Establishing Reference Guidelines for Phosphorus Fertilization in Organic Crop Production

Due to the significant decrease in Olsen P2O5 observed in French soils and given that these levels are generally lower in plots managed using organic farming (OF), it is essential to raise awareness among OF farmers about diagnosing phosphorus (P) deficiency to help them better anticipate risky situations. The reference diagnostic method for field crops, as established by Comifer (French Committee for Sustainable Fertilization Study and Development), does not seem well adapted to OF because crop yields are relatively unaffected by low P levels in the soil. To improve P deficiency diagnosis in OF, a study of crops response to soil P supply in OF was carried out and led to the proposal for response to P soil availability thresholds adapted to OF, significantly lower than those currently used in conventional agriculture.