DEFICIENCY OF POTASH

New Zealand Herald, Volume LXXIV, Issue 22627, 15 January 1937, Page 16

DEFICIENCY OF POTASH

RESULTS OF TESTS VARIATION IN RESPONSE VOLCANIC SOIL NOT BENEFITED BY UOHKRT DUNCAN The results of the wide range of trials with a mixture of potassie iind phosphatie fertilisers carried out by the Fields Division of the Department, of Agriculture afford valuable guidance in manuring practice. On the experimental plots, the potash was applied annually in tlio form of thirty per cent salts at the rate of 2cwt. per acre; the phosphate (either superphosphate or slag) at the rate of 2->'?ewt. per acre; and where lime was added, one t*<n of unburnt lime pet- acre was sown in the first year, and scwt. per acre in succeeding years. A brief account of the districts in which a good response to this combined potash and phosphate treatment was obtained will serve to indicate the localities and types of soil on which tliis kind of fertiliser is most likely to give good results. Sandy Soils Respond

In the North Auckland district, the efficacy of the potash mixture was most, marked on three classes of soil. Plots laid down in peaty sand showed notable improvement in till cases, In like manner, the red-brown soils derived from basalts gave excellent response when top-dressed with it. Swards oji the sarul.v gum-lands characteristic of parts of the North Auckland peninsula were also stimulated to an appreciable degree by the treatment. In South Auckland, it was found that the types of soil which responded in the northern part of the province were beneficially affected wherever they occurred in southern areas. Thus in Manukau and Franklin counties, the trial plots showed a high degree of susceptibility to the potassie fertiliser. On the other hand, where the soil was volcanic, the results did not show the same consistency.

In the Waikato, it has been possible to obtain results which are more truly representative in character than those secured in other districts. 1 his is due to the fact that an accurate soil map of the W'aipa county has been prepared by officers of the Government Soil Survey. As a result of the classification of soil types, the Fields Division has be:>n enabled to lay down trials on various classes of soil. Up to the present time, favourable response to potash treatment has been obtained from three trials on the Horotiu sandy loam, from one trial on Kaipaki sandy peat, and from another trial on Hamilton clay loam. It may be remarked in passing that the value of a Dominion soil map is emphasised by the fact that the small map of this district has proved of such utilitv in the conduct of the fertiliser trials at present under discussion. Striking Waihi Results

Passing from the Waikato to Waihi, one is impressed by the striking results following upon the use,of potash. It may be said that the responses from the trials in this district were more marked? than those obtained elsewhere. This is true, not only in view of the degree of improvement effected in the sward, but also when the rapidity with which the beneficial results became visible is taken into account. It is to be noted that plots on which good responses were observed were laid down on sandy loams. Alluvial soils, on the contrary, were not appreciably benefited by potash. A climatic factor which is undoubtedly associated with the stimulating effect of potassie top-dress-ing is the high rainfall which is characteristic of this district.