FOR THE FARMER.

Manawatu Standard, Volume LVIII, Issue 227, 24 August 1938, Page 5

FOR THE FARMER.

MANURES AND THE SOIL.

MERITS OF POTASH. (Concluded.) It is known that potash emits radio-active rays, feeble, yet definitely /traceable. In some countries, especially in England, it has been observed that potash seems to be of special importance in years of less than normal sunshjnc. It is presumed that potash can, under such circumstances, assist plants by its .radioactivity by stimulating growth during darkness, or when the sun’s rays arc obscured in the daytime. It has long been recognised that potash in some fashion increases the fixation of carbohydrates, such as sugar and starch. In recent years it has been discovered that this action is consequent upon the stimulation potash exercises upon the quantity and activity of chlorophyll and chlorophyll elements. Potash is of deep significance in the production of vegetables and fruit. Its importance is not yet fully realised by fruitgrowers in the Dominion, and there is still some misconception that all fruitgrowing soils are richly endowed with potash. Long years of patient re search in England have enabled scientists to state authoritatively that in the life of fruit trees forced in production as trees are now forced, there comes a time when it is imperative that potash must be used. As the supply of potash diminishes fruit loses its flavour, colour, keeping quality, and disease-resisting powers. s NEED FOR REPLACEMENT.

The frequently expressed opinion that land which was originally forest is adequately supplied with potash is erroneous. Potash is highly soluble; therefore, the. amount of potash contained in the residual ash afterburning the timber is quickly assimilated and used by pasture plants. The main effect of potash is to increase clover growth, and this increased growth ot white clover eliminates the annual species of plants and generally increases the density of the sward. When a farmer applies any fertiliser to the soil he generally does so, even if unconsciously, in recognition ot the fact that it is in replacement ot elements of fertility sold off the farm in various products. That there is need for potash replacement seems certain when it is remembered that dairy produce, beef, mutton, and wool, etc., remove practically the same quantities of phosphoric acid and potash. Potash is not yet used extensively in the Dominion, but the time must come when its use will be general It is not fully recognised that New Zealand annually exports in primary pro-' 'duce far more potash than she imports : therefore, the balance will sooner or later have to be adjusted. MAINTAINING BALANCE OF FERTILITY.

Nitrogenous fertilisers give markedly increased yields and act as stimu lants to crops. It is,, however, essential that the soil be fully and richly endowed with phosphates and potash if quick acting fertilisers such as sulphate of ammonia and nitrate ot soda are to produce economic returns without impoverishing the soil. DrsJ Askew and Stanton conducted exhaustive trials on pastures in the Nelson Province and reported as follows: .Jt is clear that, where nitrogen has been used, markedly increased yields were obtamed in the-first or early spring period, but that later in the season, where nitrogen and phosphate only were used, the yields fall below those for phosphate only, so that over the whole season the total yield in the former case may fall below that of the latter. On the other hand, when potash was added to the fertiliser treatment the depression .in yield was not so great as for nitrogen in conjunction with phosphate, and the yield from the complete treatment was actually the highest of all the treatments. For the whole season the complete treatment of nitrogen, phosphate, and potash gave the highest jueld. it has also been shown that the depres sion in growth which frequently follows a flush of growth brought about by nitrogen is to a large extent overcome by the application of potash in conjunction with nitrogen and phosFACTORS AFFECTING MANURES. Various factors such as local soil conditions, moisture, cultivation, etc., make it impossible to adhere strictly to a general course of soil treatment. Soils vary in their response to the action of various fertilisers, and loca knowledge of prevailing conditions is usually the farmer’s best guide. .. INFLUENCE OF MOISTURE.

When disappointing results are obtained from the use of manures they can be attributed in some cases to lack of moisture in the soil* at some time during the growing period ot the crop. For example, a wheat crop which has been manured with superphosphate may with adequate moisture in the early stages grow more vigorously than is warranted by the later -water content of the soil. Because this vigorous early growth cannot be sustained the plant finishes up by setting less seed than does a corresponding unmanured plant that lias not been over-stimulated. Since it is impossible to predict dry conditions prior to harvest, and because of the general increase obtained from superphosphate, it is probably desirable to not over-stimulate cereals. Another example can frequently be seen where sulphate, of ammonia lias,, been used with potatoes on light land and where a dry autumn has-been experienced. The prolific eariy growth induced by the sulphate of ammonia cannot be sustained during the dry time, and a frequent result is a larger percentage than usual ..of small-sized potatoes. Since dry autumns may be frequent, it would be. deemed advisable to use sulphate of ammonia with potatoes on medium to good .land jrather than on light land. Because of the higher yields obtained it may be taken as a fair guide that . larger quantities of manures should,be used in those areas where the average yearly rainfall is moderately liigij and is generally evenly distributed /oyer the growing season

son. • v ;/; • - . j.y- ; . ' CULTIVATION'. If manures -are to.sgiye. satisfactory results it is pssentisrt that the soil should be inf a fit. cdfidition .before applying fertilisers. If cultivation is faulty fit is-/quite possible that some condition of,?the soil' other than plant food may|:be thes .limiting factor affecting piarih growth. . Manures can-not'j-COmpenVate 'for; deficient cultivation. . - £>sjs«Ssßss/ ■ ECONOMIC/ ItKTURNS. The inerwse;- from-the use of. 'manrtVelmiust bo sufficient to' more I hail - pay,, ior the dotal cost of application. Ta'fhis-\»i.tjonneotion eye observation; may'lead to erroneous con-

clusions, and examples'-of this may- be seen oil light land where manuring may give marked increases in growth, and yet the extra return is not sufficient, to pay for the initial outlay.' Even when* small quantities of’fertilisers are applied these perforin the necessary function of supplying young seedlings with readily available plant food. As a result of this action the young plants receive stimulation and a good start, and it is this fact which is largely responsible for increased yields. -