Gao, J., K. D. Thelen, D. H. Min, S. Smith, X. Hao, and R. Gehl. 2010. Effects of manure and fertilizer applications on canola oil content and fatty acid composition. Journal of Environmental Quality 102:790-797.
Increasing fertilizer costs have resulted in more growers evaluating the use of alternative nutrient sources such as manure. Coin- cidentally, the questions about fertilizer effects on oil yield and oil fatty acid composition have been a concern. A 2-yr study was conducted to investigate nutrient source (fertilizer urea plus S and manure) and N level (0, 84, and 168 kg N ha –1 ) effects on canola seed yield, total oil content, and oil composition at East Lansing and Chatham, MI. Results indicated nutrient applica- tions were not necessary to increase canola yield (865–1991 kg ha –1 ) in fertile fields. However, N fertilizer appeared to reduce total oil content (444−536 mL kg –1 ), and at similar N levels, total oil content in canola with fertilizer was sometimes lower than that with manure application. Compared with the no nutrient control treatment, fertilizer application sometimes decreased lin- olenic acid (LN) content, and increased palmitic acid (P) and arachidic acid (A) at Chatham, while it appeared to decrease oleic acid (O) and increase P, linoleic (L) and A at East Lansing. Fertilizer applications often increased canola total saturated fatty acid content (6.80–8.32%) and decreased ratio of O/(L+LN) (2.04–2.52). Manure application had milder effects on oil composition than fertilizer application. Compared with less N (84 kg N ha –1 ) applications, greater N level (168 kg N ha –1 ) tended to lower oil quality by increasing total saturated fatty acid content and decreasing the O/(L+LN) ratio.
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