Foliage Injury, Nutrient Intake, and Yield of Soybeans as Influenced by Foliar Fertilization¹

Abstract

Yield response to foliar fertilization (N, P, K, S, solution) of soybeans [Glycine max (L.) Merr.] in Iowa has stimulated interest in the use of the same or similar materials in other soybean production areas. Inconsistent yield increases were obtained in Iowa, and it is unknown whether foliar fertilization is feasible where environmental conditions, type of soybeans, and other factors are different from those in Iowa. Field experiments were conducted on a Tifton sl (fine‐loamy, siliceous, thermic, Plinthic Paleudult) and on a Norfolk sl (siliceous, thermic, Typic Paleudult) in the Coastal Plain region of Georgia. Urea K‐polyphosphate mix (urea, K‐polyphosphate, and K2SO4) and NH4‐polyphosphate mix (urea, NH4‐polyphosphate, KCl, and K2SO4) treatments were foliar sprayed on soybeans during the seed filling period. All spray treatments damaged the foliage and suppressed yields with the greatest damage to foliage occurring with repeated application of foliar fertilizer. Three sprayings of a mixture containing 28, 2.9, 9.5, and 1.7 kg N, P, K, and S/ha resulted in an average (two sites) yield decrease of 10.9% for the K‐polyphosphate mix and 17.6% for the NH4‐polyphosphate mix. Weight of pods, whole plants, or seeds, and seed quality were not affected by spray treatments. Absorption of applied nutrients into leaf tissue and translocation to reproductive tissue were detected only in a few instances. Increased N levels were detected only in seeds, and P levels increased only in leaves, while K levels were not changed. Under the conditions of this study, foliar N, P, K, and S fertilization of soybeans does not appear practicable for increasing yields.

Potential for foliar phosphorus fertilisation of dryland cereal crops: a review

“…The appearance of leaf burn where foliar droplets have been applied has been observed in many studies (Barel and Black 1979b;Parker and Boswell 1980) and generally is not detrimental to the plant. However, some studies have resulted in leaf burn so severe that part or all of the leaf dies, causing a lower yield for foliar-applied treatments.…”

“…However, some studies have resulted in leaf burn so severe that part or all of the leaf dies, causing a lower yield for foliar-applied treatments. A study using urea, KH 2 PO 4 mix and ammonium polyphosphate mix was reported to significantly lower yield of soybeans compared with the control (Parker and Boswell 1980). This was due to considerable leaf injury through salt loading of the leaves, with P applied at 3, 6 and 9 kg P ha -1 but a corresponding N rate of 28, 56 and 84 kg N ha -1 .…”

Agricultural Management of Enhanced-Efficiency Fertilizers in the North-Central United States

“…Several studies have evaluated soybean response to foliar fertilizer applied at early vegetative growth stages (19,20) or during late reproductive growth stages (17,42,53). These studies evaluated mixed nitrogen, phosphorus, potassium, and sometimes sulfur fertilizer sources (17,19,42,43) and several studies were conducted under optimal soil test fertility levels (19,20,42). Most of the reported responses to foliar fertilizer applications did not justify the application expense (7,19,42,43).…”

Foliar Potassium Fertilizer Sources Affect Weed Control in Soybean with Glyphosate

“…Several studies have evaluated response of soybean to foliar fertilizer mixtures applied during early and late stages of soybean development (6,9,17). Soybean response to a foliar application of K 2 SO 4 increased grain yield over 10 bu/acre when compared with non-treated or MgSO 4 controls on a low to medium soil test K (16).…”