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Keywords = nitrogen-rich organic amendment

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21 pages, 5490 KiB  
Article
Impact of Reduced Chemical Fertilizer and Organic Amendments on Yield, Nitrogen Use Efficiency, and Soil Microbial Dynamics in Chinese Flowering Cabbage
by Jiaxin Xu, Jianshe Li, Xia Zhao, Zhen Liu, Hao Xu, Kai Cao and Lin Ye
Horticulturae 2025, 11(7), 859; https://doi.org/10.3390/horticulturae11070859 - 21 Jul 2025
Viewed by 306
Abstract
(1) Background: The escalating issue of soil degradation caused by excessive chemical fertilizer application poses significant threats to the sustainable development of Chinese flowering cabbage (Brassica campestris L. ssp. chinensis (L.) var. utilis Tsen et Lee) production. This research aimed to identify [...] Read more.
(1) Background: The escalating issue of soil degradation caused by excessive chemical fertilizer application poses significant threats to the sustainable development of Chinese flowering cabbage (Brassica campestris L. ssp. chinensis (L.) var. utilis Tsen et Lee) production. This research aimed to identify the impacts of reduced chemical fertilizer application integrated with organic amendments on cabbage yield and rhizosphere soil microenvironment characteristics. (2) Methods: A biennial field experiment was conducted during the 2022–2023 growing seasons at Lijun Town, Yinchuan City, Ningxia Hui Autonomous Region. Five treatments were tested: (i) Control (CK, no fertilizer); (ii) Conventional chemical fertilization (CF1, chemical fertilizer only); (iii) Reduced chemical fertilization (CF2, 30% less chemical fertilizer); (iv) CF2 + Well-decomposed chicken manure (FCM, 30% less chemical fertilizer + rotted chicken manure); and (v) CF2 + Vermicompost (FEM, 30% less chemical fertilizer + vermicompost). (3) Results: In 2023, the FCM treatment reduced electrical conductivity (EC) by 24.80% and pH by 2.16%, while the FEM treatment decreased EC by 31.13% and pH by 3.84% compared to controls. The FEM treatment significantly enhanced total nitrogen content by 12.71% and 8.85% relative to CF1 and FCM treatments, respectively. Compared to CF1, FEM increased soil organic matter content by 10.49% in 2022 and 11.24% in 2023. Organic fertilizer amendments elevated available nitrogen, phosphorus, and potassium levels while enhancing sucrase activity: FCM and FEM treatments increased sucrase activity by 23.62% and 32.00%, respectively, in 2022. Organic fertilization improved bacterial diversity and richness, optimized microbial community structure, and increased the relative abundance of Bacillus. It also upregulated microbial metabolic pathways related to carbohydrate and amino acid metabolism. Soil nutrients and bacterial community structure showed positive correlations with yield, whereas soil enzyme activities exhibited negative correlations. Key factors influencing yield were identified as Proteobacteria, Chloroflexi, available potassium, organic matter, available nitrogen, Actinobacteria, Firmicutes, total nitrogen, pH, and sucrase activity. (4) Conclusions: Integrated analysis of yield and soil microenvironmental parameters demonstrates that the fertilization regimen combining 30% chemical fertilizer reduction with vermicompost amendment (FEM) constitutes a more efficient fertilization strategy for Chinese flowering cabbage, making it suitable for regional promotion in the Ningxia area. Full article
(This article belongs to the Section Plant Nutrition)
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20 pages, 14184 KiB  
Article
Effects of Rare Earth Element-Rich Biochar on Soil Quality and Microbial Community Dynamics of Citrus grandis (L.) Osbeck. cv. Guanximiyou
by Zhiqi Chen, Liujun Feng, Zhiqiang Chen, Zhibiao Chen, Jie Wu and Qiang Lin
Agriculture 2025, 15(8), 895; https://doi.org/10.3390/agriculture15080895 - 20 Apr 2025
Viewed by 554
Abstract
Rare earth elements (REEs) are key resources of strategic importance, but pollution has increased due to uncontrolled mining. Although heavy metal hyperaccumulating plants are environmentally friendly, they require strict control during post-treatment, or they may cause secondary pollution. Therefore, their safe disposal plays [...] Read more.
Rare earth elements (REEs) are key resources of strategic importance, but pollution has increased due to uncontrolled mining. Although heavy metal hyperaccumulating plants are environmentally friendly, they require strict control during post-treatment, or they may cause secondary pollution. Therefore, their safe disposal plays a key role in the ecological restoration of REE mines. In this study, rare earth element (REE)-rich biochar was produced by pyrolyzing the REE hyperaccumulator Dicranopteris pedata. This biochar was then applied to the Citrus grandis (L.) Osbeck. cv. Guanximiyou soil amendment experiment to evaluate its effects on soil physicochemical properties and microbial indicators. Four treatments were established: CK (0% REE-rich biochar), BC1 (1% REE-rich biochar), BC3 (3% REE-rich biochar), and BC5 (5% REE-rich biochar). The BC5 treatment decreased soil REE bioavailability, thereby preventing REE pollution. The BC5 treatment also demonstrated the highest efficacy in improving soil total organic carbon (229.11%), total nitrogen (53.92%), total phosphorus (55.61%), total potassium (55.50%), available nitrogen (14.76%), available phosphorus (46.79%), and available potassium (159.42%) contents compared to CK. Furthermore, soil enzyme activities were significantly increased by BC5 treatment (p < 0.05). At the bacterial phylum level of classification, the bacterial diversity index (Chao1 and Shannon) exhibited elevated levels under BC5 conditions. Furthermore, the Chao1 index of fungal diversity exhibited a substantial augmentation of 55.67% (p < 0.05) in the BC5 treatment in comparison to the CK, and also significantly higher than the other treatments (p < 0.05). Our study showed that the composition of soil microorganisms was altered by REE-rich biochar. Proteobacteria, Acidobacteria, Actinobacteriota, and Chloroflexi are dominant among bacteria, while Ascomycota is dominant among fungi. Mantel and redundancy analyses showed that the most important environmental factor affecting the structure of soil microbial communities was pH, especially in the case of bacteria. In summary, this study showed that the application of 5% REE-rich biochar provided the best improvement in soil physicochemical properties and microbial diversity. These findings highlight its potential for soil remediation and provide new ideas for recycling heavy metal hyperaccumulating plant waste. Full article
(This article belongs to the Section Agricultural Soils)
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18 pages, 3897 KiB  
Article
Remediation of Coastal Wetland Soils Co-Contaminated with Microplastics and Cadmium Using Spartina alterniflora Biochar: Soil Quality, Microbial Communities, and Plant Growth Responses
by Jing Shi, Xiangyu Pan, Weizhen Zhang, Jing Dong, Yu Zhao, Jiao Ran, Dan Zhou, Guo Li and Zheng Zheng
Agronomy 2025, 15(4), 877; https://doi.org/10.3390/agronomy15040877 - 31 Mar 2025
Viewed by 939
Abstract
Biochar, an eco-friendly soil amendment, holds promise for remediating contaminated soils, yet its impacts on coastal wetland soils under combined microplastic (MP) and heavy metal (HM) pollution remain underexplored. This study examined the efficacy of 2% Spartina alterniflora-derived biochar (BC) in rehabilitating [...] Read more.
Biochar, an eco-friendly soil amendment, holds promise for remediating contaminated soils, yet its impacts on coastal wetland soils under combined microplastic (MP) and heavy metal (HM) pollution remain underexplored. This study examined the efficacy of 2% Spartina alterniflora-derived biochar (BC) in rehabilitating soils co-contaminated with cadmium (Cd) and two MPs—polyethylene (PE) and polylactic acid (PLA)—at 0.2% and 2% (w/w). The results indicated that biochar significantly elevated soil pH (8.35–8.43) and restored electrical conductivity (EC) to near-control levels, while enhancing organic matter content (up to 130% in PLA-contaminated soils), nutrient availability (e.g., phosphorus, potassium), and enzyme activity. Biochar reduced bioavailable Cd by 14–15% through adsorption and ion exchange. Although bacterial richness and diversity slightly declined, biochar reshaped microbial communities, enriching taxa linked to pollutant degradation (e.g., Proteobacteria, Bacteroidota) and upregulated functional genes associated with carbon, nitrogen, and sulfur cycling. Additionally, biochar boosted Suaeda salsa (S. salsa) biomass (e.g., 0.72 g/plant in A1B) and height (e.g., 14.07 cm in E1B) while reducing Cd accumulation (29.45% in shoots) and translocation. Remediation efficiency was most pronounced in soils with 0.2% PLA. These findings bridge critical knowledge gaps in biochar’s role in complexly polluted coastal wetlands and validate its potential for sustainable soil restoration. Full article
(This article belongs to the Section Agroecology Innovation: Achieving System Resilience)
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18 pages, 3226 KiB  
Article
Enhancing Clay Soil Productivity with Fresh and Aged Biochar: A Two-Year Field Study on Soil Quality and Wheat Yield
by Salih Demirkaya, Abdurrahman Ay, Coşkun Gülser and Rıdvan Kızılkaya
Sustainability 2025, 17(2), 642; https://doi.org/10.3390/su17020642 - 15 Jan 2025
Cited by 2 | Viewed by 1534
Abstract
Biochar application has gained attention as an effective soil amendment for improving soil quality and increasing crop productivity, particularly in clay-rich soils facing challenges such as compaction, poor drainage, and nutrient limitation. This two-year field study evaluated the effects of fresh and artificially [...] Read more.
Biochar application has gained attention as an effective soil amendment for improving soil quality and increasing crop productivity, particularly in clay-rich soils facing challenges such as compaction, poor drainage, and nutrient limitation. This two-year field study evaluated the effects of fresh and artificially aged biochar on soil chemical, physical, and biological properties and wheat (Triticum aestivum) yield. The experiment was conducted on clay soil with treatments including no biochar application as a control (CK), 5 and 10 t ha−1 fresh biochar (B5, B10) and 5 and 10 t ha−1 aged biochar (AB5, AB10). The results showed significant improvements in soil pH, soil organic carbon, cation exchange capacity, total nitrogen, and plant-available water capacity, particularly with higher doses of biochar. In both years, the effects of the treatments on the soil quality index area (SQI-area) were found to be statistically significant. The AB10 treatment increased SQI-area by 19% compared to the CK in the first year and by 33% in the second year. In the first year, the highest grain yield was obtained from the AB10 treatment, reaching 5.25 t ha−1, which was 13% higher than the CK. In the second year, the highest yield was obtained from the B10 treatment, reaching 4.09 t ha−1, which was 24% higher than the CK. Despite these positive changes, the correlation between SQI and yield was not statistically significant, suggesting that crop yield may also depend on other interacting variables. These results highlight the potential of biochar, particularly aged biochar, as a sustainable practice to improve soil health and productivity in clay soils. Full article
(This article belongs to the Section Sustainable Agriculture)
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14 pages, 4726 KiB  
Article
Evaluating the Liming Potential of Mytilus galloprovincialis Shell Waste on Acidic Soils
by Alexios Lolas, Katerina Molla, Konstantinos Georgiou, Chrysoula Apostologamvrou, Alexandra Petrotou, Konstantinos Skordas and Dimitris Vafidis
Conservation 2024, 4(4), 778-791; https://doi.org/10.3390/conservation4040046 - 2 Dec 2024
Cited by 1 | Viewed by 1585
Abstract
The sustainable management of aquaculture by-products is crucial for advancing circular economy practices. Mediterranean mussel shell waste, rich in calcium carbonate, presents a sustainable alternative to conventional liming materials, especially for mitigating soil acidification, a very important and common issue that limits crop [...] Read more.
The sustainable management of aquaculture by-products is crucial for advancing circular economy practices. Mediterranean mussel shell waste, rich in calcium carbonate, presents a sustainable alternative to conventional liming materials, especially for mitigating soil acidification, a very important and common issue that limits crop productivity. This study evaluated the effectiveness of processed mussel shell waste in enhancing soil pH, organic matter, and nutrient availability. A 180-day pot experiment using highly acidic soil (pH < 4.5) collected from a local field was conducted in a Completely Randomized Design. Treatments involved two grain sizes of mussel shell powder (Fine: <1 mm; Coarse: 1–2 mm) at rates between 0.1 and 6%. Treated soil pH was measured monthly, whereas organic matter, available phosphorus (P), and exchangeable potassium (K) were measured at the beginning and the end of the experiment. The results revealed significant improvements in pH, organic matter, available phosphorus (P), and exchangeable potassium (K), particularly in the Fine Powder treatments. However, total nitrogen (N) remained unaffected. These findings highlight the potential of mussel shells as an eco-friendly and cost-effective amendment, advancing sustainable agriculture and waste recycling, thus contributing to broader conservation efforts by reducing the environmental footprint of aquaculture waste and supporting biodiversity and ecosystem resilience through sustainable resource management. Full article
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15 pages, 6611 KiB  
Article
Effects of Microbial Organic Fertilizer, Microbial Inoculant, and Quicklime on Soil Microbial Community Composition in Pepper (Capsicum annuum L.) Continuous Cropping System
by Chengfu Zhang, Limin Zhang, Yang Cao, Sunjian Zhang, Chao Hou and Chaosheng Zhang
Horticulturae 2024, 10(11), 1142; https://doi.org/10.3390/horticulturae10111142 - 27 Oct 2024
Cited by 2 | Viewed by 1589
Abstract
The additions of microbial organic fertilizer (MOF), a microbial inoculant (MI), and quicklime (Q) are considered to be sustainable practices to restore land that has been damaged by continuous cropping of pepper (Capsicum annuum L.). However, the combined effects of these three [...] Read more.
The additions of microbial organic fertilizer (MOF), a microbial inoculant (MI), and quicklime (Q) are considered to be sustainable practices to restore land that has been damaged by continuous cropping of pepper (Capsicum annuum L.). However, the combined effects of these three additives on pepper yield, soil chemical properties, and soil microbial communities were unclear. The experimental design consists of 13 treatment groups: the untreated soil (control); soil amended solely with three treatments for each of MOF (1875–5625 kg ha−1), MI (150–450 mL plant−1), and Q (1500–4500 kg ha−1); and soil amended with combinations of MOF, MI, and Q at three comparable concentrations. A significant increase in pepper fruit diameter, length, yield, and soil available nitrogen, phosphorus, and potassium contents occurs upon exclusive and combined applications of MOF, MI, and Q. Pepper yield was greatest (29.89% more than control values) in the combined treatment with concentrations of 1875 kg ha−1 MOF, 150 mL plant−1 MI, and 1500 kg ha−1 Q. The application of Q increased soil pH and reduced soil–fungal richness. The application of MOF, MI, and Q increased the relative abundance of bacterial genera and the complexity of bacterial and fungal co-occurrence networks compared with control levels. The combined application of MOF, MI, and Q resulted in the greatest microbial network complexity. A Mantel test revealed the key role of soil available nitrogen content and bacterial diversity in the regulation of pepper growth and yield. We conclude that the combined application of MOF, MI, and Q improves soil nutrient availability and modifies soil microbial community composition, significantly promoting plant growth and pepper yield during continuous cultivation. Full article
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22 pages, 1732 KiB  
Article
Physicochemical Characterization of Broiler Poultry Litter from Commercial Broiler Poultry Operation in Semiarid Tropics of India
by Thirunavukkarasu Maruthamuthu, Sivakumar Karuppusamy, Ramesh Veeramalai, Murali Nagarajan, Purushothaman Manika Ragavan, Mahimairaja Santiago, Bharathy Nallathambi, Anandha Prakash Singh Dharmalingam, Karthika Radhakrishnan, Ajaykumar Ramasamy, Shri Rangasami Silambiah Ramasamy and Thriruvenkadan Aranganoor Kannan
Agriculture 2024, 14(10), 1708; https://doi.org/10.3390/agriculture14101708 - 29 Sep 2024
Viewed by 2020
Abstract
This study characterized the physicochemical properties of broiler poultry litter (BPL) produced from intensively reared commercial broilers that were collected from 110 commercial poultry farms at the end of the production cycle (sixth week). A further 20 samples were collected from the end [...] Read more.
This study characterized the physicochemical properties of broiler poultry litter (BPL) produced from intensively reared commercial broilers that were collected from 110 commercial poultry farms at the end of the production cycle (sixth week). A further 20 samples were collected from the end use point where BPL was utilized as a soil amendment by the farmers after a period of storage for improving poultry litter management practices, developing new litter treatment technologies, or enhancing its use as a sustainable resource. The dry matter (DM), moisture, ash, organic matter (OM), and organic carbon (OC) from the manure samples were 83.04, 16.96, 27.08, 72.92, and 42.39%, respectively. The pH, electrical conductivity (EC) (dS m−1), and Kjeldahl nitrogen (N) were 8.43, 5.74, and 24.2 g kg−1, respectively. The BPL from the cement floor had higher levels of P and K than the mud floor. The correlation studies revealed that the OM, C, N, and Zn had significant positive correlations; pH, moisture, and ash had positive correlations; and EC, DM, and Ca had positive correlations. The EC level of BPL negatively correlated with pH, Fe, and Mn. The N content was found to have a highly significant (p < 0.01) positive correlation with the OM, OC, Ca, and Zn content of BPL, and it was found to have a highly significant (p < 0.01) negative correlation with the ash content, pH, and K content of BPL. The P content of BPL showed a positive correlation (p < 0.01) with the K content and a negative correlation with the Zn (p < 0.05) and Fe (p < 0.01) contents of BPL. Zn was found to be negatively (p < 0.01) correlated with the ash content; the pH; and the K, Fe, and P content of BPL. According to the findings of this study, BPL as such at the end of the production cycle is rich in OM, nitrogen, macrominerals, and microminerals; however, at the point of utility (after a period of storage of 4 to 6 months), there was a loss of OM, N, and mineral concentrations, highlighting the importance of proper storage and composting. Overall, this study on the physicochemical properties of broiler poultry litter is crucial for improving agricultural practices, protecting the environment, and preserving the health and safety of human beings and livestock. Full article
(This article belongs to the Section Farm Animal Production)
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14 pages, 2508 KiB  
Article
Effect of Biochar on Composting of Cow Manure and Kitchen Waste
by Felicien Sebahire, Faridullah Faridullah, Muhammad Irshad, Aziz Ur Rahim Bacha, Farhan Hafeez and Jean Nduwamungu
Land 2024, 13(10), 1545; https://doi.org/10.3390/land13101545 - 24 Sep 2024
Cited by 2 | Viewed by 2655
Abstract
Composting is a common method for managing organic waste and creating nutrient-rich soil amendments. Recently, biochar, a carbon-rich material from biomass pyrolysis, has been noted for potentially improving composting. This study examines the impact of adding biochar to compost made from cow manure [...] Read more.
Composting is a common method for managing organic waste and creating nutrient-rich soil amendments. Recently, biochar, a carbon-rich material from biomass pyrolysis, has been noted for potentially improving composting. This study examines the impact of adding biochar to compost made from cow manure and kitchen waste through a controlled lab experiment. The treatments were labeled as CMX (cow manure), KWX (kitchen waste), and CMKWX (both) with X being the percentage of CM, KW, and CMKW minus that of biochar in the mixture. Key parameters such as temperature (T), pH, and electric conductivity (EC) were tracked during the composting processes, and the final composts were analyzed for total nitrogen (N), available nitrogen (AN), total phosphorus (TP), available phosphorus (AP), total potassium (TK), organic carbon (OC), calcium (Ca2+), magnesium (Mg2+), and organic matter (OM). The results showed that adding less than 10% biochar influenced composting positively. Specifically, 5% biochar amendment led to higher thermophilic temperatures (45–57 °C) and stable pH levels (6.3–8.7) compared to controls. However, biochar did not significantly enhance EC, which peaked at 1.78 dS/m in both the control and 5% biochar treatments. Nutrient analysis revealed that biochar increased Ca2+ (13.62 meq/g) and Mg2+ (5.73 meq/g) retention in CM composts (CM85 and CM100). The highest OM content was 16.84% in CM90, while the lowest was 3.81% in CM95. Higher OM negatively affected TN, with CM treatments having more OM and KW treatments having more TN. TP and TK were higher in control treatments without biochar. This study highlights the benefits of integrating biochar with organic waste for enhancing compost nutrient profiles and soil fertility. It was observed that the more diverse the compost feedstock, i.e., CMKW, the higher the nutrient content for treatments containing less than 10% biochar. Full article
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18 pages, 1618 KiB  
Article
Composts Obtained by Mixing Hop Leaves with Wheat Straw or Farmyard Manure Improved Soil Properties and Increased Microbial Communities
by Sandra Afonso, Ermelinda L. Pereira, Margarida Arrobas, M. Ângelo Rodrigues and Altino Choupina
Horticulturae 2023, 9(12), 1304; https://doi.org/10.3390/horticulturae9121304 - 5 Dec 2023
Viewed by 1915
Abstract
Hop (Humulus lupulus L.) leaves are rich in nutrients, particularly nitrogen (N). After harvest, they can be recycled through composting for use as a soil amendment. In this study, we report the effect of composts obtained from mixtures of hop leaves with [...] Read more.
Hop (Humulus lupulus L.) leaves are rich in nutrients, particularly nitrogen (N). After harvest, they can be recycled through composting for use as a soil amendment. In this study, we report the effect of composts obtained from mixtures of hop leaves with other organic materials (wheat straw, farmyard manure, and ash from hop stems) at different ratios on soil properties and microbial diversity. Data on total N, total organic carbon (TOC), microbial N (Mic-N), microbial C (Mic-C), soil basal respiration (SBR), metabolic quotient (qCO2), Mic-C/TOC ratio, acid phosphatase activity (APA), microbial density, and species identification were assessed after each one of the two growing seasons of potted lettuce (Lactuca sativa L.). The diversity of microbial species was evaluated using Simpson and Shannon diversity indexes, and the interactions between soil properties and the microbial community were explored. Higher microbial activity was found among the soils amended with leaves plus straw (HS), which exhibited higher levels of TOC, APA, Mic-N, and total N in the first growing cycle and higher levels of Mic-C, Mic-C/TOC, SBR, TOC, and Mic-N in the second growing cycle. Fungi identified belong to the Ascomycota and Zygomycota phyla, while bacteria belong to the Actinobacteria, Bacillota, Bacteroidetes, Firmicutes, and Proteobacteria phyla. Differences in the prevalent microbial genera were observed between compost treatments and growing cycles. Correlation analysis revealed significant relationship between soil bacteria and fungi abundance and higher levels of N and C in the soils, indicating the relevance of specific microbial genera, such Acrostalagmus, Doratomyces, Talaromyces, and Aspergillus fungi, as well as Gordonia and Bacillus bacteria. Overall, the results indicate that hop leaves-based compost, particularly with a higher proportion of leaves and straw, influenced the composition of the soil microbial community, ultimately enhancing soil N availability for plant development. Full article
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17 pages, 898 KiB  
Article
Effect of Bat Guano and Biochar on Okra Yield and Some Soil Properties
by Paulo Dimande, Margarida Arrobas and Manuel Ângelo Rodrigues
Horticulturae 2023, 9(7), 728; https://doi.org/10.3390/horticulturae9070728 - 21 Jun 2023
Cited by 10 | Viewed by 3960
Abstract
The difficulty in obtaining commercial fertilizers by smallholder farmers in sub-Saharan Africa makes it very important to optimize the use of local organic resources. In VilanKulo, Mozambique, a study was carried out on okra (Abelmoschus esculentus) over two growing seasons. The [...] Read more.
The difficulty in obtaining commercial fertilizers by smallholder farmers in sub-Saharan Africa makes it very important to optimize the use of local organic resources. In VilanKulo, Mozambique, a study was carried out on okra (Abelmoschus esculentus) over two growing seasons. The soil was a haplic, loamy-sand textured Lixisol. As organic amendments, bat guano and biochar were used. Bat guano is a phosphorus (P)-rich and low-carbon (C)/nitrogen (N)-ratio material from natural deposits on a cave floor. Biochar is a C-rich material prepared via an artisanal process using forest residues as a feedstock. Bat guano was applied at two rates (5 and 10 t ha−1) just before sowing. It was also applied at the same rates one month before sowing. Biochar was used at two rates (5 and 10 t ha−1) applied at sowing. Biochar and guano were mixed at the rates of 1 and 4 t ha−1 and 2 and 8 t ha−1, respectively, and applied at sowing. The experiment also used a non-fertilized control. Field trials were arranged in a completely randomized design with three replicates. The treatments that received high rates of guano tended to show significantly higher fruit yields (>10 t ha−1 as the two-year average) in comparison with the control, which showed the lowest average okra fruit yield (6.21 t ha−1). In the guano treatments, the apparent recovery by okra of some important nutrients, such as N, was greater than the amount of the nutrient contained in the guano itself. This result, together with many others related to the tissue nutrient concentration, soil properties and residual fertilizing value in guano plots, indicated a strong mineralization of guano during the growing season. This was probably due to its low C/N ratio and favourable environmental conditions for the mineralization process. The result also suggests some kind of manuring effect, i.e., a fertilizing effect of guano beyond what can be explained by the nutrient supply. The use of biochar increased the total organic C in the soil and cation exchange capacity (CEC) compared with the control but did not affect the variables related to plant performance. Overall, the results showed that farmers can benefit from the use of guano in the short term because it releases nutrients, while with the use of biochar, the benefits can arise in the long term by improving the soil properties. Full article
(This article belongs to the Section Plant Nutrition)
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18 pages, 1094 KiB  
Article
Biochemical Methane Potential of Mechanically and Enzymatically Pretreated Solid Olive Mill Waste
by Patrick Tai, Ruth Spierling, Jennifer Carroll and Stephanie Jung
Processes 2023, 11(3), 865; https://doi.org/10.3390/pr11030865 - 14 Mar 2023
Cited by 3 | Viewed by 2101
Abstract
Olive cake, the solid byproduct of three-phase centrifugation olive oil production, has a high organic and polyphenol content, rendering it an environmental threat when landfilled as well as limiting its animal feed potential. This residue can be a good candidate for biomethane production [...] Read more.
Olive cake, the solid byproduct of three-phase centrifugation olive oil production, has a high organic and polyphenol content, rendering it an environmental threat when landfilled as well as limiting its animal feed potential. This residue can be a good candidate for biomethane production due to its rich polysaccharide content (pectin, hemicellulose, and cellulose). Two strategies were compared to maximize biomethane production: destoning (i.e., removal of the seed fragments via mechanical means) and enzymatic pretreatment of the pulp. After 30 days of batch anaerobic digestion at 35 °C, both enzymatically pretreated and destoned olive cakes produced similar amounts of methane (~295 mL CH4/g volatile solids (VS)), 42% more than the control. A comparison of olive cake’s biomethane yields with a broad range of agricultural residues in the literature demonstrated its suitability for biomethane production. Additionally, the digestate recovered from the anaerobic digestion of olive cake had high Kjeldahl nitrogen contents (3.6%, db) and low polyphenol concentrations (0.02 mg gallic acid equivalent (GAE)/g), qualifying it as an ingredient for soil amendment. This study demonstrated olive cake can be diverted from landfills for second-generation biofuel production, and that the resulting digestate may have value for soil amendment. Full article
(This article belongs to the Special Issue 10th Anniversary of Processes: Women's Special Issue Series)
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19 pages, 7109 KiB  
Article
Beneficial Effects of Biochar Application with Nitrogen Fertilizer on Soil Nitrogen Retention, Absorption and Utilization in Maize Production
by Changjiang Li, Cunyou Zhao, Ximei Zhao, Yuanbo Wang, Xingjun Lv, Xiaowei Zhu and Xiliang Song
Agronomy 2023, 13(1), 113; https://doi.org/10.3390/agronomy13010113 - 29 Dec 2022
Cited by 43 | Viewed by 6359
Abstract
The irrational use of nitrogen (N) fertilizer has become a major threat to soil quality and food security, resulting in serious ecological and environmental problems. Holistic approaches to N fertilizer application are required to maintain a high N utilization efficiency (NUE) and sustainable [...] Read more.
The irrational use of nitrogen (N) fertilizer has become a major threat to soil quality and food security, resulting in serious ecological and environmental problems. Holistic approaches to N fertilizer application are required to maintain a high N utilization efficiency (NUE) and sustainable agriculture development. Biochar is an efficient carbon-rich material for amending soil quality and promoting crop N uptake, but knowledge pertaining to the promoting effects of biochar application on N fertilizers is still limited. In this study, a field plot experiment was designed to detect the combined effects of biochar (0, 15 and 30 t ha−1) and N fertilizer (204, 240 and 276 kg N ha−1) on the soil nutrient levels, NUE, plant growth performance and crop production of maize. The results demonstrated that the combined application of N fertilizer and biochar can significantly decrease the soil pH and increase the contents of soil organic carbon, mineral N, available phosphorus and potassium. The crop N uptake and N content were largely promoted by the addition of N fertilizer and biochar, resulting in higher leaf photosynthetic efficiency, dry matter accumulation and grain yields. The highest yields (14,928 kg ha−1) were achieved using 276 kg N ha−1 N fertilizer in combination with 15 t ha−1 biochar, and the highest NUE value (46.3%) was reached with 204 kg N ha−1 N of fertilizer blended with 30 t ha−1 of biochar. According to structural equation modeling, the beneficial effects of N fertilizer and biochar on the plant biomass of maize were attributed to the direct effects related to soil chemical properties and plant growth parameters. In conclusion, N fertilizer combined with biochar application is an effective strategy to enhance the utilization of N fertilizer and crop production for maize by increasing soil fertility, improving plant crop uptake and promoting plant growth. Full article
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13 pages, 837 KiB  
Article
Evaluation of the Effects of Returning Apple Shoots In Situ on Soil Quality in an Apple Orchard
by Enda Zhou, Sansan Lyu, Guodong Du and Deguo Lyu
Agronomy 2022, 12(11), 2645; https://doi.org/10.3390/agronomy12112645 - 27 Oct 2022
Viewed by 1864
Abstract
Fruit tree shoots are potential useful resources that are rich in carbohydrates and inorganic nutrients but that are not typically utilized in sustainable agriculture. Our objective was to evaluate the soil properties and soil quality of an orchard after returning apple shoots in [...] Read more.
Fruit tree shoots are potential useful resources that are rich in carbohydrates and inorganic nutrients but that are not typically utilized in sustainable agriculture. Our objective was to evaluate the soil properties and soil quality of an orchard after returning apple shoots in situ and to investigate the contribution rate of apple shoots as an exogenous source of organic carbon for fertility amendment of the apple root domain. One-year-old apple shoots were pruned in spring before budding, chopped into 10 cm sections and placed on the soil surface. Soil samples were collected in the first year and third year after returning the shoots. Principal component analysis, Pearson correlation analysis and soil quality index (SQI) comprehensive analysis methods, combined with fuzzy mathematics, were adopted to evaluate the effects of returning apple shoots on comprehensive soil quality, including the soil fertility indicators, soil exchangeable cations, soil neutral sugar and amino acids. Increases in soil organic carbon (SOC), available potassium (K), and available phosphorus (P) were observed in different layers of the orchard soil with returned shoots over time. The total nitrogen (N) content decreased by 18.75% and 13.79% in the 0–20 cm and 20–40 cm soil layers, respectively, in the first year, but increased significantly in the third year. Significant increases in exchangeable cations (Na+, Ca2+, Mg2+) in the 0–20 cm soil layer were also observed in the third year after returning shoots, compared to the control. In addition, obvious accumulation of glucose and xylose was observed in the 0–20 cm soil layer compared to the controls in the third year after returning shoots. The total water-soluble free amino acid contents in the third year after returning shoots were 1.08- and 1.16-times higher, respectively, than those of the controls in the 0–20 cm and 20–40 cm soil layers. The SQI in the third year was higher than that of the other treatments in the 0–20 cm soil layer. This study suggests that abandoned apple shoots used as a supplementary carbon source for orchards enhanced the soil fertility of different soil layers, regulated the soil micro environment, and improved the overall soil quality. Full article
(This article belongs to the Special Issue Nutrient Management in Orchards)
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9 pages, 269 KiB  
Article
Effects of Neem Seed Extract on Nitrate and Oxalate Contents in Amaranth Fertilized with Mineral Fertilizer and Cricket Frass
by Pranee Sriraj, Banyong Toomsan and Somchai Butnan
Horticulturae 2022, 8(10), 898; https://doi.org/10.3390/horticulturae8100898 - 29 Sep 2022
Cited by 2 | Viewed by 3449
Abstract
A vegetable’s high antinutrients, nitrate (NO3) and oxalate, could be remediated by neem seed extract. The combined use of neem seed extract with mineral fertilizer and cricket frass was conducted to evaluate their effects on amaranth’s tissue NO3 [...] Read more.
A vegetable’s high antinutrients, nitrate (NO3) and oxalate, could be remediated by neem seed extract. The combined use of neem seed extract with mineral fertilizer and cricket frass was conducted to evaluate their effects on amaranth’s tissue NO3 and oxalic acid contents by inhibiting nitrification. The effects of five soil amendments were investigated: unamended, mineral fertilizer, and three rates of cricket frass (3.125 Mg ha−1, 6.25 Mg ha−1, and 12.5 Mg ha−1), combined with two rates of neem seed extract: without (−Nm) and with (+Nm) extract. Only the neem extract applied to soils receiving mineral fertilizers decreased soil tissue NO3−N contents (0.82 g kg−1 for −Nm vs. 0.62 g kg−1 for +Nm). The oxalic acid content of amaranth decreased with mineral fertilizer (0.60 and 0.46 g kg−1 for −Nm and +Nm, respectively), yet increased with the higher rates of cricket frass (1.42–1.52 g kg−1 for −Nm, and 1.23–1.51 g kg−1 for +Nm) compared to the unamended soil (1.05 and 1.00 g kg−1 for −Nm and +Nm). Cations, including K, Ca, Mg, and Na derived from cricket frass, may enhance biosynthesis and the accumulation of oxalic acid. The neem seed extract decreased the tissue’s oxalic contents regardless of soil amendments. Full article
14 pages, 2131 KiB  
Article
Effects of Different Organic Amendments on Soil Improvement, Bacterial Composition, and Functional Diversity in Saline–Sodic Soil
by Liangliang Guo, Zhaoyang Nie, Jie Zhou, Shixin Zhang, Fenghua An, Lu Zhang, Tibor Tóth, Fan Yang and Zhichun Wang
Agronomy 2022, 12(10), 2294; https://doi.org/10.3390/agronomy12102294 - 24 Sep 2022
Cited by 24 | Viewed by 5333
Abstract
The agricultural productivity of farmland in Northeast China’s Liaohe Plain is restricted by the salinity and sodicity of the soils, which have additionally low organic matter content. In order to improve saline–sodic soils, organic amendments are frequently applied. Our objective was to clarify [...] Read more.
The agricultural productivity of farmland in Northeast China’s Liaohe Plain is restricted by the salinity and sodicity of the soils, which have additionally low organic matter content. In order to improve saline–sodic soils, organic amendments are frequently applied. Our objective was to clarify how different organic amendments affect the diversity and composition of soil microbes, as well as how these factors are related to crop yield. In 2020–2021, we conducted an experiment with different organic amendments. The treatments included the application of crop residue incorporation (SR), lignite humic acid (LHA; 6 ton/ha), or cow manure (FM; 30 ton/ha), and a control (CK). The results show that, compared with CK, the content of SOM in soil treated with organic amendments increased by 5.3–7.4 g/kg; the available potassium (AK) of the LHA treatment was significantly higher than that of the FM and SR treatments by 32.17 and 42.79 mg/kg, respectively; and the available phosphorus (AP) of the LHA treatment was significantly higher than that of the SR treatment by 7.19 mg/kg. The pH and EC1:5 values of the LHA treatment were significantly lower than those of CK by 1.36 units and 0.2 mS/cm, respectively. The application of organic amendments and changes in environmental conditions also significantly affected community structure and increased soil microbial richness and diversity. SR treatment increased the abundance of Acidobacteria. Further FAPROTAX (Functional Annotation of Prokaryotic Taxa) analysis showed that organic amendments can increase the abundance of microbes involved in the carbon and nitrogen cycle processes, such as aerobic_ammonia_oxidation, aerobic_chemoheterotrophy, nitrification, etc., which increases the kernel number per row and increases crop yield. LHA can increase the microbial abundance of the nitrogen cycle and reduce soil carbon mineralization, while also increasing soil nutrients and crop yield. This study provides a comprehensive understanding of the application of organic amendments in saline–sodic cultivated land. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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