Maintenance of Cotula Greens in Otago and Southland

New Zealand Journal of Agriculture, Volume 94, Issue 1, 15 January 1957, Page 87

Maintenance of Cotula Greens in Otago and Southland

By

S. M. J. STOCKDILL,

Fields Instructor, Department of Agriculture, Dunedin

IN recent years so-called "weed" greens have become popular with bowlers, many of whom demand a weed surface in preference to a pure browntop and chewings fescue association. Of the so-called "weeds" Cotula pulchella, which is found naturally in coastal areas of Southland and is commonly known as Pahia weed, provides the most hard-wearing and uniformly fast playing surface.

COTULA DIOICA, which is of more widespread natural distribution, is not as hard wearing and consequently is less desirable. Starweeds (Plantago triandra and P. hamiltoni) which occur naturally in association with the cotulas have also been introduced to most weed greens and though they are inclined to detract from the appearance of the green, they are hard wearing and provide a surface of similar speed and trueness to that of cotula. In some of the high-rainfall areas waxweeds (Hydrocotyle spp.) are employed, but these and other weeds, such as Pratia angulata and Selliera

radicans, offer variable resistance to the bowl and are undesirable when they occur as patches in predominantly cotula or starweed greens. The maintenance of a stable cover of cotula or starweeds, or a combination of both, is more difficult than the maintenance of a browntop and chewings fescue association. Many undesirable plants, such as S'. radicans and P. angulata, occur naturally in association with the desirable species, and great care must be taken to avoid their introduction to the green, where eradication without damaging the cotula and starweeds is impossible.

In addition both cotula and starweeds are more or less winter dormant and moss, algae, and Poa annua can be troublesome during this period of dormancy. Consequently the aim is generally to produce an association which will be cotula dominant (with or without starweeds) during the playing season, but which will contain sufficient fine grass to compete with the Poa annua, moss, and algae in winter. Fertilisers and Soil Acidity By using the non-acidifying fertilisers blood and bone, nitrate of soda, or a fertiliser of the ammonium nitrate plus calcium carbonate type a lush, soft growth of cotula can be produced, but Poa annua and worm activity will be encouraged and the green will not withstand the hard wear required of it. To produce a hard-wearing turf acidifying fertilisers must be used and a mixture of 3 parts of sulphate of

ammonia and 1 part of superphosphate has proved satisfactory. Applied at loz. per square yard in the morning when the dew is on the green and when a fine day is likely to follow, this mixture gives a contact burn which helps to control moss, clovers, and other undesirable weeds without much damage to the cotula. Great care must be taken to obtain an even spread of fertiliser, half of which should be applied in one direction and the other half crosswise.

The fertiliser should be fanned up in the air to ensure that it does not fall unevenly and cause excessive burning. The fertiliser should be applied at close of play in autumn, in spring as soon as there is evidence of growth, usually early in August, and again early in September ’ about a month before opening for play.

Continued use of the 3 to 1 mixture in this way will acidify the soil and an acidity of pH 5.0 should be aimed at on most soils. This level of acidity will tend to discourage the growth of Poa annua and clovers and inhibit the activity of worms and soil organisms, while promoting a healthy growth of cotula and fine grass and the build-up of a hard-wearing turf. Care must be taken not to carry the acidification process too far, or it will result in the formation of hard patches, typified by unthrifty growth and lack of water penetration. When this stage is reached and over-acidity is confirmed by a soil test of below pH 5.0 advice should be sought on the use of lime as a corrective. Topdressing Soils One factor in green maintenance which calls for more attention than normally is given is the selection of suitable soils for topdressing. The practice of accepting any soil which is readily available cannot be condemned too'roundly. Highly fertile soils are usually very weedy and should be avoided, as also should any soil containing stones or sandy material. Soils taken from roadsides should always be suspect.

A suitable soil is one which will remain stable and not erode should bare patches occur and for this reason it should have at least a moderately high clay content. It should also be sufficiently acid to avoid any marked alteration in the acidity of the green. The ideal would be a clay soil from an area carrying a natural cover of browntop which should be fairly acid and free from clover, Poa annua, and other undesirable weeds.

The soil should be .on hand some months before it is required so that it may be turned over several times and screened ready for use. Soil for autumn topdressing need not be screened as finely as that for use in spring and on areas which are to be

built up coarser material should be used, as it is less likely to smother the existing turf. Weed Nursery and Use of Plugs It has been emphasised that many extraneous weeds occur naturally with cotula and in obtaining plugs for renovation purposes from natural sources these undesirable plants are likely to be introduced. In addition natural plugs are often of a spongy texture, making them difficult to insert into the green successfully.

To overcome these difficulties a well-kept weed nursery is necessary. This can be cut and rolled in the same way as the green and, with a great deal of tedious work, kept free from weeds, thus providing a handy source of weed-free plugs of a consistency approaching that of the green itself.

Plugs inserted into bare patches on the green should be placed slightly below the level of the green and covered with fine soil; otherwise they may spring up and be scalped by the mower. They, should also be placed as closely together as possible, because the spread of cotula from them is usually quite slow. Autumn Renovation Before close of play all . undesirable species such as clovers and pearlwort should be removed either by spotting out with weedkiller or by removing and replacing with cotula plugs. Fertiliser as outlined previously should be applied. Bare patches can also be attended to by inserting cotula plugs or by grooving with a rake and sowing browntop and chewings fescue. Renovation must begin as soon as play ceases, when the green should be thoroughly sliced or grooved. Various machines are used for this work, but the aim of slicing is to rejuvenate the cotula by cutting the stolons and promoting fresh growth. Grooving either with a rotary or tine machine will also cut the cotula stolons, but in addition will leave a series of grooves about lin. apart which will provide an ideal seed-bed for the introduction of chaffed cbtula plants and grass seed. The grooves also ensure that the topdressing soil is incorporated into the green rather than being spread as a layer on the surface. The grass seed mixture should consist of 1 part of certified browntop to 2 parts of chewings fescue and the rate of seeding will vary from loz. per square yard on bare areas to almost nil where there is a good cover. Care must be taken to obtain seed of high purity and germination. Browntop seed containing seed of J uncus

bufonius (toadrush) should be avoided, as this weed can be troublesome on greens; and, as the germination of chewings fescue seed deteriorates fairly rapidly, new season’s seed should be used. The use of loz. of a mercuric seed dust to each 201 b. of seed mixture may guard against seedling fungous attack. Obvious bare patches which were not plugged with cotula earlier should be plugged at this stage if weed-free plugs are available. An alternative method with some merit is the introduction of lengths of cotula stolons to the grooves on the bare patches. The topdressing soil should then be spread evenly over the area with the aid of straight edges. If the green is not reasonably level, it should be surveyed so that lower areas may be built up. However, not more than Jin. of soil can be applied safely at any one time; and, if a greater build up is required, a series of Jin. applications should be made to allow the growth to come through after each successive application. Winter and Spring Treatment Throughout winter the green must be mown periodically to avoid excessive growth and should be gradually reduced to about playing height in August, when, after the application of fertiliser, a very light application of fine soil should be made to even out any minor irregularities. This should be followed in September by another application of fertiliser and the green then kept at playing height in readiness for opening in October. The mower should be set to cut at a height equivalent to about the thickness of a 2s. piece until the end of November, when it can be lowered to remove the button-like seed heads of the cotula and to provide the fast, true surface demanded by bowlers. It must, however, be remembered that by keeping the mower up in the early part of the season a better green can be expected during the latter part when competition play is in full swing. Heading photograph by E. A. Phillips.

C.R.D. to be Name of New Ryecorn

From the 1956-57 harvest all New Zealand certified ryecorn seed will be known as C.R.D. This is the name given to an improved N.1.A.8. ryecorn which is being multiplied in New Zealand under certification. Information about this new selection, which has been developed by the Crop Research Division of the Department of Scientific and Industrial Research, was given in an article in the May 1956 issue of “The New Zealand Journal of Agriculture”.