Field calibration of boron soil tests for barley

Abstract

Boron (B) deficiencies limit crop yields on clay soils rich in organic matter in eastern Canada. The objective of this study was to calibrate a B soil test for barley on Humic Cryaquepts of the Lac Saint‐Jean area, province of Quebec, Canada. Two barley (Hordeum vulgare L.) cultivars were grown on 12 sites over three cropping seasons. On average, the Mehlich 3 solution extracted less B (2.8 mg/kg) than Sr‐Citrate (3.2 mg/kg), but more than hot water (1.3 mg/kg), mannitol‐CaCl2 (0.8 mg/kg), CaCb (0.6 mg/kg), and cold water (0.5 mg/kg). The response to B fertilizer was cultivar specific. The 0.01M CaCl2 solution was most closely related to barley B uptake (r = 0.65**), whereas Mehlich 3 (r = 0.61*) best predicted fertilizer response. The relationship between fertilizer B responsiveness by barley and amounts of soil B extracted was most improved when soil pH was included in the equation. Higher critical levels of Mehlich 3‐extractable B than proposed in the literature were determined. This may be due to the large clay and ammonium oxalate‐extractable aluminum (Al) contents which increase soil B sorption capacity and decrease B intensity. The results of this study suggest that soil pH should be included in a Mehlich 3‐based soil test for B to predict fertilizer B needs of barley growing on these clay soils.

Notes

Corresponding author, contribution of the Soils and Crops Research Centre No. 513.