Effects Of Water And Water Reduction On Black Soil Aggregates And Soil Organic Carbon Composition In Greenhouse Vegetable Field

The study of soil aggregates and organic carbon fractions is important for maintaining soil ecosystem functions and promoting sustainable land use.In order to study the effects of reducing irrigation and fertilizer application on soil aggregate structure and organic carbon composition in vegetable fields of facilities eggplant in Black soils,this paper depends on the"Field Positioning Experiment in Black Soil Facility Vegetable Fields"conducted by the Horticultural Branch of Heilongjiang Academy of Agricultural Sciences.This experiment applied three treatments of conventional water and fertilizer（WF）,80%conventional fertilizer+conventional water（W80%F）and 80%conventional water+conventional fertilizer（80%WF）to analyze the changes of water-stable aggregates content and stability,as well as the changes of soil labile organic carbon fractions in different soil layers.The main findings are as follows:（1）With the increase of soil depth,the content of 2～1 mm particle size aggregates tended to increase gradually in the three treatments,and the content of 0.5～0.25 mm and<0.25 mm particle size aggregates tended to decrease gradually.Simultaneously,the percentages of water-stable aggregates in the conventional treatment were mainly concentrated in 2～1 mm,1～0.5 mm and<0.25 mm particle sizes,ranging from 12.35%to 24.05%,21.62%to 27.13%and 18.70%to 39.88%,respectively.The percentages of water-stable aggregates in the reduced fertilization treatment were mainly concentrated in 1～0.5 mm and<0.25 mm,ranging from 21.46%to 28.27%and 27.04%to 41.24%,respectively.The percentages of water-stable aggregates in reduced irrigation treatments were mainly concentrated in 1～0.5 mm and<0.25 mm,ranging from 15.99%to 31.36%and 15.74%to 45.72%,respectively.（2）The ranges of mean soil weight diameter（MWD）,geometric mean diameter（GMD）,fractal dimension（D）,and water-stable large aggregates content(DR_0.25)were0.68 to 2.01,0.48 to 1.15,2.34 to 2.73,and 54.28%to 84.26%,respectively.The reduced irrigation treatment increased MWD,GMD and DR_0.25 in the 0-80 cm soil layer and decreased D.The reduced fertilizer application treatment increased D and decreased MWD,GMD and DR_0.25 in the 0-20 cm and 40-100 cm soil layers.The lowest MWD,GMD and D_R0.25 were found in the 0-20 cm soil layer of each treatment.（3）In the 0-60 cm soil layer,the organic carbon content of soil aggregates in the conventional and reduced fertilization treatments tended to decrease and then increase as the size of the aggregates decreased,with the highest organic carbon in the>5 mm and5～2 mm particle sizes,while the organic carbon content of aggregates in the reduced irrigation treatment tended to increase and then decrease,but the differences in the organic carbon content of aggregates in each particle size were not significant.And the variation of SOC in the 60-100 cm soil layer aggregates was smaller.In the same soil layer of different treatments,the SOC content of soil aggregates of each particle size showed 80%WF>WF>W80%F.The SOC of soil aggregates of each particle size in the conventional,reduced fertilizer application and reduced irrigation treatments showed a gradual decrease with increasing soil depth（p<0.05）.The changes in total nitrogen content of soil aggregates were more consistent with the organic carbon content of aggregates.（4）The ranges of soil labile organic carbon fractions of easily oxidizable organic carbon（ROC）,light fraction organic carbon（LFOC）,dissolved organic carbon（DOC）,particulate organic carbon（POC）,and microbial biomass carbon（MBC）were 0.27 to1.84 g/kg,0.29 to 1.47 g/kg,6.98 to 22.50 mg/kg,0.65 to 5.36 g/kg,43.17 to 262.19mg/kg,respectively.The ROC,LFOC,POC,and MBC contents of each treatment showed a gradual decrease with increasing soil depth,and the differences among soil layers were significant（p<0.05）.The ROC,LFOC,POC and MBC contents were significantly reduced by the treatments of reduced irrigation and fertilizer application（p<0.05）.（5）MWD,GMD,and DR_0.25 showed highly significant positive correlations（p<0.01）with the aggregates content of>5 mm,5～2 mm,and 2～1 mm grain size soils;and highly significant negative correlations（p<0.01）with the aggregates content of 0.5～0.25 mm and<0.25 mm grain size as well as POC,ROC,LFOC,and MBC;D was the opposite.The SOC of each soil reactive organic carbon fraction and soil aggregates of each particle size were highly significantly and positively correlated with total soil organic carbon（p<0.01）.TOC and each reactive organic carbon fraction showed highly significant positive correlation（p<0.01）with the content of soil aggregates in 0.5-0.25 mm and<0.25mm grain size;and significant negative correlation（p<0.05）with 5～2 mm,2～1 mm and1～0.5 mm grain size.（6）The yield of aubergine under the three treatments ranged from 34.55 to 35.92t/hm².The reduced fertiliser and irrigation treatments both increased aubergine yield compared to the conventional treatments,but the effect of these two treatments on yield was not significant.