IRRIGATION

Manawatu Standard, Volume LIV, Issue 281, 25 October 1934, Page 5

IRRIGATION

RESPONSE OF LIGHT LAND. Experiences with the establishment and irrigation of permanent pasture on light land in Canterbury formed the subject of a paper given by Messrs A. H. Flay and jVI. H. Rogers at the recent Grassland Association conference in Palmerston North. These included notes on the method of establishment, mixture used, method and extent of irrigation, response to manurial treatment, and botanical analyses of establishing pasture under various treatments. Although the details discussed were based on a twenty-two month period of observation at Seafield irrigation farm, reference was made also to other irrigation experiments undertaken at Oxford, Hororata and Southbridge. The Seafield Irrigation Farm property, comprising nearly 700 acres, is situated about ten miles east of Ashburton, the paper stated. The herbage consists chiefly of brown top and other undesirable twitches. Sorrell and other weeds are prevalent. Accordingly, frequent cultivation and rotations of crops are desirable for cleaning purposes. The soil varies from four to six inches in depth and overlies a few inches of clay loam which overlies deep shingle. There is adequate drainage for surplus water. In March, 1932, an area of 32 acres was ploughed out of an old sod-bound sward of browntop. On one half of this area, levelling was executed for the border dyke type of irrigation. The field was fallowed until November and early December when the following seed mixture was sown broadcast on a well prepared seed-bed, no cover crop being used : —True perennial ryegrass 301 b per acre, cocksfoot (N.Z.) 101 b, red clover 31b, certified wild white clover 21b, total 451 b. One hundredweight of superphosphate per acre was applied at the time of sowing. The germination was good. Later the area was subdivided into fourteen paddocks of approximately two acres each. Seven of these were irrigated and the remainder acted as controls. In the autumn (1933) an abnormally drv period was experienced from mid-Janu-ary until May. The irrigated paddocks were watered five times between midFebruary and early May. The total amount of water applied was 8.13 inches; 7.38 inches from irrigation and 0.75 inches from rain. From mid-February to May the irrigated areas were grazed harder than that usually recommended. Since then, however, the system of controlled rotational grazing has been more ideal, the stock being shifted a day or so before really necessary. Some of these pastures were used for fattening lambs m the autumn. Winter grazing was not attempted. During the dry spell the irrigated pastures showed striking superiority in growth over the non-irri-gated, on which some young plants died. Cocksfoot and red and white clover appeared to be most seriously affected. In the late autumn a.nd winter the irrigated pastures' showed a pale yellow colour and appeared weak. This lack of vigour was more pronounced on the areas from which soil had been removed in the process of levelling. The 1.1011-irrigated pastures, which had not yet been grazed, did not appear pale and yellow, and were ready for their first grazing in August. The irrigated -fields could not be grazed until mid-September. As the spring advanced the appearance of the irrigated pastures gradually improved. The improvement was in keeping with the amount of fertiliser used. Red and white clover, ryegrass and cocksfoot, in that order, grew vigorously from early October onwards. As the spring weather continued dry irrigation was carried out in October, November and early December, and again in April, 1934. The total quantity of water received by these grazed pastures for the season (July, 1933, to June, 1934) was 38.52 inches —6.01 inches from irrigation and 32.51 inches from rain. The dry spring had an adverse effect on the non-irrigated pastures, especially during November and December. This effect continued into January, 1934, even though three inches of rain were recorded in the latter pa.rt of December and three and a-half inches in the first week of January. Observations showed that the application of fertiliser reduced during tho winter the degree of the pale yellow appearance already referred to and hastened recovery. From October, 1933, onwards a proportional increase in growth of red and white clover was noticeable and bore a parellel relationship to the amount of manure applied. Where 3cwt. of superphosphate and scwt. of carbonate of lime per acre pier annum were ajiplied ryegrass, and to a lesser extent cocksfoot, became more vigorous. In the grazed pasture no smothering effect by the clovers has been noted.

The plants behaved according to experiences on better land with a favourable distribution of rainfall, but it is significant so far that the growth of desirable 6pocies such as ryegrass, clovers and cocksfoot is being maintained and that an influx of undesirable plants is being prevented. Observations showed also that the density of the sward of herbage improved with irrigation and topdressing. In September, 1933, an irrigated topdressed area was closed for hay. Water was applied on October 13 (2.7in5.) and December 11 (5.9in5.). Two cuts of hay were taken, the first on December 6. 1933, yielding 2.86 tons per acre, and the second on February 28, 1934, yielding 1.13 tons per acre —a total of 3.99 tons per acre. OTHER OBSERVATIONS.

At Hororata and Oxford new pastures were sown for irrigation purposes. The preparation of tho seedbed, times of sowing, seeding and manuring, were much tho same as for Seafield. In these two districts observations showed that during the autumn (1933) these irrigated pastures grew strongly and gave high carrying capacities. During the late autumn and winter they were pale and weak. As the spring advanced this poor appearance gradually gave way to a better growth, especially of clovers. At Oakleign (midway between Southbridge and Rakaia) an established ryegrass and subterranean clover pasture was irrigated. Reestablishment of the subterranean clover in early autumn gave good late autumn, winter and spring growth. The chief reason for referring to the irrigation experiments at Oxford and Hororata is to show that the pale yellow discolouration and weak growth of the herbage during the establishment was not confined to the Seafield pastures, but it occurs as well, but to a lesser extent, on non-irrigated pastures sown in late spring and early summer. The fact that topdressing reduces the degree of discolouration and weakening suggests that soil fertility is a deciding factor in its development. In support of this view it was noticeable that herbage on patches filled in to a depth of two or more feet during levelling was not affected, whereas in areas where soil was removed a marked prevalence of the condition was evident. In addition, discolouration did not occur in these pastures in the late autumn and winter of 1934 _ even though one and three-quarter inches more water were received per month than when discolouration occurred.