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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #334993
Title: Topsoil thickness effects on phosphorus and potassium dynamics on claypan soils

Author
item CONWAY, LANCE - University Of Missouri
item Yost, Matt
item Kitchen, Newell
item Sudduth, Kenneth - Ken

Submitted to: North Central Extension Industry Soil Fertility Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/28/2016
Publication Date: 11/1/2016
Citation: Conway, L.S., Yost, M.A., Kitchen, N.R., Sudduth, K.A. 2016. Topsoil thickness effects on phosphorus and potassium dynamics on claypan soils. North Central Extension Industry Soil Fertility Conference Proceedings. Available: http://extension.agron.iastate.edu/nce/ncepdfs/2016/ncsfc%202016%20conway%.

Interpretive Summary: Soil thickness, or depth to claypan, varies across landscapes and may influence soil nutrient supply, crop removal, and optimal P and K fertilizer management on claypan soil fields. Therefore, a study was performed to determine if topsoil thickness could be used to improve P and K management for corn and soybean. Research was conducted on a claypan soil at the University of Missouri’s South Farm Research Center in Columbia, MO from 2009 to 2016. Each year corn and soybean were grown on 16 plots with a wide range of topsoil thicknesses. Surface soil samples for soil test P (STP) and K (STK) were collected in the early spring of 2009, 2015, and 2016. Fertilizer was applied shortly after soil sampling in 2009 and 2015 based on the University of Missouri fertilizer guidelines. Results in 2009 and 2015 showed that STP increased and STK decreased as the topsoil thickened. Most importantly, across 2015 the amount of K fertilizer needed to raise STK was 4 times greater with 18 in of topsoil than with none. These relationships show that accounting for DTC on claypan soils could help guide variable-rate P and K fertilizer applications to help raise and/or maintain STP and STK levels. Results obtained will aid stakeholders in the development of precision fertilization strategies that optimize inputs and reduce environmental harm.

Technical Abstract: Due to variable depth to claypan (DTC) across landscapes, nutrient supply from subsoils, and crop removal, precise P and K fertilizer management on claypan soil fields can be difficult. Therefore, a study was performed to determine if DTC derived from soil apparent electrical conductivity (ECa) could be used to improve P and K management for corn (Zea mays L.) and soybean (Glycine max [L.]). Research was conducted on a claypan soil at the University of Missouri’s South Farm Research Center in Columbia, MO from 2009 to 2016. Each year corn and soybean were grown on 16 plots (20 × 30 ft) with DTC ranging from 0 to 18 in. Surface (0-6 in) soil samples for soil test P (STP) and K (STK) were collected in the early spring of 2009, 2015, and 2016. Fertilizer was applied shortly after soil sampling in 2009 and 2015 based on the University of Missouri (MU) buildup recommendation. Results in 2009 and 2015 showed that STP increased 2.7 and 1.2 lb P/ac respectively, while STK decreased 9.4 and 10 lb K/ac with each 1 in increase in DTC. Most importantly, across 2015 the amount of K fertilizer needed to raise STK by 1 lb K/ac (REQK) was 4 times greater at DTC of 18 in when compared to DTC of 0 in. These relationships show that accounting for DTC on claypan soils could help guide variable-rate P and K applications to help raise and/or maintain STP and STK levels.