Cereal and legume intercropping has been widely adopted to increase crop productivity in sustainable farming systems worldwide.  Among different intercropping combinations, millet and peanut intercropping can be adapted to most water-limited areas.  However, there are few studies on the differences in yield characteristics and nitrogen use efficiency between millet/peanut intercropping and monocultures under different nitrogen (N) application rates.  The objective of this study was to determine the yield advantages and economic benefits, as well as the appropriate N application rate, of millet/peanut intercropping.  A two-year field experiment was conducted with three cropping patterns (monoculture millet, monoculture peanut and millet/peanut intercropping) and four N rates (0, 75, 150 and 225 kg ha⁻¹).  The results showed that the land equivalent ratio (LER) and net effect (NE) of the intercropping system reached their highest levels at the N input of 150 kg ha⁻¹ in 2018 and 2019 (1.04 for LER, 0.347 Mg ha⁻¹ for NE, averaged across two years).  Millet was the dominant crop in the intercropping system (aggressivity of millet and peanut (Amp)>0, competitive ratio of millet and peanut (CRmp)>1), and millet yields achieved their highest values at N inputs of 225 kg ha⁻¹ for monoculture and 150 kg ha⁻¹ for intercropping.  NUE reached its highest levels with N inputs of 150 kg ha⁻¹ for all planting patterns over the two years.  Intercropping combined with an N input of 150 kg ha⁻¹ achieved the highest net income of 2 791 USD ha⁻¹, with a benefit-cost ratio of 1.56, averaged over the two years.  From the perspective of economics and agricultural sustainable development, millet/peanut intercropping at 150 kg N ha⁻¹ seems to be a promising alternative to millet or peanut monoculture.

Improving soil quality while achieving higher productivity is the major challenge in the agricultural industry.  Wheat (Triticum aestivum L.)–maize (Zea mays L.) (W–M) rotation is the dominant planting pattern in the Huang-Huai-Hai  Plain and is important for food security in China.  However, the soil quality is deteriorating due to the W–M rotation’s long-term, intensive, and continuous cultivation.  Introducing legumes into the W–M rotation system may be an effective way to improve soil quality.  In this study, we aimed to verify this hypothesis by exploring efficient planting systems (wheat–peanut (Arachis hypogaea L.) (W–P) rotation and wheat rotated with maize and peanut intercropping (W–M/P)) to achieve higher agricultural production in the Huang-Huai-Hai   Plain.  Using traditional W–M rotation as the control, we evaluated crop productivity, net returns, soil microorganisms (SMs), and soil organic carbon (SOC) fractions for three consecutive years.  The results indicated that wheat yields were significantly increased under W–P and W–M/P (382.5–579.0 and 179.8–513.1 kg ha⁻¹, respectively) compared with W–M.  W–P

and W–M/P provided significantly higher net returns (58.2 and 70.4%, respectively) than W–M.  W–M/P and W–M retained the SOC stock more efficiently than W–P, increasing by 25.46–31.03 and 14.47–27.64%, respectively, in the 0–20 cm soil layer.  Compared with W–M, W–M/P improved labile carbon fractions; the sensitivity index of potentially mineralizable carbon, microbial biomass carbon (MBC), and dissolved organic carbon was 31.5, 96.5–157.2, and 17.8% in 20–40, 10–40, and 10–20 cm soil layers, respectively.  The bacterial community composition and bacteria function were altered as per the soil depth and planting pattern.  W–M/P and W–M exhibited similar bacterial community composition and function in 0–20 and 20–40 cm soil layers.  Compared with W–P, a higher abundance of functional genes, namely, contains mobile elements and stress-tolerant, and a lower abundance of genes, namely, potentially pathogenic, were observed in the 10–20 cm soil layer of W–M and the 0–20 cm soil layer of W–M/P.  SOC and MBC were the main factors affecting soil bacterial communities, positively correlated with Sphingomonadales and Gemmatimonadales and negatively correlated with Blastocatellales.  Organic input was the main factor affecting SOC and SMs, which exhibited feedback effects on crop productivity.  In summary, W–M/P improved productivity, net returns, and SOC pool compared with traditional W–M rotation systems, and it is recommended that plant–soil–microbial interactions be considered while designing high-yield cropping systems.