Cultivar and fertilizer S rate interaction effects on canola yield, seed quality and S uptake

Abstract

Since canola has a high requirement for S, and canola cultivars have differences in growth rate and yield potential, a differential response of canola cultivars to soil S deficiency and S fertilization can be expected. A 3 site-year field study was conducted on S-deficient soils in northeastern Saskatchewan to determine response of four canola cultivars to S deficiency and S fertilization in terms of yield (seed and straw), seed quality (oil, protein and S concentration), and S uptake (seed and straw). Two Brassica napus L. cultivars (Quantum and AC Excel) and two B. rapa L. cultivars (Maverick and AC Parkland) were compared at 0, 5, 10, and 15 kg S ha-1 rates. Both the actual values of seed and straw yield and seed S uptake and the responses to S fertilization were greater for the B. napus than B. rapa cultivars. Optimal yield response for all the four cultivars occurred at the 10 kg S ha -1 rate, though seed quality and S uptake responded up to the 15 kg S ha-1 rate. Sulphur fertilization response was quadratic for seed and straw yield, seed oil and protein concentration, and S uptake in seed, while the response for seed S concentration and straw S uptake was inconsistent. In summary, in spite of differences in magnitude of the response of tested cultivars to S fertilization, the similar nature of the response and optimal yield at the same S rate indicated that specific S fertilization recommendations for individual canola cultivars are unnecessary.