Management of Canola N Fertilization in Virginia.

In addition to being one of the six most important nutrients for plant growth, information about N use in crop production is also important due to cost and environmental-pollution issues.  In our efforts to develop a system of canola (Brassica napus L.) production in Virginia, two experiments with 50, 100, and 150 pounds N per acre were conducted with Virginia cultivar at two Virginia locations.  The objectives of these experiments were  to determine optimal rate and time of N application.  N was applied using three application times: all in fall, all in spring, or a  split application in fall and spring.  Canola seed yields following 50, 100, and 150 pounds of N per acre at Petersburg location on Abel Sandy loam soil were not different (2220, 2326, and 2038 pounds per acre, respectively).  Similarly, seed yields following three application times at Petersburg were also not different (2471, 2004, and 2109 pounds per acre).  The residual N in the experimental area was approximately 50 pounds per acre.  Canola seed yields following 50, 100, and 150 pounds of N per acre at Orange location on Starr clay loam soil were 2095, 2099, and 2421 pounds per acre respectively with 150 pounds of N resulting in yield significantly better than the other two rates.  Application of all N in Spring at Orange location resulted in yield significantly better than the other two treatments.  The residual N in the experimental area was approximately 40 pounds per acre.   This indicates that optimal N for canola production in Virginia is approximately 100 pounds N per acre.  Additional information related to N content of whole canola seed also supports this observation.