Topdressing in Mid-Canterbury

New Zealand Journal of Agriculture, Volume 62, Issue 2, 15 February 1941, Page 99

Topdressing in Mid-Canterbury

Lime and Superphosphate Have Proved Most Beneficial

T YING between the sea and the LYING between bordered and the foothills, and bordered by the Rakaia River in the north and the Rangitata River in the south, MidCanterbury contains approximately three-quarters of a million acres of land, which slopes gradually from sea level to approximately 1200 feet high at the foothills. Some few years ago a geological survey disclosed some 40 to 50 different soil types within this area.

In the main, they are composed of a silt loam overlying gravel beds of porous shingle. Near the rivers the top soil is usually free from stones, but elsewhere the surface soil has become mixed with the underlying shingle, forming soils of a stony nature. The natural fertility of the soil within this area varies considerably. In parts of Wakanui, Eiffelton, Methven, and stretches along the banks of the Rakaia, Ashburton and Hinds Rivers, the soil is very rich, and cropping with cereal and pulse crops is

carried out here on an extensive scale. In any one year as much as one-third to one-half of the total farm area may be under crop. On the other hand, there are areas in the county where the carrying capacity may be less than one ewe per acre and farm returns are obtained mainly from wool and store lambs. Between the two extremes mentioned there are innumerable soil types which vary in fertility and where the farm management practice is largely dependent on climate and relative market prices for cash crops and sheep products. From a farming point of view, however, the soil types can conveniently be classified into three main groups, namely, light, medium, and heavy. ■ ' Hi. Climate > ; J Near the coast a rainfall of 20in. to 25in. a year is usually experienced. This amount gradually increases until the foothills are reached, where the fall may exceed 40in.. Over the greater part of the county, however, the rainfall is about 28in. This rainfall is usually . ample for the system of farming practised, with the exemption of the summer months when, because of the porous nature of the underlying shingle, the hot, dry summer winds

tend to parch the , ground, particularly on the medium and light soil types. Grass growth throughout the winter months is almost negligible because of cold, frosty conditions. Snow is common around the foothills, but usually only one or two falls a year are experienced over most of this country. In the winter and spring cold southwesterly winds may make conditions unpleasant for stock, but in this respect the county is fortunate in being fairly well sheltered by plantations and gorse hedges. Pastures On the plains land of the county there are approximately 500,000 acres of sown grassland. The life of the average pasture is about four years, so that, allowing for areas which are in

permanent pasture, something like 100,000 acres are sown down to grass each year. The pure sowing of grass is the exception rather than the rule. On areas where cash crops are produced'the grass mixture is frequently spring-sown in a cereal crop or sown in the summer with rape and turnips. On the light sheep country sowing down to grass with rape and turnips is the most common practice. While these methods of grass establishment are possibly not conducive to the production of first-class pastures, over a long period of years this system has proved the most economic. The chief pasture species sown are perennial ryegrass and - red clover. Cocksfoot, crested dogstail, white

clover, and alsyke clover are used to only a limited extent. Recently, subterranean clover has been widely sown with mixed results. It is usual for most pastures to give reasonably good production over a period of two years. From then on the ryegrass and the red clover gradually diminish in quantity, and are replaced by foreign growth. On the light and medium land, browntop, sweet vernal, and hairgrass are the chief offenders, while on the heavier soil types hairgrass and various forms of flat weeds eventually replace the better pasture species. Ultimately, the pastures cease to be economic and are ploughed upusually put through a course of cropping and

then sown down to grass again for a further period. Stocking The latest figures available indicate that there are almost 1,000,000 sheep, including 750,000 breeding ewes ,and also 10,000 dairy cows on the plains land of the county. Assuming the returns per ewe to approximate 25/-, then sheep products contribute something over £900,000 annually to the wealth of the county. Butterfat returns would realise a further £IOO,OOO. Rape, turnips, and green feed certainly contribute their share, but grass undoubtedly provides the major portion of this wealth. With the exception of potatoes, peas, grass, and clover seed, there are no export markets for our surplus crops, so that any increase in production in the future will be attained largely by a higher stock-carrying capacity of our grasslands. Greater attention in the establishment and maintenance of pastures than has been the case in the past will be necessary to bring this about. Ashburton Soils , Chemical analysis of Ashburton soils carried out by Kidson show that over the greater part of the plains there is a deficiency of available phosphates. In soils of comparatively recent origin such as occur along the south bank of the Rakaia River from the Gorge to the railway, -along the Ashburton rivers from Upper Winchmore to the sea, and in certain areas along the Rangitata River—'the available phosphate content is relatively high. The old, loose soils of the plains, however, are almost without exception low in available phosphates. The area between the Rangitata and the Hinds, extending from Ruapuna to Lowcliffe, from Valette to Willowby in the Hinds-Ashburton section, and the large area between the Ashburton and Rakaia represented by Sherwood-Fairton-Dromore-Seafield-Pendarvas, all show a low available phosphate content. Unlike the main rivers, the Hinds is also associated with. soils deficient in available phosphate. The lime status of Ashburton soils was also examined at the time phosphate determinations were made, ' and the results showed that all the soil types were more or less acidic in nature. Along the banks of the three main rivers soil tests indicated a

moderately sweet soil. Elsewhere, however, the lime status was comparatively low, suggesting a soil of a rather sour nature. Topdressing Trials During the past 10 years or so some 60 or more observational topdressing trials have been laid down in various parts of the county by the Fields Division of the Department of Agriculture. The fertilisers used have been superphosphate, basic slag, ephos, sulphate of ammonia, ammoniated super, and 30 per cent, potash salts. Lime, either in the form of burnt lime or carbonate of lime, has been applied in the majority of the trials laid down. In most of these trials the response to phosphates and lime has been most marked, while in a few cases an almost negligible response has been obtained. It is of interest that the poorer re-

sponses have been recorded mainly on those soil types shown by Kidson on chemical analysis to be relatively rich in phosphates and ' lime. Present Position The area topdressed annually with artificial fertilisers varies, but it is usually about 30.000 acres, or some 6 per cent, of the total area of sown grasslands. This figure compares very unfavourably with the Dominion average for 1937-38 of 22 per cent. Figures for lime applications over the past 10 years may also be of interest. In 192829, 1526 tons of lime were used. This figure progressively increased to 3877 tons in 1931-32, 5889 tons in 1935-36. and 10,637 tons in 1936-37. . These figures indicate that while the farmer is gradually realising the necessity of lime applications, the area topdressed with lime is still compara-

tively small. Taking the latest figure of 10,637 tons, and assuming it was applied at the rate of scwt. per acre—although the quantity applied would probably be much higher—then some 44,000 acres, or only 9 per cent, of the total area of sown grassland, would receive dressings of lime. Expressed in another way, at the present rate of consumption it would take 10 years to supply scwt. per acre to our grass areas. By far the greater quantity of lime and phosphates used annually is applied to the light and medium soil types. Topdressing is concentrated mainly on those areas where sheep products, or, alternatively, grass, provide the main source of farm income. On the better class wheat land, where cash crops are extensively grown, topdressing is practised very little.

In most parts of the North Island the advisability of topdressing is not questioned, and the majority of farmers are agreed that it pays to topdress. Why, then, is it that the area topdressed annually in Mid-Canterbury is so small? The reasons are many and varied. In the first place, the soil, and particularly the climate, do not allow the spectacular results that are obtained in many parts of the North Island from topdressing. The winters are usually fairly severe, with little growth taking place, and in a normal season the pastures on the medium and lighter lands are inclined to burn up considerably in the summer. Grass growth of any consequence, therefore, only occurs during September, October, November, December, March, and Aprila period of six months, as against a period of nine months or more in most districts of the North Island. Size of Holdings The size of farm holdings would also appear to influence the amount of fertilisers used. When large areas of light to medium land are held, farmers are not inclined to practise topdressing on an extensive scale. Fear of grass grub attack to pastures and doubts as to whether an economic response can obtain with ruling prices for wool and lamb are also contributing factors tending to restrict topdressing practice. Viewed from another angle, however, an increase in the acreage topdressed annually would appear essential if production is to be increased or even maintained at its present level. At the present time Mid-Canterbury grasslands are carrying approximately two sheep per acre, and, in addition, cropping is carried out on an extensive scale. Mid-Canterbury’s wheat acreage varies between one-quarter and onethird of the Dominion total, while oats, barley, and peas are also largely grown. With most crops it is the practice to sow lewt. of superphosphate per acre and a further lcwt. if “grassing down” with the crop. Assuming that the average pasture remains down for four years, then actually all that the land has been receiving in the way of fertilisers is some 2cwt. of superphosphate per acre spread over five years. In many cases this practice has resulted in more phosphates being removed in sheep and crop products than

are being returned to the land in the form of artificial fertilisers. The drain on fertility, spread over many years, is now evident over large areas of the county, but more particularly where wheat is being, grown. The failure of clovers to establish in pastures and the general lack of vigour of clover growth are symptomatic of a phosphate and lime deficiency. Systematic topdressing over a period of years would appear to offer a mean by which the balance of fertility could be restored. Advantages of Topdressing Topdressing undoubtedly prolongs the life of the pasture, and also increases the carrying capacity. Mention was made earlier in this article that most pastures in Mid-Canterbury deteriorated fairly rapidly after the second year. . With systematic topdressing, the ingress of browntop, sweet vernal, and hairgrass could be largely controlled and the carrying capacity of the pasture maintained. Topdressing brings growth away earlier in the spring, and permits earlier lambing, with a greater percentage of milk lambs. This is an important point in a district where it is becoming increasingly difficult to grow good crops of rape. Topdressing improves the health of sheep. An analysis of pastures topdressed with lime and phosphates shows a corresponding increase in the mineral content of the herbage. Stock licks are largely used merely because pastures generally are deficient in mineral matter. Topdressing, by prolonging the life of the pastures and curtailing the area in supplementary crops, tends to reduce cultivation costs. < . Phosphates ' There is no question that the most profitable response on Ashburton soils is obtained from applications of phosphatic fertilisers. Phosphates encourage and maintain clover growth, thereby thickening the pasture and assisting the grass species in the sward. Of the three forms of phosphates available on a commercial superphosphate, basic slag, and rock phosphate former has undoubtedly given the most economic response. In all the observational topdressing trials conducted .by the Department superphosphate has proved superior

to other forms of phosphate. It is possible that on wet areas nearer the foothills slag, may prove profitable, but it is only -recently that trials containing slag have been laid down on this class of country. Rock phosphate has not given a sufficient response to warrant its use. Potash Potash, in the form of 30 per cent, potash salts, has been tried in a considerable number of experiments, but whether applied alone or in combination with superphosphate or superphosphate plus lime, it has in no case resulted in a visible increase in growth or given a noticeable sward improvement. It is possible, however, that potash may give an economic response on land which has previously been adequately topdressed with lime and phosphates. Nitrogen But sulphate of ammonia and ammoniated super have been tried out on varying soil types with no great degree of success. Both these fertilisers will produce a flush of feed in the spring, but for a short period only. The tendency with too heavy dressings or with continuous dressings is to deplete the sward of clover. As a special purpose manure, sulphate of ammonia can be used to a limited extent for producing early spring feed. Its general use, however, cannot be recommended. Lime Two forms of lime are available in Mid-Canterbury—carbonate of lime and burnt lime. The former is more popular, being easier to obtain and more congenial to handle. Results of observational topdressing trials, coupled with actual farming experience, have proved unquestionably that on most soil types lime is the basis of topdressing practice. If full value is to be obtained from applications of phosphate fertilisers lime must be used in addition. It is not necessary for the lime to be applied some months before the phosphates; equally good results will be obtained by applying both lime and fertiliser at the same time. Lime improves the physical condition of the soil, and for this reason it is to be recommended, particularly on wheat areas which are difficult to cultivate down to a good tilth or which tend to crack rather badly during dry .weather.

Relative costs should determine which form of lime is x used. Burnt lime, even on the light land, responds equally as well as the carbonate. Time of Application The time of application is not a greatly important factor. Phosphates do not leach through the soil, and they may therefore be applied whenever farm operations permit. On land which has previously received lime, applications of superphosphate may be made in the autumn. Otherwise, lime and superphosphate can be applied at any time during the winter and early spring. While lime will undoubtedly give a good response when applied to established pastures, experience suggests that in a low rainfall area the best results are obtained by applying the lime to cultivated land. It would seemand this applies more particularly to the light and medium land that the prospects of obtaining good clover establishment are enhanced if the lime is lightly covered just before sowing the grass mixture. Quantities to Apply It is difficult to recommend definite quantities of lime for any particular soil type. Intrials conducted in the county quantities ranging between scwt. and 2 tons per acre of carbonate of lime have been tried out, the larger quantities being used to gain some information on the period during which lime will continue to give a response. Cases have been noted where scwt. per acre has given quite an appreciable response, but larger applications have increased the clover content of the sward and also made the growth much more : palatable to the stock. Cost of application, type of pasture, and length of time it •is intended to leave the area in grass are all factors which must be taken- into consideration when deciding on the amount of lime per acre to be applied. In general, lOcwt. per acre of carbonate of lime should prove a reasonable dressing on the medium and light land in the county, while on the heavier class of land known to respond to lime, applications up to one ton per acre of carbonate could be used. In trial work superphosphate has been used in quantities varying between lcwt. and 3cwt. per acxe, and it has been found that the best response

though not necessarily the most economic been obtained with heavier applications. Actually, the type of soil, the class of pasture, and the rainfall should determine the amount of superphosphate to apply. On light land where topdressing is practised annually one bag of superphosphate per acre should prove ample. On the heavier land this amount could be increased with advantage to two bags per acre. General To obtain the maximum benefit from topdressing the practice must be associated with a general scheme of pasture improvement. Too often results are expected from topdressing when the fertilisers have been • applied to a poor pasture. An absence of response in such cases has led the farmer to condemn topdressing, when actually it is the pasture which is at fault and not the fertiliser. . The first consideration is a good grass cover, with a proper balance of clovers to grass. It is only by sowing good seed and giving the pasture every opportunity to establish that useful results become apparent. Both phosphates and lime encourage clover growth, and legumes must be present in the pasture to enable the fertiliser to work efficiently. On most farms are to be found pastures in varying stages of growth- good, poor, and indifferent. In cases where the area which can be topdressed is limited, farmers should concentrate on maintaining the production of their good pastures rather than endeavour to improve their older ones. Each year cases come under notice where farmers use considerable quantities of lime but no superphosphate. It is very doubtful whether this practice is wise. Lime alone has been used in several of our topdressing trials, and the response has been very poor indeed. Further, the growth on “limealone” areas has not proved nearly so palatable ,to stock as those areas which received both lime and superphosphate. Results of trial work undoubtedly suggest that farmers would be wise to topdress with superphosphate those areas which receive lime, rather than to concentrate on lime alone.

Finally, farmers ; should not expect immediate results from topdressing. Building up the fertility of the soil so that it will carry better swards must

be a gradual process. There is evidence in almost all districts in MidCanterbury that systematic topdressing extending, over a period of years will eventually lead to increased carrying capacity and more healthy stock. Answers to Correspondents Mixing Super and Lime F.M.R. (CANTERBURY):— I wish to know how long before sowing with turnips, super and lime may be mixed together without any deterioration in the ■■ mixture. Also, how long superphosphate may be kept before' use. FIELDS DIVISION:— Lime and super mixtures do not deteriorate so long as storage conditions are satisfactory. You may therefore mix lime and super for your turnip crop well ahead of the time intended for sowing. Regarding superphosphate, this fertiliser does not actually deteriorate under storage, although under long storage there is ’ a tendency for the formation of a small percentage of reverted (di-calcium) phosphate. This, however, does not materially affect the value of .the fertiliser, although rendering it somewhat slower in action than fresh material. Hygiene in Pigs Suipestifer infection continues to be responsible for a considerable mortality in pigs in several districts, states the annual report of the Director of the Livestock Division. It would appear as if . the organism became more virulent on some properties, the mortality rate being so high. . Losses in young pigs due to the disease are heavy, but on occasions the mortality in older pigs is quite a feature of an outbreak. A higher standard of hygiene in the piggery, including better and cleaner feeding, will assist in preventing outbreaks of the disease. Experiments are being conducted by field officers with regard to a special treatment of affected pigs. Although only limited trials have been so far completed, there is some room for optimism. Further trials are being arranged.

G. K. McPHERSON, Instructor in Agriculture, Ashburton.

•Jen- mt—mi—nu— mi——.mi—• mi— mi— mi——— mi—rA I Topdressing trials in Mid-Can- 1 terbury have yielded evidence 1 that in almost all districts sys- I tematic topdressing over a j period of years will eventually | lead to increased carrying cap- j acity and more healthy stock. ? It is emphasised, however, that ; to obtain the maximum benefit 1 from topdressing the practice i must be associated with a gen- 1 eral scheme of pasture im- j provement , and that farmers j | must not expect immediate j j results. j 3 = * _iiii._iiii— mi—mi—mi—mi—mi—mi—Rip