Estimates of hay yields are frequently desirable for purposes of measuring fertilizer response, studying effects of management and cultural practices, and determining animal units that can be maintained on forage produced from a given area. Estimates of forage yield can be obtained by cutting and weighing, but the random collection of forage samples for estimating yields is not a viable alternative in some cases. A convenient, quick, and accurate method of determining forage yields in situ would benefit research workers and those involved in commercial and extension agriculture operations. The purpose of this investigation was to determine the suitability of using a disk meter to estimate dry matter yield of mixed swards. A 0.5m2 disk meter was constructed from hardboard paneling, steel pipe, and a flange. Paired disk meter readings and dry matter yields from clipping were taken from 708 swards used for hay production in 1978. Swards consisting of cool season grasses, legumes, and weeds were characterized into 14 categories according to species composition and growth stage. Regression equations were determined for each category from paired disk readings and dry matter yields from clippings. The slopes of the regression lines for the different categories were not significantly different. The coefficient of determination (r2) was 0.82 when using a single regression line for all categories. The points of intercept of the regression lines on the vertical axis for the different categories were different with a definite trend for regression lines for first cutting swards to intercept higher than regression lines for aftermath. The formula which best described the relationship between disk reading and yield was: yield estimate = intercept for category + 183 (disk reading) − 1.73 (disk reading)2. In order to test the disk meter and formula method, yields on 40 swards were determined independently using two methods. The correlation coefficient between sward yields estimated using the disk meter and formula and sward yields estimated using weighed clippings was +92.
Cool‐season forage species are of major importance to the livestock industry in the northeastern part of the United States. Growth of these species is characterized by periods of high production followed by periods of low production. Purpletop [Tridens flavus (L.) Hitchc.], a warm‐season grass species, makes its major growth during the summer months when cool‐season species are unproductive. It may have potential for reducing seasonal variations in forage production when grown in association with cool‐season species. In order to evaluate purpletop for forage purposes, more information is needed on its soil requirements and agronomic characteristics. In this investigation nine indigenous purpletop stands were studied relative to edaphic factors, management, and plant characteristics associated with the stands. A stepwise regression procedure was used to determine soil properties associated with the occurrence of purpletop. The sand fraction in the top 15 cm of the soil profile, as determined by a hydrometer method, was more closely associated with the occurrence of purpletop than any other factor studied. Soil pH, available P, K, Ca, and cation exchange capacity influenced the presence of purpletop in a complex interrelationship. Purpletop was found growing under different pH's, fertilities, and grazing systems, although none of the swards was under intensive management. Number of leaves (5.7), plant height (114 cm), panicle length (29.2 cm), blade length (40.8 cm), and blade width (12.7 mm) did not vary among sites, suggesting little genetic variation among indigenous populations of purpletop in West Virginia. Forage concentrations of P (0.21%), K (1.44%), Ca (0.22%), and Mg (0.14%) varied among sites but were related to soil levels of these minerals. No obvious problems were found that would suggest poor forage potential. Further investigations are needed to determine its place as a forage in livestock programs.
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