Studies of the Availability of Soil Phosphorus and Potassium in Organic Farming Systems, and Plant Adaptations to Low Phosphorus and Potassium Availability
January 2003
in “
Organic Eprints (International Centre for Research in Organic Food Systems, and Research Institute of Organic Agriculture)
”
Studysummary This research observed that while organic farming systems in Southern Norway showed decreased phosphorus over time and variable nitrogen retention, the mulching of plant material could enhance vegetable yields, suggesting a need for innovative nutrient management strategies in organic farming.
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In organic farming systems, nutrient purchase restrictions often led to negative nutrient budgets, particularly in low animal density areas, as observed in five organic dairy farms in Southern Norway. These farms experienced a decrease in ammonium-acetate lactate (AL) soluble phosphorus (P) over time, necessitating future P supplementation. Although potassium (K) levels did not show a similar decrease, many areas had low K concentrations, indicating a need for K supplementation as well. The use of plant material as mulch increased vegetable and grain yields, but only 15-20% of the nutrients in the mulch were recovered by crops, with significant nitrogen losses. Plant adaptations to low P, such as changes in root traits, were studied, but these adaptations were deemed of limited practical significance in Nordic agricultural soils. The study highlighted the importance of developing nutrient supplies that meet organic standards and the need for organic farmers to minimize nutrient losses.