Row spacing of alfalfa interseeded into native grass pasture influences soil-plant-water relations

Abstract

Interseeding alfalfa (Medicago sativa L.) can improve forage quality of grasslands by adding a high-protein species, but this runs the risk of accelerating soil water depletion. The objective was to evaluate effects of cultivar and row spacing of alfalfa on soil water balance and plant water potentials (Ψ) of two upright-type cultivars, NuMex Bill Melton and WL 440HQ, and a prostrate-type Falcata-Rhizoma blend, interseeded into native grasses in October 2015 near Lubbock, Texas. Alfalfa was interseeded at 36-cm (narrow) and 71-cm (wide) row spacings. Soil volumetric water content (VWC) and midday Ψstem and Ψleaf were measured weekly in 2017 and 2018 growing seasons. Soil VWC was not affected by alfalfa cultivars (P >.05), whereas alfalfa row spacings differed (P .05). Soil water depletion increased with alfalfa crown density (r =.60, P