Calcium and magnesium released from residues in an integrated crop-livestock system under different grazing intensities

Authors: ASSMANN, JOICE - Federal University Of Rio Grande Do Sul; MARTINS, AMANDA - Federal University Of Rio Grande Do Sul; ANGHINONI, IBANOR - Federal University Of Rio Grande Do Sul; COSTA, SERGIO E.G.V.A - Federal University Of Rio Grande Do Sul; Franzluebbers, Alan; CARVALHO, PAULO - Federal University Of Rio Grande Do Sul; SILVA, FRANCINE - Federal University Of Mato Grosso; COSTA, ALVARO - Federal University Of Rio Grande Do Sul

Submitted to: Revista Brasileira De Ciencia Do Solo
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 4/27/2017
Citation: Assmann, J.M., Martins, A.P., Anghinoni, I., Costa, S., Franzluebbers, A.J., Carvalho, P.C., Silva, F.D., Costa, A.A. 2017. Calcium and magnesium released from residues in an integrated crop-livestock system under different grazing intensities. Revista Brasileira De Ciencia Do Solo. 41, Article No. e0160330.

Interpretive Summary: Integrated crop-livestock systems have the potential to enhance agricultural sustainability by sharing of resources, thus reducing reliance on external inputs and/or reducing nutrient losses to the environment. Data to support these concepts require investigation under a wide range of conditions. A soil scientist at USDA-Agricultural Research Service in Raleigh NC teamed with a group of scientists from the Federal University of Rio Grande do Sul and Federal University of Mato Grosso in Brazil to assess the effects of grazing intensity on calcium and magnesium release from crop residues and animal manures in a soybean cropping system with grazed winter cover crop. Moderate grazing led to greater calcium and magnesium release rates from pasture and dung residues. Grazing intensity did not affect calcium and magnesium release rates or amounts from soybean residues, but calcium and magnesium 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. Grazing intensity is, then, important for nutrient dynamics in the soil-plant-animal continuum. These results will help farmers and scientists in Brazil and in the USA develop a better understanding of how nutrients are cycled in complex agricultural systems so that agricultural efficiency can be further improved to develop robust production systems with minimal losses to the environment.

Technical 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.