THE RURAL WORLD.

King Country Chronicle, Volume V, Issue 380, 22 July 1911, Page 7

THE RURAL WORLD.

SOIL SICKNESS. EFFECTS ON PLANTS. The investigations by Dr Sweet, the winner of the David Syme Research Award, afford valuable suggestions as to the evolution of parasites in stock beins equally applicable to plant hie in the soil. Ins-tea Jof plan: diseasepreceding, or being the cause of, disorder in the soil, the more reasonable theory is that plant diseases are forerunners of what may be calied a class of diseases of the soil, that are induced by improper treatment. Growing the same class of crop from year to year, continuously, without such necessary changes as are effecte i by approval systems of rotation, is followed by nature's protest in the form of a diseased soil which ultimately affects the crops, and conse-

quently calls for a resort to mure reasonable tillage mehods. Practi cally this has been the history of the eel worm in onions, and the blignt in potatoes, while the present condition of the wheat growing lands of the State is another ease in point. That is to say, all except the new areas at present sent being broken up from the virgin sod. The older wheat lands, which now date from twenty to thirty years since their first breaking up, are only being saved from failure j by the introduction of a rotation sysI tem whose rule is that the same piece |of land will not be cropped oftener | than once every three or four years, I with the intervening period utilised ! by farrowing, the growing of green icrops, such a rape or peas, and the ; keeping of sheep for the raising of export lambs. l The rapid spread of sorrel on the i older wheat lands is a feature of the | times concerning which various explanations are being made, and of these the idea that the soil is becoming "manuie sick" by repeated applications of superphosphate during a lengthened series of years is most frequently suggested. It this there is a certain amount of truth mixed with a proportion of error. The manuring of land with superphosphate, as long as the soil is handled on correct principles, cannot be other than beneficial, and it is only under the contrary practice that the manure loses its effect and becomes a promoter of sorrel growth instead of grain. The true position is that the repeated supering is being confined to so shallow a depth that the soil is being affected in the way described as manure sick. The remedy is to give the manure a larger proportion of fresh soil to work upon, and how this can be Fdone is by adopting "The Leader" method of "deep stirring," so [called as distinguishing between that and "deep ploughing." The new system means breaking up the subsoil without bringing it to the surface, as distinct from deep ploughing, which brings the crude clayey subsoil to the surface and burying th? mellow surface soil underneath.

' The first wheat growing innovation was fallowing; then came fallow working; and deep stirring comes in as the latest improvement. What is wanted is the breaking up of the hard sole that at present exists under the ordinary furrow. For many years the older wheat growing lands have been ploughed season after season only down to the depth of the original ploughing, and upon the bed made by the sole of the plough the implement has been travelling ever since. Each | suceeding year the plough fincl3 its old I bed and goes on continually to make | the bottom of the fallow harder, until | the winter rains of the fallow are ' prevented from getting through to the I subsoil underneath. In addit'onto this | there is also the serious fact that the super manuring is only now operating upon the same old average of about three and a half inches of surface and ' cannot last for ever. The remedy is to break up the hard cake at the bottom of the furrow so as to allow the soil underneath to become ameliorated by aeration and made ready for adding a little fresh soil to the surface furrow during successive ploughings. Another important reason for this manner of treating the soil is connected with the question of moisture. One of the main benefits of fallowing consists in the conservation of moisture in the subsoil. Fallowing js an expedient to overcome the disadvantages of a dry climate by getting the rain of two winters stored into a subsoil for the support of new crop. But what is the use if the rain, by reason of an intervening furrow sole, cannot get through to the subsoil? An example of this was presented by a wet spring which in August and September promised for heavy wheat yields, and yet the crops were perished a couple of months later by a surplus of moisture. That is to say, moisture that could not get down to the subsoil, and consequently had to stay on top and destroy the crops. In this connection the Rochester district during the spring of 1906 may be taken as an example. About the end of September the Rochester crops promised a six bags average—the large bags, but five inches of rain fell during the first fortnight of October with the result that rot, take-all and fiag-rust set in, so that eventually the district yields only reached from a bag to a bag and a half and two bags to the acre. The heavy spring rains of the season in question were not permitted to get down into the subsoil, consequently they lodged on the surface round the stems of the crops and perished them. Hence a double loss was inflicted. The crops of 1906 were ruined, and also the succeeding crops of the dry year of 1907 suffered for want of the surplus moisture which, instead of being kept injuriously on the surface in 1906, should have been allowed to get down to store itself in the subsoil to make up for the dryness of 1907. The soil that is below the hard cake made by the plough sole is quite as good as that on the surface, but it requires to be gradually brought into use by the ameliorating influences of the weather. Breaking through the furrow sole enables a little of this