Growth and development of white clover (Trifolium repens L.) as influenced by P and K nutrition

The effects of varying P and K supplies on the growth and morphology of white clover were investigated in a pot experiment. Plants were treated with three rates of potassium (K) and four rates of phosphorus (P) in factorial combination, and five harvests were taken between August 1993 and February 1994. During establishment, shoot and leaf development were more adversely affected by P than by K deficiency but, by the final growth period, K deficiency was the more limiting to growth, causing dramatic reductions in leaf area index (LAI), numbers of growing points, and stolen and root masses. The adverse affects of K deficiency on shoot development were attributed to the curtailment of petiole and lamina expansion which have major requirements for K. It was noted that, under K deficiency, proportionately less assimilate was partitioned to leaf production than to stolen and root growth; this may be an adaptation enabling K-deficient plants to exploit nutrient supplies in adjacent localities. The results suggest that, provided white clover can withstand 'moderate' P stress during establishment, its persistence in swards will probably be limited more by K deficiency than by low or inadequate P supplies. However, because the experiment was conducted outside the normal growing season and with only a single white clover cultivar, it is inappropriate to make any generalizations regarding the effects of P and K nutrition on white clover in the field. (C) 1998 Annals of Botany Company.