Maize is a cold-sensitive crop, and it exhibits severe retardation of growth and development when exposed to cold snaps during and right after seedling emergence. Although different agronomic, physiological, and molecular approaches have been tried to overcome the problems related to cold stress in recent years, the mechanisms causing cold resistance in maize are still unclear. Screening and breeding of varieties for cold resistance may be a sustainable option to boost maize production under low-temperature environments. Herein, seedlings of 39 different maize genotypes were treated under both 10 °C low temperature and 22 °C normal temperature conditions for 7 days, to assess the changes in seven growth parameters, two membrane characteristics, two reactive oxygen species (ROS) levels, and four antioxidant enzymes activities. The changes in ten photosynthetic performances, one osmotic substance accumulation, and three polyamines (PAs) metabolisms were also measured. Results indicated that significant differences among genotypes, temperature treatments, and their interactions were found in 29 studied traits, and cold–stressed seedlings were capable to enhance their cold resistance by maintaining high levels of membrane stability index (66.07%); antioxidant enzymes activities including the activity of superoxide dismutase (2.44 Unit g⁻¹ protein), peroxidase (1.65 Unit g⁻¹ protein), catalase (0.65 μM min⁻¹ g⁻¹ protein), and ascorbate peroxidase (5.45 μM min⁻¹ g⁻¹ protein); chlorophyll (Chl) content, i.e., Chl a (0.36 mg g⁻¹ FW) and Chl b (0.40 mg g⁻¹ FW); photosynthetic capacity such as net photosynthetic rate (5.52 μM m⁻² s⁻¹) and ribulose 1,5–biphosphate carboxylase activity (6.57 M m⁻² s⁻¹); PAs concentration, mainly putrescine (274.89 nM g⁻¹ FW), spermidine (52.69 nM g⁻¹ FW), and spermine (45.81 nM g⁻¹ FW), particularly under extended cold stress. Importantly, 16 traits can be good indicators for screening of cold–resistant genotypes of maize. Gene expression analysis showed that GRMZM2G059991, GRMZM2G089982, GRMZM2G088212, GRMZM2G396553, GRMZM2G120578, and GRMZM2G396856 involved in antioxidant enzymes activity and PAs metabolism, and these genes may be used for genetic modification to improve maize cold resistance. Moreover, seven strong cold–resistant genotypes were identified, and they can be used as parents in maize breeding programs to develop new varieties.

Diversified cropping, as a crucial measure in modern ecological agriculture, promotes the intensification, industrialization, and diversification of agricultural production. By addressing region-specific and environmental challenges, the development of diversified cropping systems (DCS) tailored to local conditions can achieve the dual goals of improving crop quality and ensuring food security. However, existing crop quality improvement research primarily focuses on molecular techniques, with limited exploration of cropping practices. This review aims to systematically and comprehensively examine the concept, classification, and significance of diversified cropping. It highlights the critical roles and mechanisms of various cropping systems, such as intercropping, crop rotation, relay cropping, and multiple cropping, in enhancing crop quality. Furthermore, the review discusses the limitations and challenges of diversified cropping and offers suggestions for its improvement and application to advance research in this field. By proposing a scientific framework linking DCS with crop quality improvement, this review contributes to the formulation of evidence-based agricultural strategies to meet the growing demand for high-quality food, maintain environmental health, and promote long-term agricultural sustainability.

Cereal/legume intercropping enhances legume nodulation and improves nitrogen use efficiency (NUE) in cereal crops. This facilitation of symbiotic nitrogen fixation (SNF) in intercropped legumes involves a complex eco-physiological mechanism driven by multiple factors. Among them, interspecific root interactions (IRIs) are a key factor influencing SNF in intercropped legumes. Currently, it remains unclear whether and how IRIs modulate SNF to affect NUE and yield formation in legume species. In this study, maize/pea intercropping with different types of root separation [no barrier (NB) and plastic barrier (PB)] and pea monocropping (IP) were simulated in a nitrogen (N)-free nutrient matrix in pots, and the SNF, N metabolism, and N partitioning were investigated. We demonstrated that IRIs optimize SNF performance. N assimilation is positively regulated following increases in enzyme activity and gene expression in intercropped roots and nodules. Furthermore, IRIs facilitate amino acid (AA) export from nodules to roots and shoots, which is followed by an increase in AA levels in leaves (source) and leaf exudates (sink). Overall, intensive SNF drives N metabolism and alters source-to-sink N partitioning, thereby increasing NUE (by 23%) and yield (by 15%) in intercropped pea. This study reveals the positive roles of IRIs to the NUE and yield and provides useful reference material for increasing N contents derived from SNF to maximize NUE and crop yields in intercropped legumes.

Conservation tillage is widely recognized as an important way to improve soil quality, ensure food security and mitigate climate change. However, relatively little attention has been paid to the subject in terms of sustainable evaluation of environmental and economic benefits of the combination of no tillage and straw returning for maize production in arid irrigated areas. In this study, grain yield (GY) and water use efficiency based on grain yield (WUE_GY), soil carbon emission characteristics and economic benefits were investigated, and a sustainability evaluation index based on the above indicators was assessed in maize production under a wheat–maize rotation system from 2009 to 2012. Four wheat straw returning approaches were designed: no tillage with 25 to 30 cm tall wheat straw mulching (NTSMP), no tillage with 25 to 30 cm tall wheat straw standing (NTSSP), conventional tillage with 25 to 30 cm tall wheat straw incorporation (CTSP), and conventional tillage without wheat straw returning (CTP). The results showed that NTSMP treatment could effectively regulate water consumption characteristics of maize fields and meet the water conditions for high grain yield formation, thus gaining higher GY and WUE_GY. NTSMP increased GY and WUE_GY of maize by 13.7–17.5% and 15.4–16.7% over the CTP treatment, and by 5.6–9.0% and 2.3–11.2% over the CTSP treatment, respectively. Meanwhile, compared with CTP, the NTSMP treatment could effectively reduce carbon emissions from maize fields, where average soil carbon emission fluxes (AC_f), carbon emission (CE) and water use efficiency based on carbon emission (WUE_CE) were reduced by 17.7–18.9%, 11.1–11.2% and 8.8–12.8% and carbon emission efficiency (CEE) was increased by 10.2–14.7%. In addition, the NTSMP and NTSSP treatments could effectively increase total output and reduce human labor and farm machinery input, resulting in higher economic benefit. Among them, the NTSMP treatment was the most effective, net income (NI) and benefit per cubic meter of water (BPW) were increased by 16.1–34.2% and 19.1–31.8% over the CTP treatment, and by 13.2–13.3% and 9.8–15.6% over the CTSP treatment, respectively. The sustainability analysis showed that the NTSMP treatment had a high sustainability evaluation index and was a promising field-management strategy. Therefore, no tillage with 25 to 30 cm tall wheat straw mulching is a sustainable maize-management practice for increasing economic benefits and improving environmental impacts in arid irrigated areas.

Solar radiation is crucial for intercropping, while partial shading can protect intercropped soybean leaves from irradiation damage during the pod-ripening period under high solar radiation. This study explored the leaf dynamics and soybean quality for the maize–soybean system, for monoculture soybean (MS), monoculture maize (MM), two-row maize + three-row soybean (IS2-3), and four-row maize + four-row soybean (IS4-4). The results revealed that soybean leaves under IS2-3 and IS4-4 treatments showed increases in Rubisco activity of 59.8% and 12.4% compared with MS, respectively. The antioxidant capacity in soybean leaves in MS was higher than that under intercropping treatments. Soybean leaves under IS2-3 and IS4-4 exhibited higher alpha and beta diversities in their endophytes compared with MS. The relative abundance of pathotrophs under IS2-3 was reduced by 19.1% and 22.6% compared to that of those under MS and IS4-4, respectively. The total land equivalent ratio (LER) under IS2-3 was more than 1.00, and increased by 6.4% and 15.7% compared with IS4-4 in 2023 and 2024, respectively. Soybean seeds under IS2-3 and IS4-4 showed 4.1% and 4.2% increases in crude protein content compared to those of MS, respectively. Among various biosynthesis and metabolism processes, flavone and flavonol biosynthesis exerted a stronger influence on soybean seeds in MS, IS2-3, and IS4-4. Soybean seeds under IS2-3 showed elevated genistein content and reduced daidzein content compared with those of MS. Intercropping soybean treatments, especially IS2-3, maintained leaf health during the pod-ripening period and enhanced the crude protein content compared with sole soybean treatment, thus guiding the design of intercropping in areas with high solar radiation.

Legume green manure incorporation offers a potential pathway for sustainable cropping in arid irrigated areas. This study aimed to determine whether water and nitrogen inputs could be concurrently reduced without compromising maize productivity under this practice. A two-year field experiment (2024–2025) was conducted using a split-plot design with three irrigation levels (I1: 4045, I2: 3240, I3: 2430 m³·ha⁻¹) and three nitrogen rates (N1: 360, N2: 288, N3: 216 kg·ha⁻¹). Compared with conventional management (I1N1), 20% co-reduction in water and nitrogen (I2N2) maintained stable leaf area index (LAI), net photosynthetic rate (P_n), transpiration rate (T_r), DM, and GY, while significantly increasing water use efficiency (WUE) by 7.6% and nitrogen use efficiency for grain yield (NUtEg) by 11.7%. Excessive water reduction (I3) or nitrogen reduction (N3) significantly inhibited growth and reduced yield (p < 0.05). Soil water content under I2N2 did not differ significantly from I1N1 in the 0–110 cm profile, and soil total nitrogen remained higher at silking.) Structural equation model (SEM) revealed SWC and STN indirectly affected P_n and T_r via regulating LAI and SPAD (path coefficients: 0.48–0.62), which drove DM accumulation and determined GY (R² = 0.81). These short-term results suggest that moderate water-nitrogen reduction with green manure can sustain yield while improving resource efficiency, offering a promising practice for arid irrigated maize systems, though longer-term validation is needed.