Assessing potentially available nitrogen in Saskatchewan using the Illinois amino sugar-N test
A 3-year study conducted at four sites across Saskatchewan examined the responsiveness of wheat in different landscape positions to nitrogen (N) fertilizer additions. Failure to obtain a strong relationship between the traditional nitrate test and grain yield suggested the need for a soil test measurement that can more accurately predict the N-supplying power of a wide range of soils. The Illinois amino sugar-N (ASN) test, which estimates amino sugars as a potentially mineralizable fraction of soil organic matter, was performed on the study soils to determine if it could act as a more stable predictor of the responsiveness of crops to fertilizer N additions. Amino sugar-N was found to be significantly correlated to both unfertilized yield and yield response across all site-years. However, the correlation between ASN and yield response was variable between sites and landscape positions. Step-wise regressions developed to predict yield response indicated that spring nitrate levels, soil organic matter, and soil moisture are important in predicting yield response, although low R2 values suggest a large amount of variability is still unaccounted for by these variables. Additional research will be required before the Illinois ASN test can be adopted to the Canadian prairies.
Soils and Crops Workshop