Increased Soil Organic Matter Research Articles

Nitrogen retention capacity of paddy soil improved under long-term garlic-rice rotation

ABSTRACT Although significant differences in soil nitrogen levels exist under different paddy-upland rotations, the main reason for this is unclear. The nitrogen retention capacity and loss of ammonia volatilisation, leaching, etc. of paddy soil with large differences in nitrogen levels from two long-term rotations, garlic-rice and wheat-rice, were measured using the soil column simulation method. The results showed that the loss rate of leaching was only 5.4%, whereas that of ammonia volatilisation was up to 22.8%, which was the main nitrogen loss way of paddy soil under the two rotations. The average ammonia volatilisation rates under wheat-rice rotation with high and low nitrogen application rates were 12.1% and 40.2% higher than that under garlic-rice rotation, leading to a decrease in the total nitrogen loss amount and rate through ammonia volatilisation by 29.8% and 8.8%, respectively. As a result, nitrogen retention in the soil under garlic-rice rotation increased by 12.7%. In conclusion, the long-term garlic-rice rotation could significantly inhibit ammonia volatilisation, thus improving the soil nitrogen retention capacity. The straw return may increase soil organic matter content, reduce ammonia volatilisation loss, and enhance soil nitrogen retention capacity and productivity.

Conservation practices reverse soil degradation in Mediterranean fig orchards

Agriculture is an important driver of soil degradation, especially where intensive practices are applied. It is essential to reduce the impact of agriculture intensification and find different solutions to halt this. This work investigates the effect of different types of treatments: 1) tillage (Tilled), 2) Grass covered (Grass), 3) olive pomace (Pomace) and 4) Hay in different seasons (Spring, Summer, and Fall) using rainfall simulations (58 mm h−1 for 30 min). Tillage reduced bulk density (BD) compared to treatments with mulch cover. Grass-covered treatments increased soil organic matter (SOM) and water-stable aggregates (WSA). Additionally, they enhanced hydrological properties, thus mitigating sediment loss (SL) and element transport. The principal component analysis (PCA) showed strong relations between SL and element losses, as well as P soil and Cu soil with SOM. Thus, implementing soil conservation practices, such as hay used as a surface cover, is crucial for fig orchards and agricultural area management to reduce soil erosion, enhance soil quality, and mitigate element transport and SL. Further on, continuous monitoring of soil properties and hydrological responses throughout different seasons should be prioritized, along with exploring alternative methods to ensure sustainable soil management.

Evaluating the Crucial Relationships between Soil Health and Climate Change

Content of paper emphasizes the significant influence of soil health on global warming and climate stability. Soil affects the Earth's carbon cycle by acting as a source and sink of greenhouse gases. Climate is considered important a factor in soil formation, but also soils also have an impact on the climate. Therefore, soils are affected by the current climate change as well, particularly because they may release excessive amounts of carbon dioxide (CO2) and other greenhouse gases (GHG) as a result of changing their usage or poor management or human wrong practices. The pressure that climate change places on soil ecosystems has a significant impact on agriculture, biodiversity, and ecosystem services. For effective climate mitigation and adaptation policies to be developed, it is essential to understand these relationships. Worthwhile that the greatest soil management practices for reducing climate change focus on increasing soil organic matter content and water retention. The enormous carbon and nitrogen (N) store that is soil. acting as a possible regulator of the CO2, N2O, and CH4—the three main greenhouse gases in the atmosphere. Because biota is the organic matter carrier to the soil, both in living organisms and through their decomposing remains, mature soils rich in life are frequently CO2 sinks. But heterotrophic organisms that live in soil are also OM net consumers, and they release CO2 into the atmosphere through respiration. The interactions between plants, soil organisms, and abiotic soil conditions are actually changing as a result of climate change, which has an impact on plant performance, plant diversity, and community structure. The loss of soil organic matter (OM) and its development to the atmosphere quickly became a significant effect of tillage and any other activity, agricultural or otherwise, that disturbs the natural soils since then. It is anticipated that the areas affected by salinization would increase due to climate change which affects the suitability of the soil agriculture or any other development purposes.The conclusion of the current study Carbon sequestration can reduced the green house gas emission.

Variations in crop yield caused by different ratios of organic substitution are closely related to microbial ecological clusters in a fluvo-aquic soil

ContextPartial substitution of chemical fertilizer with organic fertilizer (PSCFOF) can improve soil quality and reduce the overreliance of crop yield on chemical fertilizers. However, the relationship between alterations in crop yield and soil microbial community in response to various substitution ratios is not comprehensively understood. ObjectivesThis study aimed to investigate the impact of PSCFOF on soil nutrient supply, enzyme activity, bacterial and fungal community, and crop yield. MethodsAn 11-year (2009 – 2021) field experiment was carried out in a winter wheat–summer maize double-cropping system with four fertilization regimes (no fertilizer, NF; pure chemical fertilizer, NPK; 30% organic substitution, NPKLM; and 50% organic substitution, NPKHM). Co-occurrence network analysis was applied to examine the importance of ecological clusters and keystone species in controlling microbial activities and crop yields. ResultsThere were no significant differences in soil nutrient contents and annual crop yield between the NPK and NPKLM treatments. However, the NPKHM treatment resulted in significant reductions in crop yield by 9.49%− 16.78%, despite increasing soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), and available phosphorus (AP) by 9.05%, 7.26%, 11.67%, and 26.62%, respectively. This contrasting effect was primarily attributed to the influence of a specific ecological cluster (module 2), rather than the entire microbial community. Long-term 50% organic substitution would suppress keystone species within module 2, such as Aggregatilinea, Luteimonas, Usitatibacter and Microvirga. These species were specifically correlated with soil carbon enzyme activities, including β-glucosidase, invertase, and dehydrogenase, and contributed significantly and positively to crop yield. ConclusionsOrganic substitution at different ratios altered soil nutrient content, enzyme activities and microbial community in different intensities and directions. Long-term 30% organic substitution could preserve soil fertility and microbial community, leading to stable crop yield; whereas 50% organic substitution could inhibit keystone species, reduce extracellular enzyme activity and ultimately lead to a decrease in crop yield. ImplicationsOur results highlight the importance of ecological clusters within soil microbial co-occurrence network in regulating crop yield, presenting a new perspective on the variations in crop yield resulting from varying ratios of organic substitution.

Effects of improved water retention by increased soil organic matter on the water balance of arable soils: A numerical analysis

AbstractClimate change will lead to prolonged droughts in various regions of the world, which may significantly affect agricultural production. This is particularly problematic for soils with low water retention capacity, which cannot store sufficient water for crops. In this paper, we investigate how a change in the water‐holding capacity of the soil material, as could be achieved by increasing the soil organic carbon (SOC) amount, affects the components of the soil water balance (evaporation, transpiration, and groundwater recharge). Specifically, we state the hypothesis that an increased water‐holding capacity in a shallow soil layer, as it is achieved through SOC enrichment at the soil surface, will result in more water being stored near the soil surface and lost to unproductive evaporation, thereby reducing the amount of water available to plants and groundwater recharge. The hypothesis was tested by numerical simulations, employing the Hydrus‐1D program package to model the water balance in a soil–plant–atmosphere system for an arable crop in hydrologically contrasting years. The study considered soils with varying textures and different depths of a soil layer with increased SOC content. The soil hydraulic properties (SHP) of the soil material, including the effect of SOC on the SHP, were determined using a recently developed pedotransfer model based on data from over 500 samples. We showed that both the improved water retention by SOC and its vertical distribution affect the soil water balance in a complex manner. In sandy soils, increasing the water‐holding capacity in shallow layers up to 0.1 m led to enhanced evaporation and thus a decrease in water availability for crops. However, deeper incorporated SOC could ameliorate these negative effects. Our findings suggest that not only the amount but also the vertical SOC distribution should be considered if enrichment of SOC shall be applied to mitigate the effect of droughts.

Economic Valuation of Provisioning Ecosystem Services from Groundnut Organic Farming

Provisioning ecosystem services from organic farming requires a holistic strategy that recognizes the interconnected relationships among ecological processes, agricultural productivity and the human well-being. Provisioning ecosystem services includes the cultivation of crops, fisheries and timber production, etc. The present study analysed the input use pattern of groundnut organic farmers and valuated the provisioning ecosystem services i.e., food and raw materials from groundnut organic farming in Tamil Nadu. Market price method was used to valuate the provisioning ecosystem services. The results suggested that Panchakavya was widely used by majority of the organic farmers (69.70%) demonstrating its effectiveness in promoting sustainable farming practices. Additionally, the incorporation of green manure (63.64%) and farmyard manure (54.55%) highlights farmer’s commitment to increasing soil organic matter, maintaining fertility, and optimizing crop yield. The valuation of provisioning services revealed that the economic value of the provisioning services from organic groundnut farming was estimated to be Rs. 2,75,017. These findings provide strong support for the adoption and promotion of sustainable organic farming.

The potential of coffee ground compost to enhance soil pH, growth, and production of mustard greens in acid-dry land

The deficiency of productive agricultural land was an obstacle to the development of mustard green cultivation. The utilization of acid-dry land is a solution for the development of mustard green cultivation. South Kalimantan has acid-dry land covering an area of 87.61% of the total dry land. The use of coffee grounds compost is an alternative technology for improving soil fertility in acid dry land. Coffee grounds compost can increase soil organic matter, so it can fertilize the soil and increase crop production. This study aims to determine the quality of coffee grounds compost and determine the best dosage of coffee grounds compost to increase soil pH, growth, and production of mustard greens in acid dry land. This research method used a single-factor randomized block design (RBD), namely the dose of coffee grounds compost: k0 = 0 t ha−1; k1 = 10 t ha−1; k2 = 20 t ha−1; and k3 = 30 t ha−1. The physical and chemical characteristics of coffee waste compost have met the criteria for quality compost based on SNI No. 19-7030-2004. The results showed the effect of coffee grounds compost on increasing soil pH, growth, and production of mustard greens. The best dose of coffee grounds compost in increasing soil pH, plant fresh weight, and mustard productivity was found in the K3 treatment with increases of 18.05%, 67.21%, and 67.21% respectively compared to the control. The best treatment for increasing plant height, number of leaves, and width of mustard leaves was treatment k1 with an increase of 51.34%, 31.03%, and 40.60% respectively compared to the control.

The Effect of Long-Term Farmyard Manure and Mineral Fertilizer Application on the Increase in Soil Organic Matter Quality of Cambisols

Soil organic matter (SOM) quantity and quality are important factors that significantly influence soil fertility. SOM quality indicators change throughout time. In this study, long—term field experiments (22–50 years in duration) on a Cambisol at four sites in the Czech Republic were selected. Seven crops were successively rotated in the sequence: clover, winter wheat, early potato, winter wheat, spring barley, potato, and spring barley with interseeded clover. Five treatments were investigated, including an unfertilized treatment, farmyard manure, and various combinations of farmyard manure and mineral fertilization. A total of 40 t ha−1 of farmyard manure was applied to the early potato and potato crops. Combining organic and mineral fertilizers increased soil organic matter quality and quantity over unfertilized or organic only treatment. The highest intensity of mineral fertilizers in our trials elevated the mean of carbon sequestration efficiency to 45.6% in comparison to pure manure treatment which reached only 22.9% efficiency. A strong correlation was established between the total glomalin content and soil organic matter carbon, fulvic acid, humic acid, carbon hot water extraction, potential wettability index (PWI), and aromaticity index. The PWI was also strongly correlated with these indicators. The E4/E6 ratio indicator was shown to be a much less sensitive method for reflecting the change in soil organic matter quality.

Natural grass coverage enriches arbuscular mycorrhizal fungal communities in subtropical citrus orchards through the regulation of Glomus on a regional scale

Arbuscular mycorrhizal (AM) fungi are ubiquitous soil fungi in orchard ecosystem, conferring a diverse array of benefits to citrus plants. However, how natural grass coverage, a common phenomenon in citrus orchards in southern China, shifts AM fungal communities in subtropical citrus orchards is far from being understood, especially on a regional scale, which impedes the understanding of the indigenous AM fungal adaptations. In this study, natural grass coverage rate, soil chemical properties, and soil AM fungal community in 80 sampling sites spanning 179, 700 km2 area in subtropical citrus orchards were investigated. The result of 18S rRNA gene high-throughput sequencing revealed that a total of eight AM fungal genera were identified and Glomus (90.15 %) was dominant genus in the community in citrus orchards. Natural grass coverage significantly increased soil organic matter (SOM), soil available phosphorus, and AM fungal alpha diversity, especially Glomus. Variation partitioning analysis revealed that grass coverage rate explained more variation in AM fungal alpha diversity than SOM. All the contrasting AM fungal species between different grass coverage rates and all the core AM fungal species belonged to Glomus. Null model analysis revealed that determinism played a slightly larger role in the assembly process of AM fungal communities than stochasticity with a distance-decay relationship. Moreover, natural grass coverage increased the relative importance of stochasticity in the community assembly. Taken together, these results suggest that maintaining natural grass coverage (naturally growing grass) is an effective nature-based solution for enriching AM fungal communities, which is essential for the sustainability of citrus production.

Soil Health in an Integrated Production System in a Brazilian Semiarid Region

Soil health is directly related to sustainable development goals (SDGs) and can be affected by inadequate management practices. In this work, soil edaphic respiration and changes in microbial biomass promoted by cover crops in an integrated crop–livestock system (ICLS) were evaluated using soil health indicators with the respirometry method. The design was completely randomized in a 3 × 6 factorial arrangement, and multivariate principal components analysis (PCA) was performed according to MANOVA. Edaphic respiration was determined based on the respirometry technique. The results showed that edaphic soil respiration was significant in the nine evaluation periods, demonstrating the importance of grass cover in edaphic respiration arising from the biological activity of microorganisms, which is directly related to the amount of soil organic carbon. The cover crops increased soil organic matter and consequently microbial respiratory activity.

Compost application boosts soil restoration in highly disturbed hillslope vineyard

A field trial was carried out to investigate the effects of compost application on a young Cabernet sauvignon vineyard located in a hilly area in the North-East of Italy and subjected to land terracing before plantation. The use of a compost based on manure, pruning residues and pomace at a rate of 65 t ha-1 was compared to the mineral fertilization regime recommended for the vineyards in the area (NPK: 80, 50, 200 kg ha-1). A multi-factorial approach that considered soil chemical properties, microbial community structure and function, vine nutritional and vegetative indexes, yield and quality parameters was applied in the attempt of depict interrelated effects of compost on all these factors. Results of this study show that the application of compost for three consequent years greatly increased soil organic matter content and improved the mineral nutrient availability in the soil. Soil biological fertility showed a slow but significant response to compost addition as from the second year of treatment microbial growth and enzyme activity were increased compared to those of the inorganic fertilization, with special regard to enzymes involved in P cycle. A shift in the soil microbial community structure was also observed in compost-treated soil, with higher presence of copiotrophic bacteria, indicators of soil quality, and phosphorus solubilizing bacteria. A decrease of pathogenic fungal strains was also observed. Organic fertilization increased plant nutrient uptake and vegetative growth compared to those observed in chemically fertilized vines. A trend toward increased yield and improvements for some grape quality parameters such as acidity and pH were observed in the first year of production. These results provide evidence that compost can boost soil fertility restoration in vineyard disturbed by land terracing, allowing for agronomic performances comparable or even improved than those of chemically fertilized vines.

Characterization of Technosols for Urban Agriculture

Soil characterization is essential for planning activities in urban areas in order to detect potential risks and understand the possible impacts derived from those activities. Nine soils located in Alicante (southeast of Spain) developed over construction debris were studied. Soil characteristics including mineralogy, elemental composition and metal availability were analyzed in two consecutive years, 2019 and 2020. These soils were similar to forest soils in the same area, with no evidence of asbestos clays or excess harmful elements. However, the use of DTPA extraction revealed high levels of Mn and Zn in some soils. Organic carbon and metals extracted with DTPA differed in 2019 and 2020, but no relationship between metal-DTPA and organic carbon content was observed. In general, organic matter content was higher in 2019, and elements extracted with DTPA were lower. The above-average rainfall in 2019 could have led to the washing away of dissolved materials and fine soil particles, decreasing elemental availability on the one hand, while promoting the development of natural vegetation, increasing soil organic matter, and immobilizing elements in living organisms on the other hand. The fact that the metal mobility varies depending on weather and soil characteristics is important when planning. Despite the demonstrated advantages of increasing urban green areas from an environmental and social point of view, we should not forget the materials on which urban soils are developed. Therefore, it is essential to establish annual plans for monitoring variations in the availability of heavy metals. This is of the most relevance when the plants are for human consumption. It is therefore also necessary to control the vegetables that grow on these soils and, in the event of possible problems, use the soil for gardening.

Comparative analysis of different bio-organic fertilizers on growth and rhizosphere environment of grapevine seedlings

Grapevine seedlings need to absorb a lot of nutrients from the soil during the growth process, and appropriate fertilizer can greatly promote the growth of seedlings. The purpose of this study was to investigate the effects of different bio-organic fertilizers (BOF) on shoot and root growth, soil biochemical characteristics, and bacterial communities of ‘Shine Muscat’ and ‘Kyoho’ seedlings. Four treatments were established: no fertilizer (CK), chemical fertilizer + organic fertilizer (T1), chemical fertilizer + bio-organic fertilizer 1 (T2, containing Bacillus amyloliquefaciens), chemical fertilizer + bio-organic fertilizer 2 (T3, containing Trichoderma). The results showed that BOF had better effects on growth and rhizosphere environment of grapevine seedling than organic fertilizer (OF) treated group. The shoot growth, chlorophyll content, and root growth with BOF of grapevine seedlings were generally better than those treated with OF. Compared with T1, T2 and T3 made grapevine seedlings meet the fixed drying requirement (main shoot 0.8 m) 1–4 weeks earlier. The expansion of roots and the improvement of root activity under BOF treatment were also beneficial to plant growth. Moreover, transcriptome analysis showed that BOF enhanced the phytohormones and cell wall processes in grapevine root, and up-regulated the expression of cell wall-related genes such as XTH23, EXPs, PME17, and auxin related genes such as ABCBs and GH3. In addition, BOF increased soil organic matter content, available nitrogen, available potassium, available phosphorus, and enzyme activity (soil catalase, urease, sucrase, and nitrate reductase). The Shannon and Chao values of T2 were higher than those of T1 and CK, which improved the diversity and richness of soil microbial community. As compared to CK, T2 treatment increased the symbiotic nitrogen fixing Proteobacteria by 4.10 %, and reduced Acidobacteria by 9.79 %. Actinobacteria, which is related to the degradation of stubborn polymers, was the dominant group in T2 treatment, accounting for 10.17 %. As compared to CK and T1, Actinobacteria was increased by 6.89 % and 5.66 %. In summary, BOF could promote the growth of grapevine seedlings by improving phenotypic traits, soil fertility, bacterial diversity, richness abundance, and provide theoretical and technical support for grapevine garden construction and tree management.

Synergistic effects of earthworms and cow manure under reduced chemical fertilization modified microbial community structure to mitigate continuous cropping effects on Chinese flowering cabbage.

The substitution of chemical fertilizers with organic fertilizers is a viable strategy to enhance crop yield and soil quality. In this study, the aim was to investigate the changes in soil microorganisms, soil chemical properties, and growth of Chinese flowering cabbage under different fertilization treatments involving earthworms and cow manure. Compared with the control (100% chemical fertilizer), CE (30% reduction in chemical fertilizer + earthworms) and CFE (30% reduction in chemical fertilizer + cow dung + earthworms) treatments at soil pH 8.14 and 8.07, respectively, and CFC (30% reduction in chemical fertilizer + cow manure) and CFE treatments increased soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), and available potassium (AK) contents. Earthworms and cow manure promoted the abundance of Bacillus and reduced that of the pathogens Plectosphaerella and Gibberella. The mantle test revealed that pH was not correlated with the microbial community. Random forest analysis verified that AN, SOM, and TN were important factors that jointly influenced bacterial and fungal diversity. Overall, the synergistic effect of earthworms and cow manure increased soil fertility and microbial diversity, thereby promoting the growth and development of Chinese flowering cabbage. This study enhanced the understanding of how bioregulation affects the growth and soil quality of Chinese flowering cabbage, and thus provided a guidance for the optimization of fertilization strategies to maximize the yield and quality of Chinese flowering cabbage while reducing environmental risks.

Biochar effects on NTFP-enriched secondary forest growth and soil properties in Amazonian Ecuador

Deforestation in the Amazon has resulted in large areas of depleted soils on abandoned pastures and agricultural sites that present a restoration challenge central to protecting biodiversity and ecosystem function in the region. Biochar – charcoal made from waste materials – can improve soil physical, chemical, and biological properties, but the few tropical field trials to date do not give consistent results regarding tree growth. This study presents three years of soil performance and tree growth of a secondary forest shading nontimber forest product (NTFP) plantations of Ocotea quixos (Lauraceae), Myroxylon balsamum (Fabaceae), and their mixture. Open kiln and traditional mound biochars were added at 10 t ha−1 at two sites with contrasting soil types. Biochar additions resulted in pronounced effects on soil properties that varied over time and with depth in the soil profile. Biochar additions generally increased soil organic matter, electrical conductivity, and plant nutrients (in particular K, Ca, and N), but there were interactive effects of NTFP treatments, and stronger responses on the poorer soil type. Biochar amendments resulted in increased tree growth, with a 29 ± 12% increase in aboveground biomass (AGB) on plots amended with kiln biochar and a 23 ± 9% increase in plots with mound biochar compared to controls. Tree species also varied in growth responses to biochar additions, with the largest increases observed in Jaccaranda copaia and Piptocoma discolor. Significant interactions between biochar and NTFP treatments were also seen for tree growth responses, such as Cecropia spp., which only showed increased biomass on mound biochar plots planted with Ocotea quixos. Overall, our results demonstrate a stronger effect of biochar in less favorable soil conditions, and an overriding effect of the legume NTFP in richer soils, and suggest that additions of biochar and legumes are important options to increase productivity and ecological resilience in tropical forest restoration.

Returning ryegrass to continuous cropping soil improves soil nutrients and soil microbiome, producing good-quality flue-cured tobacco.

The widespread and continuous cultivation of tobacco has led to soil degradation and reduced crop yields and quality. Green manure is an essential organic fertilizer that alleviates obstacles to continuous cultivation. However, the plant-soil microecological effects of green manure on flue-cured tobacco cultivation remain unclear. Thus, a positioning trail including two treatments, chemical fertilizer application only (treatment NPK) and chemical fertilizer application with turning ryegrass (treatment NPKG) was conducted, and the effect of ryegrass returning on the soil physicochemical properties, soil microbiome, crop yield, and quality of flue-cured tobacco in continuous cropping soil were investigated. Results showed that returning ryegrass to the field increased the thickness of soil humus layer from 13 cm to 15 cm, reduced the humus layer soil bulk density to 1.29 cm3/g. Ryegrass tilled and returned to the field increased soil organic matter content by 6.89-7.92%, increased rhizosphere soil available phosphorus content by 2.22-17.96%, and converted the soil non-exchangeable potassium into potassium that was available for plant absorption and utilization. Ryegrass tilling and returning to the field increased the potassium content of middle leaves of flue-cured tobacco by 7.69-10.07%, the increased potassium content in flue-cured tobacco was accompanied by increased total sugar, reducing sugar, and the ratio of reducing sugar to nicotine, which facilitated the harmonization of the chemical composition of cured tobacco leaves. Moreover, the increased number of markedly improved operational taxonomic units enhanced the complexity of the soil bacterial community and its compactness after ryegrass tillage and their return to the field. The available potassium, available phosphorus, total potassium content, pH, and sampling period of the rhizosphere soil had considerable effects on the rhizosphere microbial. Ryegrass tilling and returning to the field changed the soil microbiome, which increased the abundance of bulk soil Proteobacteria, rhizosphere soil Fibrobacterota, and microbes with anti-pathogen activity (Lysobacteria, Sphingomonas, Chaetomium, and Minimedusa); and reduced the abundance of pathogenic fungi Neocosmospore genus in the soil. In brief, ryegrass returned to the field, improved soil microecology and restored soil nutrients, and established a new dynamic balance of soil ecology, thereby improving the quality of cultivated land and the quality of flue-cured tobacco.

Combination of organic amendments as a soil recovering strategy at a desertification hotspot in the Brazilian semiarid

AbstractThe use of manure, organic mulch, and legume‐based fertilizers can increase soil fertility in semiarid regions. However, the effects of such practices on soils prone to desertification are unknown. This study aimed to evaluate soil fertility and herbaceous stratum yield on soils amended with different organic inputs in the desertification hotspot of Irauçuba, Ceará state, Brazil. The experiments were performed in two areas with different soils (Planosol and Cambisol), in randomized blocks with a 2 × 2 × 3 + 1 factorial design. The factors consisted of (i) mulch (presence or absence of Copernicia prunifera [carnauba palm] straw), (ii) manure (sheep or cattle), and (iii) legume‐based fertilizer (Mimosa tenuiflora [jurema], Mimosa caesalpiniifolia [sabiá], and Leucaena leucocephala [leucena]), in addition to an untreated control, with three replicates. Soil chemical attributes and herbaceous stratum yield were assessed in the two areas. Positive effects of the combined use of carnauba palm straw, manures, and legume‐based fertilizers on soil fertility were more evident for Planosol than for Cambisol. The combination of sheep manure with sabiá‐based fertilizer in Planosol, and cattle manure and leucena‐based fertilizer in Cambisol increased herbaceous stratum yield. Herbaceous stratum yield in Planosol is more responsive to the input of great amounts of soil nutrients (especially P) and it increases soil organic matter levels, while in Cambisol, herbaceous stratum yield is more associated with the ability of inputs to make nutrients readily available. The use of organic amendments can reverse, in the short‐term, degradation and desertification processes of soils in the Brazilian semiarid region.

Production of artificial humic acid from rice straw for fertilizer production and soil improvement

In this study, artificial humic acid (AHA) was produced from rice straw at room temperature. The response surface methodology was used to investigate the response of artificial humic acid to time, liquid-solid ratio, and KOH concentration. The optimal reaction conditions were determined: reaction time of 2 h, liquid-solid ratio of 6, and KOH concentration of 1.5 mol/L. The artificial humic acid content under these conditions was 32.29 g/L, which satisfied the Chinese agricultural industry standard for water-soluble humic acid fertilizers (humic acid content ≥30 g/L). Compared with chemical fertilizers, artificial humic acid fertilizer promoted chard growth and increased soil organic matter and humic acid. The stability of artificial humic acid was better, with a retention rate of 60.47 % in the soil. Water-soluble humic acid fertilizer also promoted chard growth by increasing the relative abundance of growth-promoting bacteria such as Glutamicibacter and Pseudomonas and, as well as growth-promoting fungi such as Mortierella. The application of water-soluble humic acid fertilizers has implications for both soil improvement and the reduction of agricultural carbon emissions.

Effects of allyl isothiocyanate fumigation on medicinal plant root knot disease control, plant survival, and the soil bacterial community

BackgroundAllyl isothiocyanate (AITC) is a natural product with high volatility that is used as a biofumigant to alleviate soil-borne plant diseases, and problems such as root knot nematodes (RKNs) that necessitate continuous cropping. However, little research has assessed the effects of AITC fumigation on medicinal plants.ResultsAITC significantly reduced the population of RKNs in soil (p < 0.0001) and showed an excellent RKN disease control effect within 6 months after sowing Panax notoginseng (p < 0.0001). The seedling survival rate of 2-year-old P. notoginseng was approximately 1.7-fold higher after soil treatment with AITC (p = 0.1008). 16S rRNA sequencing indicated that the AITC treatment affected bacterial richness rather than diversity in consecutively cultivated (CC) soil. Furthermore, biomarkers with statistical differences between AITC-treated and untreated CC soil showed that Pirellulales (order), Pirellulaceae (family), Pseudomonadaceae (family), and Pseudomonas (genus) played important roles in the AITC-treated group. In addition, the microbiome functional phenotypes predicted using the BugBase tool suggested that AITC treatment is more conducive to improving CC soil through changes in the bacterial community structure. Crucially, our research also suggested that AITC soil treatment significantly increases soil organic matter (p = 0.0055), total nitrogen (p = 0.0054), and available potassium (p = 0.0373), which promotes the survival of a succeeding medicinal plant (Polygonatum kingianum).ConclusionAITC is an ecologically friendly soil treatment that affects the top 10 bacterial richness but not diversity. It could also provide a basis for a useful agricultural soil management measure to alleviate soil sickness.

Microbial controls over soil priming effects under chronic nitrogen and phosphorus additions in subtropical forests.

The soil priming effect (PE), defined as the modification of soil organic matter decomposition by labile carbon (C) inputs, is known to influence C storage in terrestrial ecosystems. However, how chronic nutrient addition, particularly in leguminous and non-leguminous forests, will affect PE through interaction with nutrient (e.g., nitrogenandphosphorus) availability is still unclear. Therefore, we collected soils from leguminous and non-leguminous subtropical plantations across a suite of historical nutrient addition regimes. We added 13C-labeled glucose to investigate how background soil nutrient conditions and microbial communities affect priming and its potential microbial mechanisms. Glucose addition increased soil organic matter decomposition and prompted positive priming in all soils, regardless of dominant overstory tree species or fertilizer treatment. In non-leguminous soil, only combined nitrogen and phosphorus addition led to a higher positive priming than the control. Conversely, soils beneath N-fixing leguminous plants responded positively to P addition alone, as well as to joint NP addition compared to control. Using DNA stable-isotope probing, high-throughput quantitative PCR, enzyme assays and microbial C substrate utilization, we found that positive PE was associated with increased microbial C utilization, accompanied by an increase in microbial community activity, nutrient-related gene abundance, and enzyme activities. Our findings suggest that the balance between soil available N and P effects onthe PE, wasdependent on rhizosphere microbial community composition. Furthermore, these findings highlight the roles of the interaction between plants and their symbiotic microbial communities in affecting soil priming and improve our understanding of the potential microbial pathways underlying soil PEs.