Increasing nitrogen supply during limited irrigation improves drip-irrigated sugar beet growth, yield, and net return in arid areas

Context

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.

Methods

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.

Results

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.

Conclusions

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.

Significance

This study is of great significance for the sustainable development of local sugar beet production and the increase of farmers' income.