USE OF LIME ON FARMS

Taranaki Daily News, 15 July 1933, Page 22 (Supplement)

USE OF LIME ON FARMS

VARYING RESULTS OCCUR STUDY OF ACTION NECESSARY. MASSEY COLLEGE BULLETIN. (By F. L. C. Scrivener, B.Sc. (Agric.).) The regular' use of some form of lime or chalk was part of the accepted routine of farming as early as we possess any records of British agriculture. Scientific workers have studied the action of lime in the soil and the response of plants to the effects of liming and we now know a good deal about the reaction of different types of soil to the application of lime. Nevertheless it is surprising to find that we are still in the dark when it comes to a reliable method of testing soils for their lime requirement. In many cases the experience of the farmer in one particular district is such that he looks upon liming as the first essential in successful field husbandry. In other cases, in the absence of any visible benefits from the use of lime the deep-rooted tradition of British agriculture is sufficiently powerful to induce the farmer to lime his land in the hope that some good results will follow and in the knowledge that no harm will be done. It is apparent that further definite knowledge about liming is urgently needed more particularly at the present time when it is essential to cut down fertiliser costs on the farm to the minimum compatible with the maintenance of soil fertility. THE FUNCTIONS OF LIME. Lime plays many different parts in the processes of the soil and in the relationships between the plant and the soil. In the first place, lime is a compound of the chemical element, calcium, which is required by all plants for their normal growth. Addition of lime to the soil, therefore, ensures an adequate supply of this plant nutrient. Furthermore, lime is required by stock for bone formation and other functions in the animal body and many stock ailments are ascribed to a shortage of lime in the herbage. Clay soils which become sticky when wet and difficult to work are altered M?y heavy dressings of lime so that their physical texture is improved and cultivations made easier. There is a -tendency in all soils of moist, temperate climates to become “sour.” This is due to the washing out of certain substances by rain and the subsequent development of more acid conditions. Sourness is also • caused by the accumulation of organic matter; extreme cases are seen in peat swamps where acidity may be very highly developed. The continual use of certain fertilisers will also increase the acidity of the soil. It has been shown that, in many cases, the full value of fertilisers is not obtained unless the soil is first limed. Acidity beyond a certain degree in the soil is undesirable since many of our most valuable crops and pasture, plants will not thrive in very acid soils. Furthermore, the beneficial bacteria, the invisible workers in the soil which are continuously improving the conditions for plant growth, will not produce their best efforts in a sour soil. Lime is the cheapest and most generally accessible substance to apply to correct this acidity.

Many crops in New Zealnd are sown with a small quantity of superphosphate to encourage vigorous growth in the early stages. The germinating seeds may be injured by contact with a highly soluble substance and lime is mixed with the superphosphate to- check this injury. A further use of lime in its ability to control club-root disease. It will be seen that lime has many and varied uses in the soils and the tradition which favours its use in all types of farming receives scientific support up to a certain point. USE OF LIME IN NEW ZEALAND. The indications of the need of lime which are so useful in Great Britain cannot be used in the same way in New Zealand. All text books on British agriculture, which are often quoted in New Zealand, stress the importance of observing the growth of certain weeds such as sorrel on grassland and spurrey in cropped land as an indication of lime requirement. In New Zealand, or in the North Island at any rate, the presence of these weeds indicates general lack of fertility and particularly lack of phosphates far more than a need for liming. This example is given; in order to warn the New Zealand farmer against believing that all the finding of British workers in agricultural science will apply equally in New Zealand. The conditions of soil, climate and farm are so different that New Zealand must work out her own problems, at the same time observing the results obtained in other countries and making use of them with discrimination.

There is a very marked difference in general response to liming between the North and the South Islands. In the South Island 58 per cent, of the total fertiliser used consists of lime, whereas in the North Island the figure is only 12 per cent. In many districts of the South Island the trials conducted by the Department of Agriculture show that no response to other fertilisers can be obtained without the initial use of lime. In many districts of the North Island, however, on soils containing no more lime and showing an equal degree of acidity, no visible response of liming can be obtained. The farm of the Massey Agricultural College is a case in point. On several different types of soil, all of them acid in reaction, trials with lime have been conducted for five years, both as a top-dressing for grassland and also worked into the soil before seeding, and in only one case has any response been seed and this on an experimental plot which received a dressing of lime heavier than could possibly prove economical to a farmer. Similar cases of lack of lime responsiveness on acid soils have been reported from other countries. In order to review the possible explanations, the functions of lime already discussed will be dealt with as they apply to New Zealand conditions. The quantity of the element calcium needed by plants is not great and sufficient supplies are usually available for this particular purpose in even the most acid soils. Superphosphate and basic slag contain lime compounds in a readily available form, and since most of the farm lands of New Zealand are topdressed with one or other of these phosphatic fertilisers, there should be an adequate supply of calcium on unlimed soils. Experiments at the Cawthom Institute have shown that it is possible to increase the lime content of herbage more by applying dressings of superphosphate than by dressings of lime, so that even if some stock ailments are really due to a shortage of lime in the herbage it does not necessarily follow that liming is the best remedy. The physical properties of clay soils are greatly modified by the presence of organic matter oi’ “humus.” The stickiness of heavy clays is not so noticeable and is less readily corrected by liming when much “humus” is present. Humus accumulates under permanent pasture and it is probable that the difference in lime response between North and South Island conditions is partly due to the higher content of humus in the North and the very much greater amount ot cropping practised in the South.

SOIL ACIDITY. Our conception of soil acidity has changed considerably in recent years. It is now realised that most crop plants prefer a slightly acid soil to a perfectly neutral one. • If other conditions are favourable there is no reason why soils of a considerable degree of ‘ acidity should not support vigorous growth of good grasses and. clovers. Acidity by itself up to a certain point .does not limit the growth of good crops, but other conditions which we do not yet fully understand often make it compulsory in some soils to obtain non-acid or neutral reactions. These Conditions, which may be partly due to climatic factors, would explain the differences betwesn lime response in the North and in the South. The continual use. of superphosphate was, until a few years ago, thought to lead to soil acidity, and subsequent soil impoverishment. It is now known that supei-phosphate does not . have this effect and in fact some of the effects leading to lime responsiveness can be corrected by the use of superphosphate. The use of sulphate of ammonia or other nitrogenous fertilisers containing ammonia leads to a loss of lime from the soil and a greater development of acidity. On soils which normally respond to lime, the need for liming will be greater where these fertilisers are used. On the other hand, if the soil does not respond, to lime, there seems ‘to be no immediate need to consider / liming even in conjunction with fertilisers containing ammonia, although it is probable that the time elapsing before lime is needed on such soils will be curtailed by the use of such fertilisers. EXPERIMENTAL WORK. . It must be recognised that even in those districts where there is a complete lack of visible response to liming as shown by the appearance or quality. of pasture growth, there is a strong feeling that some ultimate improvement must result from liming either to the soil'or to the stock. In order to test this theory in the only way possible, the dairy farm of the Massey Agricultural College has been divided into pairs of paddocks, one of each pair receiving, only the normal dressings of phosphate and other fertilisers used on the faym and the other receiving in addition a heavy dressing of lime every few years. The dairy stock have been divided into herds, one herd being kept on limed. paddocks: and the other on -uhlimed paddocks. The practical difficulties involved in .controlling the grazing, of; a limited .number of pad 7 docks by two separate herds will be appreciated .by all fanners, but it is hoped to continue the experiment for a number of years.. Records of yield,, test, stock ailments, quality, of.the milk for cheesemaking and .other details, are being kept and after several years.it should be possible to make some, more definite statement concerning the. liming of apparently non-responsive' soils. In addition to this experiment, laboratory tests are being investigated which may distinguish in a reasonably snort time between those soils which need lime and those not likely to prove responsive. If such a test is found,' it will enable laboratory workers. to save the farmer useless expenditure on lime on those soils where lime is not needed and at the same- time encourage with confidence the further use of lime on lime responsive, soils. '. . ' . At the present time the only advice that can be given to a farmer is to satisfy himself by trial whether lime is, producing a ‘ visible effect or not .on nis cops and pastures. If the result is striking enough to be conclusive then the farmer can rest assured that he will be well repaid for the cost of periodical dressings of lime. If no response is visible, in the absence of proof that anj invisible benefits result from liming the farmer would be better advised to spend his money on phosphates which are known to be almost indispensible in all districts of New Zealand, and from the use of which he is much more likely to return a profit. The Great Future. There is no industry with a surer future than that of pig-keeping. In the leading producing countries beef is declining in. popularity as well as mutton, whereas pig-flesh is rapidly mercasing in general favour, followed by lamb but to a lesser degree. A case is being cited in London to prove the great popularity of pork. At one of the largest of London hotels the management gives the start and their wives hnd friends their own dinner during Christmas week. Ihe manager always leaves to the staff to decide their own menu by vote. I»ast Chrisffiias 45 per cent, voted for roast pork, 25 per cent, for roast beef, 15 per cent, only for turkey and saddle mutton was "also ran" with a few odd votes. Of course, it has to be re- . membered that people might choose a | more or less special dish for Christmas | dinner, which they would not want I every, day of the week. ]