Effects of continuous cropping and application of bio-organic fertilizer on photosynthetic performance, dry matter accumulation and distribution of sugar beet
Authors: Guo Xiao-xia , Tian Lu , Song Bai-quan , Li Ying-hao , Huang Chun-yan , Li Zhi , Zhang Peng , Jian Cai-yuan , Han Kang , Xue Chun-lei , Zhou Jian-chao , Su Wen-bin 
Published: January 2024

A major problem in the cultivation of sugar beets is continuous cropping obstruction in China. A study was carried out in the 2020–2021 season at the Agriculture and Forestry Sciences of Ulanqab, Inner Mongolia, to assess the impacts on the on photosynthetic performance, dry matter accumulation and distribution of sugar beet of various continuous cropping years with bio-organic fertilizers. A split plot system with three replications was set up to carry out the field testing. The main plots had five planting years, with the fresh cropping of each growing season serving as the control (CK) and continuous cropping for one, two, three, and four years (designated as C1, C2, C3, and C4, respectively). The subplots had two bio-organic fertilizer levels: 6000 kg ha-2 (Y) and 0 (N). The results showed that continuous cropping inhibited the photosynthesis of sugar beet and hindered the ability of dry matter accumulation and distribution in leaf, petiole and root. With the extension of continuous cropping years, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intercellular CO2 concentration (Ci) and SPAD value of sugar beet significantly decreased, and the dry matter mass of leaves, petioles and roots significantly decreased. Compared with CK, the SPAD, Pn, Ci, Tr, Gs of continuous cropping treatments were significantly reduced by an average of 10.09-48.21%, 14.60-43.19%, 12.00-42.86%, 7.77-43.83%, 9.61-37.68%, respectively. The dry matter accumulation of leaf, petiole, root, and whole plant reduced by 11.86-49.61%, 9.58-44.77%, 17.26-53.76%, 10.62-49.79%, respectively. And with the increase of continuous cropping years, the inhibitory effects were enhanced, and there were no significant differences in performance between continuous cropping for 1 year and 2 years. The continuous cropping affected the dry matter accumulation distribution of sugar beet, it significantly increased the dry matter ration of above ground and decreased the dry matter ration of root, inhibited the transfer of dry matter from aboveground to root. These impacts ultimately led to a decrease in the root shoot ratio and yield of sugar beet. Compared with CK, the root shoot ratio of continuous cropping treatments significantly decreased by 3.62-19.76%. Under continuous cropping conditions, the application of bio-organic fertilizer could effectively promote the photosynthesis of sugar beet, and better regulate the distribution and transport of dry matter of sugar beet, and the effect of bio-organic fertilizer was significant under continuous cropping for 1-2 years. Compared with C1N and C2N, the Pn, Ci, Tr, Gs of C1Y and C2Y were significantly increased by 12.79-22.50%, 14.76%-16.47%, 4.76%-13.08%, 8.51%-12.70%, and 13.69%-18.91%, 12.17%-14.60%, 5.71%-15.14%, 7.58%-15.41%, respectively. The dry matter accumulation of leaf, petiole, root, whole plant was significantly increased by 8.32%-16.18%, 10.80%-13.33%, 14.93%-20.13%, 14.12%-15.43%, and 10.65%-15.32%, 6.58%-15.63%, 15.37%-20.94%, 12.68%-16.85%, respectively. And the root shoot ration increased by 4.58%-8.56% and 4.52%-7.35%. Above all, sugar beet is one of the crops with obvious obstacles to continuous cropping, and under short-term continuous cropping, the application of bio-organic fertilizer has significant improvement effects. These results can provide scientific basis for bio-organic fertilizer to alleviate the problem of sugar beet continuous cropping.