No abstract

The disk meter technique of estimating forage dry matter yields has been used by many researchers in recent years. However, few comparisons have been made on which size, weight, and technique of use gives the most precise results, or if species of grass has any effect on the results. A simple‐disk and a weighted‐disk were evaluated as techniques for estimating forage dry matter yield on several grasses. Predictions of dry matter yield were based on settling heights measured with the meters. Yield estimates were made on annual ryegrass (Lolium multiflorum Lam.) pastures, and swards of bahiagrass (Paspalum notatum Flügge), digitgrass (Digitaria decumbent Stent.), and limpograss [Hemarthria altissima (Poir.) Stapf et C. E. Hubb]. Separate linear regression relationships between dry matter yield and settling height were calculated (Y = bX). Correlation coefficients (r) of 0.79 to 0.99 with most r values exceeding 0.92 were found between height and dry matter yield. Standard deviations from regression ranged from 73.2 to 282.4 kg/ha for different sampling techniques, disk sizes, and grass types. Increasing the disk size (0.25 to 0.75 m2) increased the correlation and regression coefficients, and reduced standard error from regression. The largest disk provided contact with a greater area of biomass and resulted in yield estimates of greater precision, but the additional precision obtained by using the 0.75‐m2 disk over the 0.50‐m2 disk does not offset the reduced ease of use of the larger disk. In addition, the 0.25‐ and 0.50‐m2 disks gave more uniform b values across grasses than the other disks. Thus, one combined b value was found to adequately describe the relationship between settling height and dry matter yield for all four grasses with these two disks. These results substantiate that the disk meter is a useful, practical, and versatile instrument for estimating forage dry matter yield in small plots and grazed pastures. The simple‐disk meter proved to be equal to the weighted meter for predicting dry matter yield, however, the simple‐disk has the advantage over the weighted meter because it is much easier to use in the field.

Synopsis Quantitative theory indicates that gain per animal is constant as stocking rate is increased to a “critical” point. Beyond this point gain per head is inversely related to stocking rate. Gain per acre increases linearly as stocking rate is increased to the “critical” point, then decreases linearly with further increases in stocking rate.

This study was conducted in central Brazil on a sandy loam soil which under normal conditions receives no fertilizer. The K, P, Ca, Mg, Cu, Mn, Fe, and Zn contents were determined on six grasses: Meilinis minutiflora Beauv., Digitaria decumbens Stent., Pennisetum purpureum Schum., Pennistetum clandestinum Hochst., Cynodon dactylon Pers., and Panicum maximum Jacq. var. ‘Gondlyodes Doell’ Significant decreases in K, P, Mg, Cu and Fe in the forages (P < .01) occurred with advance in plant age from 4 to 36 weeks. The average K content for all grasses at 4 weeks of age was 1.42% and at 36 weeks of age 0.30%. Kikuyugrass had the highest K content at 36 weeks of age (0.54%). The average P content for all grasses was 0.26% at 4 weeks and 0.12% at 36 weeks. Pangolagrass appeared to be a poor source of P at all ages studied (average 0.12%). Nitrogen fertilizer had no effect on any of the minerals studied except for Mn which increased with N fertilization. Under the conditions of the experiment, the forages could be deficient in K and P for cattle and borderline in zinc.

During in vitro digestion of forages by rumen microorganisms in polycarbonate centrifuge tubes, forage particles formed dense mats which were raised above the level of media by entrapped gas. This did not occur with polyethylene centrifuge tubes. In vitro organic matter digestion was higher in polyethylene than in poly-carbonate tubes. Vacuum infiltration of water into samples prior to inoculation increased in vitro digestion with both types of tubes but to a greater extent with samples of high than of low digestion. Regression analysis of in vivo digestibility on in vitro digestion showed that the lowest residual standard deviation was with polyethylene tubes and vacuum infiltration, but omission of vacuum infiltration gave satisfactory results.