长期秸秆还田对连作棉田秸秆腐解特性及土壤有机碳平衡的影响

发布时间：2019-01-02 14:36

【摘要】：新疆是我国重要的商品棉基地,其产量占全国的60%,由于其种植面积大、种植年限较长等因素造成土传病害加重、土壤氮磷钾含量比例失调、土壤酶活性下降等连作问题,成为新疆棉花发展的瓶颈。秸秆还田是农业持续发展的重要措施,但其在减缓棉田连作障碍的同时经雪水和雨水淋浸以及微生物分解后会释放出化感物质,从而加剧连作障碍。因此,秸秆还田技术利与弊同时存在。探究秸秆腐解规律和土壤有机碳平衡能够为评价土壤质量和肥力提供科学依据,因此,本试验基于长期连作定位试验,研究了长期秸秆还田条件下棉秆的腐解规律以及棉田土壤有机碳平衡量的变化。研究结果如下:1.不同处理棉秆地上部分和根的腐解在总体上表现出“快-慢-快”的变化趋势。1 a、10 a和20 a处理中棉秆地上部分快速腐解期为秸秆还田后的前43 d和第193~365 d期间,第43~193 d期间为缓慢腐解期;1 a中棉花根的快速腐解时期分别在第43~177 d和第193~365 d期间,而10 a、20 a中棉花根的快速腐解时期均出现在前43 d和第193~365 d期间,不同处理棉花根在其余时间段腐解缓慢。经过一年的腐解,棉秆地上部分和根的腐解率分别达到47%~58%和39%~59%。与非连作年限相比,连作在秸秆腐解的初始阶段(16 d)会促进秸秆的腐解,但一年后,不同连作处理之间的秸秆腐解率差异不显著。2.棉花秸秆被分解一年后,棉秆中的纤维素、半纤维素和可溶性糖已被大量释放,剩余的部分释放缓慢。不同连作处理不会影响纤维素、半纤维素和可溶性糖的释放,但会影响木质素的分解。3.从秸秆还田至第二年播种前(共193 d),C释放率为34.82%~39.62%,N释放率为40.48%~49.88%,P释放率为28.84%~34.09%,K释放率为95.44%~97.19%,养分释放模式均为直接释放,且不同处理的棉秆对C、N、P和K释放率的大小排序均为KNCP。通过棉花秸秆中的C、N、P和K的释放规律可以得出,棉花秸秆还田后,60%的C被固定在土壤中;同时还为土壤提供大量的氮和钾,但对磷素释放较少,因此在田间施肥过程中,可适当减少钾肥和氮肥的投入,重视磷肥的投入。4.在1 a棉田中,棉秆还田率达到72.04%时,0~20 cm土层有机碳能够达到平衡,平衡值为11.84 g·kg-1。随着还田年限的增加,土壤中有机碳的含量及其储量均在逐渐增加,当还田年限分别达到第28年、30年和39年时,0~20 cm、20~40 cm和40~60 cm土层的有机碳分别能够达到平衡,各土层的平衡值分别为17.2 g·kg-1、15.38 g·kg-1和12.72 g·kg-1。5.0~60 cm土壤有机碳储量的变化与秸秆碳投入之间虽然具有显著正相关性,但从土壤有机碳增长速率来看,棉花连作及秸秆还田5年内,土壤有机碳的增长速率最快,而5年后各土层的有机碳储量增加缓慢,当还田年限达到26年时,0~60 cm土壤有机碳的最大储量为112.2 t·hm-2。
[Abstract]:Xinjiang is an important commodity cotton base in China, and its yield accounts for 60% of the whole country. Due to its large planting area, long planting years and other factors, the soil-borne diseases are aggravated, the proportion of soil nitrogen, phosphorus and potassium is unbalanced, and the soil enzyme activity is decreased. Become the bottleneck of cotton development in Xinjiang. Straw returning to the field is an important measure for the sustainable development of agriculture, but it can release allelopathic substances through snow water, Rain Water leaching and microbial decomposition while slowing down the obstacles of continuous cropping in cotton fields, thus exacerbating the obstacles of continuous cropping. Therefore, the advantages and disadvantages of straw returning to the field exist at the same time. The study of straw decomposition and soil organic carbon balance can provide scientific basis for evaluating soil quality and fertility. Therefore, this experiment is based on long-term continuous cropping location test. The decomposition law of cotton stalk and the change of soil organic carbon balance in cotton field were studied under the condition of returning straw for a long time. The results are as follows: 1. The decomposition of the aboveground part and root of cotton stalk under different treatments showed a trend of "fast, slow and fast" on the whole. 1 the period of rapid decomposition of the aboveground part of cotton stalk in 10 a and 20 years treatment was the first 43 days after straw returning to the field and the period of the first 43 days and 365 days after the straw was returned to the field. The period of 43193d is slow decomposing period; In the first year, the rapid decomposition period of cotton roots occurred in the period of 43177d and 19335th day, respectively, while the period of rapid decomposition of cotton root appeared in the first 43 days and 193365th days in 10a and 20a, respectively. The decomposition of cotton roots with different treatments was slow in the other time periods. After one year of decomposition, the decomposition rates of the aboveground part and root of cotton stalk reached 47% and 39%, respectively. Compared with non-continuous cropping years, continuous cropping promoted the decomposition of straw in the initial stage (16 days), but after one year, there was no significant difference in the decomposition rate of straw among different continuous cropping treatments. 2. After the cotton stalk was decomposed for a year, cellulose, hemicellulose and soluble sugar in the cotton stalk were released in large quantities, while the remaining part was released slowly. The release of cellulose, hemicellulose and soluble sugar was not affected by different continuous cropping treatments, but the decomposition of lignin was affected by 3. 3%. From the straw returning to the field to the second year before sowing (the release rate of 193 d), C was 34.82% and 39.62%), the release rate of N was 40.48% and 49.88%, and the release rate was 28.84% 34.09% and 95.4444% (97.19%). The nutrient release patterns were all direct release, and the order of release rate of cotton stalk to C ~ (2 +) N ~ (+) P and K was KNCP.. It was concluded that 60% of C was immobilized in soil after returning cotton straw to the field according to the release rule of N N P and K in cotton straw. At the same time, it also provided a lot of nitrogen and potassium for the soil, but the release of phosphorus was less, so the input of potassium and nitrogen could be reduced and the input of phosphorus fertilizer could be reduced in the process of fertilization in the field. 4. In 1 year cotton field, when the returning rate of cotton stalk reached 72.04%, the organic carbon of 0 ~ 20 cm soil layer could be balanced, and the equilibrium value was 11.84 g kg-1.. With the increase of returning years, the content and storage of organic carbon in soil increased gradually. When the returning years reached 28 years, 30 years and 39 years respectively, the organic carbon of 0 ~ 20 cm,20~40 cm and 40 ~ 60 cm soil layer could reach equilibrium, respectively. The equilibrium values of soil layers were 17.2g kg-1,15.38 g kg-1 and 12.72g kg-1.5.0~60 cm, respectively, and there was a significant positive correlation between the soil organic carbon storage and straw carbon input. But according to the increasing rate of soil organic carbon, the increase rate of soil organic carbon was the fastest within 5 years after continuous cropping of cotton and straw, but the accumulation of organic carbon in each soil layer increased slowly after 5 years, when the returning years reached 26 years, The maximum soil organic carbon storage of 0 ~ 60 cm is 112.2 t hm-2..
【学位授予单位】：石河子大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S141.4

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