Winter hardiness of canola in response to alternative fertility management approaches

Meagan Adele Hughes

A field experiment was conducted during 2010-2011 to determine whether fertility treatments improve winter hardiness of canola. Measurements of chlorophyll fluorescence and overwintering survival of field-grown canola were used to evaluate the role of chloride (Cl), potassium (K), and phosphorus (P) fertility in winter hardiness. Drilling potassium chloride (KCl) and triple super phosphate (TSP) fertilizers at rates above those recommended by fertilizer guides apparently resulted in luxury consumption of Cl and increased sap Cl content with applied KCl. Chlorophyll fluorescence measurements suggested greater photosynthetic efficiency later into the autumn season with applied KCl, perhaps leading to more robust plant growth, greater cold acclimation, and increased plant survival through the winter. Survival counts the following spring were consistent with this prediction; however, seed yields were not significantly different among fertilizer treatments, suggesting canola will branch and increase pod set to fill in stands that have minor winterkill. The proportion of K, P, and Cl to total dissolved salts calculated from measured electrical conductivity suggested that other, not quantified, nutrients in the sap could have a role in winter hardiness. In a greenhouse experiment, effects of Cl on the ability of canola, grown with or without cold acclimation, to withstand exposure to short, extreme episodes of below freezing temperatures were evaluated. Sources of Cl included CaCl2, KCl, NH4Cl, and NaCl applied at 50 and 100 lb Cl ac-1. Chloride concentration in the sap after three weeks of growth ranged from 0.031 to 0.051 M with a median of 0.036 M. A difference of about 6% greater survival among the plants with high sap Cl (>0.036 M) compared to plants with sap Cl content ≤0.036 M was highly significant (X2=14.6, p<0.001), suggesting increased freezing tolerance due to Cl accumulation in the sap. Analysis of variance of survival indicated that the sap Cl content X chemical source interaction was significant, suggesting that different Cl sources resulted in different levels of Cl uptake. Collectively, these results suggest that Cl uptake from fertilizer sources may enhance cold acclimation of canola and increased frost tolerance, resulting in greater winter hardiness.

Winter hardiness of canola in response to alternative fertility management approaches

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