The effect of honey mesquite (Prosopis ghndulosa var. glanhlosu Torr.) control on herbnceous growth dynamics, forage production, and root and crown biomass was investigated in 1979 and 1980 on a site aerially treated with a 1:l mixture of 2,4,5-T plus picloram at 0.6 kg/ha in May 1974. Density, height, and canopy of honey mesquite trees 5 years after treatment were 248 plants/ha, 0.9 m, and 3.1%, respectively, compared to 963 plants/ha, 2.2 m, and 34.670, respectively, in the adjacent untreated control plot. Yet, there were no differences between sprayed and untreated plots after 6 and 7 growing seasons relative to species composition, growth dynamics, and production of herbaceous plants. Averaged across years and treatments, estimated aboveground net primary production was 2,525 kg/ha. Crown and root biomass in the top 10 cm of the soil profile averaged 685 and 3,837 kg/ha, respectively, with no significant treatment or year effects. Lack of treatment difference partially validates a conceptual model presently used for economic analysis of herbicide sprays for honey mesquite control. Further, it supports the hypothesis that honey mesquite trees provide critical habitat for the more productive midgrasses indigenous to this site; and that elimination of this habitat in sparse stands of the shrub subsequently limits post-treatment herbage response. Dense stands of honey mesquite often suppress herbage production with the degree of suppression primarily a function of stand density and the innate productivity potential of the treated site
Herbage quality of meadow bromegrass [Bromus biebersteinii Roem and Schult.], smooth bromegrass [Bromus inermis Leyss.], intermediate wheatgrass [Agropyron intermedium (Host) Beauv.], Russian wildrye [Elymus junceus Fisch.], crested wheatgrass [Agropyron cristatum (L.) Gaertn.]in mixtures with alfalfa [Medicugo s&w L.] or cicer milkvetch [Astragduscicer L.] and with the 2 legumes in pure stands at 2 dates of harvest (June 5, June 26)and with 4 rates of fertilizer (0 kg N/ha-O kg P/ha, 0 kg N/ha-22 kg PI ha, 45 kg N/ha-O kg P/ha, 45 kg N/ha-22 kg P/ha) was studied in western Nebraska in 1977 and 1978. Soil at the study site was a loam (Typic Argiustoll) and average annual precipitation is 386 mm. Alfalfa-grass mixtures maintained a higher percentage crude protein than the respective cicer milkvetch-grass mixtures, with the alfalfa-Russian wlldrye mixture producing the highest percentage crude protein. Percentage in vitro dry matter digestibility (IVDMD) of the cicer milkvetch-Russian wildrye &xture was the highest of all mixtures, and the percentage IVDMD of the cicer milkvetch-crested wheatgrass mixture the lowest. Herbage quality was higher for the June 5 harvest than the June 26 harvest. Percentage IVDMD of regrowth, which developed after the June harvests, was higher for plots harvested on June 26 than on June 5. Fertilizer rates had a variable effect on herbage quality. Russian wildrye-legume mixtures generally maIntained the highest level of herbage quality. Herbage quality of cool-season perennial grasses grown under various fertilization and harvest schemes in Canada and western United States is well documented (Mason and Miltmore 1959,
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