Cool season turfgrass is apt to be expelled by weeds because it grows worse during the summer Conseqently it is most important to eliminate weeds from the turf composed of cool season turfgrasses.
The eim of this experiment was to determine the effects of methods of weed control on growth of cool season turfgrass. Three experimental plots differing in methods of weed control were settled. They were the plot of pulling out weeds by hand [H.P. plot], the plot of eliminating weeds by herbicides [HERB plot], and control. The results of this experiment were summarized as follows:
1) In the H. P. plot, the coverage of turfgrasses decreased to about 54 % in early September, but increased again to about 94% in mid-October.
2) In the HERB plot and control, seasonal changes of the coverage of turfgrasses were significantly correlated with the coverage of weeds.
3) Shoot density of Perennial ryegrass [Lolium perenne L. ] in all experimental plots kept decreasing till late in August.
Shoot density in the H. P. plot increased again after early September, which was closely related to the increase of the coverage.
4) The differences of the number of tillers were observed among the three experimental plots.
The number of tillers was higher in the H. P. plot than the other plots.

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The selectivities and the behaviours of asulam [methyl N- (4-amino phenylsulfonyl) carbamate] in turf grass was studied, and the following results were obtained.
1. The effect of asunlam on manilagrass (Zoysia matrella) and bermudagrass (Cynodon dactylon)
(a) . The effect on the turf grass by foliar treatment
Asulam was applied on turf grass by foliar treatment and after the treatment, the weight of aboveground parts of turf grass was determined.
On account of the damage caused by asulam, the weight in manilagrass decreased a little at 20 days but the grass recovered from the phtotoxicity at 60 days after treatment.
Bermudagrass suffered from great damage at 20 days after the treatment and the weight of bermudagrass decreased greatly, and even at 60 days after the treatment, the injury did not recover.
(b) . The effect on manilagrass by root treatment in soil
Asulam was applied on manilagrass by root treatment, and the weight of aboveground part of manilagrass was determined after the treatment.
The weight of manilagrass decreased by 40-50% at 20 days after the treatment of asulam at 300-750g/10a, but no growth inhibitory effect was found at 60 days after the treatment.
(c) . The effect on manilagrass by foliar treatment in different seasons.
There were a little adverse effects on manilagrass when asulam was applied in May, June and October. There were moderate damages to the turf grass when asulam was applied in August and February.
(d) . The effect of asulam in the mixture with other herbicides.
No adverse effect on the manilagrass was obserbed except for combined use of asulam with hormone-type herbicides or with emulsifiable concentrate-formulated herbicides. The adverse effect caused by the application of above mentioned combinations was not so great and the grass soon recovered from the damage.
2. The residue of asulam in manilagrass and bermudagrass
Asulam was applied by foliar treatment at 5000 ppm, and the residue in the turf grass was determined by HPLC.
The residual concentration of asulam in manilagrass decreased gradually. The residue was 21 ppm at 6 days, 10 ppm at 10 days and 6.3 ppm at 16 days after the treatment. On the other hand, the residual concentration in bermudagrass did not show remarkable decrease. The residue was 9.9 ppm at 6 days and 8.8 ppm at 16 days after the treatment.

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The herbicidal properties of chlornitrofen (4-nitropheny1 2, 4, 6-trichlorphenyl ether) were studied in green house and fields, and the following results were obtained.
1. Weed control spectrum
Pre-emergence treatment of chlornitrofen was effective on the control of crabgrass and annual bluegrass, but not so effective on broad-leaved weed control when 250g of chlornitrof en was used per 10a. But it was effective on many of crabgrass, annual bluegrass and broad-leaved weeds when 500g of chlornitrofen was used per 10a.
2. Synergisms of chlornitrofen and other herbicides
The combinations of chlornitrofen and simazine or atrazine showed synergistic effects on the control of many weeds by pre-emergence treatment or post-emergence treatment.
3. Herbicidal effectiveness in the different soils
The herbicidal effectiveness of chlornitrofen on crabgrass and annual bluegrass varied a little depending on the kind of soils were tested.
4. Phytotoxicities to turf grasses
Chlornitrofen showed no adverse effect on Japanese lawngrass and Manilagrass by root treatment or foliage treatment at high temperatures.
5. Field experiments
The field experiments showed chlornitrofen was useful for annual grass control, but not so useful for broad-leaved weed control. But the combinations of chlornitrofen (250-500g/10a) and simazine (30-60g/10a) or atrazine (30-60g/10a) were very effective on many species of weeds.
A higher dosage (500-750g/10a) of chlornitrof en was necessary to control the weeds when the soils contained thatch.

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A pot experiment was carried out to evaluate the shading effect during the seedling stage of commercial varieties of five turf grass species, i. e., Poa pratensis. Agrostis albs, Phalaris arundinacea, Paspalum notatum and Cynodon dactylon.
Seeds were sown on the seedbed of wet vermiculite filled in 1/5, 000 a Wagner pots randomly arranged in a glass house on May 30, 1982. Pots were covered with single-and double sheets of black cheese cloth fixed on a wooden frame of 1.2 × 1.2 × 0.6m to make shade environments of 40% and 20% light penetration. Pots without shading were prepared as control. After thinning three seedlings were grown in each pot and the pots were used with five replicates. Seedlings were watered infrequently for the first ten days followed by application of 1/2 Hoagland solution for six weeks. Seedlings were sampled three times. i. e. June 30, July 10 and July 20 to check the successsive growth processes of the grasses examined.
Results obtained are as follows;
All the turf grasses tested were very sensitive to the reduced light intensities in terms of leaf area increment, relative growth rate and the dry matter production of tops and roots. Grass length did not change so much as expected under severe shading environment except in P. pratensis which elongated more.
P. arundinacea and A. albs were rather tolerant, while P. pratensis, P. notatum and C. dactylon behaved poorly under the restricted light environments.
It is advisable to clip the adult vegetations frequently when turf grasses were undersown or oversown there to improve the light environments for the stands of the young seedlings.

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It is very popular and effective for weed control to use a weed killer in park grassland. But we may not use a weed killer too much, because of the misgiving of influence to the health of children' sick person and other park users. Then mowing is expected for weed control as an auxiliary method.
Weed vegetation in the Zoysia grassland was surveyed under the different mowing condition. Zoysia grass grew rapidly when mown every four weeks, but the weed covered area was increasing too. Then the weed vegetation was dominant when mowning height was 5.5cm. When mown every one week, grass covered area was slightly increased.
Creeping type weeds were decreasing under low level (2.5cm height) mowing height. But the mowing frequency did not influence to the spector of seed life form. Rossete type weeds made appearance constantly when mown every week at 2.5cm height. But in any other mowing condition, rossete type weeds made appearance more increasingly.

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