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The cool-season pulse grass pea (GP, Lathyrus sativus L.) has the potential to provide late-spring forage in the southern Great Plains (SGP), but genetic materials for development of new cultivars is limited. Our objective was to evaluate seasonal forage production and grain yield of 10 new Mediterranean-origin GP lines, in central Oklahoma. Replicate (n = 3) plots (3 by 10 m) were disked, fertilized (60 kg ha-1 P2O5), and sown (60 kg seed ha-1) in 60 cm rows with GP lines 190, 288, 289, 290, 299, 387, 390, 736, B22, B111, and AC-Greenfix (control) that were treated with inoculum (Rhizobium leguminosarum) during early March in 2007, 2008, and 2009. Whole plant samples were collected 59, 73, 94, and 115 d after planting. Biomass collected on Day 115 was separated into seed and nonseed biomass. Biomass accumulation, N concentration and nongrain digestibility showed significant (P ≤ 0.05) line, year, and sampling date effects. Grain biomass, N concentration and digestibility also showed significant line and year effects. AC-Greenfix produced the most nongrain biomass each year [2499 kg ha-1 for AC-Greenfix vs. an average of 1899 (±145) kg ha-1 for the other 10 lines] and sampling date. Line × year interactions for grain biomass was statistically significant, with 2008 being the most productive year for all lines. Additional development is needed for these new Mediterranean GP lines to perform with the same consistency as AC-Greenfix in the SGP. [ABSTRACT FROM AUTHOR]

Sources and methods of use of organic nitrogen (N) in the southern Great Plains (SGP) need testing to find alternatives to increasingly expensive inorganic fertilizer. We examined the function of grass pea (Lathyrus sativus L.), a cool-season pulse, as a preplant N source for continuous, no-till winter wheat (Triticum aestivum L.). The study was conducted in central Oklahoma (35°40'N, 98°00' W, elevation 414 mast) from 2004 to 2008, on three replicate blocks of four experimental plots (6 by 10 m). Inoculated grass pea seed ('AC-Greenfix') was sown during late summer fallow (mid-August) in one randomly chosen plot per block (75 kg ha-1, 60-cm rows; 75% germination). Three additional plots per block mimicked summer fallow with 0 (control) 40 or 80 kg N ha-1 inorganic fertilizer applied. All treatments were repeated on the same plots throughout the study. Samples were collected from grass pea plots at flowering in early October to define aboveground biomass and analyzed for N concentration and digestibility. Aboveground biomass of grass pea was shredded with a flail mower and left on the soil surface, fertilizer treatments were applied, and wheat ('Jagger') was sown (100 kg ha-1, 20-cm rows). Aboveground wheat biomass was collected at three growth stages (elongation, flowering, physiological maturity) and analyzed for N concentration. Grass pea aboveground biomass contained enough N to meet the needs of wheat at planting in only 1 yr. Wheat biomass and amounts of N in wheat aboveground biomass in response to grass pea were intermediate between the 0 and 40 kg applied N ha-1, as was yield and N accumulated in wheat grain. Therefore, grass pea was not effective as a preplant source of N for continuous no-tilt winter wheat in the SGP. Additional research is required to define factors that limit the function of grass pea as a source of N for continuous no-till winter wheat and its potential function in other crop rotations. [ABSTRACT FROM AUTHOR]

The rising cost of commercial nitrogen fertilizers indicates that additional research is needed concerning agronomic practices required to integrate legumes into cereal-based cropping systems. This study examined how planting date affects the productivity of grass pea (Lathyrus sativus L.) in central Oklahoma. Experimental plots (3 by 20 m, n = 3) were disked and fertilized with 60 kg P2O5 ha-1, and inoculum-treated (Rhizobium leguminosarum) seeds ('AC-Green- fix') were planted at 60 kg ha-1 on 15 March, 1 April, and 15 April in 2004, 2005, and 2006. Biomass, N concentration, N accumulation per hectare, and in vitro digestible dry matter (IVDDM) of grass pea forage were determined on samples collected at 7 d of the year (DOY) after planting. Significant (P < 0.05) interactions occurred in response of biomass (DOY × year), N concentration, and IVDDM (DOY × year × planting date), and accumulated N (DOY × year; DOY × planting date). Peak biomass 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 DOY 165 and DOY 195. Peak N accumulation of 125 to 153 kg ha-1 occurred between DOY 180 and DOY 210. Grass pea is flexible in response to spring planting dates, indicating that it can be sown as a green manure or forage crop during a 30-d period in the southern Great Plains and still maximize biomass and N accumulation. [ABSTRACT FROM AUTHOR]