Optimizing seeding dates and rates for canola production in the humid eastern Canadian agroecosystems

Citation

Ma, B.L., Zhao, H., Zheng, Z., Caldwell, C., Mills, A., Vanasse, A., Earl, H., Scott, P., Smith, D.L. (2016). Optimizing seeding dates and rates for canola production in the humid eastern Canadian agroecosystems, 108(5), 1869-1879. http://dx.doi.org/10.2134/agronj2015.0209

Plain language summary

Seeding date affects crop growth and development in various ways. Optimum seeding date (OSD) increases seedling vigour such as the germination rate and percent seedling emergence, coupled with better agronomic traits including plant height, and pod and branch numbers per plant. Also, timely seeding enables earlier flowering thereby extending the reproductive growth duration and enhancing dry matter production, harvest index, seed size, thousand seed weight (TSW), and final yield. Canola seeded at optimum dates can tolerate spring frosts and avoid unfavourable hot and dry weather during the flowering period. However, the optimum period for seeding canola is largely dependent on prevailing weather conditions in a region. As canola is a cool season, spring-seeded crop in Canada and the northern USA, we hypothesize that there is a quantitative relationship between OSD and daily air temperature of a specific period from seeding to the crop establishment for canola production in the region. We carried out a field experiment to examine the effects of varying seeding dates and rates on morphological traits, canola yield, and seed quality across eastern Canada, with specific objectives to: (1) investigate the influence of seeding date and rate on stand count, yield components, yield, and seed oil and protein concentrations, and (2) develop a location-sensitive model to estimate OSD for maximizing canola yields at various regions in eastern Canada. Using the historical weather data and the experimental results across eastern Canada, a regression model of OSD as a function of average minimum air temperature in April and May at the experimental sites was derived and fit into a quadratic curvilinear function: OSD = 3.6344T2min – 32.044Tmin + 183.37 (R2 = 0.98, P < 0.01). The model was also validated with two additional years of field experimental data. Accordingly, the OSD of canola is estimated to be 24 April at Ottawa, 26 April at Guelph and Ste-Anne-de Bellevue, 29 April at Canning, 11 May at Ste-Foy, and 25 May at the Harrington site. In addition, our study indicates that increasing seeding rate may lead to increased stand mortality and reduced branch and pod numbers. Such effects may be more dramatic for early seeding than for late-seeded canola. Overall, increasing seeding rate from 2.5 to 7.5 kg ha-1 could increase seed yield for early-seeded canola, but the yield increase was not significant above a seeding rate of 5 kg ha-1. The medium seeding rate of 5 kg ha-1 was therefore recommended across the humid eastern Canadian region.

Abstract

Optimum seeding date (OSD) and seeding rate is an important management practice to improve the performance of canola (Brassica napus L.) production. A field study was conducted to investigate the influence of seeding date and rate on plant stand count, yield components, yield, and seed oil and protein concentrations, and to develop a location-sensitive model for estimating OSD for maximizing canola yield. The factorial experiment of three seeding dates (early, intermediate, and late) and three seeding rates (2.5, 5.0, and 7.5 kg ha ) was performed in 2011 and 2012 at seven locations across eastern Canada. An independent dataset from an additional 2-yr field experiment at the Ottawa site was used for model verification. Our data showed that seed yield, seed oil, and pod number per plant were significantly affected by seeding date and seeding rate. The greatest yield and seed oil concentration were obtained with the early seeding in most site-years. The OSD was a quadratic function of the long-term (30 yr) average daily minimum air temperature (T ) in April and May with R = 0.98, P < 0.01 and SE = 2.6 d. Increasing seeding rate from 2.5 to 5.0 kg ha increased seed yield for early-seeded canola in most site-years but the yield did not increase with further increases in seeding rate. Early seeding at 5.0 kg ha–1 is therefore recommended as the optimum seeding rate across eastern Canada. –1 2 –1 min