Deficit drip irrigation combined with nitrogen application improves cotton yield and nitrogen use efficiency by promoting plant 15N uptake and remobilization

Abstract

Context

Deficit irrigation has been widely investigated as a valuable crop production strategy to reduce irrigation water use in arid regions. The nitrogen (N) remobilization from vegetative organs to reproductive organs is vital for enhancing crop yield and N use efficiency (NUE). However, the effect of deficit irrigation on plant N remobilization remain unclear.

Research question

We hypothesized that deficit irrigation combined with reasonable N application can promote cotton N uptake and N remobilization from vegetative organs (stems and leaves) to bolls, thereby increasing cotton yield and NUE.

Methods

A three-year (2020–2022) field-plot experiment was conducted to investigate the impact of different irrigation levels (including full irrigation (FI) and two deficit irrigation treatments (DI1 and DI2, DI1 and DI2 corresponding to 80 and 60 % of FI, respectively) and N application levels (225 (N225), 300 (N300), and 375 (N375) kg ha⁻¹) on the cotton N uptake and yield. In order to further clarify the effects of deficit irrigation on fertilizer N (¹⁵N) uptake of cotton and its remobilization from vegetative organs (stems and leaves) to reproductive organs (bolls), a ¹⁵N-traced micro-plot experiment was established in 2022 based on the field-plot experiment.

Results

Compared with FI, DI1 significantly increased cotton N uptake and yield, while DI2 treatment significantly reduced cotton N uptake and yield. The cotton yield of DI1 treatment was 8.78 %, 9.76 %, and 7.67 % higher than that of FI treatment in 2020, 2021, and 2022, respectively. The three-year experiment (2020–2022) showed that the DI1 +N300 treatment had the highest N uptake and yield of cotton. The ¹⁵N-traced micro-plot experiment revealed that during the pre-bolling stage, the total ¹⁵N uptake of cotton plants increased with increasing irrigation and N application. During the post-bolling stage, DI1 greatly increased the bolls ¹⁵N uptake, resulting in the total ¹⁵N uptake of cotton plants was 5.57–8.72 % and 24.03–33.06 % higher than that of FI and DI2, respectively. The total ¹⁵N uptake of cotton plants peaked at the DI1 +N300 treatment. Moreover, compared with FI, DI1 and DI2 significantly increased the remobilization of ¹⁵N from vegetative organs (leaves and stems) to bolls (NR_T), especially the remobilization from leaves to bolls (NR_L), with NR_T increasing by 32.24 % and 18.77 %, and NR_L increasing by 53.14 % and 43.48 %, respectively. Under FI and DI1 conditions, NR_T reached its maximum at N300. However, under DI2 conditions, NR_T increased with increasing N application, although there was no significant difference between N300 and N375. The cotton plant ¹⁵N recovery under DI1 was 7.84 and 32.15 % higher than that under FI and DI2, respectively. The highest cotton plant ¹⁵N recovery was observed in the DI1 +N300 treatment.

Conclusions

Deficit irrigation combined with the N application of 300 kg ha⁻¹ has an advantage in increasing the ¹⁵N uptake of cotton plants and promoting ¹⁵N remobilization from stems and leaves to bolls during the post-bolling stage, thereby improving cotton yield and NUE.

Significance

This study can provide important information for achieving the synergistic improvement of cotton yield and resources use efficiency in arid regions.