Understanding the trade–off between lodging resistance and seed yield, and developing some non–destructive methods for predicting crop lodging risk in canola production

Abstract

Efficient nitrogen (N) nutrient management is important for developing sustainable strategies to increase seed yield while reducing negative environmental impacts. Motivation to increase seed yield by appropriately increasing N application rates would make crop lodging a potential problem. Fewer studies have been conducted to elucidate the trade–off between yield gain and lodging susceptibility in canola ( Brassica napus L. ), and a non–destructive and high–throughput assessment of lodging is seriously lacking. In this regard, a field study consisting of two varieties and five combinations of rates and timing of N application was conducted to explore the strength of their trade–offs for better N fertilization recommendation and to determine the feasibility of non–destructive technique for diagnosing canola lodging susceptibility. Two non–destructive techniques including root electrical capacitance and normalized difference vegetative index (NDVI) were verified in this study. The susceptibility of stem and root lodging were quantified by “safety factor” method. The results showed that there was a trade–off between seed yield and lodging resistance under conditions of seed yield greater than 1.3 t ha –1 . Under high–yielding condition of 2021 cropping season, split–N treatment, 50 kg N ha –1 at preplant plus 50 kg N ha –1 topdressed at the 6–leaf stage, increased seed yield by 20% and lodging resistance by 38% for hybrid ‘Invigor L233P’, compared with the equivalent preplant–only N application. However, under low–yielding condition, split–N treatments did not always show advantages over the equivalent preplant–only N treatments in terms of lodging resistance and seed yield, whereas the highest seed yield was generally attained under the split–N application in all experimental years. Root capacitance and impedance were significantly correlated with root morphological traits, which in turn affected lodging resistance and seed yield, while NDVI was closely related to lodging resistance (P < 0.01). A split–N application strategy with moderate N rates (100–150 kg N ha –1 ) can be highly recommended for canola production in eastern Canada. Indirect prediction of lodging susceptibility through root electrical measurements and NDVI mapping have high applicability due to their low cost and non–destructive properties, and are expected to serve as high–throughput techniques for guiding N fertilizer management to improve seed yield, while reducing lodging risk. • The trade–off between canola yield and lodging susceptibility was elucidated. • Split–N application with moderate rates can be recommended for canola production. • NDVI and root capacitance were feasible for diagnosing lodging susceptibility risk.