How to determine the soil health status effectively is the basic issue to realize the agriculture green development. In the existing soil health assessment system, the importance of soil organi-sms in the maintenance of soil health is rarely considered. From the perspective of soil biological health, we discussed the connotation of soil health, and summarized the biological indicators of soil health, including soil microorganisms, soil enzyme activity, soil micro-food web and earthworm. Based on the above-mentioned indicators, the regulation approaches were elaborated from the aspects of crop and soil management practices. In addition, the future research on soil biological health was prospected. The main aim of this study is to enhance the understanding of scientists and decision makers on the maintenance of soil biological health, and to give full consideration of the important role of soil organisms in ecosystem services.

Fruit quality and yield in orchards will decrease after long-term planting. To analyze the changes of soil quality under different planting years and identify the key factors of the declining of orchard soil quality could provide scientific foundation for optimizing fertilization management of orchard soil. In this study, we analyzed the changes of soil physical, chemical, and biological properties of loquat orchard under different planting years (<10 years, 10-15 years, 15-20 years, ≥20 years) in Ninghai County, Zhejiang Province, and evaluated soil health by using soil quality index, multifunctionality index, and sensitivity and resistance indicators. The results showed that, compared with the orchards planting less than 10 years, soil bulk density in the orchards with planting years of 10-15 years and over 20 years increased by 12.8% and 13.6%, respectively. Soil pH decreased by 8.8%, 8.6%, and 7.5% in the orchards with planting years of 10-15 years, 15-20 years and over 20 years, respectively. With the increase of planting years, soil microbial biomass carbon, soluble organic carbon, soluble organic nitrogen, available phosphorus, available potassium, total organic carbon, total nitrogen decreased, and the soil quality and multifunctionality index of loquat orchard soil decreased. Compared with the orchards planting less than 10 years, soil quality index and soil multifunctionality index decreased by 20.4% and 17.9% for the orchards with the planting years of 10-15 years, 38.1% and 25.2% for the orchards with the planting years between 15-20 years, and 50.7% and 35.5% for the orchards planting over 20 years, respectively. The key factors affecting soil quality of loquat orchards were soil soluble nitrogen, available potassium, and available phosphorus. Amongst the available nutrients, NH₄⁺ and NO₃^- were the sensitive indices in orchard soil. In conclusion, long-term planting decreased soil quality and available nutrient content in loquat orchards.

Non-grain utilization of cultivated land threatens farmland ecological environment and soil health, which restricts grain production. To identify the key obstacle factors of cultivated soil under non-grain utilization, explore the changes of soil quality and function, and evaluate the effects of non-grain utilization on the health of farmland soil, we evaluated soil health of farmland under different non-grain utilization types (vegetables, bamboo-abandoned, nursery-grown plant-abandoned, nursery-grown plant-rice) by soil quality index and soil multifunctionality index method combined with sensitivity and resistance approaches. The results showed that soil organic carbon and total nitrogen (TN) in the bamboo-abandoned soil were 95.3%, 66.7%, 65.7% and 82.6%, 57.0%, 59.5% of those under vegetables, nursery-grown plant-abandoned and nursery-grown plant-rice treatments, respectively. The electrical conductivity of vegetable soil was 2.2-2.5 times that of other soils of non-grain cultivated land. Total phosphorus and nitrate nitrogen were 1.8-2.0 times and 3.5-5.5 times of other soils of non-grain cultivated land, respectively. Among different non-grain utilization types, soil quality index and soil multifunctionality index of vegetable soil were the highest. Soil quality index and soil multifunctionality index decreased significantly in bamboo-abandoned (50.2% and 22.7%), nursery-grown plant-abandoned (38.3% and 14.4%) and nursery-grown plant-rice (27.7% and 8.5%) treatments, compared with that of vegetable soil. Random forest model analysis showed that available potassium and available nitrogen (AN) were the key factors affecting soil quality index. TN, cellulase and xylanase activities that related to soil C cycle were the key factors affecting soil multifunctionality index. In addition, available phosphorus, AN, TN and enzyme activity were sensitive indices to soil change in non-grain cultivated land. By comprehensively evaluating soil quality of non-grain cultivated land, we identified the key obstacle factors and provide a theoretical basis for the healthy soil cultivation and sustainable utilization of non-grain cultivated land.

It remains unclear how soil microbial metabolism responds to organic input and the driving factors during soil carbon fixation and fertilization in newly reclaimed farmlands. We conducted a field experiment to explore the effects of different organic inputs on soil nutrients, organic carbon fractions, extracellular enzyme activities, microbial metabolism, and microbial carbon utilization efficiency in a newly reclaimed farmland with a rice-wheat rotation in Jiande of Zhejiang in 2022. Five treatments were implemented with equivalent C return in addition to conventional chemical fertilizers (NPK): 1) NPK alone (control), 2) NPK + manure + maize straw (MS), 3) NPK + manure (M), 4) NPK + straw biochar-based manure (MBF), and 5) NPK + straw biochar (MB). The results showed that organic inputs significantly enhanced soil nutrients, soil organic carbon fractions, and microbial activity compared to NPK. In terms of soil nutrient improvements, the order was M > MBF > MS > MB, while crop yield followed the order of MS > M > MBF > MB. The active organic carbon contents followed the order of M > MS > MBF > MB, with a 91.7% increase in the M treatment compared with NPK. For recalcitrant organic carbon contents, the sequence was MB > MBF > M > MS, with a 160.7% enhancement in the MB treatment than NPK. The microbial biomass showed the order of M > MS > MBF > MB. Microbial biomass carbon, nitrogen, and phosphorus in the M treatment was increased by 81.1%, 140.9%, and 261.1%, respectively compared with NPK. Extracellular enzyme activities followed the order of MS > M > MB > MBF. The MS treatment increased C cycle-related enzyme activities (β-glucosidase, β-xylosidase, and β-cellobiohydrolase) by 176.3%, 180.4%, and 439.2%, respectively, and N cycle-related enzyme activity (N-acetyl-β-glucosaminidase) by 331.4% compared with NPK. Results of Mantel correlation analysis and redundancy analysis showed that dissolved organic carbon and microbial biomass carbon were the primary drivers of extracellular enzyme activities during the wheat and rice growing seasons. Enzyme vector models and partial least squares path modeling revealed that soil microbial metabolism in the newly reclaimed farmland was constrained by both carbon and phosphorus contents. Organic inputs alleviated phosphorus limitation by improving soil nutrient availability and decreased microbial carbon use efficiency by increasing active organic carbon content. In summary, organic inputs played a positive role in soil carbon fixation and fertilization in the newly reclaimed farmland. Among the treatments, MBF showed the best comprehensive effect on soil carbon fixation and fertilization.

Understanding the effects of potassium and trace element application on soil ecological functions and soil health in farmland can provide theoretical basis for soil nutrition management. In this study, we examined the impacts of potassium and trace element addition on soil ecological function and health in farmland with long-term application of nitrogen and phosphorus fertilizer in Changwu Agricultural Ecological Experimental Station, Chinese Academy of Sciences. There were six treatments, a control without potassium and trace elements (CK), K addition (30 kg·hm^-2 of potassium chloride), Cu addition (15 kg·hm^-2 of copper sulfate), B addition (11.25 kg·hm^-2 of borax), Mn addition (22.5 kg·hm^-2 of manganese sulfate), and Zn addition (15 kg·hm^-2 of zinc sulfate). We collected soil samples of 0-20 cm layer to analyze the soil physical and chemical properties and microbial acti-vity indicators, constructed the minimum data set and calculated the soil health index. The results showed that K addition significantly increased soil available phosphorus content by 27.2%, increased alkaline phosphatase activity by 52.2%, and improved the bioavailability of soil phosphorus. The addition of Cu significantly increased soil respiration by 40.8% and N-acetylglucosamine enzyme activity by 63.6%, enhancing soil carbon and nitrogen conversion. The content of total phospholipid fatty acids, bacterial phospholipid fatty acids, and anaerobic phospholipid fatty acids was increased by 8.5%, 7.2%, and 12.3%, respectively, and microbial biomass carbon and nitrogen contents were promoted. The addition of Zn and B significantly reduced the biomass of bacteria, arbuscular mycorrhizal fungi, Gram positive bacteria, Gram negative bacteria, and actinomycetes by 35.3%, 32.2%, 31.5%, 40.1%, 34.5%, and 22.6%, 26.4%, 20.5%, 23.9%, and 22.6%, respectively, and reduced soil respiration. The addition of Mn significantly increased soil β -1,4-glucosidase activity (45.6%), but reduced the biomass of bacteria, arbuscular mycorrhizal fungi, Gram positive bacteria, Gram negative bacteria, actinomycetes, and soil respiration. The soil health index of each treatment was as follows: K(0.94)>Cu(0.80)>CK(0.78)>B(0.75)=Mn(0.75)>Zn(0.71). In summary, K and Cu addition to farmland soil in the Loess Plateau would be beneficial for the health and stability of soil ecosystems.

We investigated the effects of earthworm and organic material application methods on soil quality on slopes where photovoltaic panels are installed, aiming to explore a new model for promoting sustainable development of photovoltaic agriculture and improving soil quality. We proposed the photovoltaic-earthworm model, which involves breeding Amynthas aspergillum with high medicinal value in the soil under photovoltaic panels. There were four treatments: surface application of cow manure between photovoltaic panels to breed earthworms (Out+S), surface application of cow manure under photovoltaic panels to breed earthworms (In+S), mixed application of cow manure between photovoltaic panels to breed earthworms (Out+M), and mixed application of cow manure under photovoltaic panels to breed earthworms (In+M), with the bare land as the control (CK). We measured soil physical and chemical properties, as well as the enzyme activities. The results showed that the content of soil mechanical stability and water stability macroaggregates, organic carbon, total nitrogen, alkaline nitrogen, available phospho-rus, available potassium, and acid phosphatase activity, were significantly enhanced in Out+M and In+M treatments compared to CK by 4.7%-18.7%, 6.2%-26.0%, 37.5%-113.9%, 39.4%-90.9%, 43.4%-196.8%, 222.9%-762.5%, 246.1%-460.7% and 25.3%-33.3%, respectively. The content of soil mechanical stability and water stability macroaggregates under photovoltaic panels (In) was increased by 13.4%-21.5% and 16.1%-16.2%, respectively, compared to between photovoltaic panels (Out). The soil alkaline nitrogen content, carbon nitrogen ratio, and acid phosphatase activity was increased by 18.5%-34.1%, 13.8%-16.8%, and 6.3%-36.5%, respectively. The content of soil mechanically stable macroaggregates, water stable macroaggregates, and water stable macroaggregates with particle size ≥0.25 mm in mixed application of cow manure (M) treatments was increased by 6.6%-14.3%, 18.5%-18.6%, and 3.2%-3.8%, respectively, compared to the surface application of cow manure treatment (S). The content of organic carbon, total nitrogen, alkaline hydrolyzed nitrogen, available phosphorus, carbon nitrogen ratio, and acid phosphatase activity was increased by 55.5%-88.2%, 37.0%-60.5%, 54.4%-74.6%, 102.4%-117.8%, 13.4%-16.4%, and 30.7%-67.7%, respectively. The destruction rate of soil aggregates decreased by 39.0%-50.9%. Soil macroaggregates were significantly positively correlated with organic carbon, soil nutrients, and acid phosphatase. Soil quality of each treatment followed an order of In+M>Out+M>In+S>Out+S>CK. In summary, In+M has the great potential for promoting local economic development, protecting the ecological environment, and improving soil quality in the development of slope photovoltaic agriculture in southern China.

The enhanced weathering technology of basalt can promote the fixation of atmospheric carbon dioxide in the form of carbonates/bicarbonates in soils. Earthworms can promote mineral weathering, further contributing to carbon fixation. In this study, we selected red and yellow-brown soil as research subjects and set up three treatments [i.e., control (CK), adding basalt powder (B), and adding basalt powder and inoculating earthworms simu-ltaneously (BE)], and explored the impact and potential mechanisms of earthworm-mediated basalt weathering on Amaranthus tricolor growth, soil respiration, microbial abundance, Ca² and Mg²⁺, soil total organic C, inorganic C and mineral-bound organic C in the field. The results showed that B and BE treatments significantly increased soil pH and Mg²⁺ content of both soils, but significantly increased Ca²⁺ content, soil respiration, aboveground and belowground biomass of A. tricolor only in the red soil. B and BE treatments significantly reduced reactive Fe and Al minerals in both soils and NH₄⁺-N content of the yellow-brown soil, but did not affect NO₃^--N content of both soils. BE treatment significantly increased bacterial abundance of the red soil, but did not affect fungal abundance of both soils. BE treatment significantly increased inorganic C content only in the yellow-brown soil, but significantly reduced Fe/Al bound organic C of the yellow-brown soil, and had no significant effect on total C and organic C of both soils. In addition, BE treatment had no significant effect on soil organic C, inorganic C and Fe/Al bound organic C of both soils compared with B treatment. The random forest model analysis revealed that fungal abundance is the key factor regulating organic carbon accumulation in red soils, while active aluminum minerals and iron-aluminum minerals are respectively identified as the critical determinants controlling the accumulation of organic carbon and iron-aluminum bound organic carbon in yellow-brown soils. Our results indicate that adding basalt powder to soil can significantly promote plant growth in the short term, but did not affect soil organic C formation. The role of earthworms in promoting basalt weathering and soil organic C sequestration in the short term is limited.

To clarify the alleviating effect of different water-saving irrigations at the seedling stage of maize under salt stress in arid irrigation area, we used ‘Xianyu 1225' maize as the test material, and set up three irrigation treatments (T1, T2, and T3) in the salinized land in the Yellow River irrigation area. T1 treatment was the surface furrow irrigation at the sowing stage and three-leaf stage (T1, irrigation amount was 65 mm at both stages). Both T2 and T3 treatments were furrow irrigation at the sowing stage and drip irrigation at three-leaf stage (the irrigation amount at the sowing stage was 65 mm, and the irrigation amount at the three-leaf stage was 39 and 52 mm, respectively). The control (CK) was furrow irrigation at the sowing stage and the three-leaf stage in non-salinized land (irrigation amount was 65 mm at both stages). We investigated the effects of water-saving irrigation on leaf morphology, photosynthetic physiology, photosynthetic tissue structure and leaf fluorescence characteristics of maize seedlings under salinity stress. The results showed that furrow irrigation combined with drip irrigation could effectively reduced soil salt content and weakened soil salinity returning to the 0-20 cm soil layer of salinized land. Compared with CK, different irrigation treatments significantly changed the morphology, reduced antioxidant enzyme activities, stomatal structure, photosynthetic pigment content, photosynthetic fluorescence performance of maize leaves under salinity stress. Such decreases were the largest under the T1 treatment, and were relieved under T2 and T3 treatments. Furthermore, T3 treatment differed little in the antioxidant enzyme activities, net photosynthetic rate, transpiration rate, effective photochemical efficiency of maize leaves compared to CK. According to the results of structural equation model analysis, the water-saving irrigation increased the maximum photochemical efficiency of maize and alleviated the inhibition of salt stress on maize growth at seedling stage by reducing the Na⁺ content of plants, protecting the photosynthetic tissue and adjusting the proportion of photosynthetic pigments. In conclusion, the T3 mode was the best irrigation strategy in the study area.

Soil health, reflecting the physical, chemical, and biological properties of the soil is closely related to soil functions and plant productivity. Soil health is crucial for ensuring food security, ecological balance, and human health. Earthworms are known as ecosystem engineers, due to their unique biological characteristics. They are not only indicators of soil health but also play an important role in improving soil health. Earthworms have profound impacts on soil health through their activities such as burrowing, feeding, digesting, excreting, and secreting mucus from their body surface. We reviewed research advances on the roles of earthworms in improving soil structure, accelerating the decomposition of organic matter, increasing soil microbial diversity, promoting nutrient cycling, and providing nutrients for plant growth. Furthermore, we elaborated the role of earthworms in collaborating with their gut microbiota to accelerate the reduction of pollutants in the soil, improve soil purification capacity, maintain ecosystem balance, promote soil health, and increase crop yields. Moreover, we provided an outlook on future researches related to earthworms and soil health.