| In this paper,the three townships(Geshan Town,Liqiao Town,Shuitian Township)near the water conservancy project in the Xiajiang Reservoir area are used as the research area.Soil sampling surveys of unlifted fields(NT),3 years,5 years,6 years,and 8 years of lifted fields,measured enzyme activity and nutrient content in paddy fields,and analyzed its temporal and spatial variation characteristics in the study area and the relationship between enzyme activity and nutrient Mutual relations,and the evaluation and prediction of soil fertility in the study area,play a guiding role for future artificial improvement measures.The main conclusions are as follows:(1)With the increase of the lifting years,the catalase activity first decreased,then increased and then decreased,and the invertase and urease activities showed a downward trend.The activities of catalase,invertase and urease in the three villages and towns are all higher than those in unlifted fields.The activities of the three enzymes in Miaoqiao Town decreased with the direction of water flow,and the activities of urease in Wenfeng Town increased with the direction of water flow.(2)With the increase of the lifting years,the p H and water content firstly decrease,then increase and then decrease,but the overall trend is downward;the soil organic carbon content shows a downward trend;the total nitrogen and total phosphorus contents first increase and then decrease The content of alkaline hydrolyzed nitrogen first decreased and then basically stabilized.The content of soil available phosphorus first decreased and then increased and then decreased.The intensity of soil nitrogen supply first decreased and then increased,and the intensity of soil phosphorus supply first decreased,then increased and then decreased.(3)The contents of organic carbon and alkali-hydrolyzed nitrogen in the three towns are all higher in unraised fields than in raised fields,while total nitrogen content is lower in unraised fields than in raised fields,and the contents of total phosphorus and available phosphorus are not obvious.The organic carbon content and available phosphorus content in the study area are all at level 3,and the total nitrogen,total phosphorus,and alkali hydrolyzed nitrogen content are all at level 5.The organic carbon and soil nutrient contents of the 13 sampling points were compared in 2019 with 2014.The organic carbon content in2019 was higher than that in 2014,and the content of alkali-hydrolyzable nitrogen and total phosphorus was lower than that in 2014.The other contents were not significantly lower than that in 2014.Elevated.(4)Correlation analysis showed that the correlation between catalase,urease,and invertase and organic carbon,available phosphorus,and alkaline hydrolysis nitrogen reached significant or extremely significant positive correlation.Path analysis shows thatthe main influencing factors of enzyme activity have comprehensive effects: catalase(available phosphorus is the largest,organic carbon is the second,and water content is the smallest);invertase(alkaline nitrogen is the largest,water content is the second,p H is the second,effective Phosphorus is the smallest);Urease(alkaline nitrogen is the largest,p H is the second,and available phosphorus is the smallest)(5)The soil quality score of cultivated land in the study area was within the range of-2.58-4.35,the highest score of 15 sampling points was at the unraised field(NT)T6sampling point,and the lowest score was at the six-year raised field(6a)T8 sampling point;The average total score of the raised field type soil is NT>8a>3a>6a>5a;with the increase of the raising period,the fertility level of the soil first decreased and then increased,but did not return to the level of the unraised field;2014 and 2019 13 It can be seen from the land quality scores of each sampling site that most of the land fertility has declined in 2019. |
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