Abstract
Weed control methods in warm season grass field were studied. The results obtained were as follows.
1. The most competitive weed in the experimental field was Polygonum lapathifolium L. subsp. nodosum Kitam. in case of seeding in May and large crabgrass (Digitaria adscendens Henr.) in June.
As the emergence of Rhodes grass (Chloris gayana Kunth) was slow in case of seeding in May, its growth suffered severe damage by P. lapathifolium L., when it was seeded soon after plowing and land preparation as common culture.
The emergence of Rhodes grass was rapid in June, and the number of stand was superior to that of large crabgrass, so Rhodes grass was damaged little.
2. The field was let alone for 8-9 days after plowing and land preparation, then the weeds emerged were controlled with paraquat or blind cultivation, following after Rhodes grass was seeded.
In consequence of above treatment, the effect of weed control with paraqurt was remarkable in case of seeding in May, and the total dry yield of Rhodes grass in full season was 211% compared with that of common culture. The effect of weed control with paraquat was not clear in case of seeding in June, because the competitive effects of weeds on the growth and yield of Rhodes grass in common culture did not occur.
The effect of blind cultivation was unclear at both cases of seeding in May and June.
3. The spray of paraquat immediately before or after seeding did not affect on the emergence and growth of Rhodes grass and African millet (Eleucine coracana (L.) Gaerth).
4. From the above-mentioned fact, it was concluded that the weed control method with paraquat was applicable to some cases as the weed control of warm season grass field. In this case, paraquat has to be sprayed on the weeds which emerged in a certain period of time after plowing and land preparation.
