Greenhouse Soil Research Articles

CONTRIBUTION OF PROTECTED AREAS TO AVOIDED DEFORESTATION IN MATO GROSSO, BRAZIL

Protected Areas (PAs) are important spaces for the protection of biodiversity, capable of halting deforestation and collaborating in the intentions to reduce climate change. The objective of this work is to demonstrate the importance of Protected Areas in the state of Mato Grosso in the avoided deforestation and to estimate their contribution to the reduction of greenhouse gas emissions and soil erosion. The methodology was based on secondary data and the use of a GIS environment. As a result, it was found that in Mato Grosso there are 120 PAs between federal, state and municipal, they protect 6% of the territorial area of the state and most are located in the Amazon biome. Mato Grosso’s Forest cover in 2019 was 49.8 million hectares, with an estimated forest carbon stock of over 16.4 GtCO2. The PAs were created over the years in the state, but the greatest number occurred between 2000 and 2005 and together, in 2019 they were responsible for preventing the deforestation of more than 726,000 hectares of forest, 10 million tons of erosion and storing 281 million tons of carbon, which if traded on the credit market would have an estimated value of more than US$1.25 million. If the PAs did not exist and if deforestation were to be carried out, the cost of replacing this area would be more than US$2.73 billion. Therefore, the importance of PAs in environmental conservation and in the economy related to forest cover is notorious.

Benefits of organic amendments on soil C stock may be offset by increased methane flux in rice paddy field

Periodic application of organic manure (OM) has been suggested to increase soil carbon stock and mitigate global warming. However, in irrigated rice fields, OM amendment greatly increases methane (CH4) emissions, which in turn may offset the effect of increased soil carbon storage on mitigating global warming. Research on the effects of OM application on net global warming potential that integrates greenhouse gas (GHG) fluxes and soil carbon stocks change in rice cultivating systems has been elusive. To determine the impact of organic amendments on global warming in a rice paddy, chemical (NPK) and organic fertilization were installed, and straw removal and recycling plots were added in two fertilization treatments. Annual CH4 and nitrous oxide (N2O) fluxes were evaluated using the static closed chamber method. Soil C stock changes were estimated using the net ecosystem C budget (NECB) which indicates the difference between C input and output. In chemical fertilization, straw removal decreased soil C stock by an average of 751 kg C ha−1 year−1, but straw recycling significantly increased soil C stock by an average of 464 kg C ha−1 year−1. In organic fertilization, soil C stock was strongly affected by cover crop productivity. Under favorable climatic conditions for cover cropping, soil C stocks were greatly increased by green manuring and even more so by straw recycling. However, under an unfavorable climate, soil C stock was not statistically increased, regardless of straw addition. Straw recycling increased annual CH4 flux by approximately 220–310 and 130–190% over straw removal in chemical (7.9 Mg CO2-eq. ha−1 year−1) and organic fertilization (40 Mg CO2-eq. ha−1 year−1), respectively, but negligibly affected N2O flux. Irrespective of fertilization background, net GWP was mainly decided by CH4 flux with 54–98% coverage, and then followed by soil C stock change and N2O flux. As a result, straw addition increased net GWP by around 110–140 and 120–150% over straw removal in chemical and organic fertilization, respectively. Rice yield was stable between years in the chemical fertilization but showed a big difference in organic fertilization, due to the difference in cover crop biomass productivity. However, rice productivity was not significantly affected by straw recycling. Organic amendment and straw applications increased greenhouse gas intensity (GHGI) by an average of 131% and 269% in a rice paddy, respectively, due to a high increase of CH4 flux but a low increase of soil C stock. In conclusion, more effective OM management which can decrease CH4 emissions and increase SOC stock is required in rice paddies.

A balance among irrigation and fertilization regimes to reduce greenhouse gases emissions from saline and alkaline soils

AbstractAgricultural practices of nitrogen and irrigation overuse bring lots of environmental problems, such as greenhouse gases (GHGs) emissions, soil, and water pollution. With the fast expansion of saline and alkaline agricultural soils in the Tarim River Basin, field practice must be very cautious facing water limitations and global warming. The GHGs were measured 1–2 times weekly and water and fertilizer use efficiency were evaluated under five treatments: (1) fallow (Control); (2) no N (kg N ha−1) and no irrigation (mm) (0N0W); (3) 200 and 355 (LNLW); (4) 230 and 475 (MNMW), and (5) 320 and 655 (HNHW) (traditional treatment) from 2018 to 2019 under maize in Aksu in the Tarim River Basin. The GHGs increased with fertilization and irrigation. The cumulative GHGs were 0.6–5.9 Mg CO2–C ha−1, 0.2–3.6 kg N2O–N ha−1, and increased significantly with biomass increase. The cumulative CH4 was −0.03 to −0.12 kg C ha−1. The MNMW resulted in the highest average water use efficiency (27 kg ha−1 mm−1), irrigation water use efficiency (32 kg ha−1 mm−1), and agronomic N use efficiency (44 kg kg−1), but the lowest greenhouse gas intensity (0.4 kg CO2‐eq ha−1 grain yield). The MNMW reduced the average of 10 mm water, 5 kg N ha−1 fertilizer, and 4 × 10−3 kg CO2‐eq ha−1 GHGI earning 1 t ha−1 maize compared to HNHW. The CO2 emission had a strong relationship with temperature (T) and soil moisture (W) (CO2 emission = (exp (a + bW + cW2)) Q10(T‐20)/10)) (R2 = 0.59–0.92). The lowest was in the LNLW treatment in 2019; the highest was in the HNHW in 2018). The emission of CO2 responding to fertilization was below the global trend, but that of N2O was above under maize in saline and alkaline soils (pH 7–9). In conclusion, MNMW was the best field management to mitigate GHGs with the highest water and fertilizer use efficiency under maize in saline and alkaline soils in Tarim River Basin, where had the higher N2O emission risk.

Dynamics of greenhouse gas fluxes and soil physico-chemical properties in agricultural and forest soils

Abstract Examination of greenhouse gas (GHG) fluxes (CO2, CH4, and N2O) in soils is crucial for developing effective strategies to mitigate climate change. In this study, we investigated the GHG fluxes in agricultural and forest soils to explore the changes in soil GHG fluxes, and assess the relationships of GHGs with other physico-chemical properties. Results show that forest soils have a higher CO2 flux, while agricultural soils have a higher N2O flux due to fertilizer application and heterotrophic nitrification. Forest soils act as a CH4 sink, which are connected with increased porosity and decreased bulk density. In agricultural soils, CO2 and N2O were strongly linked with NH4+, soil temperature, pH, soil organic carbon, total nitrogen, plant-available phosphorous, and microbial biomass nitrogen (mbN) but were negatively connected with bulk density and microbial biomass carbon (mbC). In contrast to CO2 and N2O, CH4 in agricultural soils exhibited inverse relationships with all physico-chemical properties. In forest soils, CO2 and CH4 were positively correlated with soil temperature and mbC, and mbN and N2O were negatively correlated with bulk density and pH. This study highlights the critical need to comprehend the complex relationship between soil physico-chemical properties and GHG fluxes for effective climate change mitigation.

Mung Bean Is Better Than Soybean in the Legume–Wheat Rotation System for Soil Carbon and Nitrogen Sequestration in Calcareous Soils of a Semiarid Region

Small changes in soil aggregates-associated organic carbon and soil nitrogen (N) can induce huge fluctuations in greenhouse gas emissions and soil fertility. However, there is a knowledge gap regarding the responses to long-term continuous rotation systems, especially in N-fixing and non-N-fixing crop wheat in terms of the distribution of soil aggregates and the storage of soil carbon (C) and N in aggregates in the semiarid calcareous soil of Central China. This information is critical for advancing knowledge on C and N sequestration of soil aggregates in rainfed crop rotation systems. Our aim was to determine which legume (soybean (Glycine max)– or mung bean (Vigna radiata)–wheat (Triticum aestivum) rotation practice is more conducive to the formation of good soil structure and C and N fixation. A 10-year field experiment, including a soybean (Glycine max)–winter wheat (Triticum aestivum) rotation (SWR) with yield increments of 2020 compared to 2010 achieving 18.28% (soybean) and 26.73% (wheat), respectively, and a mung bean (Vigna radiata)–winter wheat rotation (MWR) achieving 32.66% (mung bean) and 27.38% (wheat), as well as farmland fallow, was conducted in Henan Province, China. The soil organic carbon (SOC), N content in the soil, and the soil aggregates were investigated. Legume–wheat rotation cropping enhanced the proportion of the >2 mm soil fractions and reduced the <0.053 mm silt + clay in the 0–40 cm soil profile. In the 0–30 cm soil layer, the SWR had a greater increment of the >2 mm aggregate fractions than the MWR. Two legume–winter wheat rotations enhanced the C and N sequestration that varied with soil depths and size fractions of the aggregate. In contrast, the MWR had greater SOC stocks in all fractions of all sizes in the 0–40 cm soil layers. In addition, the greater storage of N in the macro-, micro-, and silt + clay fractions was observed in the 0–30 cm layers; the MWR enhanced the C/N ratios in most of the size aggregates compared with the SWR. The MWR cropping system is more beneficial to the formation of good soil structure and the increasement of C and N reserves in soil. Thus, these findings show that mung bean, in contrast with soybean in the legume–wheat rotation system of a semiarid temperate zone, may offer soil quality improvement.

Biostimulants as a Means to Alleviate the Transplanting Shock in Lettuce

When transplanting vegetable plants in the field, the transplants undergo a small or large setback in growth, known as transplanting shock. Various practices are commonly applied to reduce the transplanting shock. In the past two decades, several studies have shown that the application of microbial and non-microbial biostimulants can enhance plant tolerance against abiotic stresses. However, there is no information on the effect of applying biostimulants at the time of transplanting in mitigating the transplanting shock of lettuce transplants in the field. Lettuce seedlings transplanted into the soil of an unheated plastic greenhouse were treated with two biostimulants, one microbial (Bactiva®) and one non-microbial (Isabion®), on the day of transplanting and after 14 and 21 days. During production, plant growth, and development, chlorophyll fluorescence and compositional parameters were determined. According to the results, the application of the non-microbial biostimulant had a significant effect on some measured parameters, with the leaves of the treated plants having a higher chlorophyll index (CCI) by 8%, as well as higher fluorescence parameters Fm/Fo, Fv/Fo, and Fv/Fm and area by 7, 10, 3, and 27%, respectively, but fewer total soluble phenols and lower fluorescence parameter ABS/RC by 7 and 26%, respectively, compared to the control untreated ones. The above may constitute some effects on the transplanting shock, without, however, being accompanied by significant effects on the number of leaves/plant, the leaf color parameters (L*, a*, b*, C*, and ho), and the chlorophyll (a, b, a + b), total carotenoid, dry matter, and nitrate content, along with the antioxidant capacity and plant fresh weight at harvest. However, a notable effect was that a greater percentage of plants at harvest had a fresh weight in the 351–400 class, while the greatest percentage of the control plants had a fresh weight in the 301–350 g class. In contrast, the application of the microbial biostimulant had no significant effect on any of the parameters determined compared to the control. Therefore, under the conditions of the present study, the effectiveness of biostimulant application at the time of transplanting on lettuce transplants is questionable.

Understanding Green Food Consumption Behavior

Food consumption is one of the most significant contributors to global environmental problems being responsible for a large share of greenhouse gas emissions, water scarcity, and soil pollution, among others. The demand for unsustainable food contributes to the food sector's environmental burden. Consequently, there has been a surge in research on green food consumption in the last ten years. Still, our understanding of green food purchase behavior is rather rudimentary and needs a comprehensive view. For this reason, the current study aims to understand green food purchase behavior through a literature review approach. The study explored and analyzed relevant theories and determinants in explaining green food purchase behavior. Additionally, the study also investigated the literature to identify research suggestions given by authors to improve future studies. The current review applied key term searches on the "Web of Science" database to find related literature. The search results found 69 articles published between 2015 and 2021 in peer-reviewed English-language journals. The findings include important descriptive bibliographical analysis and patterns and trends in green food consumption. Additionally, the research identified categories of determinants explaining green food purchase behavior. The review summarized the suggestions given by scholars in the literature to help future researchers for improvement.

Uncovering the dark side of agriculture: How land use intensity shapes soil microbiome and increases potential plant pathogens

Soil microbiome plays a critical role in maintaining key soil processes such as litter decomposition, nutrient cycling, and plant productivity. In this study, we aimed to investigate the variability of soil chemicals, microbial diversity, and composition in seven ecosystems i.e., Fagus sylvatica and Quercus ilex forests, a Mediterranean grassland and shrubland, a vineyard, a horticultural cultivation in open field and under greenhouse, across a gradient of land-use intensity in Southern Italy. Soil chemistry included pH, organic matter, total nitrogen, and C/N ratio, and soil microbiota was characterized by high-throughput sequencing of 16S and ITS genes. Our results showed that greenhouse soils had the highest pH, while Fagus had the lowest. Horticultural, greenhouse, and grassland soils had low levels of OM and total N, while shrubland had relatively high levels of OM, total N, and C/N ratio. Fagus soils, on the other hand, had the highest levels of OM, total N, and C/N ratio. Bacterial diversity was lowest in horticultural soils, whereas fungal diversity was highest in shrubland soils. Pseudomonadota were the predominant bacteria in Fagus, grassland, and vineyard soils, while Actinomycetota dominated in Quercus, shrubland, and greenhouse soils. However, Cyanobacteria was predominant in horticultural soils. On the other hand, the Ascomycota was predominant in all ecosystems except Quercus soils, where the Basidiomycota was dominant. Our bipartite network analysis revealed that bacteria are often the same in different ecosystems while fungi tend to be specific to a particular habitat. Moreover, in agricultural ecosystems, fungal pathogens belonging to Alternaria, Fusarium, Gibellulopsis, Stemphylium, Acremonium, and Curvularia are more abundant, especially in greenhouse. The findings of this study provide important insights into the variability of soil microbial diversity and community composition in different ecosystems, highlighting the essential role of preserving natural ecosystems while managing agricultural ones, given their higher abundance of pathogens.

Effects of long-term organic and inorganic fertilization on greenhouse gas emissions and soil nutrient stoichiometry in a rice–rice–fallow cropping system

Long-term use of organic and inorganic fertilizers can have a negative impact on greenhouse gas (GHG) emissions and nutrient stoichiometry in paddy soil. However, production of sufficient crops to meet food and feed demands globally requires the use of fertilizer in crop production. In the present study, we assessed the environmental impacts of five fertilizer treatments in a rice–rice–fallow cropping system: no fertilizer (CK); inorganic nitrogen, phosphorus, and potassium fertilizers (NPK); manure (M); inorganic phosphorus and potassium fertilizers with manure (PKM); and inorganic nitrogen, phosphorus, and potassium fertilizers with manure (NPKM). Soil parameters were analyzed to examine the relationships between GHG emissions, net ecosystem carbon budgets (NECBs), and soil nutrient stoichiometric ratios. Both the PKM and NPKM treatments increased grain yield and the soil carbon–nitrogen (C:N), carbon–phosphorus (C:P), and nitrogen–phosphorus (N:P) ratios compared to the CK treatment; they also decreased the nitrogen–potassium (N:K) ratio. In the combined fertilization treatments, the fallow season accounted for 9–13% of annual methane (CH4) emissions, whereas early rice accounted for 55–62 % and late rice contributed 38–45 %. Compared to the CK, PKM and NPKM fertilization increased the annual nitrous oxide (N2O) emissions by 52–73 % and 103–115 %, respectively, in both the rice and fallow seasons. In early rice, the C:P ratio and GHG intensity (GHGI) were negatively correlated with CH4 and N2O emissions, whereas both yield and CH4 emissions had strong positive associations with global warming potential (GWP). In the late rice season, GHGI was negatively correlated with carbon dioxide (CO2) and CH4 emissions, and N2O had strong positive associations with GWP. CO2 and N2O emission levels were greater from late rice than from early rice, although CH4 emissions from early rice contributed more to the annual GWP, resulting in higher carbon equivalent emissions but a lower carbon efficiency ratio in early rice output. A Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) optimization analysis suggested that PKM was the best fertilization method to improve yield while minimizing negative environmental impacts, followed in descending order by the NPKM, NPK, and M treatments.

A Novel Robust Screening Assay Identifies Pseudomonas Strains as Reliable Antagonists of the Root-Knot Nematode Meloidogyne incognita.

Forty-four bacterial strains isolated from greenhouse soil and beetroots were tested for their antagonistic activity against the plant-parasitic root-knot nematode (RKN) Meloidogyne incognita, which causes significant yield losses in a number of important crops worldwide. Through a novel combination of in vitro and on planta screening assays, Pseudomonas spp. 105 and 108 were identified as the most promising bacterial isolates. Both strains were evaluated for their potential to control different RKN population densities and as root protectants against nematode infestation. Regardless of the application method, both strains significantly reduced root galling caused by M. incognita. These two strains were subjected to whole genome sequencing and de novo genome assembly as a basis for phylogenetic and future functional characterization. Phylogenetic analysis revealed that both Pseudomonas strains cluster within the Pseudomonas fluorescens clade among previously characterized RKN antagonists and Pseudomonas-based biocontrol agents of plant diseases.

Metabolomics approach: a new application in suspect screening of 36 antibiotics in soil

ABSTRACT Soil contamination by antibiotics is a worldwide environmental issue, and it is essential to develop suspect screening methods of antibiotics in soil for their comprehensive risk assessment. In this study, a novel metabolomics approach by seeking ‘marker compounds’ on behalf of 36 antibiotics in the forest topsoil was developed based on the results of high performance liquid chromatography tandem mass spectrometry. About 10 µg/kg antibiotic concentration in soil was designed for metabolomics analysis. Principal component analysis and orthogonal partial least squares discriminant analysis support the existence of variables with evident inter-group differences, which were further discerned by S-plot plots, permutation tests and variable importance in projection to pick eligible variables as ‘marker compound’ candidates. Pairwise t-test and fold change of concentration were employed to validate these candidates. The results indicate that 36 ‘marker compounds’ were all correctly screened out, together with the good practicability test in the rural greenhouse soils, proving the feasibility of this novel metabolomics method, which was expected to present great superiority and wide application future in suspect screening of pollutants. The limits of detection for 36 antibiotics in soil were calculated to be 0.6–2.6 µg/kg.

Pratylenchus zeae a causative agent of Corn Root Rot in Jiangsu Province of China.

Corn (Zea mays L.) plays an important role in China's cash crops, not only as food, but a vital raw material for animal husbandry and industry (Li et al. 2022). Pratylenchus zeae is one of the most damaging root-lesion nematodes (RLN) that can result in decreased yield and quality of crops (Liu et al. 2017). In September 2020, five root/soil samples were collected from the rhizosphere of corn (cv. Zhengdan 958), which had weak growth and root brown lesions in Chenzhou Village, Taolin Town, Donghai County, Lianyungang City, Jiangsu Province of China. Nematodes were extracted from the collected samples using the modified Baermann funnel method (Hooper et al. 2005). RLN were found in all samples, an average of 46 RLN per gram of root and 138 RLN per 100 cm3 of soil. The obtained RLN females were sterilized with 0.3% streptomycin sulfate and then inoculated on each carrot disks individually to obtain the purified population. RLN were examined by morphological and molecular characteristics to confirm the species indentification. The main morphological measurements of adult (n = 15) included body length = 524.7 μm (mean) ± 15.1 (standard deviation) (range = 490.7 to 543.6 μm), stylet = 15.2 μm ± 0.8 (14.2 to 16.8 μm), tail length = 30.3 μm ± 2.5 (26.3 to 35.3 μm), a = 25.6 ± 1.3 (24.4 to 29.3), b = 5.3 ± 0.3 (4.7 to 5.8), c = 17.4 ± 1.4 (14.9 to 19.3), two annules on the lip region. No males were found in the specimens. The morphological characters of this population are consistent with the description of P. zeae (Castillo and Vovlas, 2007). Furthermore, DNA was extracted from individual nematodes. The primers of TW81/AB28 and D2A/D3B (Subbotin et al. 2006) were used to amplified the rDNA-ITS region and rDNA 28S D2-D3 region, respectively. The purified PCR products were ligated into One step ZTOPO-Blunt/TA vector and transformed to Escherichia coli strain DH5α, and then sequenced by Sunya Biotechnology Co., Ltd (Henan, China). The obtained seqences were submitted to NCBI. The rDNA-ITS sequences (669 bp, GenBank Accession No: OP456372 and OP466367) exhibited 95.0% to 97.1% of identity with P. zeae sequences (KU198980 and KU198975). The obtained D2-D3 region of the 28S rDNA sequences (782 bp, OP441397 and OP448675) exhibited 99.7% to 100% identity with P. zeae sequences (EU130893 and KY424269). Consequently, both morphological and molecular data confirmed the identity of P. zeae. To further confirm reproduction on corn, single corn seeds (cv. Zhengdan 958) were sown in eight 2-liter pots filled with 1.8-liter of sterilized soil in greenhouse at 28°C. About 15 days after sowing, each pot with one corn plant with the same growth status was selected to inoculate with 1,000 mixed stage nematodes of P. zeae , Eight pots of uninoculated corn plants were used as controls. After 60 days, the inoculated plants were harvested and brown lesions were observed on roots. No symptoms and nematodes was detected in the control. An average number of RLN per pot was 3,752 in soil and 1,183 in roots were extracted, the reproduction factor (final population/initial population) was 4.94, indicating that P. zeae infects and reproduces well on this corn cultivar. P. zeae has only been reported on corn in Guangxi Province, southern in China(Fang et al. 1994). To our knowledge, this is the fist report of P. zeae infecting corn in Jiangsu Province, eastern in China. As P. zeae can cause great damage to corn, necessary measures should be taken to prevent the spread of P. zeae to other areas.

Cow Manure Vermicomposting and an Initial Assessment of the Vermicompost Effect on the Production of Greenhouse Organic Crop Vegetables Under the Frame of Circular Economy

During the process of vermicomposting organic residues are broken down by earthworms and microorganisms, thus promoting germination, growth and yields of plants. This research aimed to study vermicomposted cow manure in order to be used as soil amendment for the production of organic early crops vegetables, in the light of sustainable development and circular economy. In the context of the study, earthworms initially composted the mixture of cow manure and straw, while chemical and microbiological composition of the produced vermicompost was determined and assessed. Afterwards, an experiment was carried out in order; a) to investigate the effects of cow manure vermicompost application on the chemical and microbial properties of greenhouse soil of the Green Unit of the Psychiatric Hospital of Thessaloniki and b) to relate these properties to growth responses and crop production of organic early crops vegetables cultivated in the greenhouse. The crops used for the experiment were Εruca sativa, Εruca vesicaria, parsley, celery and dill that were grown in vermicomposted soil of the greenhouse. Two vermicompost applications after sowing took place and one or two harvests as well. For all the five crops cultivated in the greenhouse, growth height was regularly monitored in order to calculate the corresponding growth rates. Furthermore, foliar diagnosis was performed for every crop. The results showed positive effect on growth rates of all five crops, indicating significant contribution of vermicomposting to the enhancement of crop production

Impact of biochar amendments on soil water and plant uptake dynamics under different cropping systems

AbstractApplication of biochar amendments in agricultural systems has received much attention in recent years. In this study, we assess the 5‐year impacts of biochar application on soil water and plant interactions for an irrigated fresh market tomato (Solanum lycopersicum) and a rainfed pasture (Poaceae) cropping system. In particular, we focus on three varieties of locally produced biochar from agricultural waste materials—almond shell, walnut shell, and almond pruning residues that are pyrolyzed using a mobile pyrolysis unit. We used the soil hydrological model HYDRUS‐1D to explicitly track seasonal and annual soil water fluxes through changes in water retention, drainage, evaporation, and plant water uptake under biochar application. Modeling results show that the application of biochar at 5% increased soil water availability within the top 20 cm for a rainfed system, irrespective of biochar amendment type. This is clearly indicative of higher plant water uptake and greater water use efficiency (WUE) under biochar application. In contrast, a similar biochar amendment for the irrigated system did not affect WUE, instead reducing seasonal soil evaporation loss and thereby reducing irrigation demand. In both cropping systems, year‐to‐year variability in precipitation significantly impacted the total amount of water saved under biochar application with certain amendments retaining more water than others. Given that biochar application increased water retention irrespective of cropping systems, we further used a simple approach to determine yield trade‐off, if any, between control and biochar treatments. Our economic balance clearly demonstrates that the water saved by amending soil with biochar does not offset the yield disparity if compensated with carbon credits and therefore, application of biochar should be actively considered for both its direct and indirect benefits to potential greenhouse gas mitigation (e.g., diverting orchard waste from open burning), water savings, and soil health.

Short‐term responses of soil organic carbon and chemical composition of particle‐associated organic carbon to anaerobic soil disinfestation in degraded greenhouse soils

AbstractAnaerobic soil disinfestation (ASD) is a short‐term practice to conquer soil degradation, yet its effects on soil organic carbon (SOC) and its composition remain unclear. A field experiment was conducted in degraded greenhouse soils (C3) that were previously used for production of vegetable (VP) and flower (FP), with three treatments (i.e., control, ST [maize straw addition [C4]] and ASD [both ST and water flooding]) for 21 days. Results indicated that the control soil lost 1.3 Mg C ha−1 in VP and 0.94 Mg C ha−1 in FP, while ST increased SOC storage by over 1.0 Mg C ha−1 in both VP and FP. The ASD increased SOC storage by over 2.0 Mg C ha−1 by forming new SOC and decreasing old SOC loss. Additionally, ASD increased OC concentration in particulate size fractions, particularly in particulate organic matter (POM) with lower basal respiration, and higher hydrophobicity as indicated by an increased ratio of C–H/C=O from POM observed by FTIR. The SEM‐EDS found an enhanced C signal in particle size fractions, especially in POM. Overlap of C, O, Si, Ca, and Fe in mineral‐associated organic matter upon ASD indicated the possible crosslinking between intra‐OC and minerals containing O, Si, Ca, and Fe. The ASD also controlled soil salinization and the pathogen Fusarium oxysporum, resulting in increased tomato yields in both VP and FP. Overall, apart from increasing tomato yields, ASD can enhance SOC storage by increasing OC in particle size fractions within a short term.

Indole-3-acetonitrile is a critical molecule with weed allopathic suppression function in broccoli (Brassica oleracea var. italica).

Cruciferous plants are frequently used for ecologically benign weed control in agricultural production. The varieties were the most effective, Most effective Broccoli varieties were screened using the entropy method-based topsis model at first. Result showed that Lvwawa and Lvbaoshi were most effective in allelopathic suppression on radishes. Column and thin-layer chromatography were used to extract the allelopathic compounds from broccoli residues, which contained various herbicidal active substances; among them, purified single-molecule indole-3-acetonitrile has a stronger inhibitory effect than pendimethalin (commercial herbicide). The weed inhibition rate increased with increasing broccoli residue dosage, with a 40 g/m2 broccoli residue dose yielding the highest suppression rate. Its effect was similar to that of indole-3-acetic acid. Too much of this substance leads to the plant's death. Moreover, broccoli residues had effective control effect on weeds in natural soils in greenhouse and field trials. The results demonstrated that broccoli residue could be used for weed management in field for abundant allopathic suppression molecules to weeds, and that Indole-3-acetonitrile is one of the most important allopathic molecule.

How to remediate sulfate-nitrate salinized greenhouse soil? An optimal combination of organic amendment, fertilizer and irrigation

Greenhouse soil secondary salinization is a widespread problem along the lower-middle reaches of the Yangtze River basin, which seriously deteriorates the yield and quality of vegetables. High multiple-cropping index of the greenhouse management needs intensive application of agrochemicals and frequent irrigation which led to significant soil salinization in this area. In this study, we investigated how to remediate the salinized plastic shed soils and improve the yield and quality of vegetables using various measures, including two types of irrigation (intermittent irrigation and 80% water-holding capacity), four types of organic matter (cow manure, mushroom residue, fermented sawdust, and half-fermented sawdust) with two application rates (2 g C kg−1 soil and 8 g C kg−1 soil), and two types of inorganic fertilizers (compound fertilizer with and without sulfate). Results showed that intermittent irrigation decreased either soil electrical conductivity from 1.55 to 0.36 mS cm−1 or the concentrations of soil nitrate from 507 mg kg−1 to 31 mg kg−1 and sulfate from 664 mg kg−1 to 114 mg kg−1 in the incubation period. This effect continued to the next two periods (before seed sowing and after the first harvest). After the second harvest, all these parameters had a recover trend but remained lower than those of the original soil. Half-fermented sawdust had the best effect for soil amelioration among the four organic amendments whilst the effects were not enhanced at higher application rate. Across the two continuous growing seasons (pak choi (Brassica rapa subsp. chinensis) in first season, cherry radish (Raphanus sativus L.) in second season), especially the second harvest season, the compound fertilizer without sulfates ameliorated soil degradation and maintained greater yield compared with sulfate-containing fertilizer. Therefore, application of 2 g C kg−1 half-fermented sawdust with intermittent irrigation and use fertilizer without sulfate was optimum for the degraded greenhouse soil remediation and vegetable yield improvement. This treatment could either decreased soil EC from 1.55 to 0.325 mS cm−1 or the concentration of soil nitrate from 507 to 89 mg kg−1 and sulfate from 664 to 266 mg kg−1 after continuous two growing seasons while the radish yield in second growing season was 71% higher than CK. These findings provided an economical and practical method to remediate sulfate-nitrate salinized greenhouse soil in a short period and designed a field management mode to maintain the efficacy.

Effects of grazing and nitrogen application on greenhouse gas emissions in alpine meadow

Overgrazing and injudicious nitrogen applications have increased emissions of greenhouse gases from grassland ecosystems. To explore the effects and potential mechanisms of grazing, nitrogen application, and their interaction with greenhouse gas (GHG) emissions, field experiments were conducted on the Qinghai-Tibet Plateau for three consecutive years. Alpine meadow plots were subjected to light (8 sheep ha−1) and heavy (16 sheep ha−1) stocking rates, with or without ammonium nitrate (NH4NO3) (90 kg N ha−1 yr−1) treatment to simulate soil nitrogen deposition. During early warm growth season (May–June), peak growth season (July–September), and early cold season (October–November), static-chamber gas chromatography was used to analyze the soil's greenhouse gas emissions (CO2, N2O, and CH4). Results indicated that light stocking rate (LG) led to an increase in cumulative CO2 and N2O emissions, while also promoting CH4 uptake. Conversely, heavy stocking rate (HG) produced contrasting outcomes. Additionally, nitrogen applications significantly increased the short-term CO2 and N2O fluxes peaks. Combined treatment of nitrogen application and light stocking rate (LG + N) resulted in increased CO2 and N2O emissions while decreased CH4 uptake, consequently leading to a significant increase in global warming potential. According to the structural equation model, we discovered that nitrogen application and grazing affected GHG fluxes both directly and indirectly through their impact on the environmental factors. Our findings suggest that in the context of increasing nitrogen deposition in the Qinghai-Tibet Plateau, a moderate increase in stocking rate is more effective than reducing grazing intensity for mitigating global warming potential in alpine meadow.

Speciation and microscale distribution of phosphorus compounds accumulated in continuously fertilized greenhouse soils

AbstractThe overuse of phosphate fertilizer results in the accumulation of surplus phosphorus (P) compounds in soil, and this trend is particularly intense in greenhouse farming. We aimed to characterize P compounds in greenhouse soils by comparing their speciation in soil samples collected from greenhouses and an open field. Two soil types with different phosphate sorption abilities, namely, Ultisol and Andisol, were considered. Phosphorus compounds in the soil were characterized by bulk soil analysis via acid extraction; molecular‐scale analyses by solid‐state 31P nuclear magnetic resonance and P K‐edge X‐ray absorption near edge structure and spatially resolved analyses by electron probe microanalyzer and micro‐X‐ray absorption near edge structure. Spectroscopic results showed that a larger proportion of P compounds associated with inorganic P compounds associated with calcium (Ca‐P) was present in the greenhouse soil than in the open‐field soil. Some P compounds in the greenhouse Andisol were Ca‐P, even though Andisol has a high phosphate sorption ability due to an abundance of aluminum‐bearing sorbents. Heterogeneously distributed spots of Calcium phosphate, most likely hydroxyapatite or tricalcium phosphate, were found at the microscale in the greenhouse Ultisol soil grain. In addition to the detection of poorly‐soluble Ca‐P, a larger proportion of Ca‐P was potentially plant available. Spatially resolved analyses showed that organic amendments containing Ca‐P were incorporated into the Andisol soil grains. Our study demonstrated that Ca‐P with different solubilities can serve as a source of phosphate even in soils of high phosphate sorption ability under greenhouse conditions.

Nonlinear effects of biochar on greenhouse gas emissions and soil microbial community composition under intensive vegetable production in South China

Biochar amendment in agroecosystems is proposed to mitigate the greenhouse (GHG) emissions and enhance multiple ecosystem services. However, it remains unclear whether and how various biochar amendment rates can influence soil microbial communities linking with GHG mitigation. In a two-year field experiment with five biochar amendment rates (0, 10, 20, 30 and 40 Mg ha−1), we determined cumulative GHG emissions, soil physiochemical properties and soil microbial community composition base one total phospholipid fatty acids (PLFA) under intensive vegetable production from Ultisols in southern China. Results showed that biochar amendment significantly decreased cumulative N2O emissions by 40–66 % during the whole study period (p < 0.01), whereas effects on CH4 emissions were inconsistent across the two study years. In addition, biochar amendment significantly decreased PLFAs and fungi/bacteria ratio by 4–31 % and 12–39 %, respectively. Annual global warming potential (GWP) was effectively reduced by biochar amendment, and random forest analysis showed that soil pH, C/N, humic acid (HA) and fungal PLFAs exhibited the highest mean predictor importance. The nonlinear correlations between the biochar amendment rate and GHG emissions mainly caused by soil pH, and the 20 Mg ha−1 biochar amendment rate was recommended because it produced the lowest GWP with the lowest economic costs. These findings demonstrated that various biochar amendment rates can differently alter GHG emissions and microbial properties under intensive vegetable production, which can provide new insights on optimal biochar amendment rates for GHG mitigation in agricultural production in China.