Potassium Requirements for Corn in North Dakota: Influence of Clay Mineralogy

Abstract

Use of dry soil K soil test was most predictive of corn response in North Dakota. Consideration of clay chemistry increased the prediction of yield response by the K soil test. A smectite/illite ratio of 3.5 separated the sites into one requiring a higher critical K soil test value and one with a lower critical K value. Due to initially high soil test K values, K soil test correlation and calibration for corn in North Dakota has previously not been intensely investigated. Potassium fertilizer rate experiments were conducted on 25 sites from 2014 to 2016. The previously published soil test K critical value of 150 mg kg−1 predicted crop response correctly at 16 of the sites. Alternative soil test methods, including a resin‐based extraction at two timings, sodium tetraphenylboron extractions at two timings, and 1 mol L−1 NH4OAc extraction using moist soil were conducted; however, the currently used 1 mol L−1 ammonium acetate extraction using dry soil was most predictive. Mineral analysis of soil from all sites was determined for potassium feldspar content of whole soil, and clay species, particularly smectite, illite, and kaolinite, were determined on the clay fraction. Cluster analysis revealed that a smectite/illite ratio of 3.5 separated the sites into two unique K response data sets. Sites with a smectite/illite ratio >3.5 had a K critical level of ∼200 mg kg−1, whereas sites with a smectite/illite ratio <3.5 had a K critical level of ∼130 mg kg–1. For soils with K soil tests between 130 and 200 mg kg−1, consideration of clay chemistry improves the predictability of crop yield response with K fertilization.

Potassium availability: synchronizing nutrient supply and plant demand through 4R nutrient stewardship

“…These are aligned in layers with spaces between them where water and nutrients can reside and specifically where K is attracted to negative charges produced within the structure of the minerals. In North Dakota, Breker et al (2019) identified the ratio of an expansible mineral, smectite, to another 2:1 phyllosilicate, illite, as an additional factor to soil‐test K for identifying different critical levels in soil. They reported a critical level of 200 ppm K when smectite/illite ratios were above 3.5, whereas below that ratio, the critical level was 130 ppm K. Greater amounts of smectite, the mineral that retains K in the interlayer spaces when dehydrated, resulted in a need for higher soil‐test K for optimum crop yield.…”

Irrigated soybean response to granular fertilizer potassium application timing

“…Crop nutrient management practices are usually based on soil‐test results that predict whether the soil contains sufficient plant‐available nutrients to produce maximal crop yield and recommend fertilizer when nutrient availability is below optimum. The accuracy of soil tests for identifying K‐deficient soils varies among soils and geographic areas but, as a general rule, soil tests for K availability are reasonably accurate (Barbagelata & Mallarino, 2013; Breker et al., 2019; Slaton, Golden, DeLong, & Mozaffari, 2010; Williams, Parvej, Holshouser, Frame, & Reiter, 2018). The weakest link of soil‐test‐based fertilizer recommendations involves the calibration of the fertilizer‐K rate required to maximize yield for a given soil‐test value.…”

Potassium transformation in clay soil with contrasting K budgets in long‐term experiment

“…The K budget at field scale (Benbi & Biswas, 1999;Yadvinder-Singh et al, 2004;Yang, Sun, & Zhang, 2014) and soil K test (Mallarino, Barbagelata, & Wittry, 2004;Yang et al, 2014) or estimated exchangeable K are often used to manage K over large agricultural areas (Bailey, 1983;Tan, Jin, Jiang, Huang, & Liu, 2012). While soil test critical K levels depend on clay mineralogy (Breker et al, 2019), the contribution of non-exchangeable K…”

“…The K budget at field scale (Benbi & Biswas, 1999; Yadvinder‐Singh et al., 2004; Yang, Sun, & Zhang, 2014) and soil K test (Mallarino, Barbagelata, & Wittry, 2004; Yang et al., 2014) or estimated exchangeable K are often used to manage K over large agricultural areas (Bailey, 1983; Tan, Jin, Jiang, Huang, & Liu, 2012). While soil test critical K levels depend on clay mineralogy (Breker et al., 2019), the contribution of non‐exchangeable K (Hinsinger, 2002; Lal, Swarup, & Singh, 2007; Rupa, Srivastava, Swarup, & Singh, 2001) or interlayer K (Hinsinger & Jaillard, 1993; Øgaard & Krogstad, 2005) to plant K uptake may be substantial. Hence, soil test K quantified only as exchangeable K appears to be insufficiently informative to determine soil K supply capacity (Cox, Joern, Brouder, & Gao, 1999; Habib et al., 2014).…”