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Title: Amounts of calcium and magnesium cycled and its release kinetics in a long-term no-till integrated crop-livestock system with varying grazing intensities in subtropical region

Author
item ASSMANN, JOICE - Federal University Of Rio Grande Do Sul
item MARTINS, AMANDA - Federal University Of Rio Grande Do Sul
item ANGHINONI, IBANOR - Federal University Of Rio Grande Do Sul
item GIGANTE DE ANDRADE C, SERGIO ELY - Federal University Of Rio Grande Do Sul
item Franzluebbers, Alan
item CARVALHO, PAULO - Federal University Of Rio Grande Do Sul
item SILVA, FRANCINE - Universidade Federal De Santa Maria
item COSTA, ALVARO - Federal University Of Rio Grande Do Sul

Submitted to: Nutrient Cycling in Agroecosystems
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., Gigante De Andrade C, S.V., Franzluebbers, A.J., Carvalho, P., Silva, F.D., Costa, A.A. 2017. Amounts of calcium and magnesium cycled and its release kinetics in a long-term no-till integrated crop-livestock system with varying grazing intensities in subtropical region. Nutrient Cycling in Agroecosystems. 41. doi.org/10.1590/18069657rbcs20160330.
DOI: https://doi.org/10.1590/18069657rbcs20160330

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 Santa Maria 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. Phosphorus and potassium were effectively cycled, but differences between nutrient types and sources of nutrients from cover crop residues, soybean leaves and stems, and dung were apparent. Greatest release of calcium and magnesium were derived from moderate grazing of winter cover crops. Nutrient release from soybean residues was unaffected by grazing intensity. 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 an integrated crop-livestock production system, plant and animal residues become an important nutrient stock. Grazing management could affect both plant and animal residue amount and quality, thereby influencing nutrient dynamics through modifications in nutrient release rates. The objective of this study was to evaluate the impact of grazing intensity on calcium (Ca) and magnesium (Mg) release from pasture, dung, and soybean residues in a long-term no-till integrated crop-livestock system. This experiment was established in May 2001 in an Oxisol (Rhodic Hapludox). Treatments were a gradient of grazing intensity [determined by managing pasture sward height [black oat (Avena strigosa) + Italian ryegrass (Lolium multiflorum)] at 10, 20, 30, and 40 cm and no-grazing (NG)]. Residue decomposition and Ca and Mg release rates were determined in the 2009-2011 period with litterbags deployed in the experimental area from pasture, dung, and soybean residues during the winter cover-crop grazing and summer soybean grain cropping seasons. Moderate grazing (i.e. 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, respectively). Grazing compared with NG resulted in greater Ca and Mg released from the combination of 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.