Effects of synchronous layered fertilization with machinery on the root architecture and lodging resistance of rape

An appropriate fertilizer application can be one of the most important indicators for resistance to the downfall and high yield of direct sowing rape. Among them, the fertilizer placement and application rates can dominate the root and plant growth, development, and lodging resistance of winter rapeseed. This study aims to investigate the effects of the different ratios of layered fertilization in the deep and shallow layers under the precision combined seeder on agronomic characteristics, such as the root growth, plant resistance to lodging, and yield of rapeseed. The agricultural machinery and agronomic techniques were integrated to further improve the mechanical application fertilization of winter rapeseed. "Huayouza 62" rapeseed variety was selected as the test crop at the fertilization rate of 600 kg/hm². The control group was taken as the side deep fertilization of CK1 on the 10 cm positioning under the seed, and the shallow layer mixing fertilization of CK2. Three treatments of deep fertilization were set as the shallow and deep layer fertilization ratios of 1:3 (FL), 1:1 (FM), and 3:1 (FH) experimental groups. A total of five fertilization treatments and field trials were conducted in 2020 and 2021. The experiment site was located in the winter rapeseed area in Jingzhou, Hubei Province in the middle reaches of the Yangtze River basin. A measurement was performed on the root growth characteristics, soil firmness, shoot fresh weight, stem bending resistance and yield of rapeseed during the harvest period. A systematic analysis was then made on the five treatments, in terms of the root distribution, soil penetration resistance of topsoil, lodging index, and yield of rapeseed. The results showed that the layered deep fertilization significantly promoted the root downward migration and the root architecture of rapeseed. The average values of root surface area, root volume, root dry weight, and taproot length were 1.58, 1.47, 1.29, and 1.16 times higher than those in the CK1 treatment, while 3.63, 2.79, 1.46, and 1.28 times higher than those in the CK2 treatment, respectively. Meanwhile, the average soil penetration resistance decreased by 4.91% and 15.25%, respectively, compared with the CK1 and CK2 treatments. The overall performance was ranked in the descending order of the FM > FH > FL, in terms of the taproot length, root surface area, root volume, and root dry weight in the different layered fertilization treatments. The rape plant of root stem diameter, lodging angle, and fracture resistance of the FH treatment were 1.11, 1.25, and 1.31 times higher than those of the FM treatment. The lodging index decreased by 26.90% on average, but the field lodging angle increased by 25.14%, compared with the FM treatment. The yield, number of branches per plant, number of corner fruit, and thousand-grain weight of layered deep fertilization treatment were significantly higher than those of positioned deep fertilization and mechanical mixing fertilization treatment. the average rapeseed yield of FM treatment increased by 9.85%, 16.35%, 26.88%, and 37.75%, respectively, compared with the FL, FH, CK1, and CK2. The root distribution, soil penetration resistance, lodging index, and grain yield of winter rapeseed were considered under different fertilization treatments. The FM treatment was achieved in the better optimal fertilization for the high yield and lodging resistance of field mechanized direct sowing winter rapeseed.