Response of Malt Barley to Phosphorus Fertilization Under Drought Conditions

Abstract

ABSTRACT Drought conditions are common in the northern Great Plains of the United States, affecting crop yield and quality. Phosphorus (P) fertilizer applications have been found to increase drought tolerance, although there is a lack of published work in this area. The goal of this study was to determine the effects of P fertilization on drought tolerance in malt barley (Hordeum vulgare). Here, 60 cm tall PVC columns were filled with either a silt loam that had a medium soil test phosphorus (STP) level or with the same soil diluted 1:1 (v/v) with coarse sand (low STP). Monoammonium phosphate was incorporated into the surface soil at rates equating to 0, 7.5, and 25 kg P ha− 1 (in triplicate), seeded with malt barley, and watered to maintain water contents either slightly above –1.5 MPa (dry treatment) or slightly drier than field capacity (wet control). Fertilization with P significantly increased plant biomass, root biomass, grain yield, and water-use efficiency (WUE) in the medium STP soil, but not in the low STP soil. Growth in the low STP, coarse, dry soil was apparently limited by water, not P, based on comparisons with the wet control. Fertilization of the dry medium STP soil with P increased grain yield by at least 20-fold, although this increase was not significant due to high variability. These results suggest that adequate soil P levels can substantially offset the impact of drought on barley growth and grain yield.