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Title: Soil phosphorus compounds in integrated crop-livestock systems of subtropical Brazil

Author
item DIESS, LEONARDO - Universidade Federal Do Parana
item MORAES, ANIBAL - Universidade Federal Do Parana
item DIECKOW, JEFERSON - Universidade Federal Do Parana
item Franzluebbers, Alan
item GATIBONI, LUCIANO - University Of Santa Catarina
item SASSAKI, GUILHERME - Universidade Federal Do Parana
item CARVALHO, PAULO - Federal University Of Rio Grande Do Sul

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2016
Publication Date: 5/18/2016
Citation: Diess, L., Moraes, A., Dieckow, J., Franzluebbers, A.J., Gatiboni, L., Sassaki, G., Carvalho, P. 2016. Soil phosphorus fractions in integrated crop-livestock systems of subtropical Brazil. Geoderma. 274:88-96.

Interpretive Summary: Nutrient cycling information under cropping systems mixed with livestock grazing cover crop components needs clarification, as integrated crop-livestock systems are gaining traction as a potential method of sustainable intensification. A soil scientist at USDA-Agricultural Research Service in Raleigh NC teamed with a group of scientists from the Federal University of Parana, State University of Santa Catarina, and Federal University of Rio Grande do Sul in Brazil to analyze soil for different fractions of phosphorus. At four sites in the Brazilian states of Parana and Rio Grande do Sul, cropping systems with greater complexity (with cattle grazing of cover crops or in an agroforestry system) led to surface soil concentration of plant-available orthophosphate and lower concentration of organically derived phosphorus components. The results of this research suggest that more complex cropping systems with livestock and trees could be valuable approaches to (a) enhance phosphorus cycling and (b) mitigate losses of phosphorus to the environment to promote global security with limited phosphorus reserves.

Technical Abstract: Soil phosphorus (P) utilization and loss mechanisms may be affected by agricultural complexity, in particular when combining annual and perennial crops and livestock grazing on the same land area and at overlapping time periods. Our objectives were to (i) qualify and quantify soil organic and inorganic P fractions using sodium hydroxide-ethylenediaminetetraacetic acid (NaOH-EDTA) extraction and 31P nuclear magnetic resonance spectroscopy (31P NMR) and (ii) characterize P cycling in response to increasing complexity with integrated crop-livestock systems (ICLS) in subtropical Brazil. Soil at a depth of 0-5 cm was collected from three long-term (7 to 12 years) cropping studies with and without ruminant grazing of cover crops, while a fourth experiment was sampled with and without trees under ICLS. All sites were managed under no tillage, and treatments with livestock were managed with moderate grazing intensity. In these agro-ecosystems, greater trophic complexity compared with lower complexity had greater soil inorganic P content as orthophosphate and lower soil organic P. Moreover, fewer mono-esters, including inositol phosphates, and di-esters occurred in the organic P form. Therefore, greater trophic complexity in cropping systems with livestock (ICLS) and trees (agroforestry) may be valuable approaches to enhance P cycling and reduce losses to the environment to promote global security with limited P reserves.