NACAA

PHOSPHORUS UPTAKE BY SILAGE CORN IN SOUTHERN IDAHO

Hines,* S.L.¹; Brown, B.D.²; Chahine, M. E.³; de Haro Marti, M. E⁴; Falen, C. E.⁵; Fife, T. E⁶; Ippolito, J. A⁷; Moore, A.D.⁸; Norell, R.J.^9
1Extension Educator, University of Idaho, Twin Falls, ID, 83301
²Extension Crop Management Specialist, University of Idaho, Parma, ID, 83660
³Extension Dairy Specialist, University of Idaho, Twin Falls, ID, 83301
⁴Extension Educator, University of Idaho, Gooding, ID, 83330
⁵Extension Educator, University of Idaho, Shoshone, ID, 83352
⁶Extension Educator, University of Idaho, Twin Falls, ID, 83301
⁷Research Soil Scientist, USDA-ARS, Kimberly, ID, 83341
⁸Extension Soil Specialist, University of Idaho, Twin Falls, ID, 83301
⁹Extension Dairy Specialist, University of Idaho, Idaho Falls, ID, 83402

Abstract:

Accumulation of phosphorus (P) is a major concern in southern Idaho soils which receive manure from confined animal operations. Irrigated corn grown for silage is the main crop used for phosphorus removal in southern Idaho. National values have been used to estimate P removal by corn for silage; however little is known about the actual amounts of phosphorus removed under southern Idaho growing conditions. The purpose of this study is to estimate phosphorus removal by irrigated corn grown for silage in southern Idaho under variable soil test P concentrations. The study was conducted during the 2008 and 2009 growing season. Twenty-one fields were sampled in each growing season. Plant and soils samples were taken within one week of harvest. The soils were analyzed for Olsen P and the plant tissue was measured for total P concentration. Wet and dry yields were calculated based on plant field weights and drying of plant material. Corn P uptake figures are a major factor used to determine total amount of allowable manure application to fields specified in producer’s nutrient management plans. In Idaho those plans are written with the Idaho One Plan program. Plans written before June 2007 used 0.26% as plant tissue P. Plans written after June 2007 use 0.185% as plant tissue P. The results of this study indicate plant tissue P levels average .021%. The data from this study will be used to recalibrate the Idaho One Plan program to allow nutrient management plans to reflect southern Idaho conditions.