Moderately deep tillage enhances rapeseed yield by improving frost resistance of seedling during overwintering

Abstract

ContextLow-temperature stress limits the seedling growth during the overwintering of rapeseed (Brassica napus L.) thereby decreasing the yield in the Yangtze River Basin (YRB). Our previous study found that deep tillage could promote the growth and safe overwintering of seedlings, however, the mechanism of deep tillage to improve seedling condition during the overwintering is unclear. ObjectiveThe aim of the study was to explore the mechanism by which moderate deep tillage (MT) could improve rapeseed seedling conditions during overwintering, and to provide a theoretical basis for establishing a tillage management system for high-yield and highly efficient rapeseed production in the YRB region. MethodsA three-year field trial was conducted to determine the effect of tillage practices [shallow tillage (ST) and MT] on seedling conditions during overwintering and yield of two rapeseed varieties [ZY50 (with strong lateral roots) and XZY518 (with less lateral roots)]. ResultsMT significantly reduced soil penetration resistance, while increasing the moisture content, total nitrogen, organic matter, alkali-hydrolyzed nitrogen, available phosphorus, and available potassium in 15–30 cm soil layers, and soil temperature in 15–25 cm soil layers, compared with ST. The favorable soil conditions under MT improved the nutrient uptake of rapeseed. The green leaf area ratio was increased, while purple and yellow leaf area ratio were reduced during overwintering. The antioxidant enzymes activities were higher under MT which decreased the contents of reactive oxygen species and malondialdehyde in the roots and leaves of seedlings, indicating that seedlings were less damaged by frost. Furthermore, the thickness of palisade tissue and leaf and cell wall was reduced, which in turn increased the net photosynthetic rate and biomass of rapeseed. All these results showed that MT enhanced the frost resistance of seedlings during overwintering. Finally, the yield of rapeseed was significantly increased by 23.5 % under MT compared to ST. The yield of the two rapeseed varieties was similar under MT treatment. Under ST, the yield of ZY50 was significantly higher than XZY518, with a three-year average increase of 11.3 %, indicating that more developed lateral roots can benefit rapeseed yield under ST treatment. ConclusionsMT improved rapeseed seedling conditions during overwintering, thus benefiting high-yield acquisition for rapeseed in the YRB region. SignificanceGiven the potential benefits of the MT treatment in terms of increased rapeseed production and frost resistance during overwintering, this practice has a realistic chance of becoming widespread in the future.