Stargrass (Cynodon nlemfuensis Vanderyst) is an important tropical forage, but the interaction of stocking rate (SR) and N fertilizer rate on stargrass pastures is not well understood. The objective was to determine the effects of three SR (2.5, 5.0, and 7.5 bulls ha−1) and three N rates (112, 224, and 336 kg ha−1 yr−1) on stargrass pasture characteristics and performance of Jamaica Red Poll (Bos taurus × B. indicus) weanling bulls at St. Ann, Jamaica. Soil was a bauxitic clay loam, and pastures were rotationally stocked (7‐d grazing and 21‐d rest period). Pregraze herbage mass increased as SR decreased (2.0‐4.8 Mg ha−1 in Year 1 and 3.3‐8.3 Mg ha−1 in Year 2). Herbage crude protein (CP) and in vitro digestible organic matter (IVDOM) generally increased with increasing SR and N rate. Bull daily gain decreased curvilinearly from 0.70 to 0.26 kg in Year 1 and 0.65 to 0.35 kg in Year 2 as SR increased from 2.5 to 7.5 head ha−1 Daily gain increased linearly as N rate increased from 112 to 336 kg ha−1 The N fertilizer rate had little effect on gain per hectare at the lowest SR, but gain increased with fertilization up to 224 kg N ha−1 for a SR of 5 head ha−1 and up to 336 kg N ha−1 for a SR of 7.5. In conclusion, economic return from N fertilization of stargrass pastures is dependent upon SR, with greater N rates more likely to be profitable if SR is high.

Mass and energy exchanges with the atmosphere were compared in two soybean (Glycine max L. Merr. cv. Harosoy) isolines differing in pubescence density. The study was conducted in a field with a Sharpsburg silty clay loam soil (fine, montmorillonitic, mesic Typic Argiudoll) during the summer of 1980 at Mead, Nebr. Mass and energy exchanges were determined by means of micrometeorological techniques. Evapotranspiration (reported in terms of latent heat flux) was reduced in the densely pubescent isoline. Canopy CO 2 exchange was unchanged on a per unit land area basis. Water use efficiency (reported in terms of the CO 2-water flux ratio) was, accordingly, greater in the densely pubescent isoline. The increase in pubescence did not significantly alter the net radiation balance, turbulent mixing, canopy CO 2 exchange, or plant water status. Observed differences in the partitioning of net radiation into latent and sensible heat can be explained by greater penetration of solar radiation into the densely pubescent canopy. Leaf pubescence appears to alter the spectral characteristics of the leaf and, thus, to facilitate the penetration of solar radiation into the canopy.________

‘Florigraze’ and ‘Arbrook’ are the most widely used cultivars of rhizoma peanut (Arachis glabrata Benth.), but performance of ruminants grazing these cultivars has not been compared. The objective of this study was to determine sward characteristics and performance of Holstein replacement heifers (Bos taurus) on continuously stocked pastures of Florigraze and Arbrook growing on a loamy, siliceous, hyperthermic Grossarenic Paleudult soil. Herbage mass and allowance did not differ between cultivars during 3 yr of grazing and averaged 2840 kg DM ha−1 and 2.25 kg of forage kg−1 of animal live weight, respectively. Percentage of Arbrook in pasture herbage mass decreased from Year 1 (89%) to Year 3 (66%), while percentage of Florigraze remained relatively constant (90 to 87%). Average herbage crude protein (CP) concentration and in vitro organic matter digestibility (IVOMD) were greater in Florigraze than in Arbrook (177 vs. 161 g kg−1 and 705 vs. 661 g kg−1, respectively). Average stocking rate varied little between cultivars, and animal performance was generally similar until Year 3. With a much lower percentage of rhizoma peanut in herbage mass for Arbrook than Florigraze pastures in Year 3, average daily gain (ADG; 701 vs. 516 g) and gain ha−1 (575 vs. 418 kg) were greater for heifers grazing Florigraze than for those grazing Arbrook. Florigraze appears better suited for pasture programs with continuous stocking, primarily because of superior persistence, leading to greater animal performance with time.

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