With mounting demand for high-quality agricultural products and the relentless exploitation of arable land resources, finding sustainable ways to safely cultivate food crops is becoming ever more important. Here, we investigated the effects of the integrated cropping technique “straw return + intercropping” on the soil aggregates as well as the microbial biomass carbon (MBC) content, enzyme activities and microbial diversity in soils of maize and soybean crops. Our results show that in comparison to straw removal and monoculture, straw return and intercropping increase the rhizosphere’s MBC content (59.10%) of soil, along with urease (47.82%), sucrase (57.14%), catalase (16.14%) and acid phosphatase (40.66%) activities as well as the microbial diversity under maize and soybean. Under the same straw treatment, the yield of maize when intercropped surpassed that when grown in monoculture, with the land equivalent ratio of the intercropping treatment under straw return being highest. Overall, the intercropping of maize and soybean is beneficial for the healthy development of sustainable agriculture in the black soil region of northeast China, especially when combined with straw return to fields.

High grain yields of rice (Oryza sativa) under dry cultivation are primarily obtained through high levels of nitrogen (N) input. However, excessive inputs of N increase the risk of lodging. This study aimed to clarify the effect of N application rates on crop morphology, mechanical mechanisms of the stem, and chemical components in the basal stems of rice and their underlying mechanism in association with lodging resistance under dry cultivation. In this study, field experiments on rice were conducted under dry cultivation in early May to early October 2019 and 2020. Six rates of N applied at 0, 70, 140, 210, 280 and 350 kg ha⁻¹ were set at a sowing rate of 150 kg ha⁻¹ with Suijing 18 as the test material. The increased risk of lodging represented by lodging index (LI) and lodging rate with increasing N application was observed under both growing seasons. The plant height, basal internode length, particularly the second internode, and center of gravity height, which positively correlated with the LI, increased significantly with the increase in N application rates. In contrast, internode fullness and carbohydrate content of the basal second (S2) internode, which negatively correlated with LI, decreased significantly with increasing N application rates. A quadratic regression model between N application rates and grain yield showed that better grain yield could be achieved under an N application rate ranging from 210 to 228 kg ha⁻¹. Therefore, the N application rate of (i.e., 210–228 kg N ha⁻¹) could be recommended for the Suijing18 variety under dry cultivation in central Jilin Province for achieving high grain yield and great lodging resistance.

Chemical products, such as seed dressings, are often used to regulate crop growth and development and improve yields. In this study, we investigated a seed dressing containing 0.136% gibberellic acid (GA), indole-3-acetic acid (IAA)-, and brassinolide (BL) as a wettable powder (WP), hereafter referred to as GA-IAA-BL WP. This product is a new plant growth regulator of plant origin that can improve crop stress resistance and yield. However, its effect on maize seed germination and seedling growth under low-temperature stress is unclear. In this study, GA-IAA-BL WP was applied to maize ‘Liukexing 99’ seeds at 50, 100, 150, or 200 mg mL⁻¹, and seeds were germinated in an artificial climatic chamber at 10, 15, or 25 °C for 14 d. Application at 100 mg mL⁻¹ significantly increased the germination rate as well as seedling shoot and root length and dry and fresh weight at all three temperatures. This application rate also increased the contents of proline, malondialdehyde, soluble sugars, and soluble proteins; the activities of catalase, superoxide dismutase, and peroxidase; and root vigor. Our results demonstrate that GA-IAA-BL WP can reduce the negative impacts of low-temperature stress on seed germination and seedling growth.