基于绿肥根系分泌物特征的新垦耕地土壤微生物代谢功能改善研究

Improvement of Soil Microbial Function in Newly Cultivated Land Based on Root Exudates of Green Manure

【目的】种植绿肥是增加土壤有机质和提升新造耕地土壤质量的重要措施,但绿肥根系分泌物特征尚不清楚。【方法】本研究以无植物为对照,进行白三叶(Trifolium repens L.)、大豆(Glycine max)、黑麦草(Lolium perenne L.)的盆栽试验,探明不同绿肥根系分泌能力、根系分泌物组成以及对土壤微生物功能的影响。【结果】大豆生物量(平均单株重量9.11g)最大,而根系分泌量(TOC 8.01mg)最小,明显低于白三叶(10.37 mg)和黑麦草(14.78mg);基于单位植物和根干物质重量的根系分泌量为白三叶最高(0.408%和1.249%)、大豆最小(0.088%和0.312%),表明白三叶的根系分泌能力很强。采用乙酸乙酯萃取、GC-MS鉴定根系分泌物成分,分别检出白三叶、黑麦草、大豆29、21、28种化合物,主要为烃、酯、醇等化合物,不同绿肥各大类物质的组成存在差异;丙酸乙酯、乙酸丙酯和磷酸三丁酯等酯类物质,以及杂环类的吡啶均为优势成分,但不同绿肥占比不同。采用Biolog法评估三种绿肥土壤微生物功能特性发现,大豆土壤微生物代谢有机碳能力最强,单一碳源每孔的平均吸光值(AWCD)高低依次为大豆>白三叶>黑麦草>对照;对碳水化合物、氨基酸、羧酸、酚酸、多聚物、胺类等6类碳源的利用能力比较发现,大豆土壤微生物对前3类物质的利用最强,白三叶土壤微生物对酚酸和多聚物利用最强,黑麦草土壤微生物对胺类利用最强。【结论】豆科绿肥对土壤微生物功能的积极作用优于禾本科黑麦草,以改进土壤微生物功能为主要目的的新垦耕地推荐种植豆类绿肥。

Objective Planting green manure is proved to be an important practice to increase soil organic matter and fertility,however,the root exudates of green manure are clearly unknown.Method A pot experiment was conducted by planting white clover,ryegrass and soybean,versus control with no plants,to explore the secretion capacity and exudates compounds of green manure root,as well as their effects on soil microbial function.Result The results showed that the biomass of soybean was the highest(average 9.11 g),while its secretion organic carbon(OC 8.01 mg)was the lowest which was significantly lower than that of white clover(10.37 mg)and ryegrass(14.78 mg).The root secretion OC based on unit biomass of dry plant and root weight was the highest for white clover(0.408%and 1.249%)and the lowest for soybean(0.088%and 0.312%),indicating that white clover had a strong root secretion capacity.The exudate components were identified by ethyl acetate extraction and GC-MS analysis,there were respective 29,21 and 28 types of compounds were detected for white clover,ryegrass and soybean.The major compounds were hydrocarbon,ester and alcohol.Ethyl propionate,propyl acetate,tributyl phosphate and heterocyclic pyridine are the dominant components for all green manures,but they vary in proportion.The Biolog method was used to evaluate the characteristics of soil microbial function of three green manure.It was found that soil microorganisms had the strongest ability to metabolize organic carbon for soybean,and the average well color development(AWCD)was in the order of soybean>white clover>ryegrass>control.To the utilization capacity of six types of carbon sources including carbohydrates,amino acids,carboxylic acids,phenolic acids,polymers and amines,the first three types of carbon sources,phenolic acids and polymers,and amines were used the strongest respectively by soybean,white clover and ryegrass.Conclusion In conclusion,Legume green manure has a better positive effect on soil microbial function than grass ryegrass and was recommended for newly reclaimed land when the major purpose is improving soil microbial function.