Soil total nitrogen and available nitrogen.

The medium-intensity karst desertification environment is typically characterized by more rocks and less soil. The abandoned land in the construction areas of the dry-hot river valley hydropower station has more infertile soil, severe land degradation, and very low land productivity. Therefore, it is urgent to improve the soil quality to curb the increasingly degrading land and reuse the construction site. Few studies have focused on the effect of soil restoration and comprehensive evaluation of soil quality with multi-treatment in abandoned land in the dry-hot valley hydropower station construction area. Here, 9 soil restoration measures and 1 control group were installed at the Guangzhao Hydropower Station construction in Guizhou Province, China, for physical and chemical property analysis. In total, 180 physical and 90 chemical soil samples were collected on three occasions in May, August, and December 2022. Soil fertility and quality were evaluated under various measures using membership functions and principal component analysis (PCA). This study showed that almost all measures could enhance soil water storage capacity (The average total soil porosity of 9 soil treatments was 57.56%, while that of the control group was 56.37%). With the increase in soil porosity, soil evaporation became stronger, and soil water content decreased. Nevertheless, no decrease in soil water content was observed in the presence of vegetation cover (soil water content: 16.46% of hairy vetch, 13.99% of clover, 13.77% of the control). They also proved that manure, synthetic fertilizer, and straw could promote total and available nutrients (Soil total nutrient content, or the total content of TN、TP、TK,was presented as: synthetic fertilizer (11.039g kg-2)>fowl manure (10.953g kg-2)>maize straw (10.560g kg-2)>control (9.580g kg-2);Total available nutrient content in soil, or the total content of AN,AP,A,was shown as:fowl manure (1287.670 mg kg-1)>synthetic fertilizer (925.889 mg kg-1)>sheep manure (825.979 mg kg-1)>control (445.486 mg kg-1). They could also promote soil fertility, among which the first two reached the higher comprehensive soil quality. Fertilizer was conducive to improve soil quality and fertility, yet long-term application could cause land degradation like soil non-point source pollution, compaction, and land productivity decline. Ultimately, combining fertilizer with biochar or manure is recommended to improve soil fertility. Biochar and green manure could play an apparent role in soil improvement only when there is abundant soil water. The above views provide theoretical support for curbing soil degradation, improving soil fertility and quality, enhancing land productivity, and promoting the virtuous cycle of the soil ecosystem.

中强度喀斯特石漠化环境通常以多岩石、少土壤为典型特征。干热河谷水电站建设区域的废弃场地土壤贫瘠、土地退化严重，且土地生产力极低。因此，亟需通过改良土壤质量以遏制土地退化加剧，并实现建设场地的复垦利用。目前针对干热河谷水电站建设区废弃场地的土壤修复效果及多措施下土壤质量综合评价的研究尚少。本研究在中国贵州省光照水电站建设区域设置了9种土壤修复措施及1组对照组，用于土壤理化性质分析。研究分别于2022年5月、8月及12月三次采样，共获取180份土壤物理样本与90份土壤化学样本。采用隶属函数与主成分分析（PCA）对不同措施下的土壤肥力与质量开展评价。研究结果表明，几乎所有修复措施均可提升土壤储水能力：9种处理组的土壤总孔隙度平均为57.56%，对照组则为56.37%。随着土壤孔隙度提升，土壤蒸发作用增强，土壤含水量随之下降。但在植被覆盖条件下，土壤含水量并未出现下降：毛叶苕子处理组土壤含水量为16.46%，三叶草处理组为13.99%，对照组为13.77%。研究同时证实，有机肥、化肥与秸秆均可提升土壤全量与速效养分含量：土壤全量养分（即全氮TN、全磷TP、全钾TK的总含量）排序为：化肥组（11.039g·kg⁻²）> 鸡粪组（10.953g·kg⁻²）> 玉米秸秆组（10.560g·kg⁻²）> 对照组（9.580g·kg⁻²）；土壤速效养分总含量（即速效氮AN、速效磷AP、速效钾A）排序为：鸡粪组（1287.670mg·kg⁻¹）> 化肥组（925.889mg·kg⁻¹）> 羊粪组（825.979mg·kg⁻¹）> 对照组（445.486mg·kg⁻¹）。上述措施均可提升土壤肥力，其中化肥与鸡粪处理的土壤综合质量位列前茅。化肥虽可有效改善土壤质量与肥力，但长期施用可能引发土壤面源污染、土壤板结及土地生产力下降等土地退化问题。综上，建议将化肥与生物炭或有机肥配施，以提升土壤肥力。生物炭与绿肥仅在土壤水分充足的条件下，方可展现出显著的土壤改良效果。本研究结果可为遏制土壤退化、提升土壤肥力与质量、提高土地生产力及促进土壤生态系统良性循环提供理论支撑。