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Inner Mongolia, a major region in China for growing sugar beet, faces challenges caused by unscientific water and fertilizer management. This mismanagement restricts the improvement of sugar beet yield and quality and exacerbates water waste and environmental pollution. This study aims to evaluate the effects of reduced water and fertilizer on the growth and physiological metabolism of sugar beet taproot. Field experiments were conducted in Ulanqab, Inner Mongolia, in 2022 and 2023, using a split-plot design with three levels each of fertilization and irrigation. The study analyzed the effects of reduced water and fertilizer treatments on fresh taproot weight, respiration rate, energy metabolism, respiratory enzyme activity, and gene expression in sugar beet taproot. It was found that a 10% reduction in fertilizer significantly increased the beet taproot fresh weight. Further research revealed that during the rapid leaf growth phase and the taproot and sugar growth period, a 10% reduction in fertilizer upregulated HK and IDH gene expression and downregulated G6PDH gene expression in the beet taproot. This increased HK and IDH activities, decreased G6PDH activity, enhanced the activity of the EMP-TCA pathway, and inhibited the PPP. Taproot weight was positively correlated with the respiration rate, ATP content, EC, and ATPase, HK, and IDH activities, thereby increasing the taproot growth rate and taproot fresh weight, with an average increase of 4.0% over two years. These findings introduce a novel method for optimizing fertilizer use, particularly beneficial in water-scarce regions. Implementing this strategy could help farmers in western Inner Mongolia and similar areas improve crop yield and sustainability. This study offers new insights into resource-efficient agricultural practices, highlighting the importance of customized fertilization strategies tailored to local environmental conditions. [ABSTRACT FROM AUTHOR]

Sugar beet is a characteristic cash crop in Inner Mongolia, and water and fertilizer is an important management measure in sugar beet planting. The interaction between water and nitrogen is of practical significance in regulating the growth of sugar beet. The coordinated relationship between water and fertilizer can achieve the purpose of water saving, fertilizer saving, cost saving and efficiency increasing. The cultivation method of drip irrigation under plastic mulch was adopted in this study. The effects of water nitrogen supply on water metabolism and photosynthetic performance of sugar beet were studied through two years of field experiments in order to provide theoretical basis for improving the utilization efficiency of water and fertilizer and rational fertilization and irrigation. The results showed that the water nitrogen supply level and its proportion had influence with the water potential, Transpiration rate (Tr), Photosynthetic rate (Pn) and stomatal Conductance (Cond) of sugar beet leaves. And they were significantly positively correlated with the yield of sugar beet. When the water potential of sugar beet leaves was −0.38 ∼ −0.23 MPa in the period of leaf fast growth, root and sugar growth, and −0.45 ∼ −0.38 MPa in the period of sugar accumulation, the yield and sugar content were the highest. Under the coupling condition of water and nitrogen, the irrigation amount of sugar beet was 1350 ∼ 1427 m3·ha−1, and the nitrogen application amount was 150 ∼ 179.22 kg·ha−1. Sugar beet has the highest utilization rate of light energy and yield and sugar content. [ABSTRACT FROM AUTHOR]