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ISHS Acta Horticulturae 852: IV International Symposium on Ecologically Sound Fertilization Strategies for Field Vegetable Production

PLACEMENT OF PHOSPHATE LEADS TO A MORE EFFICIENT USE OF A FINITE RESOURCE

Authors:   A.L. Smit, A.A. Pronk, P. de Willigen
Keywords:   phosphate, placement, fertilization, vegetables, simulation, roots
Abstract:
In a desk study and in a climate chamber experiment we explored the rationale behind the low or even negative correlation between recommended P(hosphorus)-application rates and P-off-take in the Netherlands. We hypothesized that especially for short growing vegetable crops it will be necessary to maintain in the early growth stages a high P-concentration in the soil solution, despite the relatively low P-off-take at harvest. Although the daily P-demand of the crop is low immediately after germination, actual P-uptake might be limited by root length. Placement of P is then a strategy to achieve a more efficient P-fertilization. The fact that P-resources in the future will become scarce will encourage such a strategy. The interaction between soil P-fertility, rooting, P-demand and placement of P was explored with a simulation model. Placement turned out to be very effective to realize the required P-uptake in the early growth stages, more effective than increasing the P-soil fertility status. The effect of placement of P-fertilizer was verified in a climate chamber experiment. In a pot experiment P-fertilization by placement (0, 4, 13 kg P ha-1 in 3% of the soil volume) was compared with 87 kg P ha-1 mixed homogeneously through the entire soil volume. Placement stimulated juvenile growth to a great extent in several crops (including carrots, spinach, onion). Placement was equally or even more effective than the broadcasted treatment indicating that P-placement can potentially lead to a large reduction in the use of P-fertilizer. It opens the possibility to maintain crop productivity and quality at lower P-fertility levels of the soil, thereby saving valuable P-resources for the future.
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