Classification and fertility status of organically managed fields across Saskatchewan, Canada

Abstract

Records from 60 organically managed fields across Saskatchewan were obtained from 39 farmers. The records contained details of 6 yr of management practices applied to each field and details about the general farm operation under which the individual fields were managed. In addition, soil samples were collected from each field and analysed for available N, P, K and S, pH, electrical conductivity (EC) and soil organic carbon. Soil nutrient availability is reported by soil zone. Using information from the management questionnaire, the 60 fields were classified into four distinct management systems, Perennial, Summerfallow, Cereal, and Diverse, and soil nutrient availability examined according to management system. Despite classification of four systems, only the Perennial and Diverse systems had a functionally (and statistically) significant effect on selected soil properties. Inclusion of alfalfa in rotation (Perennial system) acidified the soil and reduced availability of P and K relative to the Diverse system. According to soil test results, fields in all of the systems and across all soil zones were apparently deficient in available P, deficient to marginally deficient in available N and marginally deficient in available S. Available K levels were generally optimal. Information from this study provides a baseline for fertility of soils under organic production across Saskatchewan. The overall low levels of available P, N and S identified in this study raise questions about the long-term sustainability of these organic systems, as well as the suitability of traditional soil testing for accurately assessing the soil fertility potential of organic managed soils.