TOP-DRESSING WITH COBALT

Press, Volume LXXIV, Issue 22370, 6 April 1938, Page 13

TOP-DRESSING WITH COBALT

COMBATING BUSH SICKNESS TRIALS AT NELSON Phenomenally good results have been recently obtained in the pumice areas of the Taupo district from the application of cobalt to pastures. Settlers there who have struggled against tremendous handicaps ever since the country was opened up have found that cobalt, as far as it has been tried, is a cure for practically every pasture trouble they have encountered. Round Putaruru, where the element has been given the most intensive trial, results have been startling. The greatest difficulty in that area has for years been, not to get condition on to stock, but to hold them in condition. Cattle and sheep, having reached a certain stage, were found to fall away badly and rapidly, and losses of both during the winter were always heavy. Now, high percentages of lambs are sent away fat off the mothers, and cattle are doing better than they have ever done before. The settlers who have used cobalt believe they have found a means of farming prosperously, though they admit that much experimentation has yet to be carried on. The usual application is 21b to the acre, which, with cobalt at about 4s per lb. is cheap. Investigations have recently been made in the Nelson district into the cobalt content of some pastures, and the effects of top-dressing with preparations containing cobalt. The investigations were conducted by Messrs H. O. Askew and P. W. Mansell, of the Cawthron Institute, and their conclusions are published in a paper prepared by the Department of Scientific and Industrial Research. Summarising the data from the topdressing experiment, they claim that the cobalt content of pasture plants can be readily increased by top-dress-ing with cobalt chloride, even at the low rate of 21b an acre. The effect of the cobalt dressing decreases from the large effect seen soon after top-dress-ing to a relatively stable level which is maintained until near the end of the growing season. This level is, of course, governed by the magnitude of the cobalt application. Nelson pastures, in general, have a much higher cobalt content than the unhealthy pasture at Glenhope associated with bush-sickness. With the exception of the early spring and late autumn periods, the cobalt content is relatively constant, although some fluctuations have occurred. The early spring period of pasture growth has been associated in a number of instances with high cobalt figures which cannot be explained solely on the basis of soil contamination, and which must be regarded as significant. Late autumn growth, on the other hand, has been associated in a marked way with very low figures for cobalt. The data definitely suggest that there is a pronounced seasonal variation in the cobalt content of pastures. If such a seasonal variation is established it may greatly influence farm practice in the use of cobalt top-dressings or of cobalt drenches in those areas where ailments of stock of the bushsickness type are found. The use of cobalt chloride for topdressing, even - in amounts as low as 21b an acre, has been followed by an appreciable increase in the cobalt content of pastures. It is possible, therefore, that even smaller quantities of cobalt chloride will provide the increased cobalt content of pasture necessary to maintain stock in healthy condition in affected localities. The problem of the optimum time of application requires further study. From the experiments it was established that: Top-dressing with cobalt chloride at rates varying from 1121b to 21b an acre markedly increased the cobalt content of the pasture; ground limestone decreased the Intake of cobalt, but not seriously enough to make cobalt dressings ineffective; and that there was a sudden drop in the intake of cobalt by the pasture at the end of the season. This may have an important effect in determining the time of application of cobalt top-dressings.