PHOSPHORUS AVAILABILITY IN A SOYBEAN-RUZIGRASS CROP ROTATION

• Grant number: 15/22095-9
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): September 01, 2016
• Effective date (End): July 31, 2017
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal researcher: Ciro Antonio Rosolem
• Grantee: Danilo Silva Almeida
• Supervisor abroad: Philip Matthew Haygarth
• Home Institution: Faculdade de Ciências Agronômicas (FCA). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil
• Research place: Lancaster University, England
• Associated to the scholarship: 14/23707-5 - Availability of phosphorus and soybean yield in crop rotation with Congo grass, BP.DR

Abstract

Crop rotation with Urochloa ruziziensis during soybean off-season has been widely adopted in Brazil. However, decreased yields and P leaf content of soybean have been observed when grown after U. ruziziensis, in spite of increased soil P availability measured by routine soil P analysis by resin. However, there are reports that U. brizantha do not show these effects. The main objective of this work is to determine whether the soybean yield decrease when grown in rotation with U. ruziziesis is a consequence of impaired P absorption resulting from low soil P mobility after U. ruziziensis, or resulting from the accumulation of organic P forms that are less available, as well as determine the potential of U. brizantha in increasing soil P availability by exudating organic acids. This study involve three experiments conducted in Botucatu/Brazil, part of a PhD project (2014/23707-5). Soil samples will be submitted for analysis by Diffusive Gradient in Thin films (DGT), phytase-labile organic P, and organic P speciation, in partnership with Dr. Philip Haygarth and Dr. Daniel Menezes-Blackburn, in the Lancaster University, United Kingdom. The first experiment is a long-term field experiment, in which U. ruziziensis is grown in half of the plots in the soybean off-season, whereas the other half remains fallow. Besides the treatments with and without U. ruziziensis, three levels of P (0, 30, and 60 kg ha-1 of P2O5) applied in the soybean seed furrow will be evaluated. The second, a greenhouse experiment, compares the effect of two P levels and three species of grasses (U. ruziziensis, U. brizantha, Panicum maximum) on soil P. In the third experiment will be evaluated the effect of organic acids exudated by U. ruziziensis, U. brizantha in soil P availability. The data will give fundamental support to the PhD thesis.