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Title: Effect of phosphorus, potassium, and chloride nutrition on cold tolerance of winter canola (Brassica napus L.)

Author
item EVANS, MEAGAN - Washington State University
item Skinner, Daniel
item KOENIG, RICHARD - Washington State University
item HULBERT, SCOT - Washington State University
item PAN, WILLIAM - Washington State University

Submitted to: Journal of Plant Nutrition
Publication Type: Research Technical Update
Publication Acceptance Date: 7/14/2015
Publication Date: 1/1/2016
Citation: Evans, M.A., Skinner, D.Z., Koenig, R.T., Hulbert, S.H., Pan, W.L. 2016. Effect of phosphorus, potassium, and chloride nutrition on cold tolerance of winter canola. Journal of Plant Nutrition. 39:1112-1122.

Interpretive Summary: Winter injury limits productivity of canola when planted in the fall. This study was undertaken to evaluate the impact of applied chloride, potassium, and phosphorus fertilizer on the ability of the plants remain photosynthetically active later into the season and to survive the winter. Elevated levels of chloride, but not potassium or phosphorus, were associated with greater survival and greater photosynthetic efficiency after damaging freeze events. These field results were corroborated by results from a greenhouse and growth chamber study, suggesting that chloride uptake from fertilizer sources may enhance cold acclimation and frost tolerance of canola, resulting in greater winter hardiness and spring vigor.

Technical Abstract: A field experiment was conducted to determine whether fertility treatments improve cold hardiness of canola (Brassica napus L.). Measurements of chlorophyll fluorescence and overwinter survival of field-grown canola were used to evaluate the effect of chloride (Cl), potassium (K), and phosphorus (P) fertility on frost tolerance. Increased Cl ion concentration in the sap, but unchanged K or P, suggested luxury consumption of Cl, and chlorophyll fluorescence indicated greater photosynthetic activity later into the autumn with applied KCl. Overwinter plant survival ranged from 22 to 42% across treatments with higher survival in the Cl treatments. In a greenhouse experiment, effects of Cl, supplied as CaCl2, KCl, NH4Cl, or NaCl, on the ability to tolerate short, extreme episodes of below freezing temperatures were evaluated. The median sap chloride concentration after three weeks of growth was 0.036 M. Significantly greater survival among the plants with sap Cl >0.036 M compared to plants with sap Cl =0.036 M suggested increased cold tolerance due to Cl accumulation in the sap. However, survival of plants treated with NaCl was significantly less at higher Cl concentrations, indicating that the cation supplied with Cl also influenced survival. Collectively, these results suggest that Cl uptake from fertilizer sources may enhance cold acclimation of canola and frost tolerance, resulting in greater winter and spring hardiness.