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Colorado State University (2010)

GRASS AND GRASS-LEGUME MIXES FOR IRRIGATED PASTURE USING ORGANIC PRODUCTION METHODS

Booher Matthew R.

Titre : GRASS AND GRASS-LEGUME MIXES FOR IRRIGATED PASTURE USING ORGANIC PRODUCTION METHODS

Auteur : Booher Matthew R.

Université de soutenance : Colorado State University

Grade : Master of Science 2010

Résumé partiel
Species selection and fertility management are two of the greatest challenges facing producers of organic pasture. The objectives of this study were to : 1. Identify irrigated grass and grass-legume mixtures that possess the productivity, durability, and forage quality to meet the needs of organic dairies in the western US. 2. Evaluate the use of legumes and compost as nutrient sources for pastures being managed in accordance with organic protocols. Research was conducted for two years at the Agricultural Research, Development, and Education Center located about 4 km south of Wellington, CO. Four grass mixes : tall fescue (TF), hybrid wheatgrass-tall fescue-hybrid brome (HWG-TF-HB), orchardgrass-meadow brome-smooth brome (OG-MB-SB), and orchardgrass-meadow brome-Kentucky bluegrass (OG-MB-KB), were established in fall 2007. In 2008, plots received either a compost treatment of 22.4 Mg ha-1, or were part of a control set that received no compost. Plots were harvested six times in 2008 to simulate rotational grazing, and dry matter (DM) yield, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were determined at each cutting. Fertility (compost) had no effect in 2008. Total DM yield of TF (10,864 kg ha ha-1) was higher than OG-MB-SB (9,241 kg ha ha-1) and OG-MB-KB (8,079 kg ha ha-1). Dry matter yield of TF in late-September was 120% higher than the other grass mixes. In general, forage contained higher CP and lower NDF and ADF as the season progressed, resulting in increased forage quality over time. Averaged across cutting date, CP of TF (19.8 %) was 9% lower than the other grass mixes ; however, CP remained adequate to meet most ruminant needs for all grass mixes at all cutting dates. In 2009, the 22.4 Mg ha ha-1 compost fertility treatment was divided to include an 11.2 Mg ha ha-1 treatment and a 0 Mg ha ha-1 control, in an effort to observe nitrogen mineralization from previous compost applications. Also in 2009, alfalfa, birdsfoot trefoil, sainfoin, and white clover were interseeded into the 2008 control plots to observe legume effects on yield and forage quality. Yield and quality data were taken for five cuttings in 2009. As a result of a low level of nitrogen in the compost, fertility had no effect on yield or quality in 2009. Total DM yield in 2009 averaged about 45% less than in 2008. Total DM yields of TF and HWG-TF-HB averaged 23% higher than the other grass mixes. Crude protein content averaged about 6 percentage points lower in 2009 than in 2008, most likely due to nitrogen deficiency. Similar to 2008, TF was lower in CP than the other grass mixes. In general, forage quality improved over the season. On average, TF (56.2 %) and HWG-TF-HB (56.9 %) had a 4% higher NDF content than the other grasses, while all grass mixes had a similar average ADF content of around 32%. Because legumes did not significantly contribute to harvested yield until cuttings 4 and 5 in 2009, cuttings 1-3 were not included in analyses of the legume treatments.

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Page publiée le 13 septembre 2010, mise à jour le 22 février 2019