Don't freeze that pre-sidedress nitrate soil test!

"The updated recommendation advises that soil samples should not be frozen after collection. Instead, producers and agronomists should keep soil samples cool and ship them to the laboratory as soon as possible after collection. The decision is grounded in recent peer-reviewed research demonstrating that freezing soil samples can significantly alter nitrate test results. Specifically, freezing and subsequent thawing of samples increased measured nitrate concentrations compared to samples that were not frozen."

"These changes affected nitrogen recommendations derived from PSNT results in more than 50 per cent of cases. In up to 16 per cent of cases, the altered recommendations led to under-application of nitrogen significant enough to result in economic losses exceeding $60 per acre. These findings are based on research published in the Soil Science Society of America Journal (Janovicek et al., 2024), which examined the impact of soil sample handling and storage on inorganic nitrogen determination."

"Accurate PSNT results are critical for determining appropriate in-season nitrogen applications. By improving consistency in sample handling, the updated recommendations are expected to: Enhance the reliability of PSNT-based nitrogen recommendations; Reduce the risk of under- or over-application of nitrogen; Support both farm profitability and environmental stewardship."

The Ontario Soil Management Committee updated soil sample handling recommendations for Pre-Sidedress Nitrate Testing used in corn nitrogen management. Freezing soil samples after collection is no longer recommended. Samples should be kept cool and shipped to the laboratory as soon as possible. Peer-reviewed research found that freezing and thawing increased measured nitrate concentrations compared with samples that were not frozen. Nitrogen recommendations based on PSNT results changed in more than half of cases. In up to 16% of cases, the altered recommendations caused under-application of nitrogen leading to economic losses exceeding $60 per acre. Improved handling is expected to increase reliability, reduce under- or over-application risk, and support profitability and environmental stewardship.

Read at Realagriculture