Water use and biomass production of oat-pea hay and lentil in a semiarid climate

Suitability of alternative crops in the northern Great Plains remains a question because of water limitations. Objectives were to compare water use of an oat (Avena sativa L.)—pea (Pisum sativum L.) mix grown for hay (OPH) to that of black lentil (Lens culinaris Medikus cv. Indianhead) grown as green manure (BL). Water use and plant biomass for OPH and BL were measured near Culbertson, MT (Site 1), during 4 yr. Soil water was measured by neutron attenuation. Precision-weighing lysimeters were used at Site 2, located 65 km southeast of Site 1, to measure water use. Soil was a Williams loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls). Biomass of crops was measured biweekly. Relative feed value (RFV) based on measured neutral detergent fiber and acid detergent fiber was calculated. Biomass under OPH was 34 and 46% greater than with BL at Sites 1 and 2, respectively. At Site 1, biomass accumulated at a rate of 14 kg ha-1 mm-1 water used under BL and 23 kg ha -1 mm- 1 under OPH. Biomass accumulated at a rate of 21 kg ha- 1 mm-1 under BL and 29 kg ha -1 mm -1 under OPH at Site 2. Hay RFV, at full bloom in pea, averaged 116 (Number 2 hay), and this did not change appreciably as the crop matured to soft dough stage in oat. Oat—pea hay fits the growing conditions in the northern Great Plains and meets the needs of producers for high quality hay