减氮覆膜下土壤有机碳组分含量的变化特征

The Variation Characteristics of Soil Organic Carbon Component Content Under Nitrogen Reduction and Film Mulching

【目的】明确长期优化施肥(减施氮肥)和减氮覆膜下土壤有机碳(SOC)与各组分有机碳含量特征及其对冬小麦籽粒产量的贡献,以期为黄土高原旱地土壤培肥和作物增产提供科学依据。【方法】依托山西省洪洞县7年定位试验,采集0—20 cm土层原状土样,利用连续物理分组方法进行分组,结合冗余分析,研究不同农田管理措施下冬小麦籽粒产量、SOC以及颗粒有机碳(POC)、矿质结合态有机碳(MOC)、轻组颗粒有机碳(Light-POC)和重组颗粒有机碳(Heavy-POC)含量特征,明确SOC含量与各组分有机碳含量的关系,量化其对冬小麦籽粒产量的贡献。试验共设农户施肥(FP)、测控施肥(MF)、垄膜沟播(RF)和平膜穴播(FH)4个处理。【结果】分析不同管理措施下冬小麦籽粒产量和SOC含量发现,FP处理的冬小麦平均产量最低,为3 070 kg·hm^(-2),与FP相比,MF在减少氮肥用量的情况下并未造成小麦减产,而RF和FH可进一步显著提高小麦籽粒产量,增幅分别达到27.0%和46.4%;与试验初始(2012年)土壤相比,经连续7年采用不同管理措施后SOC含量均显著提高,提高幅度从小到大依次为11.8%(MF)、22.4%(RF)、25.5%(FP)和36.1%(FH),即MF对试验地石灰性褐土SOC提升作用最小,但结合地膜覆盖会显著提升其培肥土壤的效果,FH对SOC含量提升的效果最佳。进一步分析不同处理下SOC组分的差异发现,与FP和MF相比,两种减氮覆膜措施不同程度提高了POC和Light-POC含量及Light-POC在SOC中的分配比例。结合SOC及其各组分有机碳含量与冬小麦籽粒产量的冗余分析、敏感性指数分析和SOC与各组分有机碳含量的相关性分析发现,各有机碳组分均以POC对小麦产量的贡献最大(达71.0%)并对SOC含量的变化和农田管理措施的响应最为敏感。因此,平膜穴播对作物产量和土壤肥力的提高主要是通过提高土壤有机碳中POC含量得以实现的。【结论】在减氮优化施肥的基础上进行平膜穴播,有利于提高黄土高原南部旱地褐土区土壤有机碳和活性有机碳含量,实现冬小麦可持续增产。

【Objective】The aim of this study was to clarify the effects of long-term optimized fertilization(nitrogen reduction) and nitrogen reduction plus film mulching on the characteristics of soil organic carbon(SOC) and its components content, and their contribution to winter wheat grain yield, so as to provide the theoretical support for dryland fertility and crop productivity in the Loess Plateau.【Method】Based on a 7-year location experiment, the undisturbed soil samples from 0-20 cm under different management measures were collected. The variation characteristics of winter wheat grain yield, SOC and its components content were explored, including particulate organic carbon(POC), mineral organic carbon(MOC), light-particulate organic carbon(Light-POC) and heavy-particulate organic carbon(Heavy-POC), and the relationship between SOC and its component content as well as their quantity contribution to the winter wheat grain yield were clarified. The organic carbon components were grouped by continuous physical grouping method, and their contribution for wheat yield was analyzed by redundancy analysis. The experiment set four treatments, including farmer’s practice fertilization(FP), monitoring fertilization(MF), monitoring fertilization plus ridge mulching-furrow planting(RF), and monitoring fertilization plus whole field filming(FH).【Result】The average yield of winter wheat was the lowest under FP treatment, which was 3 070 kg·hm^(-2). Compared with FP, the wheat yield under MF showed no significant difference, while wheat grain yield under RF and FH could achieve a significant increase by 27.0% and 46.4%,respectively;compared with the initial year of the experiment(2012), the SOC content showed a significant increase under different management measures during seven consecutive years, and the increase rate from low to high was 11.8%(MF), 22.4%(RF), 25.5%(FP), and 36.1%(FH), respectively. The improvement of SOC under MF was the slowest in calcareous cinnamon soil, when MF combining with plastic film mulching showed a significant improvement. The observed SOC components under different treatments showed, compared with FP and MF, RF and FH significantly increased the content of POC, Light-POC and the proportion of Light-POC in SOC. Based on the cooperation of the redundancy analysis, sensitivity index analysis and correlation analysis between SOC and its component, POC contributed the most to the improvement of wheat yield(up to 71.0%) and was the most sensitive to SOC content change and different management measures. Therefore, the improvement of crop yield and soil fertility by FH was mainly achieved by increasing POC content in soil organic carbon.【Conclusion】The monitoring fertilization plus whole field filming treatment was benefit to increase soil organic carbon and active organic carbon content in the cinnamon soil in the southeastern of the Loess Plateau, and achieve a sustainable increase in winter wheat yield.