The effect of frequency and severity of cutting on yield and persistence of Desmodium intortum cv. Greenleaf in a subtropical environment

Abstract

The effect of three cutting intervals (CI)-4,8, and 12 weeks, and three cutting heights (CH)- 3.8, 7.5, and 15.0 cm, on the yield of Desmodium intortum cv. Greenleaf over a three year period are reported. Total yield and yield of legume increased with increasing CI; the mean legume yields were 4.23, 6.54, and 8.03 tonnes DM ha-1 year-1 for the three CI treatments. Increasing the CH reduced weed yield and total yield at each CI. For yield of legume the CI x CH interaction was significant (P < 0.01 ). At 4-weekly CI a CH of 3.8 cm gave the lowest legume yield whereas at the 12-weekly CI a CH of 3.8 cm gave the highest yield. At the 8-weekly CI the CH treatments had little effect on total legume yield. Weed percentage declined as both CI and CH were increased. However, there was an increase in the grass weed component (mainly Cynodon dactylon) with time. Legume persistence was good for all treatments, but plant numbers increased linearly (P < 0.01) with increase in CH from 7.2 to 9.5 plants m-2. Growth pattern of desmodium was more closely linked to mean temperature than to either evaporation or to rainfall. As a result growth was limited to about seven months of the year and peak growth rate for the 4-weekly cutting regime never exceeded a mean of 6 g m-2 day-1 (60 kg ha-1 day-1).