DETERIORATED PASTURES

New Zealand Herald, Volume LXIV, Issue 19762, 8 October 1927, Page 8

DETERIORATED PASTURES

STRANGE CASE AT MAIEOA. LIMESTONE ROCKS ABOUND. SOIL DEFICIENT IN LIME. fIT OP-DRESSING NOT EFFECTIVE. [bt our special commissioner.} No. L Possibly the most remarkable instance cf pasture deterioration in any part of New Zealand is to be found at Mairoa, a settlement in the ranges between the Main Trunk line and the West Coast, 17 miles from Te Kuiti. Mairoa is a beautiful district; outcrops and miniature crags of high grade limestone give to its gently rolling contours a picturesqueness which seems peculiar to some parts of the King Country. When I first rode through this part of Bohe Potae, in company with one who is now a member of a great Auckland business firm, it was all in wild bush, for settlement had not yet begun in the King Country, though roads were being projected, and surveys had been made of sections for the first ballot. We had to take a Maori guide with us and to find our way through miles of forest, in places even where there was not the faintest sign of a track. The second tiriie I visited Mairoa, settlement had advanced considerably. The marvellous forest with its carpet of delicate ferns had given place to blackened stumps, standing out of luxuriant pasture. Unmistakable Signs. Mairoa became famous for its sheep and cattle. Three sheep to the acre was a common stocking; and for years it continued to produce wool and meat of a high quality to swell the exports of New Zealand. The third time 1 visited Mairoa was only a week or so ago, when I saw unmistakable signs of deterioration in some of its pastures, and listened to some of the problems and difficulties which confront its settlers. The deterioration of pasture laid down on what was once bush-covered hill country has been inevitable under our system of farming such lands, and is common ail through New Zealand and in all countries where pastures .are sown after the felling and burning of indigenous forests. During the growth of the forest, much humus is accumulated by the gradual decay of vegetable matter, and * when the forest is felled and burned there is left on the surface in the shape of wood ashes an abundant supply of an almost perfect manure. Slow But Sure Process. Grass seeds sown on the surface of such land flourish amazingly, and millions of acres of our forest pasture have been formed in this way. Slowly, but surely, as night follows day, such pasture, if unaided by top-dressirg with fertilisers, begins to lose quality. The available supply of fertility in the soil gradually dwindles under the work of producing tons upon tons of bona, meat, wool, and hides per acre. It would be interesting to know what weight of sheep and cattle have been produced on these Mairoa lands since they were first settled over 20 years ago, but though no records have been kept it is isafe to say the amount has been enormous. II; should be understood that in dealing with soil exhaustion by stock feeding, it is only the available or soluble fertile elements which can be taken up by the. grasses and supplied to the stock, and in seemingly deteriorated pasture land there may be, and usually is, vast quantities of valuable soil constituents left behind. It should also be understood that usually one soil element is exhausted *irst, and without thi3 one element, neither grass nor stock can flourish. The Absence of Lime. 'At Mairoa the stock-carrying capacity of the soil has gone down gradually in some cases from two and three, and even more, sheep to the acre, to one and less than one. The good English grasses have given placa to inferior grass-*.B and to weeds and moss. Efforts were made to retard this retrograde movement by top-dressing with fertilisers—efforts which should have been made many years previously. But—and here is the remarkable thing—-top-dress-ings with superphosphate and Nauru, with basic super, with basic slag, with phos- , phates in combination with potassic I manures, seemed to have little effect upon certain of these Wairoa farms, or, at any rate, not the marked effect they -'have upon most other classes of soils. It was stated by a public official recently that Mairoa was one of the few places where the soil failed to respond to top-dressing. This, of course, was a wild assertion. Samples of the soil were sent to Mr. B. C. Aston, chemist to the Department of Agriculture, and his report stated that analysis showed 'that there was a remarkable deficiency of lime, amounting, to 10 tons per acre, and, owing to the absence of lime, neither grasses nor stock could thrive, although, as aulysis further showed, there was still a good amount of phosphoric acid, potash and even nitrogen still left in the soil. Theory In Explanation. It seems remarkable that in a district where high percentage limestone rocks abound, where, in fact, it outcrops almost everywhere, there should be this deficiency of lime in the soil; and yet it is by no means uncommon. There is a heavy rainfall at Mairoa—something over lOOin. a year—and the theory is that the rainfall, plus carbonic acid, bleaches the lim«s out of the top layer of soil. The settlers have applied to the Government for the loan of a portable lime crusher, and it is essential that something should be done, and done quickly, to test the question whether a liberal application of lime will bring back the pastures to their old luxuriance. We know that the law of the minimum in manuring makes a missing element of supreme importance, but it would certainly ; be advisable, where top-dressing has not been done, to add to the lime application a fair amount of some phosphatic manure. But here is one of the settlers" troubles—fertilisers, owing to long railway and road carriage, cost a lot of money, and some of the settlers have not the money to purchase them. They are willing enough to work a lime crusher and distribute the lime with their own labour, but labour, however willing, cannot give them phosphates.