The increasing global food demand, the degradation of one-third of agricultural land, and climate change pose significant threats to food production. Maize and soybean intercropping can enhance yields and land use efficiency, yet the year-interval effects of continuous intercropping on yield, yield sustainability, and phosphorus use efficiency (PUE) remain unclear. This study evaluates the effects of continuous maize/soybean intercropping over year intervals on yield, PUE, and sustainability. A seven-year field trial (2017–2023) was conducted on acidic soil, comparing two cropping systems: maize monocropping and maize intercropped with soybean. The results showed that continuous maize/soybean intercropping outperformed maize monocropping across all year intervals. Over the first, third, and seventh year intervals, maize yield increased by 37%, 35%, and 58%, respectively, with a 55% average increase over the seven years. Intercropping also enhanced P use efficiency, as evidenced by AE, RE, PFP, and CPF increases. In the first year, AE, PFP, RE, and CPF increased by 48%, 37%, 27%, and 16%, respectively; after the third year interval, these metrics improved by 40%, 35%, 26%, and 14%; and after the seventh year interval, they rose by 60%, 58%, 24%, and 10.5%. The average AE, RE, and PFP increases over seven years were 53%, 52%, and 27%, respectively, while CPF increased by 13%. The SEM analysis further confirmed the substantial impact of the seventh year intercropping interval on maize yield, sustainability, and PUE. This study demonstrates that continuous maize/soybean intercropping can enhance maize yield, PUE, and sustainability, with the seventh year interval offering the most pronounced benefits. These findings provide valuable insights for improving food security and nutrient management challenges.

Phosphorus (P) application can enhance soil P availability and alter P fractions. However, the P accumulation and transformation of different P sources in low-phosphorus red soil remain unclear. Two-year (2018–2019) field experiments were conducted to investigate the effects of five P source treatments (CK—no phosphorus; SSP—superphosphate; MAP—calcium–magnesium phosphate; DAP—monoammonium phosphate; and CMP—diammonium phosphate) on the P accumulation of maize and soil P fractions in low-P red soil using the Hedley Sequential Method. The results showed that P application significantly increased P uptake, Olsen-P, total phosphorus, and most of the soil P fractions. Compared to the CMP, MAP, and DAP treatments, SSP had a relatively higher P accumulation and labile P pool, with a slightly lower moderately labile P pool. The SSP treatment mainly increased soil-available P content and crop P uptake by increasing the labile P pool (resin-P and NaHCO₃-Pi) and reducing the moderately labile P pool and non-labile P pool. The P activation coefficient (PAC%) and Olsen-P were positively correlated with labile P (resin-P, NaHCO₃-Pi, and NaHCO₃-Po) and moderately labile P (NaOH-Pi and 1 M HCl-Pi) and negatively correlated with Fe₂O₃ and Al₂O₃. The results suggest that SSP has a priority effect on the crop P uptake and soil P availability in low-P red soil.

Background and aims: This research aimed to evaluate the effects of consecutive intercropping on soil phosphorus (P) partitioning, concentrations, and sensitivity to P fertilizer application, elucidating its impact on soil P bioavailability. Methods: A field experiment investigated soil P fractions and content under continuous wheat and faba bean intercropping. Three P levels (0, 45, and 90 kg P₂O₅ ha⁻¹ denoted as P0, P1, and P2, respectively) and three planting patterns (monocropped wheat (MW), monocropped faba bean (MF), and wheat and faba bean intercropping (W//F)) were established since 2014. Aboveground P uptake by wheat and faba bean was determined. The soil P fractions and content were analyzed after six-, seven-, and eight-year continuous field experiments. Results: Wheat and faba bean intercropping increased wheat aboveground P uptake by 28.3–42.7% compared to MW under P1 and P2 levels and presented a P uptake advantage (LER_Puptake > 1), although W//F had no impact on faba bean P uptake. Consequently, continuous intercropping for 8 years decreased soil available P reserves by 9.0–23.4% in comparison to the weighted average value of MW and MF (It). Faba bean consumed greater non-labile and labile P than wheat with low P input. W//F had nearly no impact on the labile P pool but reduced the non-labile P pool by 5.0–12.1% under all P levels and lowered the moderately labile P pool by 1.7–4.7% at P0 and P1 levels compared to It with consecutive intercropping for 8 years. Consecutive intercropping of wheat and faba bean primarily decreased the proportion of Resin-P in the labile P pool and the proportion of Residual-P in the non-labile P pool. According to the structural equation model, crop P uptake mainly originated from soil available P, which was directly affected by non-labile P (Residual-P and Conc. HCl-P). In addition, intercropping changed the contribution of each P faction to crop P uptake compared to MW and MF, and P uptake in intercropping primarily depended on Conc. HCl- P and Dil. HCl-P. Therefore, consecutive intercropping decreased soil non-labile P and drove soil available P depletion, and intercropping’s increase of P uptake was related to the non-labile P mobilized to moderately labile and labile P. Conclusions: Continuous wheat and faba bean intercropping reduced non-labile P and led to soil available P depletion under low P input. This practice stimulated non-labile P mobilization, enhancing soil P fraction effectiveness and facilitating P uptake in intercropping. Continuous intercropping of wheat and faba bean is as an effective method to maximize the biological availability of soil P and reduce P application rates.

Studying the effects of maize and soybean intercropping for improving the maize yield and sustaining stability of the maize yield under different phosphate (P) application rates in red soil is crucial for promoting maize productivity, improving soil fertility and optimizing P nutrient management in southwest China. The objective of this study was to evaluate the dynamic changes in maize yield, yield stability and soil fertility under monoculture and intercropping maize with different P application rates. A six-year field experiment was conducted from 2017 to 2022 to investigate the effects of maize intercropping with soybean on the yield stability and sustainability of maize according to the changes in the maize yield, biomass, partial land equivalent ratio of yield (pLERY), actual yield loss index (AYL), contribution rate of soil capacity and fertilizer (SCR, SFCR) over time, as well as the differences in the coefficient of variation (CV) and sustainable yield index (SYI) at four P application rates (0 kg P₂O₅ ha⁻¹, P0; 60 kg P₂O₅ ha⁻¹, P1; 90 kg P₂O₅ ha⁻¹, P2; and 120 kg P₂O₅ ha⁻¹, P3) based on the two-factor randomized block design. The linear-platform model was utilized to simulate the relationship between the grain yield, the SYI and the amount of P fertilizer under different P application rates. The maize yield in intercropping was significantly superior to the maize yield in monoculture throughout the entire six-year experiment. For all planting years, the yield and biomass of the intercropping were higher than those of the matched monoculture average by 56.0% and 56.1%, respectively. Intercropping had an advantage of pLERY and AYL for maize. Otherwise, intercropping reduced the CV by 30.8% and 39.1% and increased the SYI by 39.4% and 23.0% in P0 and P3 compared with the matched monoculture, respectively. For all planting years, the average SFCR in intercropping treatment was higher than that in monoculture treatment. The linear-plateau model fitted showed that intercropping increased the yield and SYI by 19.8% and 40.7% on the platform and reduced the P application rate by 37.8% and 11.9% at the inflection point, respectively. These results demonstrate that maize and soybean intercropping could achieve a higher yield, a higher yield stability and an SYI with a lower P input than monoculture. Maize and soybean intercropping could be a sustainable practice for promoting the maize productivity and the yield sustainability in the red soil of southwest China.

Introduction: Continuous cropping challenges have gradually emerged as pivotal factors limiting the sustainable development of agricultural production. Allelopathicals are considered to be the primary obstacles. However, there is limited information on allelopathic accumulation across various continuous cropping years and its correlation with the associated challenges.Methods: Tobacco was subjected to varying planting durations: 1 year (CR), 5 years (CC5), 10 years (CC10), and 15 years (CC15).Results: Our findings unveiled discernible disparities in tobacco growth patterns across diverse continuous cropping periods. Notably, the most pronounced challenges were observed in the CC5 category, characterized by yield reduction, tobacco black shank outbreaks, and a decline in beneficial flora. Conversely, CC15 exhibited a substantial reduction in challenges as the continuous cropping persisted with no significant differences when compared to CR. Within the tobacco rhizosphere, we identified 14 distinct allelopathic compounds, with 10 of these compounds displaying noteworthy variations among the four treatments. Redundancy analysis (RDA) revealed that eight allelopathic compounds exhibited autotoxic effects on tobacco growth, with MA, heptadecanoic acid, and VA ranking as the most potent inhibitors. Interaction network highlighted the pivotal roles of VA and EA in promoting pathogen proliferation and impeding the enrichment of 13 beneficial bacterial genera. Furthermore, a structural equation model elucidated that MA and EA primarily exert direct toxic effects on tobacco, whereas VA fosters pathogen proliferation, inhibits the enrichment of beneficial bacteria, and synergistically exacerbates the challenges associated with continuous cropping alongside EA.Discussion: These findings suggested discernible disparities in tobacco growth patterns across the various continuous cropping periods. The most pronounced challenges were observed in CC5, whereas CC15 exhibited a substantial reduction in challenges as continuous cropping persisted. VA may play a pivotal role in this phenomenon by interacting with pathogens, beneficial bacterial genera, and EA.