Reducing Water Inputs with Subsurface Drip Irrigation May Improve Alfalfa Nutritive Value

Abstract

Irrigated alfalfa (Medicago sativa L.) is an important forage crop for western Kansas dairy producers. Concerns over decreasing groundwater supplies have prompted the need to develop more efficient methods of irrigation. We investigated the effects of a subsurface drip irrigation system at three levels of water inputs [70, 85, and 100% of plant evapotranspiration rates (ETr)] on resulting alfalfa production and nutritive value. Alfalfa was harvested at 0, 15, and 30 inches from established subsurface driplines within each of the three irrigation levels. Crude protein concentration and in situ dry matter disappearance, when found to be different at ETr and dripline distance combinations, tended to be greater at greater distances from the dripline and at the 70% ETr level. Fiber concentrations tended to be lower at greater distances from the dripline and at the 70% ETr level. Alfalfa yield was similar at all dripline distances and at all ETr levels in 2005 and 2007, but alfalfa yield was greater 0 inches from the dripline compared to 30 inches from the dripline in 2006. We conclude that alfalfa can be irrigated with subsurface drip systems at 70 or 85% ETr without sacrificing yield or forage nutritive value.