Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 5, 2009
Publication Date: July 13, 2009
Citation: He, Z., Honeycutt, C.W., Griffin, T.S., Olanya, O.M., Larkin, R.P., Halloran, J.M. 2009. Comparison of three soil P tests and their relationship with potato yield. Soil Science Society of America Annual Meeting. Published on CD-Rom. Technical Abstract: Potato plants have a low efficiency of acquiring soil P. Appropriate tests for evaluating soil P availability are required for optimizing P management in potato production. We evaluated three tests of available P in a Caribou sandy loam (coarse-loamy, mixed, frigid Typic Haplorthod) collected in May 2007 from multiple potato cropping systems managed with and without irrigation. Ammonium oxalate extraction produced the highest level of soil P, with more than 1400 mg P per mg of dry soil. Levels of Olsen P were modest, ranging from 100-120 mg P per kg of dry soil. The modified Morgan extraction (MMP) procedure returned the lowest levels, with P never exceeding more than 10 mg P per kg of dry soil. Modified Morgan P was the only soil P test significantly impacted by crop rotation. Furthermore, MMP measured in the spring was linearly related to the previous year’s potato yield in a negative manner for plots receiving the same amount of P fertilizer. This relationship was stronger under rainfed management (R2 = 0.92, p=0.05) than under irrigated management (R2 = 0.78, p=0.10). The strong yet negative linear relationship between Spring-sampled MMP and the previous year’s potato yield suggests that these results reflect P uptake by potato and the modified Morgan extraction procedure was a good indicator of P utilization.