The maize/cassava relay intercropping system can be a specific and efficient cropping pattern in a tropical/subtropical field. Relay intercropping systems contribute to the optimization of land use, fostering sustainable and efficient agriculture. This study entails a first-year comparative intercropping experiment using maize (Zea mays L.) and cassava (Manihot esculenta Crantz). We determined the soil nutrient contents and physicochemical properties as well as the microbial communities by high-throughput sequencing. We found that the relay intercropping system changed the bacterial community structure, especially the rhizosphere microorganisms. The bacterial community was characterized by a higher abundance of the phyla Chloroflexi, Proteobacteria, and Actinobacteria and of the genus AD3, which are related to nutrient cycling and decreased bioavailability of Cd. At the same time, the relay intercropping system reduces the relative abundance of pathogenic bacteria and biomarkers of organic pollution. The relay intercropping systems significantly boosted soil pH and available K levels in addition to the monocropping yield. The results of this study suggest that maize/cassava relay intercropping, starting from the first year, not only provides a stable supply of food and income due to the diversified cropping systems but is also beneficial for the improvement of soil quality and the soil microbial community.

Cassava is a crucial food and economic crop in tropical regions globally. In response to challenges in fertilizer use efficiency for cassava cultivation, which is traditionally compromised by extensive leaching and broad root zone distribution, a novel large-particle slow-release fertilizer (LPF) was developed in this study. This fertilizer was synthesized through solution polymerization using non-metallic minerals and seaweed extract. Compared to conventional SFs that release 99% of nutrients within 1 min, the LPF prolonged the release duration to 51 min under optimal synthesis conditions: drying temperature of 80 °C, total extrusion force of 40 t, drying air pressure of −0.40 bar, auxiliary mineral proportion of 50%, and water content of 15%. Microbeam characterization (e.g., FTIR) and kinetic modeling revealed that the superior performance of LPF resulted from mineral crystal enrichment in the outer layer of fertilizer granules, facilitating intra-particle diffusion processes and imposing boundary layer limitations on nutrient release (e.g., N, P, and K). Field experiments validated the slow-release performance of the fertilizer. Notably, soil treated with LPF exhibited superior nutrient retention in the topsoil layer (0–20 cm) both horizontally and vertically. Even with two-thirds of the nutrient content relative to conventional fertilizers, LPF also displayed significant improvements in crop yield, partial factor productivity, and agronomic efficiency by 33.56%, 200.01%, and 513.84%, respectively. These results indicate that LPF presents a promising solution for sustainable cassava cultivation.

The impacts of prolonged nutrient-deficiency fertilization on the rhizosphere soil microbial community and crop yield remains largely underexplored. This study analyzed rhizosphere soil samples collected from a 30-year cassava monoculture field, comprising six fertilization treatments: balanced fertilization (NPK), nitrogen deficiency (PK), phosphorous deficiency (NK), potassium deficiency (NP), no fertilization (-NPK) and 50% NPK supplemented with burned soil (FNPK). Measurements included storage root yield, soil properties, and microbial community. Compared to NPK treatment, deficiency fertilization (PK, NK, NP, and -NPK) significantly decreased cassava yield by 38.6%, 21.3%, 38.1%, and 61.6%, respectively, while FNPK treatment maintained yield levels. The NK treatment intensified soil acidification, and the NP treatment accelerated soil organic carbon depletion. Conversely, FNPK treatment significantly improved rhizosphere soil pH and nutrients content. Long-term deficiency fertilization showed no significantly impact on bacterial and fungal richness (Chao1 index) and diversity (Shannon index), whereas FNPK markedly increased bacterial richness and diversity and modified bacterial and fungal β-diversity in rhizosphere soil. Soil pH was emerged as the primary driver of microbial community shifts. Bacterial communities in FNPK treatment exhibited reduced abundance in Acidobacteriota and Crenarchaota phyla and an increase in genus RB41 of Acidobacteriota and MND1 of Proteobacteria. FNPK also shifted the dominant fungal phyla from Ascomycota to Basidiomycota, and reduced the genus Melanconiella, associated with decreased plant wilt incidence. Treatments PK, NK, and -NPK suppressed the functional abundance of key bacterial and fungal groups, whereas FNPK significantly enhanced bacterial Chemoheterotrophy function, positively correlated with yield, and increased the abundance of undefined saprotrophic and arbuscular mycorrhizal fungal functional groups. Collectively, these findings indicate that prolonged nitrogen-based chemical fertilization intensifies soil acidification, adversely affecting the composition and function of soil microbial communities. The integration of burned soil with chemical fertilizer demonstrates potential in enhancing soil fertility and microbial diversity, offering insights for optimizing fertilization strategies in tropical cassava production systems.