Effect of boron on alfalfa yield and quality at various water regimes

Abstract

Boron (B) application on B-deficient soil may improve alfalfa (Medicago sativa L.) yield and quality. The objective of the first study was to identify the effects of foliar-applied B on yield and forage quality of irrigated alfalfa. A two-year study was conducted in 2015/16 at Creston and Dillon, MT. The initial soil B at the Creston and Dillon sites was 0.2 and 0.8 mg kg -1, respectively. The study was designed as a randomized complete block design with four replications of five B rates: 1) 0, split-applications of 2) 0.56, 3) 1.12, 4) 2.24, and a one-time application of 5) 2.24 kg ha -1. Boron fertilization increased (P <0.05) plant B content at both locations. Application of B increased (P < 0.05) alfalfa yield only in the second cutting in 2015 at Dillon, but the influence of B was not observed in any other cuttings, nor in the total yields for either years or location. Forage quality was not affected (P >0.05) by B application. The results of this study suggested no effect of foliar-applied B on alfalfa yield or quality. The objective of the second study was to determine the effect of foliar-applied B at various water regimes on alfalfa yield and quality. The study was conducted in 2016-17 at Creston, MT. Soil at this site contained 0.2 mg B kg -1. The experiment was conducted using a split-plot design with three rates of water regimes as main-plot and five B rates as sub-plot factors. The three water regimes were rainfed, 100 percent evapotranspiration (ET), and 50ET. Boron rates and timing of application was the same as in the first study. Irrigation increased total alfalfa yield by 45% and 12% in 2016 and 2017, respectively, with no yield difference between 100ET and 50ET. In 2016, irrigation decreased (P <0.01) forage nutrient quality in the second cutting but had no effect in 2017. There was no effect of B on yield (P >0.08) for either year. Overall, this study suggested that the foliar-applied B on a B-deficient soil did not increase alfalfa yield or quality, regardless of water regime, or year.