Meeting the challenge of achieving high yields with less water utilization has raised concerns regarding developing water-saving agricultural practices. Conservation tillage and N fertilization are promising and widely used to improve water use efficiency; however, the mechanisms underlying still need to be addressed. Field experiments were conducted at the Hexi Corridor of northwestern China from 2019 to 2020, where tillage practices, i.e., conventional tillage (CT) and no-till with plastic film mulching (NTP), and N fertilizer rates (135 kg N ha−1 [N135], 180 kg N ha−1 [N180], and 225 kg N ha−1 [N225]) were applied. The results showed that NTP led to a soil water change (i.e., water consumption from the soil) increased by 101.7% during the concurrent growth period in a specific soil layer at 0–30 cm compared to CT. It also lowered the total soil evaporation (22.3%) and improved the total transpiration (13.4%). Consequently, no significant difference in evapotranspiration between the NTP and CT groups was observed. N135 decreased the soil water change by 9.0% and 15.2%, and improved the total soil evaporation by 3.4% and 8.4%, respectively, compared with N180 and N225. Tillage practices and N fertilization had an interactive effect on water productivity. Under CT, the grain yield and water use efficiency based on evapotranspiration (WUEET) of N180 were reduced by 9.4% and 7.6%, respectively, compared to those of N225. In contrast, under NTP, no significant difference was found. Structural equation modeling (SEM) analysis showed that the tillage practices improved WUEET by reducing soil evaporation and improving transpiration. However, N fertilization improved WUEET uniquely by improving transpiration. Consequently, we concluded that no-till combined with 180 kg N ha−1 could be used as an effective measure to achieve higher water productivity of spring wheat in arid areas.
No-till and cereal-legume intercropping have been recognized as favorable cropping practices to increase crop yields while maintaining soil quality in arid and semiarid environment, but the bio-logical mechanisms are poorly understood. The present study was to determine the response of soil properties, enzyme activities, and microbial community diversity and composition in mono- and inter-cropping under conventional and no-tillage conditions. We initiated a field experiment in Wuwei, a typical arid area of China, in 2014. Soil was sampled in August 2022 and, yields, soil properties, enzyme activities, and the microbial community diversity and composition were de-termined in the maize and pea strips in inter- and mono-cropping systems. Results revealed that the maize and pea strips in the no-till intercropping significantly increased yields, total and or-ganic carbon stocks, decreased NO3--N, and obtained the highest total and organic P in the soil. The α- and β-diversity of archaea and eukaryotes were significantly affected by planting patterns, while α- and β-diversity of the bacterial community were significantly affected by tillage practices. Both no-tillage and intercropped maize significantly increased the abundance of archaea phylum Thaumarchaeota and bacterial phylum Nitrospirae, benefiting nitrogen fixation of intercropped pea from the atmosphere under the no-tillage cereal/legume intercropping. No-till intercropping was conducive to the accumulation of organic carbon, while decreasing the abundance of Prote-obacteria, Acidobacteria, and Verrucomicrobia. Limited soil enzyme activities (ACP, ALP, DP, NAG, BG, AG, CB) led to decreases in organic carbon turnover and utilization. Intercropping al-tered soil microbial community diversity and composition due to changes in soil properties and enzyme activities. These findings suggest that no-tilled cereal-legume intercropping is a sustaina-ble cropping practice for improving soil properties and enhancing microbial (archaea, bacterial, Eukaryota) diversity, but the long-term persistence is not conducive to rapid turnover of soil nu-trients due to limited enzyme activities.
Above- and below-ground interactions play a crucial role in achieving higher yields in intercropping systems. Nonetheless, it remains unclear how these interactions impact intercropping crop growth and regulate interspecific relationships. This study aimed to quantify the impact of above- and below-ground interactions on crop yield by determining the dynamics of dry matter accumulation, photosynthetically active radiation (PAR) transmittance, and leaf area index (LAI) in intercropped wheat and maize. Three below-ground intensities were set for an intercropping system: no root separation (CI: complete interaction below ground), 48 μm nylon mesh separation (PI: partial interaction below ground), and 0.12 mm plastic sheet separation (NI: no interaction below ground). Two densities were set for maize: low (45,000 plants hm−2) and high (52,500 plants hm−2). At the same time, corresponding monoculture treatments were established. The grain yields in the CI and PI treatments were, on average, 23.7% and 13.7% higher than those in the NI treatment at high and low maize densities, respectively. Additionally, the grain yield for high density was 12.3% higher than that of low density in the CI treatment. The dry matter accumulation of intercropped wheat under the CI and PI treatments was, on average, 9.1%, 14.5%, and 9.0% higher than that in the NI treatment at the flowering, filling, and maturity stages, respectively. The dry matter accumulation of intercropped maize at the blister, milk, and physiological maturity stages increased by 41.4%, 32.1%, and 27.8%, respectively, under the CI treatment compared to the NI treatment. The PAR transmittance and LAI of maize at the V6 stage were significantly increased by increasing the intensity of below-ground interactions. This study showed that complete below-ground interaction contributed to a significant increase in the competitiveness of intercropped wheat with respect to maize (Awm) under the high-density maize treatment, especially at the filling stage of wheat. Moreover, the CI treatment enhanced the recovery effects of maize (Rm) after wheat harvesting. Increasing the intensity of below-ground interactions can significantly enhance the Awm and Rm in intercropping systems, favoring the accumulation of crop dry matter mass and light energy utilization to increase system yields.
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