Observations on legume establishment and grow on acid soils

The problem of establishing plants and keeping them growing on acid soils has been present as long as agriculture has been practised, and the beneficial effect of liming materials of various kinds has been appreciated for almost as long. But while they have been appreciated, their precise mode of action has not been understood. Even with the considerable advances that have been made in understanding the “acidity complex” in recent years, the full solution of the complexities of plant growth on acid soils has still to be found. Although this paper will deal only with legumes, this whole field of soil acidity and plant growth is a most interesting one, bristling with problems, and the aspects to be discussed here form a good example of the impact of modern research on an age-old traditional practice -that of liming the soil. For some years workers at Lincoln College have been interested in the establishment of clovers on the acid soils in the tussock grasslands, partly because of the interesting problems involved, and partly because these areas might confidently be expected to make an important contribution towards the production increases necessary and aimed at for the future. In these areas the lack of readily available nitrogen is one of the major drawbacks to higher production, and if thriving legumes can be established there and kept thriving by the regular application of adequate amounts of the correct nutrients in the fertilizer programmes, a big advance towards the goal will have been achieved. Originally, the nutrients sulphur and phosphorus were concentrated on but more recently the effects of broadcast lime, lime-pelleting and inoculation on legume growth have been studied. It is the results of these investigations both in field and pot trials that will be presented here, together with new problems that have arisen and the trials planned to help solve them