Effects of Continuous Cropping and Application of Bio-organic Fertilizers on Growth, Yield and Quality of Sugar Beet under Reduced Chemical Fertilizer Application

A major problem in the cultivation of sugar beet is continuous cropping cycle. A study was carried out in the 2019–2021 season at the Agriculture and Forestry Sciences of Ulanqab, Inner Mongolia, to assess the impacts on the growth, root yield, and sugar content 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 non-continuous 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 demonstrated that continuous cropping stunted sugar beet growth and lowered yield and quality. The plant height, leaf area index, root volume, root yield, and sugar yield of sugar beet significantly decreased with the extension of continuous cropping years. Compared with CKN (CKY), plant height, leaf area index, root volume, and fresh weight of C1N (C1Y), C2N (C2Y), C3N (C3Y), and C4N (C4Y) all showed a significantly decreased trend. Furthermore, the plant height, leaf area index, root volume, and fresh weight reductions had amplitudes of 5.60–27.36