time impacts soil quality. The first step in soil quality assessment is to select which indicators should be used. The objective of this study was to identify the soil attributes that discriminate soil tillage systems and can be used as indicators for soil quality assessments. Sixteen soil physical and chemical attributes were evaluated: macroporosity (MaP), microporosity (MiP), total porosity (TP), bulk density (BD), field-saturated hydraulic conductivity (Kfs), soil resistance to penetration (SRP), pH (H2O), pH (CaCl2), aluminium (Al), calcium (Ca), magnesium (Mg), potassium (K), available phosphorus (P), total organic carbon (TOC), cation exchange capacity (CEC) and base saturation (BS), of a very clayey Red Latosol, cultivated for a long period in no-till (NT), conventional tillage (CT) and minimum tillage (MT). The soil attributes (indicators) were selected using canonical discriminant analysis. MiP, Kfs, pH (CaCl2), Ca, Mg, CEC e BS were the most efficient indicators to discriminate soil tillage systems. In the indicator interpretation step was sustained MiP as the indicator that represents the function of physical stability and support, Kfs as the indicator that represents the function of water relations, BS as the indicator that represents the function of nutrient cycling and pH (CaCl2) as the indicator that represents the function of filtering and buffering. These indicators can be used for future soil quality assessment and monitoring of tillage systems in similar regions and conditions.
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