Calcium and Magnesium Released from Residues in an Integrated Crop-Livestock System under Different Grazing Intensities

Abstract

Under integrated crop-livestock production systems (ICLS), plant and animal residues are important nutrient stocks for plant growth. Grazing management, by affecting the numbers of both plants and animals and the quality of residues, will influence nutrient release rates. The objective of this study was to evaluate the impact of grazing intensity on Ca and Mg release from pasture, dung, and soybean residues in a long-term no-till integrated soybean-cattle system. The experiment was established in May 2001 in a Latossolo Vermelho Distroférrico (Rhodic Hapludox). Treatments were a gradient of grazing intensity, determined by managing a black oat + Italian ryegrass pasture at 10, 20, 30, and 40 cm grazing height and no-grazing (NG), followed by soybean cropping. Ca and Mg release rates were determined in two entire cycles (2009/11). Moderate grazing (20 and 30 cm sward height) led to greater Ca and Mg release rates from pasture and dung residues, with low average half-life values (13 and 3 days for Ca and 16 and 6 days for Mg for pasture and dung, respectively). Grazing compared with NG resulted in greater Ca and Mg release from pasture and dung residues. Grazing intensity did not affect Ca and Mg release rates or amounts from soybean residues, but Ca and Mg release rates were greater from soybean leaves than from stems. Although moderate grazing intensities produce higher quality residues and higher calcium and magnesium release rates, a higher total nutrient amount is released by light grazing intensity and no-grazing, determined by higher residue production. Grazing intensity is, then, important for nutrient dynamics in the soil-plant-animal continuum.

Systemic Soil Fertility as product of system self-organization resulting from management

“…These nutrients are released into the soil solution, incorporated into microbial biomass and soil organic matter (Anghinoni et al, , 2018. The amount of nutrients released in the grazing phase is similar to that when commercial fertilizers are applied to the crops, since the animal works as a recycler par excellence (Anghinoni et al, 2011;Assmann et al, 2015Assmann et al, , 2017. The effects of animal presence on acidity properties manifest as the greater and faster action of the lime applied to the soil surface in reaching the deeper soil layers, verified by the pH, base saturation and aluminium levels (Flores et al, 2008;Martins et al, 2014).…”

“…Many changes in soil properties in the NTS were verified over time, predominantly due to the accumulation and quality of the crop residues. This resulted in the reestablishment of the microbial biomass and the reaggregation of the soil, building a structure with a better capacity to retain nutrients and water; the shift from immobilization to nitrogen availability; the increase in organic carbon and phosphorus (Sá, 2001;Mielniczuk et al, 2003); the decrease in the effects of soil acidity (Salet et al, 1999;Alleoni et al, 2010;Martins et al, 2014), with an increase in the cation exchange capacity and nutrient cycling (Sá, 1999;Assmann et al, 2015Assmann et al, , 2017.…”

Soil chemical properties under no‐tillage as affected by agricultural trophic complexity

“…A low animal‐product export of nutrients means, for example, that up to 85% of ingested phosphorus (P through pasture consumption is returned via dung (Nash et al, 2014). The amount of nitrogen (N), P, potassium (K), calcium (Ca) and magnesium (Mg) cycled through animals and plants in these systems varies with herbage intake and residue decomposition rate, but quantities can and must be considered for altering fertilizer recommendations (Assmann et al, 2014; Assmann et al, 2017; Assmann et al, 2017). In addition to the effect of grazing livestock on nutrient cycling through dung and urine deposition, livestock can impact plant dynamics and soil functioning, which can alter plant communities and eventually affect animal production.…”