基于旱地麦田蓄水保墒技术的土壤固碳机制及其潜力研究

Dryland wheat plays an important role in agricultural production in China. Numerous environmental issues, e.g., the increase in drought frequency and large yield fluctuations, have present during dryland winter wheat production under climate change. It is significant to effectively increase soil water conservation, enhance soil carbon sequestration and obtain a stable and higher yield for the sustainable development of the dryland wheat. The “Three in Advance Technology (TAT)”, which refers to soil deep tillage, residue management and organic fertilizer application in advance during the summer-fallow season, can conserve soil moisture on winter wheat production in dry farmlands. However, soil carbon sequestration effect and its mechanism hasn’t been figured out clearly. Therefore, on the basis of former research on laws of spatial and temporal distribution and consumption of soil moisture, this project is to further analyze the changes of soil organic carbon (SOC) and its fractions under different technologies of water conservation. Soil physical and chemical properties, as well as enzyme activities related with SOC turnover, are analyzing to indicate SOC sequestration effect and its mechanism. In combination with the growth and yield formation of dryland wheat, responses of crop production to the change in SOC pool and soil water storage are evaluated. In addition, the potential of SOC sequestration and dryland wheat production are simulated by using relevant models under different technologies of water conservation. Thus, this study will provide certain theoretical support for managing scientifically SOC pool and soil water storage and raising production of winter wheat in dry farmlands.

旱地小麦在我国农业生产中占有重要的地位，随着全球气候变化的加剧，干旱发生频繁增加、产量波动较大，如何有效提高旱地土壤蓄水保墒和固碳能力，实现旱地小麦稳产高产，对旱地小麦的可持续生产有重要意义。夏闲期提前深翻或深松、提前深施肥、提前秸秆还田或覆盖的“三提前”技术具有一定蓄水保墒效果，但该耕作技术下土壤固碳效应及其机制尚不清楚。本项目以土壤-作物系统为研究对象，在前期水分时空分布与积耗规律的研究基础上，开展研究旱地麦田土壤有机碳及各组分含量的分布规律，结合土壤理化性状与碳转化相关的酶活性，明确旱地土壤的固碳效应及其影响机制；结合小麦生长发育与产量形成，探究旱地土壤水碳变化与作物生产力的关系；在此基础上，利用模型评价“三提前”技术下旱地小麦的土壤固碳潜力与生产潜力，为旱地麦田土壤水碳库的科学管理及作物生产力的提高提供一定的理论依据。

土壤固碳是应对全球气候变化经济可行的重要途径之一，旱地土壤具有巨大的固碳潜力，明确旱地土壤固碳机制及其能力对于提升土壤碳汇与旱地小麦可持续生产有重要意义。以夏闲期耕作为核心的旱地麦田蓄水保墒技术，是有机旱作的一大技术特色。本项目研究了休闲期免耕（FNT）、休闲期深翻（FPT）和休闲期深松（FST）三个处理下旱地小麦主要生育时期土壤的水分变化及作物生长动态特征，分析了下土壤有机碳（SOC）及其组分的分布特征，研究了理化生性状及其与有机碳库的关系，评价了旱地冬小麦土壤有机碳矿化潜力和作物生产潜力。主要研究结果如下:.（1）与FNT处理相比，FPT和FST处理显著增加0-200 cm剖面播前底墒，且其效果可延续至拔节期或开花期，提高了冬后植株干物质量，增加了群体分蘖，小麦增产14.46%-26.38%，提高水分利用效率10.13%-13.18%。.（2）FNT处理分别较FST和FPT处理显著提高0-10 cm层次SOC各组分含量达35.9%-141.0%和29.2%-132.7%；FPT处理下>20 cm土层SOC各组分含量高于FST，40-50 cm土层高于FNT处理。.（3）FNT处理下0-20 cm剖面SOC储量高于FST和FPT，而20-50 cm剖面则表现为FPT>FST>FNT。.（4）土壤物理性状、土壤速效养分、碳矿化相关酶以及团聚体的平均重量直径能够显著影响土壤总有机碳以及各组分有机碳含量。.（5）FPT处理分别较FNT和FST处理显著提高0-10 cm土层潜在可矿化活性碳库达32.32%-69.88%，显著提高0-30 cm土层潜在可矿化缓效性碳库达38.43%-302.06%。.（6）APSIM-Wheat模型可以较为精确的模拟不同夏闲期耕作方式下旱地冬小麦的生长发育情况和麦田土壤水分状况，采用FPT处理较FNT处理显著增加产量约23-34%，并显著提升了平水年和丰水年夏闲期土壤蓄水效率。.综上，在旱作冬小麦种植区，实施FPT处理和FST处理能够提高土壤播前底墒，提高水分利用率，进而实现旱地小麦稳产高产。FPT和FST处理较FNT处理在短期耕作年限内0-50 cm剖面表现出固碳优势，但同时两者潜在矿化量显著增强。从长期来看，FPT和FST处理能否在提升蓄水的同时增强土壤碳汇能力，仍需进一步深入研究。