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Title: Pigeon pea potential for summer grazing in the Southern Great Plains

item Rao, Srinivas
item Northup, Brian

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2011
Publication Date: 12/14/2011
Citation: Rao, S.C., Northup, B.K. 2011. Pigeon pea potential for summer grazing in the Southern Great Plains. Agronomy Journal. 104(1):199-203.

Interpretive Summary: Stocker cattle are a key part of agriculture in the southern Great Plains (SGP), where they graze different forages to gain weight before entering feedlots for finishing. Stocker producers face limited amounts of high quality forage during late-summer to early fall (July to October), which requires protein supplements to improve weight gains. We applied a study to explore the function of pigeon pea, a summer annual grain legume that not normally grown in the SGP, as grazed forage for stocker cattle. The study compared the amount of forage produced, and quality of forage, of two pigeon pea cultivars, Georgia 2 (GA-2), which is an older brown-seeded cultivar, and Minnesota 8 (MN-8) a newer white seeded cultivar. From 2008 through 2010 six-one acre pastures were planted to the two cultivars (3 pastures/cultivar) in June and allowed to grow until late August. Amounts of forage produced by pigeon pea and weedy grasses and forbs were measured each year. Crossbred stocker cattle (3 to 4/pasture) were assigned to the paddocks, weighed at the start and end of grazing periods, and at the start of when cattle switched to eating pigeon pea. An average of 125 pounds/acre of weight gain was recorded over the 20(± 7) day periods when pigeon pea was actively grazed, compared to 39 lb/acre over 14(±9) day periods when cattle were preformmaly grazing grasses and weed. While the periods when pigeon pea was utilized were relatively short (14 to 28 days), average daily gains across the three years of experiment were 0.9 lbs/day. These results show there is a need for new early-maturing pigeon pea cultivars that produce more leaf, to allow for longer grazing periods.

Technical Abstract: Stocker cattle production in the southern Great Plains (SGP) faces forage quality gaps during July through September. A study was conducted in 2008 through 2010 to determine if pigeon pea [Cajanus cajan (L.) Millsp.] could fill this deficit period. Six, 0.41 ha experimental paddocks were randomly assigned to two pigeon pea cultivars; Georgia-2 (GA-2), and Minnesota-8 (MN-8). The paddocks were sprayed with glyphosphate annually for pre-plant weed control, and received 26 kg/ha P prior to planting. Seeds were inoculated, planted (2-cm deep; 60-cm row spacing; 25 kg/ha seeding rate) in late-May to early June, and fenced enclosures (9 m^2) were established to measure biomass accumulation and fractions, N concentrations, and in vitro digestible dry matter (IVDDM). Crossbred stocker cattle assigned to paddocks were weighed at start of grazing, the time when cattle shifted to grazing pigeon pea (at flowering), and end of grazing periods. Average daily gains (ADG), and total gains/ ha were calculated to identify responses (pre and post flowering of pigeon pea). The only significant effects (P< 0.05) in animal responses were time of grazing season. An average of 140 kg/ha gain was recorded for 20(±7)-day periods when pigeon pea was actively grazed, compared to 44 kg/ha for the 14(±9)-day pre-flowering periods. Average daily gains were 0.1(±0.2) and 1.0(±1) kg in the pre and post-flower periods, respectively. Results indicate the need for early-maturing pigeon pea cultivars with higher leaf:stem ratios, to provide longer grazing seasons and higher stocking rates.