Increased Soil Organic Matter Research Articles

Controlled release fertilizers (CRFs) for climate-smart agriculture practices: a comprehensive review on release mechanism, materials, methods of preparation, and effect on environmental parameters.

Fertilizers play an essential role in increasing crop yield, maintaining soil fertility, and provide a steady supply of nutrients for plant requirements. The excessive use of conventional fertilizers can cause environmental problems associated with nutrient loss through volatilization in the atmosphere, leaching to groundwater, surface run-off, and denitrification. To mitigate environmental issues and improve the longevity of fertilizer in soil, controlled release fertilizers (CRFs) have been developed. The application of CRFs can reduce the loss of nutrients, provide higher nutrient use efficiency, and improve soil health simultaneously to achieve the goals of climate-smart agricultural (CSA) practices. The major findings of this review paper are (1) CRFs can prevent direct exposure of fertilizer granule to soil and prevent loss of nutrients such as nitrate and nitrous oxide emissions; (2) CRFs are less affected by the change in environmental parameters, and that can increase longevity in soil compared to conventional fertilizers; and (3) CRFs can maintain required soil nitrogen levels, increase water retention, reduce GHG emissions, lead to optimum pH for plant growth, and increase soil organic matter content. This paper could give good insights into the ongoing development and future perspectives of CRFs for CSA practices.

Organic Amendment Types Influence Soil Properties, the Soil Bacterial Microbiome, and Tomato Growth

The overuse of chemical fertilizers deteriorates soil quality, and the application of organic amendments has been proposed as an alternative to mineral fertilizers. This study aimed to investigate the effects of organic amendment types on soil properties, the soil microbiome, and tomato growth. Tomato seedlings were grown in soils applied with ten fertilizer treatments, including a no fertilization control, a chemical fertilization control, and eight organic amendment treatments. Compared with the chemical fertilization treatment, the application of manure compost significantly increased the shoot dry weight of tomato plants. In addition, manure compost and tea seed meal remarkably increased soil organic matter (SOM) in comparison with the no fertilization and chemical fertilization treatments. Moreover, manure compost significantly increased soil-exchangeable K and Mg. The application of neem cake and manure compost significantly increased both bacterial diversity and richness. The relative abundance of Lysinibacillus was significantly positively related to the shoot and total dry weights of tomato plants, and its relative abundance was positively influenced by SOM and soil-exchangeable K. Overall, the manure compost used in this study can increase SOM, soil-exchangeable K and Mg, and the relative abundance of Lysinibacillus, consequently promoting tomato growth.

Biochar-based microbial agent reduces U and Cd accumulation in vegetables and improves rhizosphere microecology

Microbial remediation of heavy metals in soil has been widely studied. However, bioremediation efficiency is limited in practical applications because of nutritional deficiency, low efficiency, and competition with indigenous microorganisms. Herein, we prepared a biochar-based microbial agent (BMA) by immobilizing the microbial agent (MA, containing Bacillus subtilis, Bacillus cereus, and Citrobacter sp.) on biochar for the remediation of U and Cd in soil. The results showed that BMA increased soil organic matter, cation exchange capacity, and fluorescein diacetate hydrolysis activity and dehydrogenase activity by 58.7%, 38.2%, 42.9%, and 51.1%. The availability of U and Cd were significantly decreased by 67.4% and 54.2% in BMA amended soil, thereby reducing their accumulation in vegetables. BMA greatly promoted vegetable growth. Additionally, BMA significantly altered the structure and function of rhizosphere soil microbial communities. Coincidently, more abundant ecologically beneficial bacteria like Nitrospira, Nitrosomonas, Lysobacter, and Bacillus were observed, whereas plant pathogenic fungi like Fusarium and Alternaria reduced in BMA amended soil. The network analysis revealed that BMA amendment increased the tightness and complexity of microbial communities. Importantly, the compatibility of niches and microbial species within co-occurrence network was enhanced after BMA addition. These findings provide a promising strategy for suppressing heavy metal accumulation in vegetables and promoting their growth.

Remediation and Micro-Ecological Regulation of Cadmium and Arsenic Co-Contaminated Soils by Rotation of High-Biomass Crops and Sedum alfredii Hance: A Field Study

Rotation of high-biomass crops and hyperaccumulators is considered to be an effective, safe and economical method for the remediation of medium-mild heavy metal contaminated soil, but the present studies pay more attention to the removal efficiency rather than changes in soil micro-ecology. In order to explore the remediation effect of hyperaccumulators rotated with high-biomass crops on Cd and As co-contaminated soil, Cd hyperaccumulator ecotype (HE) Sedum alfredii Hance and crops were selected to construct a field experiment, five rotation modes including Sedum alfredii Hance-Oryza sativa L. (SP), Sedum alfredii Hance-Sorghum bicolor (L.) Moench (SS), Sedum alfredii Hance-Zea mays L. (SM), Sedum alfredii Hance-Hibiscus cannabinus L. (SK), Sedum alfredii Hance-Trichosanthes kirilowii Maxim. (ST), and investigated the effects of these modes on the removal efficiency, soil physiochemical properties and micro-ecological effects (soil nutrients, enzyme activities and microbial diversity) through a field experiment. The results showed that total soil Cd from the five rotation modes (SP, SS, SM, SK and ST) decreased by 25.1%, 20.3%, 34.5%, 6.3% and 74.3%, respectively, and total soil As decreased by 42.9%, 19.8%, 39.7%, 39.7% and 45.7%, respectively. The rotation significantly increased soil organic matter by 47.39–82.28%, effectively regulated soil pH value and cation exchange capacity. The rotation modes also significantly increased soil alkali-hydrolysable nitrogen by 9.09–50.91%, but decreased soil available phosphorus and rapidly available potassium. Except for urease, the soil enzyme activities increased overall. The Alpha diversity increased, and soil microbial structure optimized after rotation. ST mode was the most effective remediation mode, which not only reduces the content of Cd and As in the soil, but also effectively regulates the soil micro-ecology. The results from this study have shown that it is feasible to apply Sedum alfredii Hance and the high-biomass rotation method for the remediation of Cd and As co-contaminated soil.

Effects of long-term fertilization with different substitution ratios of organic fertilizer on paddy soil

In recent years, the abuse of chemical fertilizers has caused numerous environmental problems, such as soil acidification and compaction. Replacing chemical fertilizers with organic fertilizers can effectively alleviate these problems. However, the effects of alternative organic fertilizers remain unclear. To explore the effects of organic fertilizer substitution on rice yield and paddy soil physicochemical properties and bacterial community structure, we conducted a 5-year experiment using different proportions of organic fertilizer substitution in a double-cropping rice field in Jiangxi, China. Our results showed that replacing chemical fertilizers with organic fertilizers can reduce soil acidification, increase soil organic matter content, nutrient contents, and enzyme activities, improve soil physicochemical properties and microbial community, and enhance soil metabolism. Appropriate organic substitution also had positive effects on rice production. These findings enhance our understanding of the effects of different alternative organic fertilization methods and have important theoretical significance for the promotion of the use of organic fertilizers in the future.

Effect of chicken manure and chemical fertilizer on the yield and qualities of white mugwort at dissimilar harvesting times

One of the key components that affects soil productiveness, plant growth, and crop quality is fertilization. The effect of fertilizer, both organic and chemical, on the extremely acidic (pH 4.10) sandy loam soil chemical properties, yield, and quality of white mugwort grown were evaluated in this study. The field experiment arranged in a randomized complete block design, with four replications was conducted in Prachin Buri province, Thailand. There were six treatments, no fertilization (control), chemical fertilizer (25-7-7 + 46-0-0) applied at 187.50 (66.56 N:6.77 P2O5:6.77 K2O kg ha-1) kg ha-1 and applied at 375.00 (133.12 N:13.13 P2O5:13.13 K2O kg ha-1) kg ha-1, chicken manure applied at 3.36, 6.72, and 10.08 t ha-1. After harvesting, application of chicken manure tended to increase soil organic matter compared to the control, however, the application of chemical fertilizer did not show the same effect. The fresh weight of white mugwort increased with the rise in both fertilizer levels. Chicken manure application at 10.08 t ha-1 produced the highest fresh weight at all times. The level of accumulated nitrate was significantly greater when fertilizer rates increased. In addition, the total phenolic content of the white mugwort fertilized with chicken manure was higher than that fertilized with chemical fertilizer. However, there was no association between the DPPH radical scavenging capacity at harvesting times and different fertilization. Based on the results, chicken manure applied at 10.08 t ha-1 gave the best yield and higher total phenolic content of white mugwort, which was probably due to the improved soil organic matter.

Biochar-induced changes in the soil diazotroph community abundance and structure in a peanut field trial

Biological nitrogen fixation (BNF) can help replenish available nitrogen (N) in cropland and reduce the use of chemical N fertilizers, with diazotrophs playing an important role. However, the response of diazotroph community and BNF activity in biochar amendment soil, especially in the deep soil horizon, are poorly understood. In this study, soil samples were collected from topsoil (0–20 cm) and subsoil (20–40 cm) in the field experiment (established in 2013) comprising treatments with no chemical fertilizer (CK), chemical fertilizer (NPK), biochar (BC), and biochar plus chemical fertilizers (BNPK). Here, we investigated the diazotroph community using real-time PCR and high-throughput sequencing of the nifH gene, and assessed the soil N2 fixation rate (RNfix) using acetylene reduction assay (ARA). Results showed that in the topsoil, the treatments with biochar significantly increased nifH gene copies and RNfix, which was consistent with the increased soil organic matter (SOM), total carbon-to-nitrogen ratio (C/N), dissolved organic carbon (DOC) and pH. In the subsoil, applying chemical fertilizers (NPK) strongly decreased RNfix, but had no effect on diazotroph abundance; in contrast, biochar application (BC) had no effect on RNfix, but suppressed the growth of bacteria and diazotrophs while increasing the abundance of Rhizobiales order. Diazotroph and bacterial gene copies were significantly and positively correlated in both top- and sub-soil, and they were mainly influenced by SOM and total nitrogen (TN). In addition, soil nitrate nitrogen (NO3−–N) was the major factor in shaping the vertical stratification of diazotroph community structure. Although nifH gene abundance was significantly correlated with RNfix in the topsoil, the structure equation modeling (SEM) showed the highest correlation between diazotroph community structure and RNfix. Hence, we suggested that soil carbon and nitrogen sources were the key factors correlated with changes in the vertical pattern of diazotroph abundance. Biochar induced the dominant diazotroph community succession and increased soil carbon content and pH, which contributed to the BNF activity. Changes in the BNF activity were driven by the variation in diazotroph community structure.

Green Synthesis of Nanoparticles by Mushrooms: A Crucial Dimension for Sustainable Soil Management

Soil is the main component in the agroecosystem besides water, microbial communities, and cultivated plants. Several problems face soil, including soil pollution, erosion, salinization, and degradation on a global level. Many approaches have been applied to overcome these issues, such as phyto-, bio-, and nanoremediation through different soil management tools. Mushrooms can play a vital role in the soil through bio-nanoremediation, especially under the biological synthesis of nanoparticles, which could be used in the bioremediation process. This review focuses on the green synthesis of nanoparticles using mushrooms and the potential of bio-nanoremediation for polluted soils. The distinguished roles of mushrooms of soil improvement are considered a crucial dimension for sustainable soil management, which may include controlling soil erosion, improving soil aggregates, increasing soil organic matter content, enhancing the bioavailability of soil nutrients, and resorting to damaged and/or polluted soils. The field of bio-nanoremediation using mushrooms still requires further investigation, particularly regarding the sustainable management of soils.

Orychophragmus violaceus-maize rotation increases maize productivity by improving soil chemical properties and plant nutrient uptake

Appropriate use of cover crops and crop rotation in agriculture can contribute to food security and sustainable production. However, the impacts of Orychophragmus violaceus ( O. violaceus ) as rotation cover crop in maize on soil physicochemical properties and crop nutrient uptake have rarely been verified and quantified via field studies. With a conventional wheat ( Triticum aestivum L.)-maize ( Zea mays L.) rotation used as a control, a field experiment was conducted on the North China Plain in 2017–2018 and 2018–2019 to evaluate the dynamic variations in soil chemical properties and maize agronomic indexes and the impacts on maize nutrient uptake and yield under continuous maize and O. violaceus -maize rotation. We observed that rotation of O. violaceus with maize positively impacts soil chemical properties and subsequent maize productivity. Compared to those in the wheat-maize rotation, the mean contents of soil organic matter (SOM), soil alkali–hydrolyzable nitrogen (SAN), soil available phosphorus (SAP), and soil available potassium (SAK) in the O. violaceus -maize rotation increased by 8%, 11%, 13% and 18%, respectively, within the 0–60 cm soil layer, thereby increasing the maize N and P uptake and yield at maturity. According to correlation analysis and path model results, the most powerful direct factor affecting the maize yield was plant nutrient uptake rather than biomass accumulation. The O. violaceus -maize rotation was superior to the wheat-maize rotation and continuous maize in term of SOM, SAN, plant agronomic indexes, and maize nutrient uptake and yield. Overall, O. violaceus -maize is a reasonable rotation system for use on the North China Plain and provides new insight into the mechanisms and processes underlying crop yield and nutrient uptake. • O. violaceus -maize greatly increased soil organic matter and soil available nitrogen. • The maize nutrients uptake was increased at maturity in O. violaceus -maize system. • Replacing wheat or fallow field with O. violaceus increased maize yield by 8%−12%. • The relationship between soil chemical property and maize yield was quantified.

Effects of drilling waste combined with exogenous organic matter on physicochemical properties of aeolian sandy soil and growth of spinach

An indoor potted experiment was carried out to study the application effects of water-based waste drilling mud (WBDM) and drill cuttings combined with humic acid and woody peat in aeolian sandy soil.We analyze their effects on the growth of spinach, in order to provide a reference for the resource utilization of drilling waste and the improvement of aeolian sandy soil. A total of three individual experiments were set up: 4 treatments in the basic group, taking aeolian sandy soil as the control (CK), mixing aeolian sandy soil and drill cuttings at a mass ratio of 1:1, then added with 0, 2%, and 4% WBDM (dry basis) respectively. The basic group treatment was added with 1% humic acid, 1% humic acid+3% woody peat mixture respectively, as the humic acid group and woody peat group. The results showed that in the basic group, drilling waste application significantly increased soil organic matter content (SOM), pH and electrical conductivity, the 2% WBDM significantly promoted the growth of spinach. Humic acid and woody peat reduced soil pH and increased SOM content and electrical conductivity. Plant growth indicators such as plant height, total leaf area, fresh weight and dry weight of the humic acid group were higher than the corresponding treatments in the basic group. The mixed addition of humic acid and woody peat did not affect plant growth. The treatment with the best performance was to add 2% WBDM to the humic acid group, and the SOM was 13.1 g·kg-1, spinach's plant height, total leaf area, fresh weight and dry weight significantly increased by 49.7%, 93.4%, 83.3%, and 34.6% than CK after 40 days of sowing. The application of drilling waste with organic matter could significantly increase SOM content and promote spinach growth. Aeolian sandy soil + drill cuttings + WBDM (2%) + humic acid (1%) was the best combination mode.

Simulated Cropping Season Effects on N Mineralization from Accumulated No-Till Crop Residues

The adoption of no-till management practices has increased in the United States over the last decade. In the state of North Dakota, approximately 5.7 million hectares of cropland is managed under no-till or conservation tillage management practices. Even though conservation tillage is known for building soil health, increasing soil organic matter, capturing soil moisture, and reducing wind and water erosion, it also presents a unique best management practice since an increased mass of crop residue remains on the soil surface. Producers are concerned about whether plant needs are being met by nitrogen fertilizer that is currently being applied based on current North Dakota recommendations for long-term no-till systems. A Forman clay loam soil (fine-loamy, mixed, superactive, frigid Calcic Argiudolls) was used in this study, as it represented glacial till soils of the region. We examined whether N mineralization from surface-applied crop residue would result in similar or different results when compared to crop residue mixed into the soil. Soil freeze-thaw contribution to soil N mineralization was also evaluated. Six residue treatments with different C/N ratios including corn (Zea mays L.), soybean (Glycine max L.), forage radish (Raphanus sativus L.), winter pea (Pisum sativum L.), spring wheat (Triticum aestivum L.), and winter wheat (Triticum aestivum L.) were used. Five 10–14-week cycles with a three-week freeze period between each cycle at 0 ºC were evaluated for NO3-N production. Crop residues with a narrow C/N ratio contributed to greater instances of N mineralization during each incubation cycle, and the accumulation of crop residues with a wide C/N ratio over each incubation cycle following the first incubation did not offset the immobilization trends observed in the first incubation. A change in N mineralized in the untreated control soil during the last two incubation cycles may have been caused by freeze-thaw effects or a shift in microbial population due to a lack of fresh C inputs.

Genotypic Diversity Improves Photosynthetic Traits of Hydrocotyle vulgaris and Alters Soil Organic Matter and N2O Emissions of Wetland Microecosystems

In plant communities, genotypic diversity can impact the plant community structure and ecosystem functions, but related research has focused on native plants. Therefore, whether genotypic diversity affects the growth of invasive plants and then changes the wetland microecosystem remains unresolved. In this study, six different genotypes of Hydrocotyle vulgaris, a common invasive plant in China, were selected to construct populations with three different genotypic diversity levels (one, three, and six genotype combinations, respectively) to explore the effects of different genotypic diversity levels on the growth and physiological traits of H. vulgaris, and soil nutrients and greenhouse gas emissions of the wetland microecosystem under flooding conditions. We found that genotypic diversity improved the leaf area, root to shoot ratio and photosynthetic physiological traits of H. vulgaris, especially under flooding. Moreover, genotypic diversity increased soil organic matter (SOM) contents in the wetland microecosystem, while it reduced the cumulative nitrous oxide emissions under flooding conditions. Overall, genotype diversity improved photosynthetic traits of H. vulgaris, further increased SOM, and reduced the N2O emissions of the wetland microecosystem. The results of this study can provide a theoretical basis for exploring how genotypic diversity levels affect the invasiveness of invasive plants and ecosystems in wetland microecosystems.

Effects of tillage systems on soil organic carbon and some soil physical properties

AbstractConservation tillage by increasing soil organic carbon can improve soil structure, especially in arid and semiarid regions. In this study, the effects of three tillage systems [conventional (CT), reduced (RT), and no‐till (NT)] in a wheat‐maize crop rotation on soil organic carbon content (SOC) and some physical properties of a clay loam soil were investigated. The field experiment was set up in a randomized complete block design with three replications in the third year in northeastern Iran. Samples of disturbed and undisturbed soil were collected from 0–15 and 15–30 cm depths and analyzed to quantify SOC content, pore size distribution, hydraulic properties, and aggregate stability. SOC was higher in NT than in the RT and CT treatments, due to the use of cover crops (clover) and the retention of crop residues in this system. The highest water‐stable and macro‐aggregate content were also obtained in the NT system. The highest water contents (for most of the matric suctions) were found in the treatments CT and RT, which also had a high total soil porosity. It was found that tillage in CT and RT loosened the soil and thus increased the total porosity. The highest air‐entry value was found in the CT treatment at 15–30 cm depth, which contained the most micro‐aggregates. However, the maximum n‐value (shape parameter of the water retention curve) was obtained in the treatment with the largest pores, that is, NT at a depth of 15–30 cm. X‐ray images of the pore space and pore function data (dmean, dmode, and dmedian) showed that the largest soil pores were found in the NT treatment, probably due to the high SOC in the NT system. The results of this study showed that the effects of tillage systems on soil physical properties are strongly dependent on SOC. Based on the results of this study, the use of a no‐till system with crop rotation that includes cover crops and crop residue retention is recommended to increase soil organic matter and thereby improve soil structural stability in arid and semiarid regions.

Irrigation effects on the formation of soil organic matter from aboveground plant litter inputs in semiarid agricultural systems

In semiarid agricultural systems, irrigation may increase soil organic matter (SOM) due to higher biomass production. However, aboveground production tends to increase more than belowground biomass, and in no-till systems SOM responses to irrigation would strongly depend on the fate of crop residues left on the soil surface. Litter decomposition and SOM formation can also be affected by irrigation due to changes in water dynamics, but little is known about the impacts of irrigation on the pathways of SOM formation. We used dual 13C and 15N labeled maize litter to quantify the effect of irrigation on the contribution of aboveground crop residues to SOM formation in semiarid, no-till agricultural systems. We incubated the litter in a continuous maize cropping system with two treatments, dryland and irrigated, and measured litter decomposition and its contribution to different SOM pools. Irrigation had a larger effect on litter C and N losses than on the formation of new SOM. After 13 months the C and N losses from the litter layer were 24% higher under irrigation, but there were no treatment differences in the litter-derived C and N recovered in SOM. Most of the litter-derived organic matter (OM) was found in the mineral associated OM pool (MAOM), but irrigation did not affect the amount of litter-derived OM found as MAOM or as particulate organic matter. Irrigation increased the amount of litter-derived OM found in macroaggregates, and this observation was more related to a higher aggregation than to aggregate enrichment in the irrigated treatment. Our results suggest that a smaller proportion of aboveground crop residues will form SOM in irrigated systems compared to dryland conditions and may help to partially explain why irrigation has a stronger relative effect on crop productivity and C inputs than on SOC stocks in semiarid agricultural systems.

Residual Effect of Green Manure on Soil Properties in Green Manure- Transplant Aman-Mustard Cropping Pattern

Background: Conventional monoculture or cereal-cereal sequence systems insist farmers to use excessive application of chemical fertilizer in agriculture resulting reduce the soil organic matter contents and structures. The inclusion of green manuring crops in a rotation is vital to improve the biochemical and physical properties of the soil via increasing the labile of organic matter and ultimately increased crops yield. Some complex molecules of green manuring crops takes a longer time of decomposition and thus nutrients reserve in soil and release latter which provide nutrients to the succeeding and following crops. So the current experiment aimed to study the residual effect of different in situ green manuring crops to the sub-sequent and following soil. Methods: The field experiment conducted during 2015 to 2016 with eight green manuring crops and rice and mustard was the subsequent and following crop. In situ incorporation of GM crops with 100% (F1) and 50% (F2) fertilizer, the prior and post-harvest soil (cropping pattern) of experiment field (0-15 cm) was collected and analyzed. Result: After two consecutive year, GM-T.aman-Mustard cropping pattern increased soil organic matter 0.04% to 0.07% and 0.02% to 0.03% (T1 and T2 with F1 and F2) and nitogen 0.05% (T1, T2 and T7 with F1 and F2) and K 0.2 to 0.5 meq/100 g (M. pudica with F1 and F2) and P 2 ppm to 15 ppm (T1, T2, T3 and T7 with F1 and F2) compared to initial soil. Rice yield with T1, T2, T3 and T6 shown higher with both fertilizer doses. Nitrogen fertilizer rates could be reduced after the incorporation of green manures in the succeeding and following crops.

Low N apparent surplus with higher rice yield under long-term fertilizer postponing in the rice–wheat cropping system

Nitrogen (N) fertilization increases rice yield, but inappropriate N fertilizer application increases N loss and the risk of environmental pollution. Short-term fertilizer postponing (FP) generally reduces N apparent surplus and increases rice yields, but the effects of long-term FP on N surplus and rice yields remain unknown. Our study was the first to investigate the impacts of long-term FP (11 years) on N apparent surplus and rice yields. FP effects in the short term (≤6 years) did not affect rice yields, whereas FP effects in the long term (>6 years) increased rice yields by 13.9% compared with conventional fertilization (CF). FP did not affect panicles per unit area, 1000-kernel weight, and filled-kernel rate, but spikelets per panicle increased over time due to spikelet formation stimulation. FP also reduced the N apparent surplus over time more strongly than CF owing to higher N accumulation and N utilization efficiency. FP effects in the long term also significantly increased soil organic matter, total N, and NH4+-N content. Our results were supported by a pot experiment, showing that rice yields in soils with a history of FP were significantly higher than those for soils without a history of FP, indicating that FP increased rice yields more strongly in later years mainly because of soil quality improvement. Our findings suggest that long-term FP can reduce N loss while increasing rice yields by improving soil quality.

Tea plant growth and soil nutrients in response to the application of fertilizer in Guizhou province, China

AbstractMore than half of the total production of tea [Camellia sinensis (L.) Kuntze] in China is produced in the Guizhou province. However, in this region soils generally have low soil fertility, so new techniques to improve the productivity and fertility are needed. The aim of this study was to evaluate the effects of application of seven types of humic acid‐based organic–inorganic compound fertilizer (HTOF) on tea quality and productivity. Two different cultivars of tea (cultivars Shiqiantaicha and Fudingdabaicha) were used as model plants. In the research, seven different HTOF fertilizers were tested at two sites. Application of the HTOF increased soil pH to a range closer to that most suitable for the growth of tea plants and relatively increased soil organic matter, ammonium‐N, inorganic P, and extractable K. In addition, HTOF increased tea bud weights and density. Application of HTOF‐1 also produced the best responses among all products tested. Findings from this study indicate that formula is recommended for application during the production of young C. sinensis tea plants.

No Tillage Increases SOM in Labile Fraction but Not Stable Fraction of Andosols from a Long-Term Experiment in Japan

No tillage (NT) fosters carbon (C) sequestration, increases soil organic matter (SOM) stock, and improves soil health. However, its effect on SOM accumulation in Andosol, which has high OM stabilization characteristics due to its specific mineral properties, remains unclear. In this study, we evaluated the effect of NT on SOM content and its distribution by the physical fractionation method and assessed the quality of accumulated SOM in each fraction. We collected soil samples at 0–2.5, 2.5–7.5, and 7.5–15 cm depths from NT and conventional tillage (CT) plots in a long-term (19 years) field experiment of Andosols in Ibaraki, Japan. The soil samples were separated into light fraction (LF), coarse-POM (cPOM: 0.25–2 mm), fine-POM (fPOM: 0.053–0.25 mm), and silt + clay (mOM: <0.053 mm). The C, nitrogen (N), and organic phosphorus (Po) contents of each fraction were analyzed. The C content of cPOM and fPOM in NT at 0–7.5 cm was higher than in CT, while there was no clear difference in the mOM fraction or deeper layer (7.5–15 cm). NT increased the C, N, and Po contents in the labile POM fractions at the surface layers but did not increase the stable fraction or change the quality.

Conservation and Conventional Vegetable Cultivation Increase Soil Organic Matter and Nutrients in the Ethiopian Highlands

Agriculture in Africa is adversely affected by the loss of soil fertility. Conservation agriculture (CA) was introduced to curb the loss of soil fertility and water shortages and improve crop productivity. However, information on how CA practices enhance soil quality and nutrients is scarce in the sub-Saharan Africa context. The objective of this study was to investigate the effects of CA and conventional tillage (CT) on soil organic matter and nutrients under irrigated and rainfed vegetable on-farm production systems. During the dry and wet monsoon phases in the northern Ethiopian Highlands, a four-year experiment with CA and CT was carried out on ten vegetable farms under rainfed and irrigated conditions. Although the increase in concentration of organic matter in CA was generally slightly greater than in CT, the difference was not significant. The average organic matter content in the top 30 cm for both treatments increased significantly by 0.5% a−1 from 3% to almost 5%. The increase was not significant for the 30–60 cm depth. The total nitrogen and available phosphorus concentrations increased proportionally to the organic matter content. Consequently, the extended growing season, applying fertilizers and livestock manure, and not removing the crop residue increased the nutrient content in both CA and CT. The increase in CA was slightly greater because the soil was not tilled, and hay was applied as a surface cover. Although CA increased soil fertility, widespread adoption will depend on socioeconomic factors that determine hay availability as a soil cover relative to other competitive uses.

Perennial cereal grain cultivation: Implication on soil organic matter and related soil microbial parameters

Novel perennial grains in agriculture have the potential of providing soil ecosystem services and boosting plant-soil microbial relationships via increasing soil organic matter (SOM). Hence, we evaluated the implication of perennial intermediate wheatgrass agroecosystems (+/− alfalfa intercrop) in contrast to organic and conventional rotation systems on SOM and related soil microbial parameters. Soil samples were obtained from perennial intermediate wheatgrass (IWG), sole (IWG-SC) or intercropped with alfalfa (IWG-IC), as well as organic (ORG-A) and conventional (CON-A) rotation systems of annual wheat. Soil samples were taken in two depths (0–30 cm and 30–60 cm) and analyzed for total and fractionated soil organic C (SOC), microbial biomass C and N (MBC and MBN), basal microbial respiration (Rb), potential enzyme activities related to C and N cycling (Cellobiohydrolase (CBH), Leucine-aminopeptidase (LAP)), and abundance of functional genes related to N cycling (amoA, nifH) and 16S rRNA genes. Despite the lack of fertilization in the IWG systems, SOC concentration and the amount of C in the particulate organic matter were higher in the 30–60 cm depth of IWG systems than ORG-A and CON-A. Higher MBN and LAP activities were observed in the 0–30 cm depth of ORG-A than both IWG and CON-A. Mass specific CBH activities and metabolic quotient qCO2 were lower in the 30–60 cm depth of IWG systems, implying reduced C losses and high C use efficiency in these systems. Similarly, we observed higher amounts of 16S rRNA in the 30–60 cm depth of IWGs than ORG-A and CON-A. Hence, IWG systems increased SOC and microbial biomass and activities in the 30–60 cm depth than ORG-A and CON-A. However, the more diverse IWG (+ alfalfa intercrop) did not increase microbial biomass and activities than IWG monoculture. Our study provides a reflection of how perennial grain agroecosystems, in conjunction with organic rotation systems, induce a positive influence on SOC and microbial activities than CON-A. It further suggested that perennial grain cultivation goes beyond the reach of organic farming dominated by annual crops to induce SOC and support relevant soil microbial functions in subsoils.