Special Issue "Organic Wastes as a Source of Innovative Fertilizers, a Down-to-Earth Principle for Sustainable Agriculture"

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Soil and Plant Nutrition".

Deadline for manuscript submissions: closed (15 February 2021).

Special Issue Editor

Dr. Francesc Xavier Prenafeta Boldú
E-Mail Website
Guest Editor
Program Head at the Programme of Integral Management of Organic Waste (GIRO) , Institute of Agrifood Research and Technology (IRTA), Torre Marimon, E-08140 Caldes de Montbui, Spain
Interests: microbiology; environment; soil; molecular biology; energy; sustainability agricultural
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Special Issue Information

Dear Colleagues,

Turning agricultural organic wastes into fertilizers, soil improvers, growing media, and biostimulants is a keystone for the global development of circular bioeconomy. Organic byproducts generated along the whole food production chain (agricultural and industrial organic wastes, food losses, sewage sludge, etc.) contain nutrients, organic compounds, and microorganisms that can be transformed into a wide range of high-value bio-based products. These nutrients can replace conventional fertilizers manufactured or extracted from nonrenewable sources on which modern agriculture relies (i.e., synthetic ammonia, phosphate rock, and peat). Besides closing the cycle of nutrients, incorporating organic matter into the soil might contribute to the mitigation of climate change and to the long-term preservation of soil functionality and biodiversity. Yet, the utilization of organic wastes must also take into account biosafety and sustainability issues encompassing environmental, social, and economic impacts.

This Special Issue will focus on “organic wastes as a source of innovative fertilizers”. We welcome novel research, review, and opinion pieces covering all related topics, including the development of new organic fertilizers and related products, agronomical aspects, soil chemistry and microbiology, management and modelling solutions (i.e., life cycle assessment), case studies from the field, and policy positions.

Dr. Francesc Xavier Prenafeta Boldú
Guest Editor

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Keywords

  • circular economy
  • environmental emissions
  • nutrient cycles
  • organic fertilizers
  • organic wastes
  • soil biostimulants and biofertilizers
  • soil microbiology
  • sustainable agriculture

Published Papers (19 papers)

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Article
Microbiological Activity during Co-Composting of Food and Agricultural Waste for Soil Amendment
Agronomy 2021, 11(5), 928; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11050928 - 08 May 2021
Cited by 3 | Viewed by 818
Abstract
This study aims to establish the relationship between ambient parameters and the diversity, composition, and function of microbial communities that predominate at each stage of the co-composting of food and agricultural waste. Culture-based and culture-independent methods were used to investigate the changes in [...] Read more.
This study aims to establish the relationship between ambient parameters and the diversity, composition, and function of microbial communities that predominate at each stage of the co-composting of food and agricultural waste. Culture-based and culture-independent methods were used to investigate the changes in the microbiota. The favorable conditions of high initial humidity and C/N ratio caused a decrease in the richness and biodiversity of the microbiota when such conditions existed. During the thermophilic stage, the total microbial number increased, and active mineralization of organic matter was carried out by members of the genera Bacillus, Caldibacillus, Aspergillus, and Penicillium. The fungal community was sensitive to drastic temperature changes. Byssochlamys dominated among fungi during the transition from the mesophilic to the thermophilic stage and during cooling. The biodiversity increased with time and was associated with the dynamics of germination and nitrification indices, so that the more diverse the microbial community, the higher the properties of compost that stimulate plant growth and development. The microbial community of the mature compost, together with mineral plant nutrients ready for consumption and humic compounds, make this compost a good soil additive. Full article
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Article
A Rhizogenic Biostimulant Effect on Soil Fertility and Roots Growth of Turfgrass
Agronomy 2021, 11(3), 573; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11030573 - 18 Mar 2021
Cited by 2 | Viewed by 686
Abstract
The excessive use of chemical fertilizers can lead to severe environmental damages. In recent decades, the application of biostimulants to improve soil composition and stimulate plant growth has contributed significantly to environmental preservation. In this paper, we studied the effect of a rhizogenic [...] Read more.
The excessive use of chemical fertilizers can lead to severe environmental damages. In recent decades, the application of biostimulants to improve soil composition and stimulate plant growth has contributed significantly to environmental preservation. In this paper, we studied the effect of a rhizogenic biostimulant, obtained from fulvic acids, probiotics, and prebiotics, on the fertility of two types of soils, sandy and sandy loam soils, in which turfgrass was growing. Soil samples from plots treated with biostimulant and controls (untreated plots) were collected. The analyzed parameters from the soil include organic matter, microbial activity, soil chemical composition, catalase, dehydrogenase, and phosphatase enzyme activities. Moreover, root lengths was examined and compared in turfgrass species. The biostimulant application improved microbial activity, organic matter, and enzymatic activity in both types of soils. The soil calcium, potassium, magnesium, and phosphorus content increased with the biostimulant application, whereas pH and electrical conductivity decreased. The most relevant improvement was a 77% increase of calcium for sandy loam soil and 38% increase in potassium for sandy soil. Biostimulant application led to a significant increase in turf root length. This increase was greater for sandy soil than in sandy loam soil with an increment of 43% and 34% respectively, compared to control. Full article
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Article
Use of Agri-Food Composts in Almond Organic Production: Effects on Soil and Fruit Quality
Agronomy 2021, 11(3), 536; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11030536 - 12 Mar 2021
Viewed by 631
Abstract
The objective of this work was to study the agronomic effects of the application of agri-food composts in almond trees (Prunus dulcis L.) cultivated in two different areas with different almond varieties (cv. Guara and cv. Ferraduel), with both in organic [...] Read more.
The objective of this work was to study the agronomic effects of the application of agri-food composts in almond trees (Prunus dulcis L.) cultivated in two different areas with different almond varieties (cv. Guara and cv. Ferraduel), with both in organic farming conditions throughout two cropping cycles. To reach this objective, almond production and quality issues (seed production, kernel yield, nutrient contents and kernel quality), as well as several physico-chemical and biological properties of the amended soils at the beginning and at the end of each campaign were studied. The four composts used (C1, C2, C3 and C4) were elaborated mainly using exhausted grape marc (EGM) and other wastes (waste from orange juice production, OW; waste from tomato soup production, TW; cattle manure, CM; and sheep manure, SM). Two treatments were used as control treatments, one based on sheep manure and another without any amendment. The composts used produced similar results in kernel yield and production compared to the traditional treatment (sheep manure). However, the thickness of the kernel was higher in the treatments using composts with exhausted grape marc and sheep manure or tomato soup waste. In relation to the almond quality, few differences related to the effect of treatments were observed, except for the content of proteins, sucrose, some fatty acids and vegetal sterols. Full article
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Article
Animal Slurry Sanitization through pH Adjustment: Process Optimization and Impact on Slurry Characteristics
Agronomy 2021, 11(3), 517; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11030517 - 10 Mar 2021
Cited by 2 | Viewed by 851
Abstract
Sanitization by pH adjustment of dairy and pig slurries was evaluated for potential use as organic fertilizer in horticulture. This requires absence of Salmonella in 25 g of slurry and less than 1000 Escherichi coli colony-forming unit per gram of fresh slurry (Regulation [...] Read more.
Sanitization by pH adjustment of dairy and pig slurries was evaluated for potential use as organic fertilizer in horticulture. This requires absence of Salmonella in 25 g of slurry and less than 1000 Escherichi coli colony-forming unit per gram of fresh slurry (Regulation (EU) 2019/1009). Additives used in the alkalinization and acidification treatments, included hydroxide-salts and nitrogen-based reactants to increase slurry pH to a basic range (9.0–11.0) and concentrated H2SO4 to decrease slurry pH to an acidic range (5.5–3.5). While low-cost urea was unable to increase the slurry pH above 9.5, ammonia efficiently increased slurry pH to the targeted values (but enhanced the emissions risk), whereas the effect of Ca(OH)2 was hindered by its low solubility. Slurry sanitization by alkalinization was achieved at a pH of 9.5 for both slurries, using similar quantities of KOH or NaOH. KOH was selected for further tests since it provides a plant macronutrient. Acidification with concentrated H2SO4 was able to achieve sanitization by lowering the pH to 5.0. After a 60-d storage experiment with raw and treated slurries, the level of E. coli was below the sanitization limit for all samples. Storage had no significant impact on slurry characteristics, except for ammonium-nitrogen content. Acidification treatment minimized ammonia losses. Full article
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Article
Assessing the Effects of Digestates and Combinations of Digestates and Fertilizer on Yield and Nutrient Use of Brassica juncea (Kai Choy)
Agronomy 2021, 11(3), 509; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11030509 - 09 Mar 2021
Cited by 3 | Viewed by 723
Abstract
Anaerobic digestion of organic wastes produces solid residues known as digestates, which have potential as a fertilizer and soil amendment. The majority of research on digestate focuses on their fertilizer value. However, there is a lack of information about additional effects they may [...] Read more.
Anaerobic digestion of organic wastes produces solid residues known as digestates, which have potential as a fertilizer and soil amendment. The majority of research on digestate focuses on their fertilizer value. However, there is a lack of information about additional effects they may have on plant growth, both positive and negative. Understanding the effects of digestate on plant growth is essential to optimizing their use in agriculture and helping close the loop of material and energy balances. This greenhouse study evaluated the effects of two different digestates, a food waste digestate (FWD) and a lignocellulosic biomass digestate (LBD); a liquid fertilizer; and various combinations of fertilizer and digestates on plant growth, nutrient uptake and nutrient use efficiency (NUE) of Brassica juncea (kai choy) plants. It also evaluated potential negative attributes of the digestates, including salinity and possible biohazards. Combinations of LBD and fertilizer performed as well or slightly better than the fertilizer control for most parameters, including aboveground biomass and root length. These same combinations had significantly higher nitrogen use efficiency than the fertilizer control. Inhibitory effects were observed in 100% LBD treatments, likely due to the high electrical conductivity of the media from digestate application. Based on this research, LBD could partially replace mineral fertilizers for kai choy at up to 50% of the target nitrogen rate and may lead to increased plant growth beyond mineral fertilizers. FWD could replace up to 100% of the target nitrogen application, without causing significant negative effects on plant growth. Increasing the use of digestates in agriculture will provide additional incentives for the anaerobic digestion process, as it produces two valuable products: biogas for energy and digestate for fertilizer. Full article
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Article
Acidified Biogas Residues Improve Nutrient Uptake and Growth of Young Maize
Agronomy 2021, 11(2), 344; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11020344 - 15 Feb 2021
Cited by 1 | Viewed by 868
Abstract
Biogas residues (BGR) contain a variety of plant nutrients and are, therefore, valuable fertilizers. However, ammonia (NH3) emissions occur during slurry and BGR application. These emissions can be reduced by lowering the pH of the BGR. Acidification technology works well for [...] Read more.
Biogas residues (BGR) contain a variety of plant nutrients and are, therefore, valuable fertilizers. However, ammonia (NH3) emissions occur during slurry and BGR application. These emissions can be reduced by lowering the pH of the BGR. Acidification technology works well for slurry, but little is known about the effects on fertilizer properties of acidified BGR (ABGR). This study aimed to examine the impact of acidification on the chemical composition of BGR and its influence on plant growth of juvenile maize and the soil pH, as well as the soluble soil phosphorous (P) and manganese (Mn), after application of ABGR. The soluble amount of nutrients in BGR was compared with that in ABGR. In an outdoor pot experiment, BGR and ABGR were incorporated in soil, and maize was grown for 8 weeks. Two different BGR P levels were compared with (NH4)2HPO4 and a control treatment without additional P. BGR acidification increased dissolved amounts of P from 15% to 44%, calcium from 6% to 59%, magnesium from 7% to 37%, and Mn from 2% to 15%. The dry matter of ABGR-fertilized maize was 34%, 45% higher than that of BGR-fertilized maize. The soluble Mn content in the soil was 74% higher with the low ABGR dose and 222% higher with the higher ABGR dose than the BGR treatments. The fertilizer efficiency of ABGR was higher than that of BGR, indicating that the absolute amount of applied fertilizer could be reduced in systems using ABGR. Full article
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Article
Combined Acidification and Solar Drying of Pig Slurries for Nutrient Recovery and Controlled Atmospheric Emissions
Agronomy 2021, 11(2), 222; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11020222 - 25 Jan 2021
Cited by 1 | Viewed by 623
Abstract
The solar drying of pig slurries was tested in a pilot-scale greenhouse (10 m2 footprint), operated with forced ventilation under low and high solar irradiation in Mediterranean conditions. Gaseous emissions were prevented through slurry acidification and by the biofiltration of exhaust gases. [...] Read more.
The solar drying of pig slurries was tested in a pilot-scale greenhouse (10 m2 footprint), operated with forced ventilation under low and high solar irradiation in Mediterranean conditions. Gaseous emissions were prevented through slurry acidification and by the biofiltration of exhaust gases. Air relative humidity and temperature in and out the greenhouse, as well as the weight of a slurry sample, were monitored online to command the ventilation regime. Daily average drying rate values ranged from 0.3 to 2.8 kg m−2 d−1 and displayed a direct dependency with solar radiation until the pig slurry lost a 60% of its initial weight, with a solar energy efficiency of about 26%. Upon further drying, the water content from pig slurries stabilized at around 10%. Mass balances between the initial slurry and dried product were closed for total solids and organic matter, but the recovery of nutrients ranged from 69% to 81%, apparently because of precipitation and incrustation phenomena. The NPK composition of the final product was 4.3–2.5–3.8 and fulfilled current regulations for solid organic fertilizers. Operational costs of the drying process and fertilizing quality parameters were also discussed. Full article
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Article
Effects of Vermicompost, Compost and Digestate as Commercial Alternative Peat-Based Substrates on Qualitative Parameters of Salvia officinalis
Agronomy 2021, 11(1), 98; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11010098 - 06 Jan 2021
Cited by 6 | Viewed by 1083
Abstract
Peat is a common substrate used for the cultivation of potted plants. However, the use of peat in horticulture has recently been questioned from an environmental standpoint, since it is a non-renewable resource and plays a major role in atmospheric CO2 sequestration. [...] Read more.
Peat is a common substrate used for the cultivation of potted plants. However, the use of peat in horticulture has recently been questioned from an environmental standpoint, since it is a non-renewable resource and plays a major role in atmospheric CO2 sequestration. The aim of this work was to assess the potentialities of substrates obtained from vermicompost, compost and anaerobic digestion processes to partially substitute peat for sage (Salvia officinalis L.) cultivation. Therefore, we planned an experiment to assess the effect of these substrates on essential oil (EO) yield and composition, as well as on leaf nutrients concentration of sage plants. The three substrates were mixed with commercial peat (Radicom) at a ratio of 40% of alternative substrates and 40% of commercial peat. The chemical properties of the alternative substrates did not affect the leaf content of macro and micronutrients, as well as of heavy metals. Moreover, the EO yield and quality was not affected by the substrates and did not differ among them. Results provided evidence that the three alternative substrates can be used to partially substitute peat in soilless cultivation of sage plants. However, due to the higher values of the electrical conductivity of the substrates obtained from composting and anaerobic digestion processes, such substrates must be used with caution. Full article
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Article
Sustainable Valorisation of Biowaste for Soilless Cultivation of Salvia Officinalis in a Circular Bioeconomy
Agronomy 2020, 10(8), 1158; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10081158 - 07 Aug 2020
Cited by 4 | Viewed by 1025
Abstract
The aim of this work is to assess the usefulness of biowaste deriving from Circular Bioeconomy (CBE) processes (i.e., vermicompost, compost and digestate), as growing substrates for the partial or total replacement of peat, by measuring the vegetation biometric parameters of sage ( [...] Read more.
The aim of this work is to assess the usefulness of biowaste deriving from Circular Bioeconomy (CBE) processes (i.e., vermicompost, compost and digestate), as growing substrates for the partial or total replacement of peat, by measuring the vegetation biometric parameters of sage (Salvia officinalis L.)—leaf area; Soil Plant Analysis Development (SPAD) value (index of chlorophyll concentration); fresh and dry weight of leaves; stem weight; root length. The results showed that vermicompost positively influenced most of above parameters (+16.7% for leaf area, +7.3% for fresh leaf weight, +6.4% for dry leaf weight, +8.5% for fresh stem weight, +0.9% for dry stem weight, +16% for root length) and, therefore, can be used as a sustainable growing substrate, alternative to peat, for the sage soilless cultivation. Yet, the results of some biometric parameters are better with peat rather than with compost (−7.2% for SPAD value, −47.3% for fresh leaf weight, −46.8% for dry leaf weight, −32.9% for fresh stem weight, −39.1% for dry stem weight, −52.4% for fresh root weight, −56.6% for dry root weight) and digestate (−30.2% for fresh leaf weight, −33.6% for dry leaf weight, −23.9% for fresh stem weight, −27% for dry stem weight, −51.8% for fresh root weight, −34.4% for dry root weight, −16% for root length). Therefore, these results are interesting for potted plants in nursery activity, while the above differences must be verified also after the transplanting of the tested plants in open field. However, the use of all the above growing substrates alternative to peat allows the sustainable valorization of food industry by-products, plant biomass, animal manure and the Organic Fraction of Municipal Solid Waste (OFMSW). Full article
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Article
Impact of Digestate Application as a Fertilizer on the Yield and Quality of Winter Rape Seed
Agronomy 2020, 10(6), 878; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10060878 - 19 Jun 2020
Cited by 1 | Viewed by 1038
Abstract
The operation of an agricultural biogas plant is associated with the formation of a large amount of digestate. The basic trend in digestate management, after taking into account its physicochemical properties, should be its use as a fertilizer. The possibility of the agricultural [...] Read more.
The operation of an agricultural biogas plant is associated with the formation of a large amount of digestate. The basic trend in digestate management, after taking into account its physicochemical properties, should be its use as a fertilizer. The possibility of the agricultural use of digestate as a fertilizer was determined. Digestate obtained from the agricultural biogas plant was tested for the content of macronutrients and heavy metals. The content of macronutrients was also determined in soil for winter rape cultivation. The analysis showed an increase in the yield depending on the digestate dose applied. In addition, an increase in the fat and protein content was found in winter rape seeds. The best results of mean values were obtained during the application of the 50,000 L ha−1 dose. The average diameter of the stem base was 1.48 cm. The average height was 36.20 cm. The seed yield was 3.44 t ha−1. The thousand seed weight was—5.34 g. The fat and protein contents were 43.62% and 22.95%, respectively. By applying a digestate dose of 50,000 L ha−1, the highest content of macronutrients, as well as polyunsaturated fatty acids (PUFA) (31.17%), monounsaturated fatty acids (MUFA) (61.89%) and saturated fatty acids (SFA) (6.87%), was recorded. Full article
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Article
A Comparative Study of Composts Prepared from Various Organic Wastes Based on Biological and Chemical Parameters
Agronomy 2020, 10(6), 869; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10060869 - 18 Jun 2020
Cited by 5 | Viewed by 1183
Abstract
One of the principles of the circular economy requires the effective recycling of organic waste, especially since its volume is increasing from year to year. Therefore, one of the best solutions to solve this problem is the composting of organic waste. This paper [...] Read more.
One of the principles of the circular economy requires the effective recycling of organic waste, especially since its volume is increasing from year to year. Therefore, one of the best solutions to solve this problem is the composting of organic waste. This paper presents the results of a comparative study of 10 different composts in terms of their quality. The composts varied with regard to waste materials used for composting, the adopted composting method, and the degree of compost maturity. Both biological (seed germination rate and intensity of plant root growth) and chemical methods (contents of macro- and micronutrients, presence of heavy metals, as well as the quality and quantity of humus compounds) were applied to evaluate the fertilisers, providing comprehensive characteristics of individual composts. It was found that composts prepared on the basis of sewage sludge had the highest contents of macro- and micronutrients as well as heavy metals. In addition, these composts contained the greatest amounts of humic substances, although these were of low quality. These composts also strongly inhibited seed germination and plant root growth. The least desirable chemical composition was found for the composts based on yard trimmings and household wastes prepared in home composters. These composts contained good quality humus compounds and had a positive effect on seed germination and plant root growth. Full article
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Article
Reclaimed Wastewater to Irrigate Olive Groves and Vineyards: Effects on Soil Properties
Agronomy 2020, 10(5), 649; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10050649 - 03 May 2020
Cited by 4 | Viewed by 958
Abstract
Having drinking water is one of the sustainable development goals (SDG no. 6) that is not always easy to ensure, especially in countries like Spain or arid regions marked by water deficit. The reuse of treated water should be considered when planning water [...] Read more.
Having drinking water is one of the sustainable development goals (SDG no. 6) that is not always easy to ensure, especially in countries like Spain or arid regions marked by water deficit. The reuse of treated water should be considered when planning water resources, but it is necessary to verify that this effectiveness is applicable to real situations. A field trial was carried out in several study areas distributed in agricultural parcels of south east Spain. Soils from two olive groves and two vineyards irrigated with treated wastewater (TW) were monitored for to compare with other plantations irrigated with conventional well water (WW) since July 2016–September 2018. Five different irrigation water sources were analyzed (two from well water and three from reclaimed wastewater). No microbiological, metal content, toxicity or organic compounds (PAHs and PCBs) in the studied water samples were detected and reclaimed municipal wastewater was comparable in quality to the conventional sources at all the demonstration sites, except for higher electrical conductivity. Soils irrigated with TW had higher values for electrical conductivity, N, K, Na, Mg, Mn and cation exchange capacity. The main precautions to be considered when irrigating with treated wastewater are its salt content and its tendency to high values of electrical conductivity. Otherwise, they are an interesting contribution of nutrients to soil. Hence adopting this water type to irrigate orchards, vineyards and olive groves could help to save primary water resources. Full article
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Article
Microelement Variability in Plants as an Effect of Sewage Sludge Compost Application Assessed by Different Statistical Methods
Agronomy 2020, 10(5), 642; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10050642 - 01 May 2020
Cited by 7 | Viewed by 905
Abstract
This research deals with the effects of soil amendment with sewage sludge compost (SSC) on the accumulation of microelements (Cu, Zn, Mn, Ni, Fe) in plants—white mustard (Sinapis alba), triticale (Triticale) and white lupine (Lupinus albus)—cultivated on [...] Read more.
This research deals with the effects of soil amendment with sewage sludge compost (SSC) on the accumulation of microelements (Cu, Zn, Mn, Ni, Fe) in plants—white mustard (Sinapis alba), triticale (Triticale) and white lupine (Lupinus albus)—cultivated on two contrasting soils (light vs. medium agronomic class). Additionally, the influence of experimental factors on variability of the harvest index (HI) was determined for individual plants and micronutrients. A 3-year pot experiment was conducted and SSC at the rate of 6 t·ha−1 was applied into the soils. These changes were determined by ANOVA and subject to regression analysis and subsequently visualized. The study clearly demonstrated that SSC as an organic fertilizer had a significant, but weak effect on the microelements level variability in the shoots and grains of plants cultivated in crop rotation. Regardless of the experimental factors, on average, the plants accumulated higher amounts of Cu, Zn and Mn in the grains, and Fe and Ni in the shoots. Harvest index values confirmed the significance and variable translocation of microelements within plant organs. The influence of SSC on micronutrient contents in plant organs was more significant in the case of medium soil. Full article
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Article
Nutrient Recycling, Wheat Straw Decomposition, and the Potential Effect of Straw Shear Strength on Soil Mechanical Properties
Agronomy 2020, 10(2), 314; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10020314 - 24 Feb 2020
Cited by 3 | Viewed by 1316
Abstract
This study aimed to explore the release rate (RR) of wheat straw nutrients during straw return to a paddy field and examined the possible relationship between wheat stalk shear strength and the content of the remaining components in wheat straw. We used the [...] Read more.
This study aimed to explore the release rate (RR) of wheat straw nutrients during straw return to a paddy field and examined the possible relationship between wheat stalk shear strength and the content of the remaining components in wheat straw. We used the nylon mesh bag technique to study the decomposition of straw nutrients such as total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), lignin, and cellulose over time. During the time span of 0–90 days, results showed a rapid decomposition rate with a diverse trend under different tillage operations. Furthermore, the decomposition rate was higher under the plough (PRP) conditions than under dry conditions (RP) or water rotation (PR). Moreover, under PRP conditions, the RR of TOC, TK, lignin, and cellulose increased, while the RR of TK was higher than 95% initially and then increased slightly. However, the carbon to nitrogen ratio was first increased and then decreased; similarly the RR of TP first increased and then decreased; a fluctuating pattern was observed for TN. Additionally, we found a strong correlation between wheat stalk shear strength and the remaining contents of lignin, hemicellulose, and cellulose, with R2 ≥ 0.91, which was higher than 0.82 after computing adjustments. Furthermore, the changing trend of nutrients and components and the relationship between shear strength and the content of the remaining components in wheat straw were used to evaluate the release characteristics of nutrients under straw return. The potential effects of the straw shear strength on soil mechanical properties were determined, providing a remarkable opportunity for acquiring nutrients for sustainable application of soil. Full article
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Article
Combined Addition of Bovine Bone and Cow Manure: Rapid Composting of Chestnut Burrs and Production of a High-quality Chestnut Seedling Substrate
Agronomy 2020, 10(2), 288; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10020288 - 18 Feb 2020
Cited by 3 | Viewed by 969
Abstract
In China, chestnut burrs (CB) are produced at a rate of a million tons per year as the major byproduct of chestnut orchards. It is necessary to utilize the chestnut forest green waste and convert it into a valuable seedling media for the [...] Read more.
In China, chestnut burrs (CB) are produced at a rate of a million tons per year as the major byproduct of chestnut orchards. It is necessary to utilize the chestnut forest green waste and convert it into a valuable seedling media for the sustainable cultivation of chestnut seedlings. In this study, we composted CB with two waste products of cattle farming, namely cow manure (CM) and bovine bone (BM). We also evaluated the potential of CB compost application in chestnut forest sustainability. Results indicated that the best combination was the addition of 15% BM and 55% CM. This combination significantly improved the composting environment by increasing pH, enhancing phosphorus concentration and mineral elements such as Ca, Na, Mg and Zn, and shortened the composting period to 38 days. This combination also resulted in the highest content of citric acid-P (109.20 times than the control treatment) and the lowest content of NH4+–N (0.28 times than control treatment) indicating a better N and P structure of the final compost product. This combination achieved a greater degradation rate of CB cellulose (61.45%), hemicellulose (37.87%), and a more significant degradation of outer epidermis structure. When CB compost was used as a growing media, a significant decrease in photosynthesis stress of chestnut seedlings was observed, which was mainly manifested as a decrease in photochemical quenching (qP) and an increase of the maximum efficiency of PSII photochemistry under dark-adaption (Fv/Fm). Addition of 10% CB compost (in volume basis) is suggested, which resulted in the tallest chestnut seedlings (59.83 cm) with a stem diameter of 0.91 cm after six months of growth. In summary, this research provides an environmentally friendly strategy for chestnut orchard sustainability: rapid composting of CB, then immediate application as a high-quality substrate for chestnut seedlings. Full article
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Article
Comparison of the Agricultural Use of Products from Organic Waste Processing with Conventional Mineral Fertilizer: Potential Effects on Mineral Nitrogen Leaching and Soil Quality
Agronomy 2020, 10(2), 226; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10020226 - 04 Feb 2020
Cited by 2 | Viewed by 1272
Abstract
Currently, there is an increasing emphasis on the use of renewable sources. The Czech Republic is no exception. There has been an increase in the number of biogas plants and composting plants. The main purpose of these facilities is to process organic wastes [...] Read more.
Currently, there is an increasing emphasis on the use of renewable sources. The Czech Republic is no exception. There has been an increase in the number of biogas plants and composting plants. The main purpose of these facilities is to process organic wastes of various origins in order to utilize the waste, both for energy production and as soil fertility enhancers. Last but not least, the biogas station produces digestate, which could be further utilized. The present work deals with the assessment of the effect of digestate (doses of 220; 150 and 80 kg N ha−1), mineral fertilizer (150 kg N ha−1), and compost application (150 kg N ha−1) on selected indicators of soil environment: (a) soil microbial activity (basal and substrate-induced respiration); (b) plant nutrient content (P, K, Ca, Mg); (c) leaching mineral N from the soil; and (d) production of plant biomass of model plant Lactuca sativa L. Furthermore, the work aims to assess the individual doses of digestate and to determine the optimal one. The above effects were studied within a pot experiment for 63 days in controlled conditions. There were significant differences in Nmin leaching, which was significantly the highest in the variant with the application of a mineral fertilizer and lowest in variants with the application of digestate (variant 150 and 80 kg N ha−1) and compost (150 kg N ha−1). In terms of soil microbial activity, a significant effect of digestate application (150 kg N ha−1) on basal respiration versus the mineral fertilizer application was found (difference > 20%). This dose of digestate also had the highest positive effect on substrate-induced respiration, proven against all other variants, except for the digestate application at 220 kg N ha−1. Particularly, as compared with the mere application of mineral fertilizer, the application of digestate dose at 150 kg N ha−1 had the best positive effect on plant biomass production (+20%). On the other hand, compost application most positively affected the increase in available contents of nutrients and thus long-term soil fertility. Therefore, the dose of 150 kg N ha−1 digestate may represent an interesting alternative to increase actual soil fertility and thus to partially replace conventional mineral nutrition. Full article
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Review

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Review
Sugarcane Distillery Spent Wash (DSW) as a Bio-Nutrient Supplement: A Win-Win Option for Sustainable Crop Production
Agronomy 2021, 11(1), 183; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy11010183 - 19 Jan 2021
Cited by 5 | Viewed by 1177
Abstract
Industrial pollution has been continuously soaring and causing serious threats to the soil, water, and air quality. The increase in industrialization has not only covered the large areas, but also created a large quantity of wastewater which is difficult to handle. The water [...] Read more.
Industrial pollution has been continuously soaring and causing serious threats to the soil, water, and air quality. The increase in industrialization has not only covered the large areas, but also created a large quantity of wastewater which is difficult to handle. The water produced from different industries is getting its place in the agriculture. However, the challenge is to properly use wastewater, so that the application of wastewater does not cause any soil and environmental problems. The distillery spent wash (DSW) is a liquid waste that is produced from the sugarcane industry. It contains a large load of both organic and inorganic substances. Also, DSW contains a sufficient amount of macronutrients (nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and Sulphur (S)) and micronutrients (zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn)), which in turn improves the growth and yield of crops. The optimized doses of DSW substantially improve soil enzymatic and microbial activities, organic carbon, nutrient uptake, soil porosity, water holding capacity, aggregate stability, and anti-oxidant activities, which in turn improve the photosynthetic efficiency, growth and yield. However, the inadequate knowledge about the DSW characteristics and methods of its agricultural application present questions concerning environmental quality for groundwater pollution. Therefore, to obtain a better understanding about the DWS, here, we discussed the effects of DSW on soil quality, crop yield, and its implications for agriculture and water quality. Full article
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Review
Recycling of Organic Wastes through Composting: Process Performance and Compost Application in Agriculture
Agronomy 2020, 10(11), 1838; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10111838 - 22 Nov 2020
Cited by 28 | Viewed by 2536
Abstract
Composting has become a preferable option to treat organic wastes to obtain a final stable sanitized product that can be used as an organic amendment. From home composting to big municipal waste treatment plants, composting is one of the few technologies that can [...] Read more.
Composting has become a preferable option to treat organic wastes to obtain a final stable sanitized product that can be used as an organic amendment. From home composting to big municipal waste treatment plants, composting is one of the few technologies that can be practically implemented at any scale. This review explores some of the essential issues in the field of composting/compost research: on one hand, the main parameters related to composting performance are compiled, with especial emphasis on the maturity and stability of compost; on the other hand, the main rules of applying compost on crops and other applications are explored in detail, including all the effects that compost can have on agricultural land. Especial attention is paid to aspects such as the improvement of the fertility of soils once compost is applied, the suppressor effect of compost and some negative experiences of massive compost application. Full article
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Review
Recovery of Phosphorus from Waste Water Profiting from Biological Nitrogen Treatment: Upstream, Concomitant or Downstream Precipitation Alternatives
Agronomy 2020, 10(7), 1039; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy10071039 - 18 Jul 2020
Cited by 8 | Viewed by 1777
Abstract
Mined phosphate rock is the largest source of phosphorus (P) for use in agriculture and agro-industry, but it also is a finite resource irregularly distributed around the world. Alternatively, waste water is a renewable source of P, available at the local scale. In [...] Read more.
Mined phosphate rock is the largest source of phosphorus (P) for use in agriculture and agro-industry, but it also is a finite resource irregularly distributed around the world. Alternatively, waste water is a renewable source of P, available at the local scale. In waste water treatment, biological nitrogen (N) removal is applied according to a wide range of variants targeting the abatement of the ammonium content. Ammonium oxidation to nitrate can also be considered to mitigate ammonia emission, while enabling N recovery. This review focuses on the analysis of alternatives for coupling biological N treatment and phosphate precipitation when treating waste water in view of producing P-rich materials easily usable as fertilisers. Phosphate precipitation can be applied before (upstream configuration), together with (concomitant configuration), and after (downstream configuration) N treatment; i.e., chemically induced as a conditioning pre-treatment, biologically induced inside the reactor, and chemically induced as a refining post-treatment. Characteristics of the recovered products differ significantly depending on the case studied. Currently, precipitated phosphate salts are not typified in the European fertiliser regulation, and this fact limits marketability. Nonetheless, this topic is in progress. The potential requirements to be complied by these materials to be covered by the regulation are overviewed. The insights given will help in identifying enhanced integrated approaches for waste water treatment, pointing out significant needs for subsequent agronomic valorisation of the recovered phosphate salts, according to the paradigms of the circular economy, sustainability, and environmental protection. Full article
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