MANURING OF GRASS.

Otago Witness, Issue 3097, 23 July 1913, Page 17

MANURING OF GRASS.

Mr R. E. Alexander .contributes the fob lowing to tho Canterbury Agricultural College Magazine:— The average farmer in Canterbury nowadays would hardly dream of putting in hia wheat, oats, turnips, or rape, or in fact any crop, without a suitable dressing of manure, and when asked why ho does so the answer invariably is, he could not get a crop without it, for ho had tested the effects from a missed drill width here and there. There is no doubt that the reasoning is sound, and the application of manurmg to these crops is a good investment and yields a big profat. Has the saute consideration and reasoning been brought to bear on the treatment of grass and lands in grazing? If so, why are lands laid down to grass as a rule without manures and lands in grass absolutely neglected so far as manurial .treatment is concerned? If we first consider lands which are to ba laid down in grass, we find there are generally two or three reasons for laying lands down. the. chief being that tho land i« ( crop-sick and wants rest. The term “crop-sick ' generally moans that tho available p'nnt-food is depleted, and,the land is laid down in the hope that tho vegetable matter will accumulate as "tho r ” successive growtlis of grass eaten oft. This accumulation of vegetable matter can only take place if (a) the grasses aro wc.l supplied with food and (h) proper grasses are sown. We will neglect the latter condition, and in regard to the former we may ask if the land is too poor to grow crops, how can it grow grasses if no manure is supplied? Of course if grasses do not grow well, we are not getting the cattle, food that our land should yield if well farmed nor do we get the accumulation of vegetable matter to plough down as food for succeeding crops—land is only “resting” when a good sole of grass is formed on it. where the sole is poor and thin no good results are obtained from keeping the'land m grass. Quite often recently I have hoard and seen statements to the effect that tho crops obtained nowadays after gnus aro not anything like what they used to be, even when manures are applied. How can the crons be as good to da v? Lands ploughed out of “the native" had tho accumulated vegetable matter of hundreds of years. Wo expect to get. die same returns after ploughing up a sickly grass paddock only down a few years, and laid down in poverty. Plants do not bring mineral matter to the soil, and it has on!v so far been definitely proved that one “family—that to which the clovers belong—can fix nitrogen in the soil. How do pastures then increase the fertility of the soil? A pa.-lin e with a lot of clover growing in it will increase the nitrogen eupnly, 0 but only when there is a plentiful supnly of available phosphates, lime, and potash” present. The action of the grasses is more mechanical than chemical— a vigorous growth of grass generally moans also a stiong root-growth. ‘lbis root development acts more or Jess like a subsoiler and pulveriser combined; the result is, that when hairs have penetrated to the subsoil and finer tilth can bo obtained, an the fine roothairs have penetrated to the subsoil and between too particles of soil, breaking them up and making tho passage of the- roots of quick-growing crops easy. In addition to this mechanical action, tho root-airs in their passage through tho interspaces of the soil exert an influence on tho mineral matter in the soil by means of their excretions, the result of this action being that the mineral matter is left in a more soluble condition and is therefore more available for a succeeding cTop. Tho net result front laying land down in grass is that a finer “and better seedbed is ensured, and more available plant food is present for a succeeding crop. This result is magnified or lesened according to tho treatment of the land and mixture of grasses sown. A double advantage can therefore be obtained from manuring lands when laying them down to grass—viz., more stock feed and heavier crops afterwards. It is unnecessary to point out that grasses make a strong demand on (he four food constituents which are generally termed the essential constituents; but tho analyses of 30 bushels of wheat and one ton and a-half of hay (either of which would he considered a fair crop) show fairly clearly what the comparative exhausting effects are ;

Taken all round, hay is really the most exhausting crop, and yet we expect a crop of hay without manure, and supply manure to our wheat crops. Even when no hay is cut and tho gra‘s « only grazed off. tha land is being depleted of its constituents, as we sell off the products of the grass ae hoof, lambs, or milk. Take the two important New Zealand products—lamb and milk, -and estimate the produce of an aero as 2001) lamb and 30001 b milk per annum, and we find the land has lost:—

In cither case much more lime is lost than when wheat is grown arid one-third to onefourth the quantity of the other constituents, so that if the fertility of the land is to be maintained a suitable dressing of manuret nZiould be applied every three or four years to permanent pastures. The topdressing of pasture lands has not as a rule been considered up to the present, hut if farming is to become more intense then part of the curriculum must be the manuring of the pastures. When considering the question of manartu we will find that two of the constituents. are likely to be more necessary than the others. Experiments and analyses have shown that phosphates and lime are present in only limited quantities in tho average New Zealand soil, and in most case* a dressing containing these constituent? will ensure a good solo of grass. On heavy clay and boggy lands it may he necessary to add potash. In most of our best soils, especially where there is an admixture of sand or gravel, there is a sufficient supply of potash present if made available by proper cultivation. A liberal supply of manure* containing the above constituents is almost certain to encourage a good growth of clovers, and as these plants enrich the soil in nitrogen, the problem in regard to thi»

constituent is not raiich tlie supplying of it but the encouragement of plants that fix it in the soil, and at the game .time increase the feeding qualities of the pasture. What is the best dressing for grass lands? The reply to this question is that it depends on circumstances. If lime is available and : cheap, then a dressing of 51 tons Hmo and j 2cwt applied separately, once in a rotation. ! If applied when the land is being sown down, the lime should be broadcasted on ' the top just before or after the grass seed is sown. Lime has a tendency to sink in the soil, and should therefore be bent as near the top as possible. Super may lx? drilled in. If lime is not available, then 3cwt to 4cwt of high-grade basic elag or 3owt to 4cwt basic super may be used as a top-dressing—loss would do in a short course rotation where lands have been ■ploughed and are not likely to bo sown. Boggy land or cold clay might respond bettor to a 3 to 1 mixture of basic slag and kainit or basic super and kainit applied at the rate of 3cwt to 4cwt per acre on old grass lands and IgCwt to 2cwt per acre on lands being sown down. All these manures being more nr less insoluble should be applied in the early winter if possible, but they should not bo applied in very wet weather or if the land is in a sodden condition. This precaution also holds good when dressing with lime. It might be asked why such a heavy dreeing is recommended for old grass, when the general policy in supplying manures is “a little and often.” Experiments on old grass in Britain have shown that one good dressing of manures has given a better and more lasting return than small dressings at shorter intervals. The explanation is that very often the poor herbage found on an old pasture is due trv a certain extent to acidity of the soil. One largo Jressing of basic elag may overcome this. ( md stimulate the better grasses, whereas ■ even frequent small dressings do not neutralise the acidity, and better grasses i never get a start. i I

Nitrogen. Phos. acid. Potash, Lons 11)3 lbs lbs !!„ ,t0 bushels wheat contain .. .'51 It 9i I 1t tons hay contain 19 12i 51 32

Nitrogen. Phos. acid. 1’ota‘b. Lime. lbs lbs Mij ibi 2001b 1 iamb .. 4 24 i 2J 30001b milk IS G 5 5i