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.
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