SUBTERRANEAN CLOVER

Wairarapa Times-Age, 1 July 1938, Page 3

SUBTERRANEAN CLOVER

BENEFITS FROM APPLICATIONS OF SUPERPHOSPHATE. BUILDING UP FERTILITY. It has been frequently shown that subterranean clover will do very little good unless treated to adequate applications of superphosphate. Farmers generally have followed the advice in this respect, and where their stands have not been affected by adverse circumstances they fully realise that the practice is absolutely necessary. The writer met a grower the other day who volunteered the opinion that after a few years the benefit of super top-dressing commenced to decline, posibly because the saturation point was being neared. To put the matter to a test he applied potash with the super, and the response was notable.* The conversation is recalled by an article in a recent issue of the Victorian Journal of Agriculture, in which state apparently the same development has taken place. The journal remains that with' proper management superphosphate enables soil fertility to be built up to such an extent that a greatly improved pasture can be obtained, but where no effort is made to build up the general fertility of the soil, improvement of the pasture is likely to be temporary only. Used in this way superphosphate must be regarded as a means of exploiting the plant food reserves of the soil. In last year’s report the value of potash in maintaining soil fertility when the land is subjected to a heavy drain of plant food was shown. During the last year similar responses to the application of potash have been obtained. The journal, in concluding its comments, says that the marked responses to potash now being obtained must be taken as indicating a condition which may have to be met in the future, and suggests that efforts should be made to conserve the present soil potash supply rather than to wait until the trouble occurs and then attempt to remedy it with expensive potash fertilisers. Where pastures have reached a stage where they do not respond satisfactorily to superphosphate alone, better results would probably be obtained by using a mixed phos-phate-fertiliser. Potash exerts its most valuable effect in stimulating the establishment of weakened clover and a satisfactory response cannot be expected if the grasses are permitted to grow tall and choke out the clover. On pastures that have been kept short potash has fostered the growth of the clovers, but where the grass has been permitted to make tall growth in the late spring the clovers have continued to be suppressed, despite the use of potash. The Victorian experience emphasises that an application of potash should not be left too late, or rather until other grasses get the upper hand, a development that has been noticed in Canterbury crops. This development has been accepted as satisfactory in that the result is a good mixed pasture, but the process must eventually mean that the subterranean clover will disappear. This is not desired in many cases.