Intercropping has benefited the global agricultural sector in several ways. It is a critical farming practice for long-term productivity, agro-ecological improvement, land management, and land use. It is a well-known method to increase soil health and crop productivity. The impact of intercropping on the yield and production of maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) has been investigated at the leaf, stem, and root level. However, there is limited information about how to determine the best planting density for maize-soybean intercropping (MSI). The benefits and drawbacks of MSI are discussed in this review. Intercropping maize and soybean improves resource use, lodging resistance, and pest and weed control according to the existing research. Furthermore, soybean has low light use efficiency (LUE) and radiation use efficiency (RUE) due to the deep shade created by the maize canopy. As a result, more research is required to discover the optimal planting density to improve light and radiation efficiency.

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.

Despite our extensive knowledge on the effects of long-term straw returning on soil, little is known about the effects of short-term straw returning. We identified three study sites and evaluated their soil organic matter (OM), pH, and enzyme activity after two years of straw returning treatment. Bacterial diversity and community were determined by 16s RNA sequencing. We observed elevated OM content and pH after short-term straw returning treatment. The bacterial phyla Proteobacteria and Bacteroidetes exhibited similar dynamics on straw application. We observed reduced levels of Actinobacteria and Chloroflexi bacterial phyla after straw returning. Reduced Actinobacteria and Chloroflexi may be due to competition from dominant bacteria. In general, OM content and enzyme activity had the same trend that closely correlated with the amount and community of microorganisms in the soil. Proteobacteria and Bacteroidetes were the critical phyla in straw degradation and might improve soil OM content. Proteobacteria and Actinobacteria were identified as copiotrophic taxa. In summary, straw returning treatment might maintain soil stability and bacterial diversity better. The bacterial phyla Proteobacteria and Bacteroidetes were dominant over other microbial fractions during straw decomposition. The survival competition might be one of the main reasons for the decrease of Actinobacteria and Chloroflexi. Short-term straw returning to the field can markedly improve soil quality. However, soils in different locations respond differently to straw return practices and their responses are influenced by the soil’s basic parameters and climate.

A three-year field experiment was conducted to evaluate the effects of straw combined with potassium fertilizer on maize yield, potassium utilization efficiency and soil potassium balance. The study consisted of two straw treatments (S1: straw returning; S0: no straw returning) and five K levels (0,30,60,90,120 kg K ha⁻¹). The results showed that compared to S0, the maize yield and available K content in S1 increased by 2.9%~6.2% and 19.3%~37.4%. The average of agronomy efficiency and surplus rate in S1 were 7.3%~35.4% and 24.8%~84.7% higher than S0 respectively, but the recovery efficiency, partial factor productivity under S0 and S1 were statistically identical. When the surplus rate is 0, the amount of potassium fertilizer required and the corresponding yield to maintain the soil K balance in S1 were 87.9 kg ha⁻¹ and 12,424.6 kg ha⁻¹. Compared to S0, S1 can decrease potassium fertilizer application rate by 10.2% while increasing maize yield by 3.5%. Overall, straw return combined with potassium fertilizer can improve maize yield and soil available potassium content, it can also reduce chemical fertilizer input while increasing fertilizer utilization efficiency, and play a positive role in keeping soil K balance simultaneously.

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.