Green Manure Amendment Research Articles

Green manuring alters reactive N losses and N pools in arable soils: A meta-regression study

Green manuring is a conservation agricultural practice that improves soil quality and crop yield. However, increasing the active nitrogen (N) and carbon (C) pools during green manure (GM) amendment may accelerate soil N transformation and stimulate N loss. Previous studies have reported the effects of cover crop incorporation on N2O emission; however, the driving mechanisms and other N losses remain unclear. Therefore, we conducted a comprehensive meta-analysis of 109 published articles (517 paired observations) to clarify the effects of GM amendment on soil reactive N (Nr) losses (N2O emissions, NH3 volatilization, and N leaching and runoff), N pools, and N cycling functional gene abundance. The results showed that green manuring increased soil microbial biomass N (MBN) and NO3−-N concentrations and stimulated N2O emission but significantly lowered N leaching and yield-scaled NH3 volatilization. Practices of green manuring made a dominant contribution to the variation in N2O emissions and NH3 volatilization after GM application. Furthermore, applying legume-based GM, using N derived from GM (GMN) as an additional input, and short-term GM amendment each stimulated N2O emissions. In contrast, adopting non-legume GM, using GMN to partially substitute mineral N, and applying GM to the soil surface or paddy field mitigated NH3 loss during GM amendment. Additionally, the variation in NH3 volatilization was positively related to soil pH and N application rate (NAR) but had a negative relationship with mean annual precipitation (MAP). This study highlighted the marked effects of green manuring on soil N retention and loss. Agricultural operations that adopt GM amendment should select suitable GM species and optimize mineral N inputs to minimize N loss.

Leguminous green manure amendments improve maize yield by increasing N and P fertilizer use efficiency in yellow soil of the Yunnan-Guizhou Plateau

The low utilization efficiencies of chemical N and P fertilizers largely threat the sustainability of agriculture. Green manure is conducive to increasing crop yield. This study aimed to explore the effects of leguminous and non-leguminous green manures on the maize production, and N and P fertilizers use efficiency. A green manure-maize rotation experiment was conducted in the Karst region of the Yunnan-Guizhou Plateau. The responses of maize yield, N (NUE) and P (PUE) fertilizer use efficiency to winter fallow fields treated with no fertilizer (CK) and traditional chemical fertilizers (WF), WF with alfalfa (AL), common vetch (CV) and oilseed rape (OR) green manures in 2020 and 2021. The results showed that compared with WF, the maize yield was significantly increased on average by 22% and 15% in AL and CV, respectively, while it was hardly affected in OR. AL significantly increased NUE and PUE by an average of 103% and 66%, and CV increased NUE by an average of 74% and 41%, respectively, while RA had no significant effects on PUE, and decreased NUE by 39% in the second year. Structural equation modeling (SEM) showed that green manures indirectly affected NUE and PUE due to soil available N and P, which directly and indirectly influenced maize N and P uptake, and then enhanced NUE and PUE. Linear regression results showed that maize production had positive relationships with NUE and PUE. Our findings highlight that non-legume green manure would hardly influence grain yield, while legume green manure could be effective for increasing maize production by increasing NUE and PUE, especially for alfalfa in yellow soil of the Yunnan-Guizhou Plateau.

Increasing the Efficiency of the Rice–Wheat Cropping System through Integrated Nutrient Management

The advancement of effective nutrient management strategies has been instrumental in enhancing crop productivity and economic viability. Thus, we investigated the effect of green manure and organic amendments at varying nitrogen levels in rice and their residual effect on wheat crops. A two-year research study (2018–2019 and 2019–2020) was conducted at two distinct locations: Punjab Agricultural University in Ludhiana and a Research Station in Dyal Bharang, Amritsar. The experimental design employed was a split-plot design. The main plot treatments consisted of four treatments (green manuring, farmyard manure, poultry manure, and no organic amendment (control)) and four subplot treatments (No N control, 50 kg N ha−1, 75 kg N ha−1, and 100 kg N ha−1), replicated four times in the rice crop, and its residual effect was studied in wheat. The study found that applying organic amendments at different nitrogen levels significantly increased rice–wheat productivity, growth, yield qualities, nutrient uptake, and efficiency (p < 0.05). Poultry manure increased rice grain yield more than other modifications. It significantly increased grain yield by 67.3% and 61.4% over the control in both years of the research. Poultry manure (41.9 kg, 60.0%) increased AE (kg grain kg−1 N uptake) and ANR (%) compared to control due to higher total N (177.4 kg ha−1), P (31.6 kg ha−1), and K (179.6 kg ha−1). Grain production was positively correlated with total nitrogen (N), phosphorus (P), and potassium (K) intake (r = 0.992**, 0.931**, and 0.984**, respectively). Total N uptake was positively correlated with P and K uptake (r = 0.963** and 0.991**, respectively). Poultry manure improved soil health by increasing total microbial count and alkaline phosphatase activity. In the subsequent wheat crop, rice grown with poultry manure yielded 24.3 and 24.4 percent more than no organic amendment control in rabi 2018–2019 and 2019–2020. The findings suggest that poultry manure and 100 kg N ha−1 or 75 kg N ha−1 afforded equivalent yields. This shows that even less nitrogen may be enough to boost rice and wheat yields.

Spinach (Spinacia oleracea) as green manure modifies the soil nutrients and microbiota structure for enhanced pepper productivity

Spinach has been suggested as a potential rotation crop for increasing crop yield by enhancing beneficial fungal microbes in continuous monocropping. However, no research on the use of spinach as a green manure has been reported. Thus, we tested the effects of spinach and Korean mustard cultivars (green and red mustards) (10 g pot −1) as green manure on soil chemical properties, pepper productivity, and soil microbiome of long-year pepper-monocropped soil. Spinach improved the soil nutrition (e.g., pH, SOM, TN, NH4+, and K), weed suppression, and pepper growth. Spinach had by far the highest fruit yield, over 100% pepper fruit yield increment over the mustard green manures and control. Our study showed that the major influencing factors to cause a shift in both bacterial and fungal community assemblies were soil pH, TC TN, and K. Following green manure amendment Bacillota, especially Clostridium, Bacillus and Sedimentibacter, were enriched, whereas Chloroflexi and Acidobacteriota were reduced. In addition, spinach highly reduced the abundance of Leotiomycetes and Fusarium but enriched Papiliotrema. FAPROTAX and FUNGuild analysis revealed that predicted functional profiles of bacterial and fungal communities in spinach-amended soil were changed. Spinach-treated soil was differentially abundant in function related to hydrocarbon degradation and functional guilds of symbiotrophs and ectomycorrhizal. This study contributes significantly to our understanding of how the soil fertility and soil microbiome alteration via spinach green manure application as a pre-plant soil treatment might help alleviate continuous cropping obstacles.

Green Manure Amendment Increases Soil Phosphorus Bioavailability and Peanut Absorption of Phosphorus in Red Soil of South China

Peanut (Arachis hypogaea L.) is one of the most important crops produced worldwide. Peanut is the dominant crop in the typical upland red soil areas of China; however, phosphorus bioavailability in red soil is very low, which severely affects peanut production. To improve the phosphorus bioavailability, which substantially promotes the green development of peanut production, a peanut–green manure rotation field experiment was conducted with six treatments (milkvetch; radish; brassica rape; mustard rape; winter fallow and no-tillage), commencing in September 2017 in the red soil area of Jiangxi province, China. The results show that compared with no-tillage (NT) treatments, different green manure returning treatments had significant effects on soil pH, soil phosphorus components and available potassium content. The particulate phosphorus and soil available phosphorus contents in the green manure treatments were significantly higher than those in the winter fallow (WF) treatment. Compared with the WF treatment, the content of particulate phosphorous in brassica rape (BR), radish (R) and milkvetch (MV) treatments was significantly increased by 6.55%, 3.66% and 2.50%, respectively; the available phosphorus content in mustard rape (MR), BR, R and MV was significantly increased by 20.93%, 25.60%, 23.76% and 18.10%, respectively. In addition, the total phosphorus content of peanut shell in the MV and R treatment was significantly higher than that in the WF treatment, increasing by 33.47% and 60.66%, respectively. Compared with the WF treatment, the peanut biomass of MR, BR and R treatments increased significantly by 19.51%, 29.83% and 19.77%, respectively. The total phosphorus accumulation in all green manure treatments was higher than that in the WF treatment, and the MV treatment reached a significant level at 18.83%. Based on these results, the particulate phosphorus (PP) and available phosphorus were significantly affected by different green manure treatments; green manure amendment improves peanut phosphorus uptake. The use of green manure (especially milkvetch and brassica rape) can be recommended to improve phosphorus bioavailability and yield of peanut in red soil areas.

Green Manure Amendment in Paddies Improves Soil Carbon Sequestration but Cannot Substitute the Critical Role of N Fertilizer in Rice Production

Clarifying the benefits of carbon sequestration and crop production of continuous green manure amendment is crucial for sustainable agricultural development. Here, using a long-term located experiment, we assessed the effects of 18 years’ ryegrass/milk vetch amendment with (NF, 150 kg N ha−1) or without nitrogen (N) fertilizer input (CK), on soil carbon management indices, paddy methane (CH4) emissions and rice yields. The results showed that green manure, rather than fertilization, played a critical role in soil CMI, increasing the carbon pool index but reducing the carbon management index. The increased soil organic carbon and the reduced labile organic carbon were the main causes for this performance. Additionally, the effects of both fertilization and green manure amendment on CH4 emissions were insignificant; however, fertilization significantly increased grain yield by 39.30% compared to CK. As a result, the methane emission intensity under fertilization treatment was notably lower than that from CK. The findings suggest that green manure amendment is a profitable manipulation for enhancing carbon sequestration without increasing paddy CH4 emissions. However, this cannot substitute the critical role of N fertilizer in rice production.

Effect of mineral and organic fertilizers on some soil chemical and biological properties in a 90-year-old long-term experiment

The Westsik’s long-term crop rotation experiment was set up in 1929 at the Nyíregyháza Experimental Station (NE Hungary) on a slightly acidic Arenosol. Besides fallow crop rotation (CR), effects of different organic amendments (lupine as green manure, lupine as main crop, straw manure, and farmyard manure (FYM) were studied with or without N or NPK-fertilizers. The crop rotation consisted of rye, potato, lupine, and oat with common vetch. The soil of potato plots was analysed in 2019 at the 90th anniversary of Westsik’s crop rotation experiment.The following chemical and microbiological soil parameters were determined: soil pH, available nutrient contents, organic carbon (OC) and nitrogen (ON) contents, microbial biomass carbon (MBC) and nitrogen (MBN), soil respiration, net nitrification, and activity of some soil enzymes.In the CRs, the soil pHH2O varied from acidic to weakly alkaline and it largely differed from pHKCl. The results showed a significant increase in the content of nitrate, available phosphorus and potassium in most of the fertilized plots. Applying straw, green manure, or FYM significantly increased the OC and ON contents. The total count of cultivable bacteria increased upon the application of the organic manures. Combined application of straw manure and N-fertilization heavily improved the abundance of the microscopic fungi.While all the applied organic manures significantly enhanced the MBC, the MBN increased only by the green manure amendment. Our results revealed higher soil respiration rate in the plots receiving straw or FYM than in the control. Both green manure and FYM elevated the net nitrification rate. Phosphatase, saccharase, urease, and dehydrogenase enzymes showed a hesitating response to the manure application in the different CRs.The soil respiration and dehydrogenase activity correlated to most of the measured chemical parameters. Among microbiological properties, the MBC and MBN, as well as dehydrogenase and other enzyme activities displayed a positive correlation. Results proved the need for the exogenous application of organic matter in the form of organic manures to enhance the nutritional status and health of the soil.

Organic amendments and nitrogen levels influences grain quality of Rice (Oryza sativa) – Wheat (Triticum aestivum) cropping system

A field experiment was conducted at Ludhiana and Amritsar during kharif and rabi 2018–19 and 2019–20 to see the effect of different organic amendments and nitrogen levels on grain quality parameters of rice and wheat. The results revealed that at both locations milling quality such as brown, milled as well as head rice recovery and L:B of rice grain were found significantly higher with treatment in which poultry manure (PM) was applied to rice followed by green manure (GM) and farmyard manure (FYM). N100 recorded better milling quality and L:B which was at par with N75. Residual effects of green manure and organic amendments on physical grain characteristics, viz. grain appearance score, hectolitre weight, grain hardness and chemical grain characteristics, viz. sedimentation value, protein content, gluten content of succeeding wheat crop were recorded higher in PM which was significantly superior than GM and FYM at both locations. Whereas, N100 and N75 found to be superior as compared to N50 and control. The improvement in grain quality may be attributed to the increased availability of nutrients coupled with increased absorption and assimilation by plants on long term basis.

Physiological and metabolic responses in broccoli plants fertilized with green manure

Grasses and legumes affect differently the amount of N in the soil over time, mainly due to the differences in the chemical characteristics of its mass. Changes in the availability of N influence the absorption and assimilation of N, which will influence physiological processes in the plants. The objective of this paper is to evaluate the changes in gas exchange, chlorophyll fluorescence and biochemical activity in leaves of broccoli grown under different green manure amendments. The experiment was designed in a complete randomized block design, using the mass of jack bean (JB) and millet (M) pure and in mixtures and one control, totaling six treatments: Control, 100JB, 75JB25M, 50JB50M, 25JB75M, 100M, with four replicates. The canopy area, N content, gas exchange, and biochemical analyzes were evaluated on the broccoli index leaf 40 days after broccoli transplantation. The higher ratio of jack bean, the higher the canopy area, the N content and the amino acid, protein and malate content, and lower starch content, possibly due to the higher N mineralization in this green manure.

Combined effects of green manure and zinc oxide nanoparticles on cadmium uptake by wheat (Triticum aestivum L.)

Cadmium (Cd) toxicity in agricultural soils is serious concern these days which needs continuous attention. Little is known about the combined use of berseem and/or maize residues soil applied as a green manure alone or along with foliar dressing of zinc oxide nanoparticles (ZnONPs) on Cd accumulation in wheat (Triticum aestivum L.). A pot experiment under ambient conditions with wheat grown in Cd-contaminated soil was performed after soil applied different green manure amendments and foliar dressing of ZnONPs was done during plant growth and plants were harvested at full maturity. Compared with control, plant growth attributes and biomass of above ground parts substantially increased with applied amendments being maximum with combined use of ZnONPs + B75 (berseem residue, 75 mg/kg) followed by ZnONPs + M75 (maize residue, 75 mg/kg). All the treatments improved the leaf chlorophyll contents and improved the leaf antioxidant enzyme activities thereby reduced the leaf electrolyte leakage. The Cd accumulation in roots and aboveground parts of the wheat was reduced especially in ZnONPs + B75 followed by ZnONPs + M75. The higher rate of soil applied amendments along with NPs minimized the available Cd in soil extracts but soil post-harvest pH was not much affected by the applied amendments. In conclusion, incorporation of berseem and maize residues as a green manure applied in Cd-contaminated soil combined with foliar NPs may decrease Cd phytoavailability and its accumulation in wheat grains. However, substantial field studies are required under various environmental conditions before final recommendations at field levels.

Alfalfa green manure amendment improved P use efficiency and reduced P losses from paddy fields

Alfalfa green manure amendment improved P use efficiency and reduced P losses from paddy fields

Green manure incorporation accelerates enzyme activity, plant growth, and changes in the fungal community of soil.

Green manure can sustain agricultural production, preserve biodiversity, and mitigate soil degradation caused by long-term application of chemical fertilizers. Moreover, the application of green manure can improve soil health through increased soil biological activities. Nevertheless, little attention has been paid to the effects of leguminous and non-leguminous plants on phosphorus- and carbon-related enzyme activities and fungal community composition in soil. In this study, a pot experiment was carried out to elucidate the effects of two green manures on plant growth promoting potential, phosphorus- and carbon-related enzyme activities, and soil fungal community composition. Two green manure treatments (Brassica juncea and hairy vetch), poultry compost and control (no amendment) were applied and soil samples were collected after incorporation of green manure and after plant harvest. The results revealed that plant growth with hairy vetch was significantly higher than that with B. juncea and poultry compost, and soil enzyme activities were markedly higher with hairy vetch than with B. juncea. Both green manure amendments altered the soil fungal community composition. It is possible that the incorporation of green manure into soil and their mineralization and decomposition were controlled by the carbon: nitrogen ratio of the manures and that these manures were easily degradable by soil fungi. In particular, the incorporation of leguminous (hairy vetch) green manure with a low carbon: nitrogen ratio resulted in better plant growth through fast mineralization. Our findings suggest that green manure incorporation is an effective practice and provides substantial benefits to the soil-plant system.

Green Manure Amendment Can Reduce Nitrogen Fertilizer Application Rates for Oilseed Rape in Maize-Oilseed Rape Rotation.

Excessive use of chemical fertilizers has led to a reduction in the quality of arable land and environmental pollution. Using green manure to replace chemical fertilizers is one of the most effective solutions. To study the effect of green manure on the requirement for nitrogen fertilizer in oilseed rape, a field experiment with maize–oilseed rape rotation was conducted. Green manure was intercropped between rows of maize and returned after the maize harvest, with no green manure intercropped as control. Different nitrogen fertilizer treatments (0, 65%, 75% and 100% N rates, respectively) were applied during the oilseed rape season. The results showed that with a 35% reduction in nitrogen application rate, the rapeseed grain yield was significantly higher with the maize intercropping with green manure returned to the field than with the maize monocropping treatment at the same nitrogen level. Under conditions of intercropping and return of green manure, compared with the full standard rate of nitrogen fertilizer treatment, a reduction in nitrogen application of 25–30% in the rape season had no significant effect on rape yield. The agronomic efficiency of nitrogen fertilizer on oilseed rape increased significantly, by 47.61–121%, with green manure incorporation. In addition, green manure incorporation significantly increased the soil organic matter content and the soil-available nitrogen content when chemical nitrogen fertilization was abandoned. Benefit analysis showed that a 25–35% reduction in chemical nitrogen fertilizer applied to oilseed rape crops could be achieved by intercropping green manure in the maize season before the sowing of rapeseed in the experimental area. In the long-term, this measure would increase nitrogen utility, reduce production costs, and have concomitant environmental benefits of improving the quality of cultivated land.

Continuous milk vetch amendment in rice-fallow rotation improves soil fertility and maintains rice yield without increasing CH4 emissions: Evidence from a long-term experiment

Catch crop (green manure) planting is considered an efficient strategy to improve soil fertility in agro-ecosystems. Methane (CH4) emissions from paddies subjected to continuous green manure amendment though is a topic that remains unexplored. To clarify the impact of continuous green manure amendment on rice yield and CH4 emissions, a long-term trial (established in 2003, Yixing, China) was designed with the field observations conducted between 2019 and 2020. Two green manure crops (milk vetch, ryegrass) were selected as the catch crop with fallow as the control, all trialed at two N application rates i) low N dosage deriving from the optimum effect between yield-N fertilizer (LN, 200 kg ha-1), and ii) a higher N dose as the empirical farmer's dose (HN, 270 kg ha-1). The results showed that continuous green manure amendment notably increased soil organic carbon (SOC) compared to that of the control, while HN significantly increased the dissolved organic nitrogen compared to LN. The rice yield among treatments remained similar, ranging from 8.6 t ha-1 to 9.4 t ha-1 (two years’ average). CH4 emissions were notably related to green manure, and remained unaffected by N application rate. Ryegrass amendment after 18 years remarkably stimulated the CH4 emissions compared to other treatments, while the difference between milk vetch-amended and fallow treatments was found insignificant. Ryegrass increased soil mcrA gene with the abundance becoming the highest under HN. Methanogens abundance and SOC content were the main factors affecting CH4 emissions under ryegrass addition. Moreover, the CH4 emission intensity was aligned with CH4 emissions mainly due to the similar rice yield. Overall, continuous milk vetch planting is a recommended catch crop strategy that increases soil fertility and maintains rice yield without increasing CH4 emissions.

Potential of Sentinel-2 Satellite Images for Monitoring Green Waste Compost and Manure Amendments in Temperate Cropland

Increasing attention has been placed on the agroecological impact of applying exogenous organic matter (EOM) amendments, such as green waste compost (GWC) and livestock manure, to agricultural landscapes. However, monitoring the frequency and locality of this practice poses a major challenge, as these events are typically unreported. The purpose of this study is to evaluate the utility of Sentinel-2 imagery for the detection of EOM amendments. Specifically, we investigated the spectral shift resulting from GWC and manure application at two spatial scales, satellite and proximal. At the satellite scale, multispectral Sentinel-2 image pairs were analyzed before and after EOM application to six cultivated fields in the Versailles Plain, France. At the proximal scale, multi-temporal spectral field measurements were taken of experimental plots consisting of 14 total treatments: EOM variety, amendment quantity (15, 30 and 60 t.ha−1) and tillage. The Sentinel-2 images showed significant spectral differences before and after EOM application. Exogenous Organic Matter Indices (EOMI) were developed and analyzed for separative performance. The best performing index was EOMI2, using the B4 and B12 Sentinel-2 spectral bands. At the proximal scale, simulated Sentinel-2 reflectance spectra, which were created using field measurements, successfully monitored all EOM treatments for three days, except for the buried green waste compost at a rate of 15 t.ha−1.

Long-Term Effects of Organic Amendments on Soil Organic Matter Quantity and Quality in Conventional Cropping Systems in Switzerland

Increasing soil organic carbon (SOC) in agroecosystems is a promising solution to simultaneously address climate change mitigation, adaptation, and food security. Yet, the best management practices that could achieve these goals remain to be identified. Here, we analyze the long-term effects of application of green manure, cereal straw, farmyard manure, and cattle slurry on SOC in a 37 year long field experiment in Switzerland. The treatment effects were compared against control conditions that received only optimal mineral fertilization. More specifically, this study aimed at evaluating the effect of organic amendments on SOC accumulation and distribution in different soil particle-size fractions by means of a set of indicators about organic matter quality (biological reactivity, humification index) and microbial activity (extracellular enzyme activities). In the absence of organic matter input, application of mineral fertilizers alone resulted in the lowest SOC content and the highest humification index of the bulk soil organic matter. Among the organic amendments, cereal straw, farmyard manure, and cattle slurry promoted a higher SOC content and a lower humification index due to an increase of SOC in the clay-size fraction. The annual C accrual reached 4.4‰ per year over 37 years with farmyard manure. The higher biological reactivity measured for the green manure and cereal straw amendments was associated with higher soil enzymatic activities, while C retention coefficients decreased by at least 2.5 times compared to animal-derived amendments. The low availability of nutrients in green manure and straw amendments as suggested by the high phosphatase and N-acetylglucosaminidase activities may indicate a reduction in C retention of organic matter inputs due to nutrient microbial mining with plant-derived amendments.

Direct seeding to restore tropical seasonal forests: effects of green manure and hydrogel amendment on tree species performances and weed infestation

Although direct tree seeding may be a potentially useful restoration practice, many biotic and abiotic barriers prevent seedling emergence and early development, reducing its success and applicability. To overcome these barriers, we undertook a field experiment to test the effects of using green manure and hydrogel alone, or in combination, on seedling performances of 14 native tree species that were planted by direct seeding in a deforested tropical seasonal forest area in southern Brazil and to examine how green manure affected the initial weed coverage in the study plots. We evaluated competing vegetation coverage and tree seedling emergence and early development for 2 years after sowing. Weed infestation was significantly higher in the experimental plots with no green manure; however, neither green manure nor hydrogel improved tree seedling emergence and early development at any time of measurement. Our results suggest that the use of green manure and hydrogel alone, or in combination, were not effective in guaranteeing direct seeding success; however, green manure can be an effective method to reduce weed infestation. Direct seeding techniques for tree species still need to be improved in order to restore tropical seasonal forests on a larger scale.

Restoring soil quality of woody agroecosystems in Mediterranean drylands through regenerative agriculture

Regenerative agriculture (RA) is gaining increasing recognition as a plausible solution to restore degraded agroecosystems. In Mediterranean drylands, RA is at incipient state of development and has been limitedly adopted by farmers, partly due to the lack of empirical evidence on its impacts. To support its large-scale adoption, we carried out a participatory monitoring project in southeast Spain, involving local farmers applying different RA practices in 9 almond farms. To assess the effect of RA, in each farm we selected one field with regenerative management and one nearby field with conventional management based on frequent tillage (CT). We clustered fields under regenerative management based on the RA practices applied by farmers and distinguished 4 types of RA treatments: 1) reduced tillage with green manure (GM), 2) reduced tillage with organic amendments (OA), 3) reduced tillage with green manure and organic amendments (GM&OA), and 4) no tillage with permanent natural covers and organic amendments (NT&OA). We evaluated the impacts of RA compared to CT by comparing physical (bulk density and aggregate stability), chemical (pH, salinity, total N, P, K, available P, and exchangeable cations) and biological (SOC, POC, PON, microbial activity) properties of soil quality and the nutritional status of almond trees (leaf N, P and K). Our results show that GM improved soil physical properties, presenting higher soil aggregate stability. We found that OA improved most soil chemical and biological properties, showing higher contents of SOC, POC, PON, total N, K, P, available P, exchangeable cations and microbial respiration. RA treatments combining ground covers and organic amendments (GM&OA and NT&OA) exhibited greater overall soil quality restoration than individual practices. NT&OA stood out for presenting the highest soil quality improvements. All RA treatments maintained similar crop nutritional status compared to CT. We conclude that RA has strong potential to restore the physical, chemical and biological quality of soils of woody agroecosystems in Mediterranean drylands without compromising their nutritional status, thereby enhancing their resilience to climate change and long term sustainability.

Precomposting and green manure amendment for effective vermitransformation of hazardous coir industrial waste into enriched vermicompost

Vermitransformation of coir pith (CP) into enriched vermifertilizer has been achieved by amending a green-manure plant, Sesbania sesban (SS) for the first time, and cow dung (CD) in five different combinations: T1(1:0:1), T2(4:3:3), T3(5:3:2), T4(5:4:1) and T5(1:1:0). The substrates were 28 days precomposted with Pleurotus sajor-caju followed by 50 days vermicomposting with Eisenia fetida and Eudrilus eugeniae. Results showed a significant reduction in cellulose, lignin, organic carbon, C/N ratio, C/P ratio and an increase in plant nutrients compared to control. The fertilization index and efficiency of nutrient recovery rate were higher in SS and CD amended CP vermicompost, with a maximum in T2(4:3:3) for E. fetida and T3(5:3:2) for E. eugeniae. The activity of dehydrogenase, urease and cellulase, and phytotoxicity assays further revealed vermicompost stability. The study concludes that T2(4:3:3) and T3(5:3:2) combinations respectively for E. fetida and E. eugeniae is suitable for vermitransformation of CP into enriched vermicompost.

Co-application of poultry-litter biochar with Azolla has synergistic effects on CH4 and N2O emissions from rice paddy soils

Poultry-litter biochar and Azolla as green manure amendments are reported to enhance paddy soil fertility and rice yields. However, whether their co-application in lowland rice paddies has synergistic effects and whether those benefits are accompanied by greenhouse gas (GHG) emissions remains unknown. The objective of this study was to determine the effects of poultry-litter biochar (hereafter: biochar) and its co-application with Azolla as green manure (hereafter: Azolla), on the simultaneous methane (CH4) and nitrous oxide (N2O) emissions from a lowland paddy soil planted with rice during a single rice growing season in Tsuruoka, Yamagata, Japan. Biochar and Azolla amendments were applied once before rice was transplanted at a density of 20 t ha−1 and 133.9 kg N ha−1, respectively. Compared with NPK, NPK + biochar, and Azolla only treatments, Azolla and biochar co-application (i.e., Azolla + biochar) significantly increased CH4 emissions by 33%–197.6% in the early stages of rice growth (before 63 days after transplanting, DAT), but did not significantly influence CH4 emissions at both late rice growth stages (after 63 DAT,) and whole rice growth period (112 DAT). Conversely, Azolla + biochar significantly reduced N2O emissions by 83.0%–97.1% before 63 DAT, and by 76.4%–95.9% during the whole rice growth period at 112 DAT, with a significantly high interaction between biochar and fertilizer amendments. There were no significant N2O emission differences among all treatments after 63 DAT. Additionally, Azolla + biochar significantly increased rice grain yield by 27.3%–75.0%, and consequently, decreased both yield-equivalent CH4 emissions by 24.7%–25.0% and N2O emissions by 81.8%–97.7%. Our findings suggest that the co-application of poultry-litter biochar and Azolla as green manure offers a novel approach to increase rice yield while reducing the emissions of non-carbon dioxide greenhouse gases.