Solving Spring Survival for Winter Canola in Montana.

Canola is a minor acreage crop in Montana due to a key adaptation challenge for spring canola in this semiarid environment; chronic ET deficit coincides with bloom period. The growth cycle of winter canola is better timed with growing season rainfall patterns, which increases water use efficiency, and yield, compared with spring canola. However, survival of winter canola is uncertain in Montana. Rain in early September, or irrigation, is required to germinate canola timely to reach the 5-lf stage. However, even when this is achieved, apparently healthy stands at snowmelt often decline severely in early spring. This study tested effects of alternate stubble microclimates on fall and spring growth of winter canola, and searched for pathogenic organisms that may contribute to spring stand decline. The experimental design included treatments for row direction (E-W vs N-S), crop stubble (pea, short wheat, or tall wheat), cultivar (DKW 46-15 or HyClass 154W), and N fertilizer regime (all applied at fall seeding or 22 kg ha-1 applied at seeding and 178 kg ha-1 spring broadcast). The climatic context for this study was exceptional drought, with 2012 and 2013 the two driest crop-years in the 47-yr record for the Bozeman research farm. Half (142 mm) of the total Sep/Aug 2012/13 crop-year precipitation (287 mm) came May 16 – June 20. Canola plots were sown 5 Sep 2012 into stubble treatments, and immediately irrigated to promote emergence. Otherwise plots were rainfed. There were no treatment effects on fall stand counts (overall mean = 198 m-2). Seedling biomass on 30 Oct 2012 was affected only by fertilizer N regime, where full application at seeding increased seedling biomass by 33%. Bi-weekly spring stand counts began 15 Mar 2013 with an overall mean density of 127 plants m-2 reflecting an overwinter decline of 36%. Spring density declined to 110 plants m-2 by 29 Mar and did not change through 18 Apr when counting was discontinued. Final stand density was not affected by any treatment. E-W row orientation had 22% greater pre-bolting biomass (measured May 8) than N-S row orientation, consistent with observations from adjacent studies in 2011. A cultivar x stubble interaction was observed where the taller cultivar, HyClass 154W had greatly reduced biomass (530 vs 1250 kg ha-1) compared with the average of other cultivar x stubble combinations. Maturity in tall wheat stubble was 2.6 d later than in short wheat stubble, while maturity in pea stubble was intermdiate. DKW 46-15 matured 5 d earlier than HyClass 154W, and the split N regime matured 2 d later than full N application at seeding. Row orientation had no effect on any harvest parameter. Overall average dry matter seed yield was 3340 kg ha-1, impressive given this droughty context. Pea stubble yielded 380 kg ha-1 (12%) greater than short wheat stubble and DKW 46-15 yielded 460 kg ha-1 greater than HyClass 154W, likely due to earlier maturity. Fertilizer N regime did not affect yield, seed oil concentration, or oil yield. Overall seed oil concentration was unusually low (mean = 39.4%). Oil yield was 150 kg ha-1 (12%) less for short wheat stubble than the other two crop stubbles. DKW 46-15 had 250 kg ha-1 greater oil yield than HyClass 154W. The droughty context of this study was not conducive to detecting possible pathogenic agents on winter canola seedlings.