Soybean yield and composition responses to potassium management alternatives following long-term no -till

Xinhua Yin, Purdue University

Abstract

Surface broadcasting is still the predominant mode of potassium (K) fertilizer application for soybeans in no-till (NT) systems even though K is relatively immobile and vertical soil K stratification is often evident in NT fields. Soybean yield in conservation tillage systems may be improved by banding K fertilizer below seeding depth. Certain soybean seed quality parameters may also be affected by K fertilizer management systems since K is so essential in plant enzymes. The objectives of this research were to investigate K nutrition, yield, and quality responses of soybeans resulting from alternate K fertilizer placements (band placement versus surface broadcasting, and applied directly before soybeans versus residual effects associated with application to previous corn) in various tillage (such as zone-till, fall disk, and NT) and row-width systems imposed after long-term NT. All 17 experimental site-years had a minimum 5-yr NT history prior to treatment initiation. Soybean responses to K placement were generally unaffected by tillage and row width (from 18 to 76 cm) on medium- to high-exchangeable K soils. Trifoliate leaf K concentrations were increased by K application even on medium- to high-testing K soils. Yield responded positively to direct K fertilization most frequently on low K soils. Despite vertical soil K stratification, deep banded K increased yield, relative to broadcast K, only on low K soils and only when most soybean rows were in close proximity to fertilizer bands. On low-testing soils, leaf K concentrations and yield were over 10% higher for NT soybeans planted over previous corn rows, compared to those between rows, even when corn received no K fertilizer. Soybean seed K concentrations increased up to 3 g kg−1 after both direct and residual K applications. Potassium fertilization increased daidzein, genistein, and total isoflavone concentrations in soybean seeds. Seed isoflavone concentrations were positively correlated to yield, seed K and oil concentrations. There was no apparent yield or seed composition benefit from banded versus broadcast K application except on low K soils. Possible preceding corn row impacts on horizontal soil K distribution should be considered when narrow-row NT soybeans follow corn on soils with low to medium K concentrations.

Degree

Ph.D.

Advisors

Vyn, Purdue University.

Subject Area

Agronomy|Soil sciences

COinS