• ISSN 1008-505X
  • CN 11-3996/S
曾莉, 张鑫, 张水清, 王秀斌, 梁国庆, 周卫, 艾超, 张跃强. 不同施氮量下潮土中小麦秸秆腐解特性及其养分释放和结构变化特征[J]. 植物营养与肥料学报, 2020, 26(9): 1565-1577. DOI: 10.11674/zwyf.20181
引用本文: 曾莉, 张鑫, 张水清, 王秀斌, 梁国庆, 周卫, 艾超, 张跃强. 不同施氮量下潮土中小麦秸秆腐解特性及其养分释放和结构变化特征[J]. 植物营养与肥料学报, 2020, 26(9): 1565-1577. DOI: 10.11674/zwyf.20181
ZENG Li, ZHANG Xin, ZHANG Shui-qing, WANG Xiu-bin, LIANG Guo-qing, ZHOU Wei, AI Chao, ZHANG Yue-qiang. Characteristics of decomposition, nutrient release and structure change of wheat straw in a fluvo-aquic soil under different nitrogen application rates[J]. Journal of Plant Nutrition and Fertilizers, 2020, 26(9): 1565-1577. DOI: 10.11674/zwyf.20181
Citation: ZENG Li, ZHANG Xin, ZHANG Shui-qing, WANG Xiu-bin, LIANG Guo-qing, ZHOU Wei, AI Chao, ZHANG Yue-qiang. Characteristics of decomposition, nutrient release and structure change of wheat straw in a fluvo-aquic soil under different nitrogen application rates[J]. Journal of Plant Nutrition and Fertilizers, 2020, 26(9): 1565-1577. DOI: 10.11674/zwyf.20181

不同施氮量下潮土中小麦秸秆腐解特性及其养分释放和结构变化特征

Characteristics of decomposition, nutrient release and structure change of wheat straw in a fluvo-aquic soil under different nitrogen application rates

  • 摘要:
    目的 秸秆腐解与元素转化涉及复杂的生物化学过程,提高土壤氮素水平是加速秸秆腐解和养分释放的关键措施。研究不同施氮水平下潮土中小麦秸秆腐解特性、养分释放特征及其结构组分变化规律,深入了解秸秆腐解过程与机制,为完善作物秸秆还田技术、实现秸秆资源的高效利用及农田可持续发展提供科学依据和技术支撑。
    方法 本试验点位于河南省原阳县,土壤类型为潮土,种植制度为小麦–玉米轮作,以小麦秸秆为研究对象,设置0 (SN0)、180 (SN1) 和240 (SN2) kg/hm2 3个氮肥用量,进行187天的秸秆包填埋试验,利用超高分辨场发射扫描电镜 (SEM)、固态核磁共振 (13C-NMR) 等方法研究小麦秸秆腐解过程中的养分释放和结构组分动态变化规律。
    结果 1) 小麦秸秆腐解呈现前期快后期慢的特征,前两周为快速腐解期,该阶段秸秆平均腐解率为46%,整个玉米季 (100天) 秸秆平均腐解率为71%;高氮营养环境对前两周的秸秆腐解率无显著影响;从第二周开始,施用氮肥处理加速了秸秆腐解,SN1和SN2处理秸秆腐解率平均高于SN0处理6个百分点,但SN1和SN2处理间无显著差异;秸秆碳释放率与秸秆腐解率变化趋势基本一致。2) 腐解187天后,秸秆氮磷钾养分最终释放率大小顺序为钾 (96%~97%) > 氮 (52%~86%) > 磷 (29%~45%),其中钾在前两周基本完全释放,而氮、磷释放率在后期有负增长现象。3) 纤维素、半纤维素腐解率与秸秆腐解规律基本一致,均表现出前期快后期慢的特点,而木质素则在中后期腐解较快;纤维素、半纤维素和木质素最终腐解率分别为78%~87%、86%~91%和66%~73%(187天后)。4) 扫描电镜结果显示,小麦秸秆结构逐渐遭到破坏,表面变得粗糙,断层增多,空洞增大,纤维束变得松散,形成近似网状结构;高氮处理下小麦秸秆表观结构受破坏程度大于不施氮处理。5) 核磁共振结果显示,不同有机碳官能团信号强度分布表现为:烷氧碳 (47.02%~60.13%) > 烷基碳 (11.41%~17.38%) > 双烷氧碳 (10.79%~13.31%) > 甲氧基碳/烷氮碳 (7.53%~12.02%) > 芳基碳 (2.70%~7.18%) > 羧基碳 (1.07%~2.60%) > 酚基碳 (0.75%~2.02%);腐解过程中烷基碳、甲氧基碳/烷氮碳、酚基碳和羧基碳相对含量显著增加,而烷氧碳相对含量显著降低。6) 相关分析表明,秸秆残余物所有有机碳官能团均与腐解率、碳释放率有显著或极显著相关性;有机碳官能团中只有烷氧碳、甲氧基碳/烷氮碳与氮释放率有显著相关性;烷氧碳、双烷氧碳与纤维素、半纤维素和木质素腐解率均呈极显著负相关,羧基碳和甲氧基碳/烷氮碳均与木质素腐解率呈现极高的正相关性。
    结论 施用氮肥能够促进小麦秸秆腐解和碳释放,其效果在秸秆还田两周后才能显现出来;在腐解过程中,秸秆残余物中代表易分解碳水化合物的烷氧碳相对含量随腐解时间延长而不断降低,且占比均高于其它碳官能团,对指示秸秆腐解进程具有重要意义;固态核磁共振技术更有利于监测秸秆腐解过程中不同有机碳官能团结构变化,从而更深刻地认识秸秆腐解机制。

     

    Abstract:
    Objectives Straw decomposition and element transformation are involved in complex biochemical process. Improving soil N content is a key measure to accelerate straw decomposition and nutrient release. Through the research on the decomposition rate, nutrient release and changes in structure and components of straw residues under different application N levels, we can further understand the mechanism of straw decomposition. The outcome through this research would be of great practical significance for high-efficient use of straw resources and sustainable development of farmland.
    Methods The experiment site was located in Yuanyang, Henan Province. The soil type was fluvo-aquic soil, and the cropping system was wheat-maize rotation. The wheat straw decomposition was studied using a 187-day straw-bag burying method with three different N fertilizer rates, including 0 (SN0), 180 (SN1) and 240 (SN2) kg/hm2. Ultra-high resolution field emission scanning electron microscopy(SEM), solid-state nuclear magnetic resonance (13C-NMR) and other methods were used to study dynamic changes of decomposition rate, nutrient release and structure of wheat straw.
    Results 1) The decomposition of wheat straw was fast in the early stage and became slow in the later stage. The first two weeks were the rapid decomposition period. The average decomposition rate of straw in this stage was 46%, and that of the whole maize season (100 days) was 71%. High N nutrient level had no significant effect on the decomposition rate of straw in the first two weeks, but the application of N fertilizer accelerated the decomposition of straw after the second week. The decomposition rates of SN1 and SN2 treatments were on average 6 percentage points higher than that of SN0 treatment, but there was no significant difference between SN1 and SN2. The trend of C release rate was basically consistent with the straw mass loss rate. 2) The order of final release rate of straw N, P and K nutrients after 187 days was K (96%‒97%) > N (52%‒86%) > P (29%‒45%), in which K was released completely in the first two weeks, while the release rate of N and P increased negatively in the later period. 3) The decomposition rate of cellulose and hemicellulose was basically consistent with the decomposition rate of straw, also showing a faster decomposition rate in the early stage and a slower one in the late stage. However, lignin decomposed faster in the middle and late stages. The final decomposition rates of cellulose, hemicellulose and lignin after 187 days were 78%‒87%, 86%‒91% and 66%‒73%, respectively. 4) Scanning electron microscopy showed that the structure of wheat straw was gradually destroyed, with the surface becoming rough, faults and cavities being increased, and fiber bundles becoming loose. The straw residues finally formed a network structure. The damage degree of the surface structure of wheat straw under high N rate was more apparent than that under no N treatment. 5) Nuclear magnetic resonance (NMR) results showed that the signal intensities of different organic C functional groups were as follows: O-Alkyl-C (47.02%‒60.13%) > Alkyl-C (11.41%‒17.38%) > di-O-Alkyl-C (10.79%‒13.31%) > Methoxyl-C/N-Alkyl-C (7.53%‒12.02%) > Aryl-C (2.70%‒7.18%) > Carbonyl-C (1.07%‒2.60%) > Phenol-C (0.75%‒2.02%). The relative contents of Alkyl-C, Methoxyl-C/N-Alkyl-C, Carbonyl-C and Phenol-C were significantly increased with straw decompisition, while O-Alkyl-C significantly decreased. 6) Correlation analysis showed that all organic carbon functional groups of straw residues had a significant or extremely significant correlation with the decomposition rate and C release rate. Among all organic C functional groups, only O-Alkyl-C and Methoxyl-C/N-Alkyl-C were significantly related to N release rate. O-Alkyl-C and di-O-Alkyl-C were significantly negatively correlated with the decompositions of cellulose, hemicellulose, and lignin. Moreover, Carbonyl-C and Methoxyl-C/N-Alkyl-C were both highly correlated with lignin degradation rate.
    Conclusions The application of N fertilizer could promote the decomposition and C release of wheat straw, and this stimulating effect can only be observed when the straw is returned to soil for two weeks. During decomposition process, the relative content of O-Alkyl-C, which represents a dominant and easily decomposable carbohydrate in the residue of the straw, keeps decreasing with time, suggesting a key role in indicating the process of straw decomposition. Solid-state nuclear magnetic resonance technology shows a good capability to monitor the structural changes of different organic carbon functional groups during straw decomposition, so as to gain a deeper understanding of the mechanism of straw decomposition.

     

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