Oilseed Crop Fertility
Project Investigators: Richard Koenig, WSU; Robert Stevens, WSU; William Pan, WSU; Ashley Hammac, WSU
January, 2008 Progress Report
What is known:
A review of the existing literature reveals that canola requires more nitrogen, phosphorus, potassium, and sulfur per unit of yield than cereals such as wheat or barley. Due in part to a low harvest index (proportion of aboveground plant dry matter that is seed) and high nutrient concentration in the residue, canola also leaves more nutrients in the field after harvest than comparable yields of cereals. Cycling of nutrients in this residue to subsequent crops is one important rotational benefit of canola. Fertilizer rates for canola are a function of residual soil nutrient levels and the yield potential of the site. For optimum yields, canola requires approximately 6 to 8 lbs of N supply (fertilizer+soil sources) per 100 lbs expected seed yield. Phosphorus, potassium, and sulfur recommendations can be based on soil test levels with interpretations similar to those of cereals. Canola has a lower tolerance of seed-placed starter fertilizers than cereals so rates of nitrogen+potassium should be below 5 lb/acre.
What is not known:
- In existing literature, nitrogen recommendations for canola are somewhat variable, ranging from 4 to 11 lbs nitrogen supply per 100 lb seed yield.
- There is also debate over the optimum timing of nitrogen application for winter canola to ensure high yields but minimize the potential for winterkill.
- Optimal placement of banded fertilizer at planting and canola root responses to banded fertilizer is poorly understood.
- Nutrient impacts on canola winter hardiness and frost tolerance needs to be better defined.
- Little is known about how fertility management affects oil yield in oilseed crops since the majority of studies assess only management effects on seed yield.
- Little is known about camelina nutrient requirements to optimize oil yield.
Current research:
This cross cutting project involves a series of experiments designed to assess canola and camelina seed and oil yield responses to nitrogen and sulfur rates, and nitrogen application timing. The study design is a randomized complete block with four replications at locations near Prosser, Davenport and Pullman, WA. Winter canola studies were initiated at each location in fall 2007. Spring canola and camelina studies are planned for 2008 at Davenport and Pullman. Camelina will also be sampled intensively over time and will also be quantified to develop baseline dry matter and nutrient uptake curves for this new crop.
Winter canola failed to establish at Pullman due to inadequate seed zone moisture. Establishment was spotty at Davenport but will likely result in sufficient stands for this study. Fall establishment of winter canola is a major challenge that will have to be overcome in order for this crop to be successfully grown in dryland environments.
Links to other extension resources on canola fertility:
Ontario, Canada: http://www.omafra.gov.on.ca/english/crops/pub811/8fert.htm#table81
Great Plains, U.S.: http://www.oznet.ksu.edu/library/crpsl2/mf2734.pdf
North Dakota: http://www.ag.ndsu.edu/pubs/plantsci/soilfert/sf1122w.htm
Montana: http://landresources.montana.edu/FertilizerFacts
Oregon State University: http://extension.oregonstate.edu/catalog/pdf/em/em8943-e.pdf
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