Effects of leachates from swards of Bothriochloa pertusa and Urochloa mosambicensis on the growth of four test species, B-pertusa, U-mosambicensis, Stylosanthes hamata cv. Verano and S-scabra cv. Seca and an assessment of the endophyte status of the grasses

In a previous grazing trial, the percentage of Stylosanthes hamata cv. Vera no was much lower when grown with Bothriochloa pertusa cv. Bowen than when grown with Urochloa mosambicensis cv. Nixon. Reasons for this depression in the presence of Bowen have been investigated. In this study, the possibility of allelopathic effects on Verano and on Sty losanthes scabra cv. Seca from leachates of the grasses Bowen and Nixon was examined. Leachates from soil-filled boxes with or without Bowen or Nixon were used to water seedlings of Verano, Seca, Bowen and Nixon grown in pots along with a control treatment watered with demineralised water. Plant hei ght, tiller or shoot number, leaf number and top and root weights were meas ured over a 12-week period to harvest. With Verano, there were no significant adverse effects of leachates from sw ards of the two grasses compared with the water control. Leachates from Bow en actually gave the highest yields of Verano. These results give no suppor t to the hypothesis that Bowen had allelopathic effects on Verano. With Sec a, lowest yield and plant height occurred with leachates from Bowen while t he highest yield and plant height were obtained with leachates from bare so il. This indicates Seca is more susceptible to adverse effects from some fa ctor in Bowen. Leachates from bare soil had no allelopathic effects on the growth of the four species. Failure to detect endophytes in Bowen or Nixon rules out the possibility that these are involved in the poorer performance of Verano grown with Bowen in the field.