Optimizing Nitrogen Fertilization of Hybrid Canola in Semiarid Regions
By Adrian Johnston, Scott Murrell, Stewart Brandt, and Guy Lafond1
Canola is the dominant oilseed crop grown across the northern Great Plains states and provinces. It is used primarily for the production of edible oil and high protein meal for feeding livestock. Recent plant breeding developments have resulted in the release of hybrids with yields superior to the current open pollinated varieties.
Fertilizer nitrogen (N) prices are impacted by natural gas prices, given that it represents a significant portion of the production cost. Periodically the price of natural gas rises with demand, increasing the price for fertilizer N. This brings up the question, how does the price of fertilizer N influence the decision on the optimum rate of N for canola?
A data set developed by Agriculture and Agri-Food Canada (AAFC) research scientists in Saskatchewan evaluated the response of hybrid canola to fertilizer N inputs. Financial support for this work was provided by the Saskatchewan Canola Development Commission, and the Matching Investment Initiative of AAFC. The study was managed by Mr. Stewart Brandt at the Scott Research Farm, with data collection also carried out by Dr. S.S. Malhi at the Melfort Research Farm, and Dr. Guy Lafond at the Indian Head Research Farm. Data from the three locations were grouped by years. For 2000, an above average precipitation year, yields ranged from 1,500 to 2,500 lb/A. In 2001, a below average precipitation year, yields from the three locations were less than 1500 lb/A. Average soil nitrate-N to 24 inches was 43 lb/A (range 17 to 74) in 2000, and 30 lb N/A (range 22-40) in 2001.
Canola is a high N consuming crop, taking up about 3.0 lb N/bu during growth, and removing about 1.9 lb N/bu in the seed (50 lb/bu). It also removes large amounts of phosphorus (P) and potassium (K), at 0.91 lb P2O5/bu and 0.46 lb K2O/bu, respectively. The impact of yield potential (dry vs. wet sites) had a major influence on the optimum N rate selected, with dry sites requiring approximately 35 lb N/A less than wet sites (Table 1). The canola prices presented represent the range that has been recorded in the market over the last decade. This was considerably greater than the change in optimum N rate with changing canola prices, or N prices, supporting the conclusion of the researchers that growing conditions have a much greater effect on N rate decisions than the price of canola or fertilizer N. In semiarid environments, the assessment of spring soil water at seeding, in combination with precipitation probabilities, form the basis for risk management decisions related to crop inputs like fertilizer N. The impact of fertilizer N prices increasing by 50% ($0.20 to $0.30/lb) on optimum N rate is minor, regardless of canola price, when compared with the environmental conditions of the year.
Farming in semiarid environments requires careful attention to all of the available tools when making N management decisions. These include:
A regionally developed soil analysis method to provide a good estimate of soil residual nitrate-N levels.
Pre-seeding assessment of soil water to establish an estimate of plant-available water. This combined with precipitation probabilities for the region allow for a “best estimate” of optimum N rates.
Understand the N requirements to grow high yielding canola. These range from 2.5 to 3.5 lb N/bu, with adequate P, K and sulfur to balance the N rates. Remember, over 70% of all soil tests run on fields in the northern Great Plains are at a level of P that would respond to fertilizer additions.
In areas affected by drought in 2002, select those fields with high residual nitrate-N levels to grow high N-demanding crops like canola. This will minimize the fertilizer N required to optimize return.
Source: S. Brandt, D. Ulrich, G. Lafond, S. Mahli, and A. Johnston. 2002. Management for optimum yield of open pollinated and hybrid canola. Proceedings of 2002 Saskatchewan Soils and Crops Workshop on CD-ROM. Available: Extension Division, University of Saskatchewan, Saskatoon, SK.
1 Dr. Johnston is PPI Western Canada Regional Director, e-mail: ajohnston@ppi-ppic.org
Dr. Murrell is PPI Northcentral Regional Director, e-mail: smurrell@ppi-far.org
Mr. Brandt is an agronomist with Agriculture and Agri-Food Canada in Scott, SK
Dr. Lafond is an agronomist with Agriculture and Agri-Food Canada in Indian Head, SK
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