Carbon and Sulfur Concentrations are Negatively Correlated in Seeds of Canola

ABSTRACT

Seeds collected from canola grown under a wide range of soil nitrogen (N) and sulfur (S) fertility conditions were analyzed for their carbon (C) and S concentrations to investigate the relation between the two, and their interactive reactions to seed yield. The treatments involved applications of three S fertilizers [elemental S (SF); gypsum (CS), calcium sulfate (CaSO₄); and ammonium sulfate (AS), (NH₄)₂SO₄], representing differing S availability, in a S-deficient soil at three rates, and a control treatment (CT) receiving N only. In another soil high in available S, urea [(NH₂)₂CO] applications were made at two sites with four rates at each site. All rates were replicated four times. Despite divergences in yield and seed C and S concentrations, a significant negative linear correlation between seed C and S concentrations was found in each of the experiments (P < 0.05∼0.001), where S and N relationships varied. Seed C : S ratios were curve-linearly correlated to the yield and the relationships were described by second order polynomial equations. This C : S ratio explained 52 to 74% of variability in yield. Optimum yields were obtained with C : S ratio around 70∼100. Seed C : S ratios outside of this range were often associated with reduced yields.

Keywords:

• canola seed
• N and S fertilization
• seed C
• seed S
• C:S ratio
• yield

ACKNOWLEDGMENTS

The authors would like to express their sincere thanks to Mr. Ken Greer, Julian L. Charles and to the Prairie Agriculture Machinery Institute for their assistance in the field operation. The first author also gratefully acknowledges the support of K. C. Wong Education Foundation, Hong Kong.

Notes

¹Nd: not determined.

²Electrical conductivity.