Improvement Pattern In Central Otago

Press, Volume C, Issue 29709, 30 December 1961, Page 7

Improvement Pattern In Central Otago

’T'HE belief that with continned control of the | rabbit, spelling of depleted country, oversowing and topdr easing of fescue tussock areas with sulphurised superphosphate, and introduction of lucerne and cocksfoot in drier areas the pastoral lands of Central Otago will make an important contribution to New Zealand's economy was expressed at Lincoln College this week by Mr T. E. Ludecke, a scientific officer of the Department of Agriculture at Alexandra. Mr Ludecke is on leave from the department and is studying at Lincoln under Professor T W Walker for the degree of master of agricultural science. For his thesis he is seeking to correlate soil chemical data with field responses to sulphur and phosphate in Central Otago. It was well known that the key to successful pasture improvement in New Zealand was good legume growth, said Mr Ludecke discussing his work. It had been shown that if clovers were to fix 10 to 151 b of nitrogen per acre lib of sulphur was required, and in the South Island one of the main factors limiting good legume growth was an acute deficiency of sulphur, which was probably because of low at-

mospheric return of sulphur. Twenty rates of sulphur and phosphate trials in a very wide range of soil types in Central Otago had shown that in all tussock grassland areas these soils were all extremely deficient in sulphur, but they varied in phosphate requirement These trials had shown that in dry areas with an annual rainfall of 13in to 20in the response was entirely caused by sulphur In these soils there were very large reserves of inorganic phosphate, and they gave a high phosphate test, according to the Department of Agriculture’s quick test for phosphate. These were the areas where dryland lucerne was grown, and here maximum production could be obtained with lewt an acre of the 8001 b mixture of sulphurised superphosphate applied with a topdresser every two or three years Because of the risk of explosion in the hopper of an aircraft the maximum quantity of this mixture that could be distributed aerially was 5001 b Mr Ludecke said that on the Moutere property of R. Jopp and Son, with an esti mated rainfall of 17in. the use of the 8001 b fertiliser mixture had increased production from dryland lucerne pastures under trial from 6501 b of dry matter an acre to 40001 b. In the native state this formerly depleted scabweed country would carry only one sheep to two to three acres, he said. There were two methods f establishing dryland lucerne pastures in Central Otago, he said One was the conventional method of land development evolved by Messrs W A Lunn and R. C. Schofield, and the other the direct surface introduction of lucerne and cocksfoot developed by Messrs J. M. Hercus, J C Tothill and himself. This was for improvement on the extensive scale, with the only costs to the farmer being for seed and fertiliser, but, as in other districts, inoculation of the lucerne was very critical. These scabweed areas had been shown to improve very markedly merely by spelling during the seeding period of grasses. This, of course, involved closer subdivision, so that better control of stock was possible. Higher up the. mountains between 1500 ft and 3000 ft on a typical mountain range in Central Otago was the fescue tussock country, which was capable of considerable improvement by aerial oversowing and topdressing. Here, on country with a rainfall of more than 20in to 25in, the inorganic phosphate content of the soil decreased, and trial results had sh->wn that these soils required sOlb of elemental sulphur with the phosphate in lewt of super to attain maximum production. The most economical way of

applying this amount of sulphur and phosphate was in licwt an acre of the 4001 b mixture of sulphurised super. If ordinary super was used, 4cwt would be needed to supply the 501 b of sulphur. Trial results had shown that use of the correct fertiliser in fescue tussock country lifted production from 11001 b of dry matter to the acre to 45001 b. Trials were at present in progress to determine how often it was necessary to apply fertiliser dressings to maintain maximum production, and at present it seemed that a dressing was required at least every third year.

It had been observed that if all herbage from this improved pasture could be eonserved it would support two to two and a half ewes to the acre, but production was high to the spring and early summer and then fell off markedly in the late summer and autumn when the summer drought set in. These seasonal differences in production were important from a management angle, as the availability of sulphur and nitrogen depended on sheep and cattle utilising the increased teed and excreting the element* in dung and urine. Thus adequate fencing. enough stock to enable areas to be managed correctly, and sufficient winter feed were essential. Third Zone The third major zone of tussock country to Central Otago was ; the snowgrass country, where the amount of economic improvement that could be made was severely limited by adverse climatic conditions To use this high country for summer and autumn grazing the farmer was forced to burn the vegetation Soil scientists had emphasised the seriou consequences of burning on soil and water conservation, and in this area there were a number of irrigation and hydro-electric schemes dependent on water supplies from these snowgrass catchments However, carried out judiciously under the supervision of catchment boards, burning was in many cases an essential management practice to protect the country against out-of-season fires in the summer or autumn, which could do untold harm. Mr Ludecke said that soil scientists and conservators and agriculturists recommended that grazing pressure should be eased on higher snowgrass country where there was evidence of overgrazing, and depleted scabweed country should be spelled to encourage natural regeneration. “Today we are able to show runholders to Central Otago that if they improve the fescue tussock country on their properties and develop areas of dryland lucerne they can carry out these very desirable soil and water conservation practices," he said. Mr Ludecke said he had found that there was a very good correlation between the Department of Agriculture’s quick test tor phosphate, the amount of inorganic phosphate in the soil, and response* to phosphate. It should mean that farm advisory officer* would only have to take soil tests to determine the phosphate requirement. Then it should be possible to recommend to the fanner what fertiliser mixture he should use to secure the most erooomical improvement of his country. Meantime, however, the spread of sweet briar was a serious limiting factor to run improvement to Central Otago, said Mr Ludecke, but Mr A. A. Duncan, farm advisory officer at Alexandra, was engaged to research into its control from both an ecological and chemical point of view.