Yield and selected chemical and morphological responses of several soybean cultivars to soil pH

Yield responses of soybeans to soil pH have been difficult to demonstrate on most soils in Tennessee. Yet, liming has consistently been recommended as a practice to maintain productive soils near neutral. A study was conducted with 21 soybean cultivars on a productive West Tennessee soil to evaluate several chemical and morphological characteristics of these cultivars and determine which of the characteristics had any impact on yield.

Twenty-one soybean cultivars belonging to three maturity groups (IV, V, and VI) were planted in three soil pH levels of 5.3, 5.9, and 6.8 in a split-plot arrangement of treatments in a randomized complete block design having four replications. The soil pH levels were the main plots and the cultivars were assigned to the split plots. The study was conducted on a Loring silt loam (Typic Fragiudalf) soil at Ames Plantation.

Results indicated that in 1981 as soil pH level increased from 5.3 to 6.8, single and double seeded pods on the main stem, triple seeded pods on the branches, branches per plant and leaf Ca increased. In 1982, yield, triple seeded pods on both main stem and branches, seed weight, leaf Ca, and N increased as soil pH increased. Leaf P decreased in 1982 while leaf Mn decreased as pH increased in both years of the study. Soybeans were treated with supplemental Mo in 1981 but not in 1982.

Stepwise regression suggested that leaf P-concentration or soil pH were the best single variable models, expressing 42 to 80 percent of the variation in yield for most of the cultivars in maturity group VI in 1981 and 1982, respectively.