EFFECT OF FERTILISERS.

New Zealand Herald, Volume LXVIII, Issue 20922, 11 July 1931, Page 16

EFFECT OF FERTILISERS.

JUDGING RESULTS. OBSERVATION INADEQUATE. INVISIBLE • DIFFERENCES. J \ - ' BY R.r. ' One frequently hears that certain areas of land have been treated with fertilisers without any apparent result. ... This is a fairly common experience, and one that concerns all classes of fertilisers as well as all types of pastures and crops. In such cases the conclusion usually arrived at is that the fertiliser used is of no use on that particulai- soil, whereas the real reason may have very little to do with the soil, but quite a good deal with the class of pasture or crop covering that soil. It is because of the apparently conflicting results recorded over a series of trials or a number of years that the work of prescribing artificial fertility calls for close study aud becomos so fascinating. It has been slated frequently in recent times that a nitrogenous fertiliser, such as sulphate of ammonia or nitrate of soda, has the effect of spoiling the clover balance in a pasture and of rendering the pasture less palatable to stock. Both of these faults may follow the improper use of nitrogenous fertilisers, but thoy novel occur where nitrogen is used correctly.

Observations at Fault, Those why lay down nianuria l ex peri ments and propose to depend wholly upon observation 'to determine results _ are undertaking a task of great responsibility. In the first place any difference m crop or pasture that can be measured by the eye is a very great difference indeed. Anyone who has had experience in judging and weighing root crops in the field, knows very well that a 20 per cent, difference between good crops cannot bo detected with any accuracy until the rospective plots are put over the scale. It is on record that in a wheat manunal trial, carried out in Canterbury, a sixbushel difference between two iioor crops stood out almost from the day crops germinated until they were threshed, while a twelve-bushel difference between two good crops was not even suspected until after both crops were threshed. i Trusting to observation to determine the effects of manures is akin to judging the butter-fat content of milk by looking at it. Much the same thing may be expected in pastures as is well understood already in regard to other crops, namely, that real differences exist which are invisible to the eye.

Lime Response, In the May issue of the New Zealand Journal of Agriculture, Mr. It. P. ConnelJ discusses this question when referring to the practice of applying lime to pasture land. Ho says:—" In some instances field results point definitely to the advisability of liming; in other instances which almost certainly are of more Irefluent occurrence—fiold results provide no evidence that, liming is either definitely profitable to the farmer or even benehciql to the pasture. Such widely differing r°* suits are hardly surprising in view of the great diversity of soils and climates which are embraced in our farming- But the practical farmer may ask: How am I to know when to lime and when not to lime? " The task of answering this question is made especially difficult by the fact that although there may be no visible evidence it doe? not follow that the lime is having no influence. r i his is because in certain cases influence of lime may be reflected in altered feeding-value, but not in altered appearance of the hevnage, Invisible changes may take place in the pasture growth, because °f liming, and these changes, may so beneficially affect steelv as to make the liming worthwhile. Professor jßtapletoii indicates the general position thus: "It is only occasionally, and in very bad cases, that liming actually adds to the bulk or weight of grass per acre, but it very has a considerable influence on quality.

Effect on Stock. This suggests that the correct places to look for the influence of lime or fertilisers are in the health of stock, volume of production, OT quantity of stock carried. It stands to reason that as we are continunlly taking out of the land all that goes to make up the volume of our exports, we must replace at least some of the essential elements unless we ftra prepared to work for complete exhaustion. Ajs with lime, so it is with manures; disappointments sometimes follow the expenditure on fertilisers, and one would need to be something in the nature pf a super,optimist to justify the outlay in view of the results. In the majority ot caa§s, however, there is a, perfect'\ feasible explanation, if only o«e knows just where to look for it, Not long ago the writer had occasion to investigate a aeries of reports to the effect that settlers in a certain locality in the North could get no results from fertilisers of any sort, and had very nearly uqwe to conclusion that they nan reached the limit of production. Investigations showed that several sorts of fertilisers had been tried on various crops, but the results had always been disappointing- Analysis disclosed the fact that the sod 'U this area had a high soluble iron and alumina content and because of this phosphates failed to give any response worth while. The cure lor this condition is to lime freely, so that the lime content of the soil may be raised to counteract the effects of the iron and alumina. It is difficult to say just, where observational results break "down, hut as a general rule it is when the most cursory examinations are made. It is possible that under manurial treatment a pasture is undergoing a complete botanical change without the owner being aware of it. Or it niav be that stock have developed a great/'liking for the treated pasture, Init because it is not showing tons more growth to the acre the judgment is that i! manuring docs not pay." Crux of the Question,

The writer was taken over an old Southland pasture on one occasion, and was asked to suggest a top-dressing mixture for it. The suggestion was that, _it should be ploughed and put in turnips a,nd then kept up for another year or two before being sown down to permanent grass, after which top-dressing would be in order. Eighteen months later the owner was cutting l'ye-grass tor seed oil' this paddock, and the only treatment it had had was 10cwt. of carbonate of litne and 3cwt. of super an acre. My observation led me to suggest, the use of th<> plough, but the. owner said that manure would bring the pasture back. It did, yet on this man's good grass land, manures failed to show up to any marked extent, though no ono would suggest, they were not necessary.

The crux of (he question seems to lie that "the conditions of soil and pasture must suit the fertiliser to ari outstanding dog fee if perfectly obvious results are. to follow." In other words, lime will show up best on n totally lime-deficient soil: phosphates show up plainly on a soil sadly depleted of this mineral, and nitrogen'is most effective on nitrogen-deficient areas or where a very high-class pasture is capable of showing a profit on the investment.

Often a fertiliser is hampered in the exertion of its maximum influence b.v the absence of another important element in plant, nutrition. For instance in the absence of sufficient lime, "super will not du all that it is capable of doing in the way of stimulating growth. Again' a deficiency of potash is.frequently n limiting factor in crop yield, despite liberal dressings of phosphate fertilisers.