Changes in Herbage Production and Botanical Composition in An Orchardgrass Hayfield Under Winter Grazing.

Management strategies to extend the grazing season and reduce the amount of hay to be fed, can improve the profitability of forage based livestock systems. The objective of this study was to compare the effect of two winter grazing managements systems on herbage production and botanical composition in an orchardgrass hayfield at the WVU Reedsville Experimental Farm (Preston County, WV). The experiment was conducted in an area under hay production in spring (first cut) and summer (aftermath), and for grazing in fall and winter. Stockpile started after August 1^st, and winter grazing was initiated in early November.  In early spring, soils in the experimental area were fertilized in (NPK) following WVU Soil Test Lab recommendation, the nitrogen application rate was 84 kg/ha and was also applied after each hay cutting.  Two winter grazing management treatments were established: Treatment 1 (TR1) consisted in leaving steers grazing in the field during the “winter grazing” period from November to January; Treatment 2 (TR2), consisted in leaving steers in the field from November to April, however, between January and April the animals were fed with haylage. In each treatment, four steers (Angus and Hereford crossbred) were assigned to 0.81 ha plots; treatments were replicated three times.  Fifty pasture heights for biomass estimation were taken every two weeks using a 0.2 m² plate meter, along three regularly spaced transects within each plot, 1m buffer zone from the fences was kept.  These transects were also used to measure botanical composition; five clip samples at ground level were taken monthly, each sample was harvested in an area of 0.07 m² using a manual electric hedge clipper .  Samples were placed into paper bags, transported to-, and processed in- the laboratory for forage botanical composition, by manually separating into grasses, legumes, weeds and senescent material. To determine the percentage of each botanical component within plots, the biomass (kg/ha) for each component was measured.
Results indicated that for our experiment, TR1 produced in average more dry matter (DM) in the 1st hay cut than TR2. Two factors could contribute to this difference: TR1 had additional weeks of re-growth in early spring as compared to TR2, and the additional damage produced by hay feeding management and animal movements in TR2 during those additional “grazing” weeks. The aftermath yields were similar for both treatments, no treatment by year interactions were observed.  During the hay period, no statistically significant differences for cumulative dry matter yields (CumDM) were observed between treatments (9949 kg/ha for TR 1 and 9596 kg/ha for TR 2). Stockpiled dry matter (SDM) yield were 3689 kg/ha and 3619 kg/ha for TR1 and TR2 respectively, no statistically significant differences were observed. Annual production (hay + stockpile) was above 13,000 kg/ha but no differences between treatments were found. The proportion of grass in the botanical composition tended to maintain similar values during the entire hay period (first cut and aftermath) over the length of our experiment. During stockpile, differences in the proportion of grass were found between TR1 and TR2. Legumes were consistently more abundant in TR2 than in TR1, but statistically significant differences were found only for aftermath. Weeds seemed to increase in TR2, however during the hay period differences were not found between TR1 and TR2. During stockpile differences in the proportion of weeds between TR1 and TR2 were statistically significant.  The proportion of dead material was consistently similar in TR1 and TR2 and no differences were found for the first cut, aftermath or stockpile.  With appropriate fertilization and weed control, it might be possible to maintain a sustainable winter grazing in orchardgrass hayfields.