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Background: Properly reduced irrigation combined with nitrogen (N) application can be used to improve crop water use efficiency (WUE) in arid regions, but its effect on sugar beet is unknown at present. A two‐year field experiment was conducted to evaluate the effects of N application (N0, 0; N1, 150; N2, 225 kg N ha−1) on the canopy production capacity (CPC), yield and WUE of sugar beet under normal irrigation (W1, 70% of field capacity (FC)) and deficit irrigation (DI) (W2, 50% FC) in the early growth stage (EGS). Results: The results showed that the W2 treatment reduced the CPC by reducing gas exchange, leaf area index (LAI) and chlorophyll content (SPAD value) of sugar beet leaves compared to the W1 treatment. However, DI combined with N application increased these parameters. Specifically, N application increased the net photosynthetic rate by 40.7% by increased gas exchange, SPAD and LAI compared to the N0 treatment. In addition, N application increased WUE by 12.5% by increasing thickness of upper surface, stomatal aperture and cross‐sectional area of petiole. This ultimately led to a significant increase in taproot yield (TY; 19.7%) and sugar yield (SY; 57.6%). Although the TY of the N2 treatment was higher than that of the N1 treatment, the SY and WUE did not increase significantly and the harvest index decreased significantly by 9.3%. Conclusion: DI combined with 150 kg N ha−1in the EGS of sugar beet increases the WUE in arid areas while avoiding yield loss by improving the CPC. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Regulated deficit irrigation (RDI) can suppress excess vegetative growth of crops and improve water use efficiency. However, the effects of RDI combined with split application of nitrogen (N) fertilizer on sugar beet in arid regions are not clear. Therefore, in Xinjiang, China (2019–2021), N fertilizer (0 kg N ha−1 (N0); 150 kg N ha−1 (N1); 225 kg N ha−1 (N2)) was applied before sowing and at the canopy rapid growth stage (CRGS) of sugar beet in three ratios (20%: 80% (T1); 30%: 70% (T2); 40%: 60% (T3)). Besides, RDI was also applied at the CRGS of sugar beet. Finally, the responses in water and N use efficiency, dry matter accumulation, and yield of sugar beet were analyzed. The results showed that the root yield, water use efficiency for root yield (WUEry), and water use efficiency for sugar yield (WUEsy) of sugar beet in the N2 treatments increased by 3.71%–11.80%, 8.17%–24.84%, and 9.47%–16.46%, respectively, but the agronomic N use efficiency (aNUE) reduced by 1.12%–24.91%, compared with those in the N1 treatments. Besides, compared to mode T3, mode T1 increased dry matter accumulation and yield by enhancing leaf gas exchange, and finally significantly increased aNUE, WUEry, and water use efficiency for sugar yield (WUEsy) by 48.54%–82.39%, 8.75%–24.58%, and 9.95%–35.71%, respectively. The results of 15N isotope tracing showed that under RDI and N1 level, increasing the proportion of topdressed N could reduce the 15N loss by 16.02% and increase the 15N accumulated in plants by 19.31%. In conclusion, increasing the N topdressed at the CRGS combined with RDI could improve the water and N use efficiency and yield of drip-irrigated sugar beet in arid areas. • Nitrogen (N) fertilizer management increased water and N use efficiency of sugar beet. • N fertilizer management increased sugar beet yield under regulated deficit irrigation. • N fertilizer management coupled with regulated deficit irrigation reduced 15N loss. [ABSTRACT FROM AUTHOR]

Limited irrigation is a measure to avoid sugar beet yield reduction and improve water use efficiency in arid areas. However, it is unclear whether the optimization of traditional nitrogen fertilizer management under the limited irrigation conditions can further improve sugar beet yield and economic benefits. In this three-year field experiment in the arid region of northwest China, N fertilizer (150 (N1, recommended N application rate) and 225 kg ha−1 (N2, traditional N application rate) was applied in three methods, i.e., N fertilizer was applied at the ratios of 20: 80 (T1), 30: 70 (T2), and 40: 60 (T3, traditional N fertilization method) before sowing and at the rapid canopy growth stage. Then, the effects of the above N fertilizer managements on the growth parameters, canopy productivity, nutrient uptake, yield, and economic benefits of drip-irrigated sugar beets under limited irrigation was explored. To avoid the subjectivity of human evaluation, four comprehensive evaluation models were used for the evaluation of the N fertilization managements. The results showed that under the two N application rates, T1 treatment promoted plant nutrient uptake by increasing the available N content in the soil compared with the T3 treatment. This then increased the shoot and taproot growth rates by an average of 18.8 % (p < 0.05) and 26.5 % (p < 0.05), respectively by increasing the leaf area duration (LAD) during 45–120 DAE (days after emergence). In addition, T1 treatment increased the leaf senescence rate (LSR) of sugar beet during 120–150 DAE, which promoted yield formation and increased the taproot yield (TY) by 17.3 % (p < 0.05) compared with T3 treatment. Although N2T1 treatment resulted in higher net return (NR) than N2T3 (traditional N management method) and N1T1 treatment, N2T1 treatment did not increase marginal benefit (MB) and N use efficiency compared with N1T1 treatment. The results of the four comprehensive evaluation models showed that the N1T1 treatment had the highest evaluation value and the highest ranking compared with the other treatments. When limited irrigation is carried out in sugar beet cropping in arid areas, it is suggested that the traditional N fertilizer application rate can be reduced to 150 kg ha−1, and the proportion of topdressed N during limited irrigation can be increased. This study is of great significance for the sustainable development of local sugar beet production and the increase of farmers' income. • N management needs to be optimized to promote limited-irrigated sugar beet growth. • Increasing topdressed N increases plant nutrient uptake and reduces N leaching risk. • Accelerating leaf senescence promotes the taproot growth of sugar beet. • Optimized N fertilization increases taproot yields by accelerating taproot growth. [ABSTRACT FROM AUTHOR]

Crop growth is highly susceptible to drought stress due to water scarcity in arid areas. Silicon (Si) fertilizer could improve the tolerance of crops to drought stress, but the effect of drip fertigation of Si fertilizer on the growth and yield of sugar beets under drought stress is still unclear. In this field experiment conducted in 2022 and 2023 in the arid northwest China, the effects of different Si fertilizer application rates (0 kg ha−1 (Si0), 15 kg ha−1 (Si1), 38 kg ha−1 (Si2), 75 kg ha−1 (Si3)) on the growth, yield, and resource use efficiency of sugar beets (cultivars Beta356 (BT) and Strube13092 (ST)) under deficit irrigation (60 % of crop evapotranspiration (ETc), W2) were explored. The results showed that deficit irrigation (W2Si0) reduced the taproot and fibrous root growth, leaf net photosynthetic rate (Pn), leaf relative water content (LRWC), and leaf area index (LAI) of cultivar BT compared with full irrigation (100 % of ETc, W1). Under deficit irrigation, Si application (W2Si1, W2Si2, and W2Si3) alleviated the drought stress by increasing the number of fibrous roots in 17.5–70.0 cm soil layer and promoted the growth of taproots. Besides, it also increased the leaf moisture and photoassimilate production by increasing plant Si uptake, LRWC, LAI, and Pn. This finally increased the taproot yield (TY), irrigation water use efficiency (IWUE), and partial factor productivity of nitrogen (PFPN) by 11.2 % - 22.9 %, 6.5 % - 19.3 %, and 6.3 % - 19.3 %, respectively in cultivar BT and by 8.8 % - 27.1 %, 13.4 % - 30.8 %, and 13.4 % - 30.8 %, respectively in cultivar ST, compared with W2Si0. Regression analysis showed that the Si fertilizer application rate 64 kg ha−1 could maximize the TY of cultivar BT, but the net revenue (NR) was significantly lower than that of the W1 treatment. The Si fertilizer application rate 71 kg ha−1 could increase the TY of cultivar ST and achieve a NR similar to that of the W1 treatment. Therefore, in arid regions, Si application could alleviate the adverse effects of drought stress on drip-irrigated sugar beet root and shoot growth and improve yield, but the Si application rate varied with sugar beet cultivars. • Taproot silicon (Si) uptake was the highest (89 %), followed by leaf's and petiole's. • Si fertilizer increased fibrous roots in 17.5–70.0 cm soil layer compared with no Si. • Si fertilizer increased deficit-irrigated taproot yield by 25.0 % compared with no Si. • Suitable Si rates for cultivars Beta796 and Strube13092 were 64 and 71 kg ha−1. [ABSTRACT FROM AUTHOR]

Sugar beet has strong drought resistance and requires a large amount of nitrogen (N) during growth. Can deficit irrigation combined with low N supply of sugar beet improve water productivity (WP) and N use efficiency (NUE)? In this field study in 2020–2021, two irrigation regimes (W1, field capacity (FC) of the 0–60 cm soil layer was not lower than 70 % from 45 days after emergence (DAE) to harvest period; W2, FC of the 0–60 cm soil layer was not lower than 50 % in 45–90 DAE, but was consistent with that of W1 after 90 DAE) and three N application rates (0 (N0), 150 (N1), and 225 (N2) kg N ha−1) were designed. Then, their impacts on taproot yield (TY), water consumption (WC) and N uptake (NU) were explored. The results showed that there was no significant difference in TY between W2 and W1 treatments under the N1 and N2 levels. Under the N1 and N2 levels, the daily water consumption (DWC, 0.121 and 0.125 mm ℃d−1) and daily N uptake (DNU, 53.6 and 71.6 g N ℃d−1) of W2 treatment were significantly lower than the DWC (0.161 and 0.164 mm ℃d−1) and DNU (60.6 and 86.5 g N ℃d−1) of W1 treatment in 0–90 DAE. The W2N1 treatment had similar WP and higher NUE compared with the W1N2 treatment. In addition, the fertilizer-15N recovery rate in W2N1 treatment was 8.8 % higher than that in W1N2 treatment, the fertilizer-15N loss rate was 6.6 % lower than that in W1N2 treatment, but there was no difference in the fertilizer-15N residue between the two. This study clarified that implementing W2 deficit irrigation (50 % FC at the canopy rapid growth stage (45–90 DAE)) and N1 nitrogen application rate (33 % nitrogen reduction based on 225 kg N ha−1) could not reduce TY but improve WP and NUE. [Display omitted] • Increasing the daily water consumption of sugar beet negatively impacts yield. • Nitrogen uptake in the early growth stage is positively correlated with yield. • Deficit irrigation and low nitrogen supply at canopy growth stage don't reduce yield. • Deficit irrigation and low nitrogen supply improve water and nitrogen use efficiency. [ABSTRACT FROM AUTHOR]