Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/5/2008
Publication Date: 7/1/2008
Citation: Rao, S.C., Northup, B.K. 2008. Planting date affects production and quality of grass pea rorage. Crop Science. 48:1629-1635. Interpretive Summary: The rising cost of commercial inorganic fertilizer has renewed interest in legumes to reduce the input of commercial fertilizers. Legumes fix atmospheric nitrogen and make it available to both legume and subsequent non-legume crops. Grass pea is a cool season grain legume that has been noted for its tolerance to dry conditions and adaptability to difficult environments. Proper agronomic practices and planting date are important management factors necessary to maximize the yield of grass pea. This study examined the influence of planting date (March 15, April 01, and April 15) on the yield and nutritive values of grass pea in the southern Great Plains Region. The differences in standing crop were minimal among planting dates, however nitrogen accumulation varied. Nitrogen accumulation was 135 kg N ha-1 for March 15, 153 kg N ha-1 for April 01, and 125 kg N ha-1 for April 15, planting dates. These results suggest that planting grass pea in southern Great Plains Region on or before April 01, will maximize N accumulation and provide high quality forage when winter wheat forage quality declines and summer perennial grasses are unavailable for grazing animal.
Technical Abstract: The rising cost of commercial nitrogen (N) fertilizer has generated interest in including legumes in cropping systems. Research on agronomic practices required to integrate legumes into cereal-based systems of the Southern Great Plains (SGP) is required. This study examined how planting date affected the productivity of grass pea (Lathyrus sativus L.). Experimental plots (3 x 20 m, n=3) were disked and fertilized with 60 kg ha-1 P2O5, and inoculum-treated (Rhizobium leguminosarum) seeds (cv ‘AC-Greenfix’) were planted at 60 kg ha-1 on 15 March, 01 April and 15 April in 2004, 2005 and 2006. Standing crop, N concentration, N accumulation ha-1, and in vitro digestible dry matter (IVDDM) of grass pea forage were determined on samples collected at seven Julian dates (JD) since planting. Significant (P<0.05) interactions occurred in response of standing crop (JD x year), N concentration and IVDDM (JD x year x planting date), and accumulated N (JD x year; JD x planting date). Peak standing crop in 2004, 2005 and 2006 was 3900, 5800 and 3500 kg ha-1, respectively. Maximum accumulated N related to years was 115 to 157 kg ha-1 between JD 165 and JD 195. Peak N accumulation related to planting dates was 125 to 153 kg ha-1 between JD 180 and JD 210. Grass pea was flexible in response to spring planting dates, and can be sown during a 30-d period to maximize standing crop and N accumulation for use as green manure or forage in the (SGP).