Is Less Top-Dressing Practicable?

Press, Volume XCVII, Issue 28701, 26 September 1958, Page 11 (Supplement)

Is Less Top-Dressing Practicable?

By

A. F. R. ADAMS,

Senior Lecturer in Soils and Fertilisers,, Canterbury Agricultural College, Lincoln. A question which is concerning many farmers canbe’made^ “ reduction in the use of fertilisers After the recent fall in prices overseas for our products, many farmers, who either recently or over a long period have been using lime and fertilisers regularly, are looking at their accounts with an eve to cutting down on their expenses; • 4K° ne l h . e . items which looms lar £e in the list is the cost of lime and fertilisers. Furthermore it is a recurring cost.

It is to be expected that this Item of expenditure is likely to be chosen as a “probable” for reduction. At this stage, though, with the fertiliser bill about to be cut, a doubt begins to assail the farmer.

What will happen if he cuts out part of his normal fertiliser or liming programme? Will his pasture deteriorate, will his crop yields fall, will his lucerne cut that extra hay which would be so acceptable this season? What he wants to know in fact is whether he can do without lime or super, or with less lime and super, for a year or two without a drop in production. Little Known Unfortunately little is really known about this question which relates to the residual effect of superphosphate and lime already applied and the amounts needed to maintain production. We know that the production from grassland or any other form of cropping is determined by a great many factors, including the nature of the soil and the climate, about which we can do very little; the management—undoubtedly a very potent factor, but one which is unlikely to change suddenly for the better in any particular instance; the

quality of the pasture, taken in this case to mean composed of improved strains of clovers and grasses, and the plant food supply. It is known that high-producing pasture is a gross feeder and that phosphates and sulphates—whicn make up super—are particularly

important in the nutrition of clovers, so once more we are back to the question of the plant foods—lime and fertiliser. At this stage we might become a little sceptical and ask what the contribution of fertilisers, together with the normal accompaniment of better species, has been to the productivity of the country. Opinions differ on this point, but two years ago Mr A. H. Cockayne was emphatic in listing the recognition of grass as a crop, together with topdressing, as two of the major factors contributing to the increased production of this country. He quoted the increase of 17 million ewe equivalents on virtually the same grassland acreage over the period 1920-1950 as evidence for this.

He also pointed out that in the five years from 1950 to 1955 our stock numbers rose at the rate of one million per annum to the accompaniment of increased super from 4-1 million tons. In Canterbury, though, it appeared in 1951 that our stock numbers had not increased at anything like this rate, in spite of topdressing. The question was asked—why?

In view of the fact that over the period 1944-49 only 110,000 acres on an average received topdressing and 200,000 acres received lime out of our two thillion acres of ‘ grassland. I would suggest that one strongly contributing factor was the lack of sufficient topdressing in Canterbury. During the 1953-54 season the corresponding figures were 540,000 acres topdressed with superphosphate, of which 170,000 received lime as well, while an additional 190.000 received lime only. Below Average There appears little doubt, therefore, that the rate of top-' dressing in Canterbury has been

stepped up very considerably in recent years, although even with the above figures, only one-quar-ter of the pastures receives topdressing each year—still less than the average for New Zealand. Nevertheless, this greatly accelerated topdressing in recent years could, and probably should, mean that those Canterbury farms which have been treated appreciably better than the average are in a position to relax slightly their normal fertiliser practices.

pronounced where topdressing has been a regular annual practice. It should, be remembered that one way which could help our products to be sold on new markets is to lower the costs of production—to keep up or even increase production and reduce costs.

This means that every component of the cost of the farm 1 unit—interest on capital invest-! ment, cultivation costs, seeds and fertilisers—must either be spread over a greater yield, obtained no 4 from new acreage, but by more efficient management of the same area, or non-productive costs such as repairs and maintenance must be reduced while maintaining present production. Either way, seeds, lime, and fertilisers are an integral part of the programme and should be the last, not the first item cut.

It is known for lime, provided the initial requirement has been adequately met, that the lasting power of a dressing of one ton per acre on the plains land may be several years. Just how long will depend on the conditions but it appears from recent results that it may be longer than we have been accustomed to thinking. It is known, too. in a general way that superphosphate may exert slight residual effects for a

period of up to three or four years or perhaps longer, and of course this Residual effect will be more

It has been reported that no drop in production occurred on a group of farms in Northland during the period of fertiliser shortage of the war, and it is suggested that probably little reduction in production would occur from the cutting down of lime and fertiliser applications for one season or perhaps even two, on those relatively few farms where really adequate amounts have been applied. Elsewhere it is doubtful if production could be sustained, but if it must be done, then the re-

duced amounts should be used to the best effect. Treat new pastures and lucerne generously treat good pastures well; the rest will have to take their chance.

•Research Needed It is unfortunate that there is a lamentable lack of factual material concerning matters of this kind—for example, the most profitable rate of application of lime and fertilisers and their residual effects when applied to grassland. Some progress is being made along these lines with respect to lime. To get such information for fertilisers would be a tremendous undertaking but one which perhaps should be tackled. It is certain, however, that until we do have this knowledge we cannot give definite answers to the questions at present being asked.