ON THE LAND

Hawke's Bay Tribune, Volume XX, Issue 162, 28 June 1930, Page 12

ON THE LAND

Intelligent Top-dressing

Increasing the Returns From Manures

Stimulating Growth When Most Valuable

(By

“Sundowner.”

(Written for tho “Tribune.” All Rights Reserved.)

Although considerable increase in production has been secured in New Zealand as the result of the adoption of the practice of top-dressing, it appears that, as yet, we are not getting the maximum return from these applications. This is so because even those whose business it is to investigate the composition and action of chemical manures can hardly claim to know all that is to be learned of the subject, and at present can do little more than suggest to the practical farmer methods that are likely to give best returns. . . No set rule fqr either time or quantity of application has yet been arrived at, nor are we really certain which manures are likely to give best results on any particular soil, or at any particular time of the year. We do know, however, that the bulk of New Zealand land, and particularly the North Island, is deficient in available phosphate and that applications of this manurein a water soluble form, as in superphosphate, greatly stimulates the growth and increases the nutritive value of all vegetable growth.

WASTE WITH HEAVY DRESSINGS.

In the early days of superphosphate top-dressing, and even in some instances continued to-day, it was the practice to give a heavy dressing of from three to four hundred pounds of manure every three or four years. The idea was to save expense and labour in frequent lighter dressings at shorter intervals. This practice has been proved to be far from satisfactory, and in waste of manure is really more costly and produces much less growth than frequent dressings.

fhe reason is that so soon as superphosphate is applied to land the icids in the soil water dissolve it, and then commences a process whereby any of this phosphate in solution which is not used by the plants fairly soon, combines with other minerals in the soil and becomes insoluble, or at best very slowly soluble. The amount of superphosphate which it pays to apply at any one time, therefore, depends on the number and type of plants present to absorb it within, say, three months of the time of application. Anything applied in excess of this quantity is largelywasted, although there is some residuary effect, the extent of which has not yet been accurately computed, and which depends to a large extent on the normal water content of the soil.

There is very little of even the best grass land that will respond profitably to a heavier dressing than two hundred pounds of superphosphate per application. If, as is often done, the farmer applies from three to five hundred pounds of super, at infrequent intervals on inferior pasture, he is ..really reaping the benefit from only half this amount. Practically double the effect in increased grass growth would be secured were he to make two applications of this quantity during the same period, and probably very nearly three times the result if he made three applications of about 1J hundred per applicar tion. This extra growth would be secured at the cost of distribution only.

This principle is being carried still further nowadays, and it is becoming common practice to make two, or even more applications of superphosphate per annum, at such times of the year when increased growth will be most valuable on the farm. It certainly appears that the “little and often” principle of super applications much more than pays for the extra cost of spreading the fertiliser. WHEN TO TOP-DRESS. Next comes consideration of when to top-dress to secure the greatest pecuniary return. Early winter top-dressing has been practically done away with now, as it has been found that super applied at this dormant season is only 50 per cent, available by the time spring growth commences. Late winter top-dressing has now become popular to encourage early and abundant spring growth for ewes and- fattening lambs. Again applications are becoming popular in late .summer to encourage early autumn growth which may be carried on into early winter, according to the‘date of application. It has been observed that superphosphate has little effect when there is insufficient moisture in the soil to promote rapid growth, hence there is little prospect of a profitable return from an application made during summer. Also, grass does • not profitably respond to super during cold, sunless weather,

hence winter applications, to encourage growth during that season are unprofitable. This leaves us with autumn and late winter dressings as the ones most likely to produce the greatest amount of valuable feed, for in autumn the soil is fairly warm and a moderate amount of sunshine is usually experienced, while rain may also be expected to co-operate with the manure. In l<N.e winter there is usually an abundance of rainfall, and lengthening days with increasing sunlight to encourage growth. The late winter dressing is particularly important. First because it encourages early growth in a season when all the superphosphate applied can be used, secondly because super applied at this season encourages clover growth which, besides being valuable fodder, helps materially to maintain the soil’s supply of nitrogen, and thirdly because phosphate encourages deep rooting of the pasture grasses and thus enables them to carry on growth through a longer period of the dry summer. If only one application is given yearly, therefore, the late winter dressing is the most valuable, and this is even more so since the making of ensilage from surplus spring growth for use in late summer or winter has become popular. TWO APPLICATIONS YEARLY PAY. Where small areas are being dealt with, and particularly on dairy farms where grass growth continued into early winter is particularly valuable, two applications per annum would certainly pay, the time of making the second application varying from December onwards, according to the time when the greatest growth is desired. It is well to remember in this connection that when weather conditions are favourable, grass responds to superphosphate in from a month to six weeks. THE TIME TO USE NITROGEN. It has been stated in this article that in wet, sunless seasons, and during winter, superphosphate has little, effect in encouraging extra growth. It is possible, however, that even under these conditions it does increase the flavour and nutritive value of the grass. Experiments now being undertaken should give us some reliable data on these points. In a damp and sunless climate, and in drier climates during the winter time, it is probable that nitrogen in the form of sulphate of ammonia will give the biggest returns in increased bulk of growth. It is probable that even in the North Island where the climate is fairly dry and bright sulphate of ammonia will pay handsomely to use for late autumn and winter dressings, the former to promote winter growth, and the latter to provide an early flush of feed in the spring and bulk of growth for the making of hay or ensilage.