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Salt stress is a vital factor limiting nitrogen uptake and cotton growth in arid regions. The mechanisms underlying salt stress tolerance in cotton plants under high soil salinity have not been fully elucidated. Therefore, the aim of this study was to examine the proportion and mechanism of cotton nitrogen uptake under salt stress using the 15N isotope labeling technique. Cotton plants were grown in four undisturbed saline soils (1, 3, 6 and 9 dS m−1), and the experiment was designed using the ENVIRO-GRO (E-G) model. The results showed that the dry matter of roots, stems and leaves of the cotton parts in slightly saline soil (C2, 3 dS m−1) was not significant compared with the non-saline soil (C1, 1 dS m−1). The cotton fruit grown in low-salinity soil (C2, 3 dS m−1) had significantly higher dry matter than that grown in the other treatments, implying that cotton plants grown in 3 dS m−1 soil have the best nitrogen uptake and salt tolerance. Cotton plants grown in weakly (C3, 6 dS m−1) and moderately (C4, 9 dS m−1) saline soils exhibited premature senescence. The distribution of total nitrogen and nitrate content in cotton was the best explanatory variable of total 15N recovery, of which cotton 15N recovery was between 26.1% and 47.2%, and soil 15N recovery was between 7.7% and 14.9%. Our findings provide guidance for further exploitation and utilization of saline soil resources and sustainable development of the agricultural soil ecosystem in arid regions. [ABSTRACT FROM AUTHOR]

Soil salinization is a vital factor limiting crop yield in dryland oasis cropland. A film‐mulched drip irrigation and subsurface pipe drainage (MDI‐SPD) system has been proved to be highly efficient at mitigating salination globally. However, the soil salt balance in time and spatial dimension is unclear in this system. A MDI‐SPD experiment was conducted for 4 yr (2015–2019) in a field in Manas River Basin, western China. The subsurface drainage pipes were installed at a depth of 1 m with a space of 15 m. Three long‐term observation points were set at 0, 5, and 7.5 m horizontal from the subsurface pipe and served as long‐term observation points in 0‐to‐20‐, 60‐to‐80‐, and 180‐to‐200‐cm soil layers. Results after 4 yr indicated that the total salt output in the irrigated area was 260 t, with 103 t of salt drained by the subsurface pipe (40% of the total salt output in the irrigation area), and the seed cotton yield increased by 52%. Soil salt balance indicated desalination. The electrical conductivity (EC) of subsurface pipe drainage was positively correlated with drainage flow and salt discharge and negatively correlated with drainage discharge and time (P <.05). If salt leaching stops, soil EC at the 0‐to‐200‐cm depth could reach 15 dS m–1 in 8 yr. Thus, two or three uses of MDI‐SPD measures in the next 8 yr should suffice to maintain the soil salt at a low concentration. An increase in shaft drainage would also reduce the deep seepage of salt. Core Ideas: Results from a 4‐yr study showed that using drip irrigation with subsurface pipe systems improved cotton yield.Subsurface pipe systems drained 103 t salt, 40% of the total salt discharge over 4 yr.We quantified salt accumulation due to shallow groundwater recharge in the tillage layer.Subsurface pipe systems increased cotton yield by 52% in saline alkali land.Soil salt should be leached once every 3 yr without changing the leaching measures. [ABSTRACT FROM AUTHOR]

Salinization is recognized as a threat to agricultural productivity and land resources in global arid desert regions. To date, field soil improvement schemes have met with minimal success to date. We aimed to improve saline–alkali soils by assessing the effects of combining subsurface pipe (P a) and vertical well (S a) drainage measures on agricultural soils ecosystem. In a five-year field experiment, soil was sampled 0.5 m, 5 m, 7.5 m horizontally away from the P a , and 0.5 m, 30 m, 60 m horizontally away from the S a. Findings indicate that the soil electrical conductivity (EC) decreased from 16 dS m−1 to 3 dS m−1 at a 0–80 cm depth, and the soil desalination efficiency was great at the 0–300 cm depths (≥ 32%) than at the 400–700 cm depths (−14%–74.7%). The combined P a and S a drainage measures significantly decreased the species richness and quantity of soil microbial communities, and their negative impact on observed species was irreversible within 1 year. The farther the horizontal sampling conducted from the P a and S a , the greater the structural similarity of the microbial community at the genus level, higher the catalase, acidic protease, and neutral phosphatase activities, and lower the alkaline phosphatase activity. The overall decrease in groundwater level from 2016 to 2020 was 5.7 m. The seed cotton yield increased by 3.2 t ha−1. The results suggest that the value of saline–alkali soil can be improved by combining P a and S a drainage measures. Our research provides guidance for further effective utilization of agricultural water and soil resources and the sustainable development of the soil ecosystem in arid desert areas. [Display omitted] • Use drainage measures to improve the saline–alkali soil in agricultural ecosystem. • The cheapest way for reclamation of saline alkali soil is leaching of salts by irrigation water. • Salt discharge were positively correlated with the decrease of groundwater level and soil EC. • The farther away from drainage measures, the greater the similarity bacteria community. • The soil desalination rate of 0–300 cm depths was greater than 400–700 cm depths. [ABSTRACT FROM AUTHOR]