亚热带岩溶区土壤改良剂用量对土性与玉米生长影响OA

Soil resources in subtropical karst regions constitute a critical yet fragile component of agricultural arable land,playing a pivotal role in ensuring local food security and ecological stability.The unique geological setting dominated by carbonate rocks in these areas profoundly shapes the properties of the derived calcareous soils.A prominent challenge of such soils is their inherently heavy and sticky texture,stemming from high clay content and poor aggregation,which severely impedes water infiltration and root penetration.Concurrently,the region's high rainfall and porous bedrock accelerate nutrient leaching,exacerbating the soils' low water and fertilizer retention capacity,which leads to the frequent nutrient deficiencies,the obstruction of crop growth,and the decrease of agricultural productivity.Over time,these limitations have not only constrained yields of maize-a staple crop in many karst regions-but also exacerbated soil degradation and ecosystem vulnerability,highlighting the urgent need for effective soil improvement strategies.Against this backdrop,research on soil improvement technologies tailored to subtropical karst zones is essential for enhancing maize health,optimizing nutrient use efficiency,and providing actionable technical references for calcareous soil amelioration and balanced fertilization. To address this need,our study focused on developing a novel soil conditioner,specifically formulated to mitigate the constraints of karst calcareous soils.The conditioner was designed to improve soil structure,enhance nutrient retention,and promote nutrient availability,with the overarching goal of creating a more favorable growth environment for maize.To systematically evaluate the efficacy of the conditioner,we conducted controlled pot experiments involving combined applications of chemical fertilizers and varying concentrations of the conditioner.The experimental design included six treatments:T0(control,no conditioner+43 g per basin fertilizer)and T1-T5(43 g per basin fertilizer combined with 1.35,2.70,4.05,5.38,and 6.73 g per basin of the conditioner,respectively),with each treatment replicated three times to ensure result reliability.Over a 106-day growth period,we monitored soil physicochemical properties(pH,organic matter content,cation exchange capacity,and concentrations of macronutrients-N,P,K,S-and micronutrients-Ca,Mg,Fe,Cu,Zn,Mn,B,Mo,Cl)and maize biological traits(plant height,stem diameter,leaf area index,and aboveground biomass).A central component of our analytical framework was the integration of the Diagnosis and Recommendation Integrated System(DRIS),a robust method for assessing crop nutritional status by comparing nutrient ratios against optimal reference values.For mature maize leaves,we quantified 11 essential nutrients(N,P,K,S,Ca,Mg,Fe,Cu,Zn,Mn,B)and calculated DRIS indices to evaluate nutrient balance,identified limiting factors,and determined the Nutrient Imbalance Index(NII)—a composite metric reflecting overall nutritional status. The results revealed several key findings:(1)Regarding soil properties:in treatments T1-T5,concentrations of macronutrients such as N and P increased significantly with higher application rates of the conditioner(P＜0.05),attributed to the conditioner's ability to inhibit nutrient leaching and promote mineralization.In contrast,concentrations of micronutrients including Ca,Cu,Mn,Cl,and Mo decreased with increasing conditioner dosage.(2)Concerning nutrient content in maize leaves:all T1-T5 treatments exhibited higher leaf nutrient concentrations compared to T0.(3)DRIS-based nutrient diagnosis indicated that the overall fertilizer requirement order for maize in karst regions was Fe＞Cu＞S＞K＞Ca＞Mg＞N＞P＞Zn＞B＞Mn,which has underscored the critical role of micronutrients such as Fe and Cu-often overlooked in conventional fertilization regimes-in limiting maize growth in these soils.Integrating soil nutrient data,leaf nutrient concentrations,DRIS indices,and NII values,the T4 treatment(5.38 g/basin HH conditioner+43 g/basin fertilizer)was identified as the optimal combination.This treatment not only improved soil structure but also resulted in the lowest NII(1.23),indicating the most balanced nutritional status,and the highest maize biomass(38％higher than T0). In conclusion,the combined application of soil conditioner at optimal rates with chemical fertilizers effectively alleviates the constraints of karst calcareous soils,enhances nutrient availability,and promotes maize health.The DRIS-based approach provides a scientific basis for formulating tailored fertilization strategies in karst regions,contributing to sustainable agricultural development and soil conservation in these ecologically sensitive areas.