低山丘陵坡耕地秸秆覆盖轮耕土壤WSOC的荧光特征

Fluorescence Characteristics of Soil WSOC Under Straw Cover Rotation on Slope Farmland of Low Mountains and Hills

为了提高坡耕地的秸秆还田效率,增加土壤有机质,探索一种适于坡耕地的基于种养结合的保护性耕作方式。采用田间小区试验,研究了秸秆覆盖轮耕技术(包括当季秸秆覆盖+休闲、上季秸秆覆盖+旋耕)与常规耕作(秸秆移除后旋耕)对土壤水溶性有机碳(WSOC)荧光特征及团聚体有机碳的影响。结果表明:砂质暗棕壤坡耕地秸秆覆盖旋耕(SRT)、秸秆覆盖休闲(SFT)与秸秆不还田的常规耕作(CRT)处理土壤WSOC均解析出C1,C2,C3和C4等4组荧光组分,主要为紫外光区与可见光区类富里酸(Peak A和Peak C)、类胡敏酸(F)和短波类色氨酸(类蛋白B、D峰)等成分。秸秆覆盖旋耕处理提高了类富里酸(Peak A和Peak C)和类蛋白组分C4含量,C1和C2组分较覆盖休闲和常规耕作分别提高112.73%,109.35%和107.77%,66.07%,C4组分较SFT与CRT处理提高28.26%和42.31%,差异显著,而常规耕作处理来自于自生源腐殖质组分的胡敏酸C3含量增加,较覆盖旋耕和覆盖休闲处理分别增加16.76%和49.74%;0~20 cm耕层土壤团聚体有机物主要分布在<0.053 mm的矿物质结合态(MOM)中,平均占比为63.90%,其次为0.25~0.053 mm细颗粒态有机物(oPOM),占比为23.8%,粗颗粒态有机物(>0.25 mm)中含量最低,仅为11.2%;与秸秆不还田比较,坡耕地秸秆覆盖还田增加了植物来源的新鲜有机质的形成,表现为>0.053 mm的闭蓄态有机碳(oPOC)含量的增加,以覆盖旋耕处理oPOC增加较大,而秸秆不还田的CRT处理增加了MOM占比;覆盖旋耕处理FI和HIX值增大,土壤腐殖质积累趋势增强,为低山丘陵区坡耕地实施秸秆覆盖还田的保护性耕作技术提供了科学依据。

In order to improve the efficiency of straw returning and increase the soil organic carbon,a protective tillage method based on the combination of planting and feeding on sloping farmland was explored.The effects of straw mulching and rotation tillage technology on soil water-soluble organic carbon(WSOC)fluorescence characteristics and aggregate organic carbon through field experiments were studied,which included current season straw mulching and leisure,last season straw mulching and rotary tillage.Compared with conventional farming,which was rotating tillage after straw removal.The results show that WSOC resolved into 4 groups C_(1),C_(2),C_(3),C_(4),under the above three treatments on the sandy dark brown soil,in which fluorescent components mainly include fulvic acid(Peak A and Peak C)in the ultraviolet and visible regions and humic acid(F)and short-wave tryptophan(protein-like B,D peaks)and other components.SRT treatment increased the content of fulvic acid(Peak A and Peak C)and protein-like component C_(4).Compared with SFT and CRT,whose components of C_(1) and C_(2) increased by 112.73%,109.35%and 107.77%,66.07%and the group C_(4) increased by 28.26%and 42.31%,the difference was significant.While increased the content of humic acid C_(3) from the autogenic humus componentunder the CRT treatment was increased by 16.76%and 49.74%compared with the SRT and SFT treatments.Soil aggregate organic matter in 0~20 cm cultivated layer was mainly distributed in the mineral bound state(MOM)of<0.053 mm,with an average proportion of 63.90%,followed by 0.25~0.053 mm fine particulate organic matter(oPOM),accounting for 23.8%,and the content of coarse-grained organic matter(>0.25 mm)was the lowest,only 11.2%.SRT treatment significantly increased the content of oPOC,and the values of FI and HIX increased,which means the accumulation of soil humus increased.The accumulation trend was strengthened,providing a scientific basis for implementing protective tillage techniques for straw mulching and returning to the field in low mountain and hilly areas.