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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #329621

Title: Claypan depth effect on soil phosphorus and potassium dynamics

item CONWAY, LANCE - University Of Missouri
item Yost, Matt
item Kitchen, Newell
item Sudduth, Kenneth - Ken
item MYERS, DAVID - Dupont Pioneer Hi-Bred

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/21/2016
Publication Date: 7/31/2016
Citation: Conway, L.S., Yost, M.A., Kitchen, N.R., Sudduth, K.A., Myers, D.B. 2016. Claypan depth effect on soil phosphorus and potassium dynamics. In: International Conference on Precision Agriculture Proceedings, July 31-August 3, 2016, St. Louis, Missouri. Available:

Interpretive Summary: Substantial soil erosion during decades of row crop production on claypan soils has led to varying topsoil thickness across fields in the Midwest. This contributes to variable yields across fields and landscapes. Understanding how this erosion has affected crop nutrient removal and long-term soil test change is crucial for maximizing grower inputs. Research was conducted near Columbia, MO from 2009 to 2016 to determine if accounting for topsoil thickness could enhance fertility management, as well as enhance current University of Missouri fertility guidelines under an annual corn and soybean rotation. Results indicated that phosphorus and potassium removal and soil test phosphorus increased as topsoil thickness increased. Conversely, soil test potassium and the amount of fertilizer required to raise soil test potassium levels decreased as topsoil depth increased. These findings illustrate that accounting for topsoil thickness could result in more efficient use of phosphorus and potassium fertilizers. This information will help farm advisors and farmers in determining efficient and profitable amounts of fertilizer to apply.

Technical Abstract: Understanding the effects of fertilizer addition and crop removal on long-term change in spatially-variable soil test P (STP) and soil test K (STK) is crucial for maximizing the use of grower inputs on claypan soils. Using apparent electrical conductivity (ECa) to estimate topsoil depth (or depth to claypan, DTC) within fields could help capture the variability and guide site-specific applications of P and K. The objective of this study was to determine if DTC derived from ECa could be used to improve P and K management for corn (Zea mays L.), soybean (Glycine max [L.]), and switchgrass (Panicum virgatum L.). Research was conducted at the University of Missouri’s South Farm Research Center in Columbia, MO from 2009 to 2016. Each year, corn, soybean, and switchgrass were grown on 16 plots (5.2 or 6.1 × 10 m) with DTC ranging from 0 to 94 cm. Soil ECa data were collected in the spring of 2009 using a DUALEM-2S, and were calibrated to measured DTC. Surface (0-15 cm) soil samples for P and K were collected in the early spring of 2009, 2015, and 2016. Fertilizer was applied shortly after soil sampling in 2009 and 2015. Crop type did not influence results so data were analyzed across crops. Results showed that DTC affected STP, STK, P buffering index (PBI), and the amount of K2O required to raise STK 1 kg ha-1 (RK). The PBI increased from -16 to 12 kg P2O5 ha-1 as DTC increased 0 to 44 cm. The RK increased from 1.75 to 11 kg K2O ha-1 as DTC increased from 0 to 40 cm. These relationships show that soils with shallow DTC likely need less fertilizer K, but more fertilizer P to achieve and sustain desired STP and STK levels, with the opposite occurring on soils with deeper DTC. Accounting for these differences could help guide variable-rate P and K applications, especially on fields with high variability of DTC. Therefore, accounting for DTC derived from ECa could be used to enhance P and K management on claypan soils.