Peanut Precursor Surpasses Soybean and Breaks the Maize-Wheat Paradigm by Engineering a Superior Rhizosphere to Boost Soil and Yield

The intensive maize-wheat double-cropping system underpins food security in China's Huang-Huai-Hai Plain but drives soil degradation through nutrient depletion and biodiversity loss, necessitating sustainable diversification. This study mechanistically compared legacy effects of five preceding summer crops-maize (control), soybean, peanut, pepper, sweet potato-on subsequent winter wheat performance, explicitly quantifying impacts on root architecture, soil enzymatic activity, and yield formation. Results demonstrated peanut’s unparalleled efficacy: it increased seedling-stage wheat shoot biomass by 37-41% and root biomass by 184% versus maize, while expanding root surface area (51%) and volume (54%) through optimized rhizosphere engineering. These morphological advantages persisted through maturity and correlated with significantly enhanced soil functionality-peanut elevated soil organic matter (25-37%), nitrate-N (138-148%), and ammonium-N (71-128%) while reducing C:N ratio. Crucially, peanut residues stimulated microbial metabolism, increasing β-glucosidase activity (governing C cycling) by 33-89% and urease activity (N mineralization) by 40-109%, whereas catalase activity showed context-dependent responses. This accelerated nutrient mineralization translated to agronomic superiority: peanut-wheat rotation yielded 10.5% more grain than maize-wheat, exceeding soybean-wheat by 3.4% despite lower 1000-grain weight, primarily through 26.6% higher ear density. Soybean provided intermediate soil N benefits but weaker root stimulation, while pepper suppressed enzymes and sweet potato inconsistently affected fertility. We conclude that peanut’s unique residue composition-low C:N ratio, abundant labile carbon, and rhizodeposits-primes a self-reinforcing root-microbe-soil loop that enhances nutrient synchrony, breaks maize-wheat yield ceilings, and offers a validated pathway for ecological intensification in cereal systems.