Rapid and reliable techniques for estimating herbage mass (HM) are essential for germplasm evaluation and proper grazing management. Since hand‐clipping small quadrats is time consuming, mathematical relationships between easy to use, nondestructive techniques and hand‐clipped estimates of HM (double sampling) have been utilized. This study was conducted to quantify relationships between HM and three commonly utilized nondestructive sward measurement techniques [plant height (HT), settled disk meter height (DISK), and capacitance (CAP)] in field plantings of ‘Brazos’ bermudagrass [Cynodon dactylon (L.) Pers.]. Estimates of HM, HT, DISK, and CAP were obtained from the same location in irrigated plots and nonirrigated, grazed pastures. Linear equations were observed to describe the relationship between HM and HT [ Y = 414 + 12.9X (r2 = 0.86), Y = 37 + 21.7X (r2 = 0.86)] and CAP [ Y = ‐1276 + 2.4X(r2 = 0.77), Y = 1289 + 2.8X (r2 = 0.89)] for plots and pastures, respectively. The relationship between HM and DISK was linear [ Y = 282 + 29.3X (r2 = 0.91)] and quadratic [ Y = 421 + 44.9X ‐ 0.7X2 (r2 = 0.80)] for the pasture and plot studies, respectively. For all HM relationships, the ability to predict HM was generally better in pastures than in small plots. Problems associated with lodged herbage in plots greatly influenced the HM predictive relationships of all techniques presumably by increasing the variability at high HM levels. Due to the large differences in the range of HM, in tiller height and tiller density, separate equations were required to predict HM in pastures and plots, regardless of the technique utilized. No single technique was observed to best predict HM. In the pastures, CAP and DISK were more efficient at estimating HM, while in the plots HT was the most efficient estimator of HM. This study suggests, while double‐sampling may allow for the estimation of HM in bermudagrass, factors such as tiller height and tiller density will influence the predictive relationships of all techniques requiring separate prediction equations to be developed where differences in sward composition are expected.

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Bermudagrass [Cynodon dactylon (L.) Pers.] is a major warmseason perennial grass grown on improved pastures in the South. Available forage and its digestibility vary widely in a normal grazing season on bermudagrass pasture. A method is needed to predict steer (Bos sp.) gains from the amount and digestibility of available forage. Five bermudagrass cultivars differing in digestibility were grazed at different grazing pressures to produce four levels of available forage. Forage was classified by concentration of in vitro digestible dry matter (IVDDM) as high (>600 g kg−1 IVDDM), medium (530 to 600 g kg−1 IVDDM), or low ( <530 g kg−1 IVDDM) digestibility. At each level of IVDDM, average daily gain (ADG) of steers was fitted to an asymptotic function of available forage. On high, medium, and low digestibility forages, approximate asymptotic ADG values were 0.94, 0.74, and 0.31 kg, and 68,83, and 89 g forage kg−1 body weight day−1, respectively, were needed to produce the asymptotic ADG values. For steers to maintain their weight on high, medium, and low digestibility forage, 14,18, and 43 g forage dry matter kg−1 body weight day−1, respectively, must be present. Because the quantities of available forage required for maximum steer gains or even for maintenance were far in excess of what the steers could physically consume, it appears that opportunity for selective grazing is necessary.

Grazing trials in which treatments are compared at only 1 gruing intensity greatly outnumber those in which treatments are compared at several grazing intensities. This suggests that, compared to other treatments and the need for replication in grazing trials, researchers consider grazing intensity lower in priority. In this study, a regression modeling approach for analyzing and interpreting data was developed to enhance the vahte of grazing intensity trials. As an example, results from 5 irrigated bermudagrasses (Cynodon dkctylon (L.) Pen) (Caliie, Coastal, Brazes and experimental hybrids S-54 and S-16) which were continuously grazed without field replication by Santa Gertrudis steers at 4 grazing intensities were considered. The relationships between average daily gain (ADG) and stocking rate, ADG and herbage present (ML/ha), and between stocking rate (animals/ha) and herbage present were well described by linear functions for all cultivars, with correlation coefficients(r) mostly above 0.9. CaMcients of determination (R*) for linear regression models derived for ADG vs stocking rate, ADG vs herbage present, and stocking rate VI herbage present were 0.90**, 0.89++, and 0.87**, respectively. Significant cultivar X grazing intensity (as measured by stocking rate or herbage present) interactions (p10.01) were observed. Furthermore, estimated stocking rates which provided maximum gain/ha ranged from 6.6 to 9.4 animals/ha, and the range in herbage present which provided maximum gain/ha was 0.35 to 1.95 Ml/ha. Callie provided an estimated maximum gain/ha of 881 kg/ha/season, while maximum gain/ha for the other cultivars ranged from 613 to 687 kg/ha/season. Comparison between these 5 cuitivars at only 1 grazing intensity would have had very narrow application. The procedure described allowed statistical comparison of cultivars without replication, and inferences about the separate effects of forage quality and quantity on animal performance could be made. Herbage present and cultivu were descriptors of the pasture. Since there was a substantial range of values for herbage present and stocking rate, ail important assumptions underlying linear regression were met and designs utilized in analysis of variance were not needed.

Leaf sections from 15‐day old kleingrass (Panicum coloratum L.) plants grown under moisture stress, optimal moisture conditions, and an intermediate moisture level were examined by light microscopy. The proportion of cell volume of parenchyma bundle sheath cells occupied by the protoplast and vacuole was markedly less for plants grown at the lower moisture levels than for plants at the highest moisture level. Increased sclerenchyma tissue development and increased thickness of the metaxylem cell walls were noted with reductions in moisture. Selective staining also revealed increases in lignification with moisture stress. These histological observations indicate that an increased proportion of cell wall components and increased lignification of kleingrass plants grown under moisture stress could account for at least some of the reduced digestibility reported previously with moisture‐stressed kleingrass forage.