Climate, nitrogen and grass. 6. Comparison of yield and chemical composition of some temperate and tropical grass species grown at different temperatures.

Abstract

For part 5 see NAR 43, 148. 6. Lolium perenne, Festuca arundinacea and 2 tropical grasses, Axonopus compressus and Brachiaria ruziziensis, were grown in pots under day/night temperatures of 19 deg /12 deg , 24 deg /18 deg , 28 deg /23 deg and 34 deg /30 deg C and regrowth was cut after 18 and 35 days. The stemmy Brachiaria was much more productive than the others which remained vegetative. The optimum production temperature was 24 deg or less for the temperate grasses but >30 deg for the others. Yield was greatest after 35 days and with high N fertilization. Lolium had the highest average content of N, soluble carbohydrates and digestibility in vitro and Brachiaria the lowest. Digestibility declined with increase in temperature and age, most for Brachiaria. These effects were caused by an increase in content of cell-wall constituents and a decrease in their digestibility. N fertilization had no effect on digestibility. Results support the hypothesis that the low digestibility of tropical grasses is mainly due to the high temperature during growth but may be improved appreciably if stem formation is suppressed. ADDITIONAL ABSTRACT: Lolium perenne, Festuca arundinacea, Axonopus compressus and Brachiaria ruziziensis were grown in pots in a glasshouse under day/night temperatures of 19/12, 24/18, 28/23 or 34/30 deg C with intermediate or high N and regrowth was harvested after 18 and 35 days. Reproductive B. ruziziensis was much more productive than the other vegetative species. Optimum day temperature for production was 24 deg or lower for temperate grasses but >30 deg for tropical species. L. perenne had the highest contents of N and soluble carbohydrates and in vitro digestibility and B. ruziziensis the lowest, differences being smallest at the low temperature. There was a consistent decline in digestibility of all species with increase in temperature and age which was correlated with an increase in cell wall constituents but was not related to amount of N applied. [For Part 5 see HbA 43, 1557] (Abstract retrieved from CAB Abstracts by CABI’s permission)