In order to prove the usefulness of NSK-850 as a turf herbicide, pre-emergence herbicidal activity of the chemical and its influence on the growth of turfgrasses were examined by pot tests in green house. The results obtained were summarized as follows.
1. Pre-emergence herbicidal activity
(1) Herbicidal spectrum of NSK-850 by preemergence treatment.
NSK-850 effectively controlled annual grassy weeds such as Poa annua,
Setaria viridis and
Digitaria cilialis. at a dosage of less than 3
g a.i./a. Broadleaved weeds including
Bidens pilosa, Ipomoea indica, Capsella bursa-pastris were rather tolerant to the herbicidal and were not controlled even at a dosage of 100
g a.i./a (Table 3) .
(2) Effects of soil water content on the preemergence herbicidal activity of NSK-850.
An excellent control of
Setaria viridis was obtained at the highest soil water content (39.3%, W/W) (Fig. 1) .
(3) Effects of spray volume on the preemergence herbicidal activity of NSK-850.
In general, spray volume greatly affected the efficiency of the applied herbicide, and an optimum spray volume for the control of
Digitaria ciliaris and
Setaria viridis was 10 1/a (Fig.2) .
2. Influence of NSK-850 and simazine on the growth of turfgrasses.
(1) Treatment after cutting off the shoots of turfgrasses.
NSK-850 did not affected the growth of both
Zoysia japonica and
Zoysia matrella but showed a slight phytotoxicity on
Agrostis palustris.
(2) Treatment after top dressing.
When Utsunomiya upland soil (diluvial loam soil) was used for top dressing, the growth of
Zoysia matrella was inhibited by simazine but not by NSK-850. Both of the herbicides, however, inhibited the growth of the turfgrasses when Kinugawa coast soil (alluvial sandy loam) was used for top dressing.
(3) Root treatment
When the herbicides were applied to the roots of the turfgrasses, among them
Agrostis palustris showed the highest susceptibility to NSK-850 and simazine.
In conclusion, it was suggested that NSK-850 is an useful preemergence herbicide for the control of annual grassy weeds in
Zoysia japonica and
Zoysia matrella, but it should not be applied directly to the roots
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