A COMPARISON OF THE EFFECTS OF RESIDUAL AND FRESHLY APPLIED FERTILIZER ON THE GROWTH AND YIELD OF DWARF FRENCH BEANS (PHASEOLUS VULGARIS)
Experiments on several crops have shown that freshly applied fertilizers are not very effective at supplying the potassium and phosphorus requirements of crops. To study these effects various levels of residual potassium and phosphorus were established on a series of plots within a single field, by applying different rates of triple superphosphate and muriate of potash. Natural leaching over a year removed any excess fertilizer salts leaving a uniform soil conductivity over the field but with the required pattern of residual nutrients. French beans were then established on the subplots, with and without freshly applied broadcast fertilizer. There was a marked response to residual phosphorus (but not to freshly applied phosphorus) when plants were sampled at 32 days from sowing, but by the time of final harvest this early effect had disappeared. In contrast, there was no response to residual potassium at the early sampling, but by the time of final harvest, there was an increase in pod yield of 54% attributable to the residual potassium in the soil. However, there was no benefit from freshly applied fertilizer at either time. These results support the belief that crops which show no response to freshly-applied fertilizer might still be severely constrained by their nutrient supply. In farming practice the results would suggest that more attention should be given to the placement of nutrients or to the use of larger and less frequent fertilizer applications in order to increase the residual levels of nutrients.
Costigan, P.A. (1988). A COMPARISON OF THE EFFECTS OF RESIDUAL AND FRESHLY APPLIED FERTILIZER ON THE GROWTH AND YIELD OF DWARF FRENCH BEANS (PHASEOLUS VULGARIS). Acta Hortic. 220, 281-288