Description
Organic systems rely heavily on biological nitrogen fixation from legumes. They can achieve high nitrogen use efficiency, but outcomes vary with specific management practices and overall farm intensity. Many organic farms have low soil test phosphorus levels, but some studies show adequate crop P nutrition despite this.
Findings
Nutrient dynamics in organic systems are complex and influenced by management intensity as much as organic/conventional designation. Enhanced biochemical and biological turnover of organic phosphorus may contribute to adequate P nutrition even at low soil test levels.
Stats
Soil test P levels <10 mg/kg reported for many Canadian organic farms
In one study, jeevamrit prepared from cow dung and urine contained 0.04, 0.04, 0.28 and 0.43 g/l of nitrogen, phosphorus, potassium and sulphur respectively
Research on Ontario dairy farms found forage yields and biological N2 fixation were not inversely related to soil test P levels in long-term organically managed soils One study found organic potato yields were ~20% lower than conventional
In a long-term Swedish study, organic crop management resulted in lower nitrogen use efficiency than conventional.