ChileanJAR

In a second season (1984/85), the effect of different heights at cutting on a red dover pasture was analized. Materials and methods were similar fo those described by López, Silva and Pascual (1987), excepted a top dressing with 20.1 kg of P/ha, applied in autumn, 1984. Also, laboratory analysis were done to determine the presence of root and soil pathogenes. Net.growth rate (TCN) levels achieved in this season were lowerthan in the first one,showing a persistent decrease along the season. Accumulated degree-days and solar radiation affected negatively this variable. Net assimilation rate (TAN) did not presenf a consistent pattern, and contrary to the first season, the treatments cut at low height were not the most efficient. Also, Ihere was no clear relationship between TCN and TAN, suggesting that the behaviour of TAN was due, in a large extent, fo a loss of foliar tissue. In the first two utilizations, the yields of photosynthesizing herbage (FITOF) were higheras the height at cutting augmented, showing significatives differences between treatments (P < 0.05). However, at the third cut a high increment of the weed component was observed, affecting FITOF. Soil and root pathogenic fungi were also observed at the third cut. Accumulated yield of FITOF was lower than in the first season and, though there were significative differences between treatments (P < 0.05), a good relationship between the management of the pasture (treatments) and yield, was not observed. The arger variability in yield can be attributed to the pasture health condition and to the nature of the species under study.