ALTERNATIVE CROPS Water Use and Biomass Production of Oat–Pea Hay and Lentil in a Semiarid Climate

Zentner et al., 2001). Johnson (1982) found that income variability was reduced under summer fallow and that Suitability of alternative crops in the northern Great Plains remains summer fallow maximized return to land at low yields, a question because of water limitations. Objectives were to compare water use of an oat (Avena sativa L.)–pea (Pisum sativum L.) mix low wheat prices, and high N prices. grown for hay (OPH) to that of black lentil (Lens culinaris Medikus Progress in crop breeding and management coupled cv. Indianhead) grown as green manure (BL). Water use and plant with desire to improve economic advantages of crop biomass for OPH and BL were measured near Culbertson, MT (Site rotations have resulted in attempts to establish new 1), during 4 yr. Soil water was measured by neutron attenuation. rotations in traditional fallow–grain production areas Precision-weighing lysimeters were used at Site 2, located 65 km (Campbell et al., 2002). Legumes have historically been southeast of Site 1, to measure water use. Soil was a Williams loam included in crop rotations. Concern over loss of soil (fine-loamy, mixed, superactive, frigid Typic Argiustolls). Biomass of organic matter and cost of fertilizer N prompted a rediscrops was measured biweekly. Relative feed value (RFV) based on covery of green-manure crops for semiarid wheat promeasured neutral detergent fiber and acid detergent fiber was calcuduction systems even in light of the literature base that lated. 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 suggested green-manure farming systems were not profof 14 kg ha 1 mm 1 water used under BL and 23 kg ha 1 mm 1 under itable in the Dakotas and Canadian Prairie Provinces OPH. Biomass accumulated at a rate of 21 kg ha 1 mm 1 under BL (Pieters, 1917). Conclusions from studies started in and 29 kg ha 1 mm 1 under OPH at Site 2. Hay RFV, at full bloom Montana in the early 1900’s and reported after 28and in pea, averaged 116 (Number 2 hay), and this did not change apprecia43-yr periods (Army and Hide, 1959) were similar to the bly as the crop matured to soft dough stage in oat. Oat–pea hay fits conclusions drawn by Pieters (1917). However, recent the growing conditions in the northern Great Plains and meets the studies on the Canadian Prairies show that annual leneeds of producers for high quality hay. gumes have potential as green-manure crops (Rice et al., 1993). In grain lentil–wheat rotations, there has been a gradual reduction in fertilizer N requirement after W limits crop production in the semiarid northabout 6 yr (Campbell et al., 1992). Pikul et al. (1997) ern Great Plains, and consequently, cropping opconcluded that available N limited wheat production tions are limited. Wheat (Triticum aestivum L.) is the more than did soil water in rotations where green mamajor crop in Montana, accounting for nearly 58% of nure was the sole source of N. Black lentil has been all crop receipts in 2000 (Montana Agric. Stat. Serv., identified as having good potential as a green manure 2001). There were about 1.9 million ha of wheat (70% because of low seed cost, intermediate top growth, and spring wheat) in Montana in 2000, all being nonirrigated. N yield (Townley-Smith et al., 1993). Nearly 70% of that wheat was produced on land followSuitability of alternative crops and rotations in the ing fallow. Because of climatic, economic, or cultural traditional semiarid wheat production areas remains a constraints, summer fallow is still a common practice. question. Annual legume species have different N fixaFallow has accelerated soil C loss (Rasmussen and Partion capabilities and water use efficiencies. Biederbeck ton, 1994; Aase and Pikul, 1995), soil erosion (especially and Bouman (1994) tested water use characteristics of where there are meager amounts of crop residue cover), BL, Tangier flat pea (Lathyrus tingitanus L.), chickling and development of saline seeps (Black et al., 1981). vetch (Lathyrus sativus L.), and feed pea. Annual leSoil water storage efficiency of fallow ranges from about gumes that produce high quantities of phytomass had 15 to 40% (Black and Power, 1965; Tanaka and Aase, water use efficiencies that were greater than legume 1987; Peterson et al., 1996). However, even with low species that produced less phytomass. Feed pea and water-storage efficiency, rotations that included fallow chickling vetch used water more efficiently than other were found to have the lowest level of financial risk legumes tested. Green manure may ultimately improve soil condition; however, costs associated with this pracJ.L. Pikul, Jr., USDA-ARS, Northern Grain Insects Res. Lab., 2923 Medary Ave., Brookings, SD 57006; J.K. Aase (retired), USDA-ARS, Abbreviations: ADF, acid detergent fiber; BL, black lentil grown as Northwest Irrig. and Soils Res. Lab., 3793 N. 3600 E., Kimberly, a green manure; CV, coefficient of variation; ET, evapotranspiration; ID 83341; and V.L. Cochran (retired), USDA-ARS, Northern Plains GDD, growing degree days; NDF, neutral detergent fiber; OPH, oat– Agric. Res. Lab., 1500 N. Central Ave., Sidney, MT 59270. Mention pea mix grown for hay; RFV, relative feed value; SW–BLc, spring of trade names is for the benefit of the reader and does not constitute wheat–black lentil rotation where black lentil was terminated by chemiendorsement by the USDA over other products not mentioned. Recal; SW–BLd, spring wheat–black lentil rotation where black lentil was ceived 23 Apr. 2003. *Corresponding author ([email protected]). terminated by disking; SW–CF, 2-yr rotation of spring wheat–chemical fallow (no tillage during fallow); SW–OPH, 4-yr rotation of spring Published in Agron. J. 96:298–304 (2004).  American Society of Agronomy wheat–buckwheat–fallow–oat/pea mix grown for hay; WW–OPH, 4-yr rotation of winter wheat–buckwheat–fallow–oat/pea mix grown for hay. 677 S. Segoe Rd., Madison, WI 53711 USA