Recent Research Work WHEAT

New Zealand Journal of Agriculture, Volume 85, Issue 2, 15 August 1952, Page 129

Recent Research Work WHEAT

DATA which provide a measure of yield differences resulting from various rotational practices and of fertiliser responses have been given by research work conducted in Canterbury by the Extension Division of the Department of Agriculture. Results given on this page place yield figures on the value for wheat of nitrogen provided either by a preceding leguminous crop or by nitrogenous fertilisers.

PLACE OF WHEAT IN ROTATIONS

A SURVEY in the Ashburton area showed that two-thirds of all wheat crops were taken after grass or a fed-off crop. Among other rotations wheat

after peas yielded 3.1 bushels per acre more than average and the yield after another wheat crop was 2.9 bushels less than average. In the Christchurch district the best yields were obtained after grass, 3.3 bushels per acre better than average, and the poorest were after wheat, 4.1 bushels below average. The yield difference was 3.2 bushels per acre in favour of rotations which placed the wheat crop within 2 years of grass over rotations where the field had been cropped for 2 years before wheat.

NITROGENOUS FERTILISERS

AN ANALYSIS has been made of 196 wheat trials conducted by the Division which included a spring topdressing of either sulphate of ammonia or nitrate of

soda. These trials were begun in the 1926-27 season and since then no general change in the level of nitrogen responses has occurred, though in some periods responses were greater than in others. Therefore this factor was removed in the analysis, and in the process any differences between the effects of nitrate of soda and sulphate of ammonia ■ were removed, as nitrate of soda was used only in the first few years of trials. Similarly, the effect of different wheat varieties was removed, most trials, before 1937 being sown with Solid Straw Tuscan and most of those after 1937 with Cross 7. The analysis considered the factors which seemed to have the greatest effect on nitrogen responses of trial, district, previous crop, soil type, time of application of nitrogen, and yield of crop. The mean response to nitrogen over the 196 trials was 2.8 bushels per acre, and the greatest responses are to be expected when wheat follows a previous wheat crop, on “recent to young” alluvial soils, and from applications made in late September.

DISTRICT DIFFERENCES

AVERAGE RESPONSES to nitrogen in different districts were as follows, differences exceeding 1.4 bushels per acre being considered statistically significant: —

These figures do not represent the actual mean nitrogen response in each district, but the mean response freed from

the effect of other factors. The .high responses in South Canterbury and North Otago are linked with the fact that many trials in these areas were grown under conditions associated with small responses to nitrogen, the two most common factors being “pan” soils and the placing of wheat after grass in the rotation. Correcting for these factors results in high mean nitrogen responses in South Canterbury and North Otago.

PRIOR CROPS ’

MARKED DIFFERENCES between nitrogen responses were found when the trials were ' grouped according to the crop in the ground the season before the wheat of the trial was sown: —

EFFECT OF TIME OF APPLICATION

Differences of more than 1.1 bushels are statistically significant. The outstanding feature is the large response to nitrogen when wheat follows wheat and the small response when wheat follows grass. The difference between these two items is highly significant.

ANALYSIS showed clearly that the extent of the response was associated with the time the nitrogen was applied. The “response curve” rose from zero

(no response) to mid-August applications to a maximum of 4.7 bushels per acre response to applications on 26 September and then declined to reach zero again on 7 November. It is clear that nitrogen can be applied too early or too late in spring and that the best time in most years is late September. B. LYNCH and J. G. MILLER

NEW WHEAT VARIETIES

£ . ID. U/bU U . ILL £ J—J J—J£-J £ v He ❖ ❖ TRIALS incorporating new varieties of wheat bred by the Crop Research Division, Department of Scientific and Industrial Research, continue to form a large proportion

of the experimental work in arable districts. In the 1951-52 season 43 replicated variety and manurial trials were carried out. Some new crosses from the Crop Research Division have given very promising results in recent years. Cross 7 is used as a standard variety in trials and, whereas a few years ago it was usually one of the highest-yielding varieties, in the past few years it has been usually one of the lowest-yielding. Extensive testing of these new crosses is necessary before their release to farmers. Such new material must be satisfactory in milling and baking quality as well as high yielding and must have desirable agronomic characters such as strength of straw, resistance to “shaking”, and all the factors that go to make a good “heading” wheat. There is reason to hope that one or more new varieties, as desirable as Cross 7 to the grower but considerably higher yielding, may be available for distribution to farmers in

a few years’ time.

P. B. LYNCH

District Average response to nitrogen (bushels per acre) Number of trials North Canterbury . . .. 1.2 38 Christchurch .. 2.9 38 Ashburton .. 2.2 40 South Canterbury . . . . 5.2 39 North Otago .. 4.0 28 Others .. Nil 13

Number Rotation Mean response of trials (bushels per acre) of trials Wheat after grass . . 0.6 58 Wheat after. wheat . . 5.5 51 Wheat after rape or chou moellier .. . . 2.2 32 Wheat after other crops .. 2.9 55