## 1 Introduction  
Maize (_Zea mays_ L.) is a globally vital cereal crop for food security and agricultural economies [1]. In China, it represents over 30% of total grain production, with the northeast region being the primary cultivation area [2]. Two fungal diseases significantly threaten maize productivity. Northern corn leaf blight (NCLB), caused by _Exzerobium turcicum_, reduces yields by 30-50% through foliar damage [3]. The pathogen persists in crop residues, increasing the disease risk in conservation tillage systems [4]. _Fusarium_ stalk rot, primarily caused by _Fusarium gmainerum_ and _F. verticillioides_, leads to lodging and yield losses while producing hazardous mycotoxins [5]. Both pathogens demonstrate strong survival in soil and plant debris [6]. Conservation tillage has emerged as a sustainable alternative to conventional practices, offering significant potential for soil quality improvement, carbon sequestration, and environmental impact mitigation. However, its complex relationship with disease risk presents a dual challenge that requires careful consideration. The reduction in soil disturbance and retention of crop residues characteristic of conservation tillage can alter the soil microbial community structure and enzymatic activity, potentially modifying the disease dynamics. For instance, long-term conservation tillage (e.g., no-till with straw mulding) may lead to shifts in the abundance of specific pathogenic or beneficial microorganisms. While some studies report an increased abundance of beneficial rhizosphere nitrogen-fixing bacteria under conservation tillage, altered soil conditions (e.g., water saturation) could simultaneously elevate the risks of N2O and NH3 emissions, indirectly compromising soil health [7; 8; 9]. The modification of soil physicochemical properties via conservation tillage may further exacerbate disease risks. Long-term no-till practices can result in surface organic matter accumulation but uneven nutrient distribution in deeper soil layers, creating microenvironments conducive to pathogen proliferation. Additionally, changes in soil pH and C/N ratio under conservation tillage may compromise plant disease resistance, particularly when nutrient availability (e.g., ammonium and nitrate nitrogen) becomes misaligned with microbial metabolic activity [10; 11]. The heterogeneous effects on soil enzyme activities, with differential responses among enzyme classes (e.g., hydrolases vs. oxidases), may disrupt organic carbon degradation processes and subsequently affect soil suppressive-ness [7; 12; 13; 14]. Practical implementation challenges are compounded by limited farmer awareness of tillage-disease interactions. Many growers hesitate to adopt conservation practices due to concerns about yield penalties or increased disease management complexity, especially in the absence of precision agriculture support [15; 16; 17]. Current research remains inconclusive regarding conservation tillage-disease relationships, with studies reporting both suppressive and promotive effects of straw retention depending on climatic conditions and crop types [10; 18; 19], underscoring the need for long-term monitoring and region-specific management strategies. Our investigation focused on maize straw return effects in Liaoning Province, where this practice has significantly exacerbated the northern corn leaf blight severity (20% disease index increase in Fumeng County) while showing neutral effects on _Fusarium_ stalk rot. Building on local farmers' predominant use of difonoconazole, we demonstrated that its integration with _Trichoderma_ fermentate achieved superior disease control (72.4% suppression of leaf blight, 0.61% stalk rot incidence), outperforming conventional fungicides. These findings provide actionable insights for balancing conservation agriculture benefits with sustainable disease management.