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Agronomic and Environmental Evaluation of Soil Phosphorus With Continuous Draw-Down.

Poster Number 1303

Tuesday, November 5, 2013
Tampa Convention Center, East Hall, Third Floor

Tiequan Zhang, Greenhouse and Processing Crops Research Center, Agriculture and Agri-Food Canada, Harrow, ON, Canada, Chin Tan, Greenhouse and Processing Crops Research center, Agriculture and Agri-Food Canada, Harrow, ON, Canada and Tom Welacky, GPCRC, AAFC, Harrow, ON, Canada
Research advances indicate that residual phosphorus (P) in soils is mainly in absorbed forms that can desorb and be available to crop uptake and/or losses in water discharge. A study was conducted to evaluate the agronomic and water quality consequences of continuous P draw-down in a clay loam soil under corn-soybean rotation from 2008 to 2012. Both surface runoff and tile drainage water discharges were year-round continuously monitored for flow volumes and sampled for P determination.  Corn grain yields with P draw-down were largely identical to those with continuous P addition. However, soybean yields with P draw down were 6-8% lower than those with continuous P addition, indicating that soybeans with small and shallow rooting systems may need a booster of fertilizer P to compromise the temporal shortage of soil available P, especially in early spring. Soil test P (Olsen P) remained unchanged for the draw-down treatment over the 4-year period, while for the continuous P addition treatment it increased, with 5 kg P ha-1 addition of fertilizer P required to increase each mg P kg-1. Water extractable soil P decreased with continuous P draw-down, but increased with continuous P addition, both at the same numerical value, 0.48 mg P kg-1 year-1.  Soil P losses in all forms, including dissolved reactive P and particulate P, in both surface runoff and tile drainage decreased with cropping for the P draw-down, while they increased for the continuous P addition. It appeared that water extractable P was more sensitive that Olsen P to indicate soil P losses. Soil P draw-down can be recommended as a BMP for management of P in high P soils, but supplemental P application may be required for soybeans to ensure the maximized production.     
See more from this Division: ASA Section: Environmental Quality
See more from this Session: Challenges and Opportunities For Drawing Down High P Soils

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