Acidic Soil pH Research Articles

A report of Siwalik forest around Letang Raja-Rani wetland, Morang, eastern Nepal

Species composition, phytosociological status and soil characteristics of Siwalik forest occurring around Raja-Rani wetland, Letang municipality, eastern Nepal was studied. A total of 47 tree species belonging to 40 genera and 26 families were reported. Dominant and co-dominant trees were Shorea robusta (IVI=133.4) and Schima wallichii (IVI=70.6), respectively. In the forest total tree density, basal cover area, seedling density, fallen dead density and dead standing density were 378.4 trees ha-1, 163.7 m2 ha-1, 105250 individual ha-1, 4 trees ha-1 and 1.6 trees ha-1, respectively. Irregular girth class distribution and high stump density (136.8 tree ha-1) denote disturbance. Soil physicochemical characteristics were: acidic soil (pH 4.8), moisture (12.5%), water holding capacity (50.05%), bulk density (1.17 g cm-3), porosity (0.55%), humus (8.6%), organic carbon (0.52%), nitrogen (0.1%), phosphorus (33 kg ha-1), and potassium (300 kg ha-1). Regulating human encroachment to ensure natural regeneration of species to maintain the viability of the Letang Raja-Rani wetland site and integrity of the local ecosystem is strongly recommended.

Expression levels of genes involved in metal homeostasis, physiological adaptation, and growth characteristics of rice (Oryza sativa L.) genotypes under Fe and/or Al toxicity.

Acid sulphate soil contains high amounts of iron (Fe) and aluminum (Al), and their contamination has been reported as major problems, especially in rainfed and irrigated lowland paddy fields. Rice is sensitive to Fe and Al grown in acid soil (pH < 5.5), leading to growth inhibition and grain yield loss. The objective of this study was to evaluate Fe and/or Al uptake, translocation, physiological adaptation, metal toxicity, and growth inhibition in rice genotypes grown in acid soil. Fe and Al in the root tissues of all rice genotypes were enriched depending on the exogenous application of either Fe or Al in the soil solution, leading to root growth inhibition, especially in the KDML105 genotype. Expression level of OsYSL1 in KDML105 was increased in relation to metal uptake into root tissues, whereas OsVIT2 was downregulated, leading to Fe (50.3 mg g-1 DW or 13.1 folds over the control) and Al (4.8 mg g-1 DW or 2.2 folds over the control) translocation to leaf tissues. Consequently, leaf greenness (SPAD), net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (E) in the leaf tissues of genotype KDML105 under Fe + Al toxicity significantly declined by 28.4%, 35.3%, 55.6%, and 51.6% over the control, respectively. In Azucena (AZU; Fe/Al tolerant), there was a rapid uptake of Fe and Al by OsYSL1 expression in the root tissues, but a limited secretion into vacuole organelles by OsVIT2, leading to a maintenance of low level of toxicity driven by an enhanced accumulation of glutathione together with downregulation of OsGR expression level. In addition, Fe and Al restrictions in the root tissues of genotype RD35 were evident; therefore, crop stress index (CSI) of Fe + Al-treated plants was the maximum, leading to an inhibition of gs (53.6% over the control) and E (49.0% over the control). Consequently, free proline, total phenolic compounds, and ascorbic acid in the leaf tissues of rice under Fe + Al toxicity significantly increased by 3.2, 1.2, and 1.5 folds over the control, respectively, indicating their functions in non-enzymatic antioxidant defense. Moreover, physiological parameters including leaf temperature (Tleaf) increment, high level of CSI (>0.6), SPAD reduction, photon yield of PSII (ΦPSII) diminution, Pn, gs, and E inhibition in rice genotype IR64 (Fe/Al-sensitive) under Fe + Al treatment were clearly demonstrated as good indicators of metal-induced toxicity. Our results on Fe- and/or Al-tolerant screening to find out the candidate genotypes will contribute to present screening and breeding efforts, which in turn help increase rice production in the Fe/Al-contaminated acid soil under lowland conditions.

Soil Physico-Chemistry in the Habitat of Rafflesia in Kinabalu Park, Sabah, Malaysia.

This study was conducted to identify the type of soil texture, and its relationship with Tetrastigma sp., a host of the Rafflesia sp. in Kinabalu Park, Sabah, Malaysia. The soil samples were collected from five study areas: Losou Podi, Losou Minunsud, Sayap Substation, Langanan and Gansurai. The plot was selected when the host exhibited traits of being infected by Rafflesia, either by the presence of buds, flowers or residual scar marks found on the host. The result reveals that the soil in the habitat of Rafflesia sp. and their host is sandy loam type, with a high volume of sand compared to silt and clay, between 65.40-79.25%. The soil moisture in the area is low, ranging from 14.89% to 27.96%. The soil in the plots was less fertile due to low value of soil organic matters (1.12-1.40%), with slightly acidic soil pH value (4.08-4.73). The most abundant elements contained in the soil were Fe, Al and Mg. The different Rafflesia habitats were observed to have a relationship with different soil factors: either physical, chemical, or both to promote the growth of Rafflesia. There was relationship between Sayap Substation with some chemical elements in the soil, rather than the soil’s physical characteristic. Both Langanan and Losou Podi were only influenced by the physical characteristics of the soil. In comparisons, the Gansurai and Losou Minunsud have a relationship influenced by a combination of physical properties and chemical elements in the soil. From this study, it can be concluded the presence of Tetrastigma sp. in the different Rafflesia habitats has its own relationship with the soil and is not influenced by one factor.

Mycorrhizal dependency and growth response of A. chinensis (Osbeck) Merrill and Pongamia pinnata (L.) pierre in soil media with low pH and high aluminium

Silica sand post mining has low nutrient soil, acidic soil pH (3.2), hight Al content (7.70 cmol/kg) which are the limiting factors of plant growth. Therefore, soil quality might be improved by the addition of soil ameliorant and fertilizer application. MycoSilvi is consortium of Arbuscular Mycorrhizal fungi and Mycorrhizal helper bacteria (MHBs). This study was aimed to analyze the dependence of plants against FMA contained in MycoSilvi. There are three variants of MycoSilvi, both single or in combination with soil ameliorant to enhance Albizia chinensis (Osbeck) Merrill and Pongamia pinnata (L.) Pierre growth. The research design was a factorial sheme with two factors, MycoSilvi (M) consists of four levels (M0=Without MycoSilvi, M1=MycoSilvi variant 1, M2 = MycoSilvi variant 2 and M3 = MycoSilvi variant 3) and Soil ameliorant (LC) consisting of four levels (L0C0 = Without soil ameliorant, L1C0 = Lime, L0C1 = Compost, L1C1 = Lime and Compost). Data were analysed using analysis of variance (ANOVA). Dry weight of shoot and root, top root ratio, percentage of mycorrhizal colonization, growth response and the relative dependence of mycorrhiza were observed after 12 weeks of planting. The results showed that combination of MycoSilvi and soil ameliorant can made dry weight of a shoot, root and top root ratio better than all treatment. Whereas the best growth response and mycorrhiza dependency was shown in MycoSilvi variant 3 without lime and compost (M3L0C0). The results showed that A. chinensis and P. pinnata plants had a high degree of dependence on FMA for their life force.

Risk Assessment of Heavy Metals in Chromolaena odorata Collected Around Gemstone Mining Site in Ijero-Ekiti

In Nigeria, like many developing nations, the resultant effect of land degradation: aggravated soil erosion, flood disasters, salinization or alkalisation, and the desertification have been a major public health concern for the past decades, however this study highlighted some of the factors that leads to the menace of soil fertility. The study was conducted at a gemstone mining site in Ijero Ekiti, Ekiti State, Nigeria. The soil samples were collected at a depth of 0-15 cm top soil and 0-30 cm subsoil. A line transect of 20 cm was drawn and soil sample was collected, all samples were kept in a clean container and labeled accordingly before been transported to the laboratory for analysis. The plant samples were thoroughly washed with distilled water to remove dust and other particles, air dried in a dust free wire meshed cage. All data obtained from this research were subjected to one-way analysis of variance (ANOVA). The result obtained in this study indicated that the levels of heavy metal concentration tested were still within the permissible limit in the root and shoot of Chromolaena odorata between the mine and control site. The implication of this is that Chromolaena odorata is safe for human and animal consumption. The said plant can readily undergo photosynthetic activity to aid growth by exploiting the presence of these metals either as a macro-nutrient or micro-nutrient as seen from the Translocation Factor and Metal Transfer Factor. The study concludes that soil at Ijero-Ekiti mine site were slightly acidic soil pH, reduced organic carbon, total nitrogen, available phosphorus, exchangeable cations and averagely elevated heavy metal contents.

Volatile fatty acid concentration, soil pH and soil texture during anaerobic soil conditions affect viability of Athelia (Sclerotium) rolfsii sclerotia

Volatile fatty acid concentration, soil pH and soil texture during anaerobic soil conditions affect viability of Athelia (Sclerotium) rolfsii sclerotia

The ubiquitous soil verrucomicrobial clade 'Candidatus Udaeobacter' shows preferences for acidic pH.

Members of the verrucomicrobial clade 'Candidatus Udaeobacter' rank among the most dominant bacterial phylotypes in soil. Nevertheless, despite this global prevalence, in-depth analyses with respect to pH preferences of 'Ca. Udaeobacter' representatives are still lacking. Here, we utilized a recently designed primer pair, specifically targeting 'Ca. Udaeobacter', to investigate links between soil pH and the abundance as well as phylotype composition of this largely unexplored verrucomicrobial clade. Based on 150 forest and 150 grassland soils, comprising a broad pH range, we determined the highest total abundance of 'Ca. Udaeobacter' in strongly acidic soil (pH, ~5.1) and, noteworthy, in ultra-acidic soil (pH< 3.5) and at a pH≥ 7, its abundance drastically declined. When we analysed the six most dominant amplicon sequence variants affiliated with 'Ca. Udaeobacter' separately, their abundances peaked within a pH range of approximately 4.7-5.2, and only in one case at slightly acidic soil pH (pH, 6.1). Our study benefits from a combination of quantitative real-time PCR and high-throughput amplicon sequencing, enabling for the first time a highly specific abundance analysis of representatives affiliated with 'Ca. Udaeobacter', which revealed that this globally abundant verrucomicrobial clade shows preferences for acidic soil.

Release Pattern of Dissolved Silicon and Its Budgeting under Rice Planted and Unplanted Condition in Acidic, Neutral and Alkaline Soils

ABSTRACT Release of silicon (Si) from different Si sources and Si budgeting in varied types of soils are required for the exploration of sustainable rice production. Si products are shown to be effective in improving crop growth and yield; however, its reactivity differs based on the soil type. A pot experiment was conducted by using three Si sources (calcium silicate (CaSiO3), diatomaceous earth (DE), and rice husk biochar (RHB)) in acidic, neutral, and alkaline soils under rice planted and unplanted conditions for a single season. A large variation in Si uptake by rice existed amongst the different sources of Si and was found to be higher in neutral soil followed by acidic and alkaline soil. Application of calcium silicate followed by diatomaceous earth recorded higher Si uptake in acidic (547.17 ± 39.15 mg pot−1) and neutral (632.65 ± 112.21 mg pot−1) soil whereas, rice husk biochar in alkaline soil (35.32 ± 4.60 mg pot−1). Application of calcium silicate and RHB significantly increased the plant available Si in post experimental soil. The soil solution pH of acidic, neutral and alkaline soils ranged from 5.62– 8.59, 6.62– 9.13, and 7.64– 9.37, respectively, with the application of different rates and sources of Si during the experimental period. The application of CaSiO3 followed by RHB increased the dissolved Si in acidic and neutral soil whereas RHB and DE in alkaline soil. The amount of DSi with the application of different sources and levels of Si ranged from 47– 447, 139– 751, and 161– 374 µmol L−1 in acidic, neutral, and alkaline soil, respectively. About 16 to 28% of Si in acidic and neutral soil and 10 to 19% Si in alkaline soil was accounted by irrigation water.

Morphophysiological responses of table beet irrigated with saline water under application of humic substances

The use of saline water is an alternative for irrigating agricultural crops, especially in the Brazilian Northeastern semi-arid region, where water quality is limited in most cases. Thus, the objective was to evaluate the morphophysiological responses of table beet cv. “Wonder” irrigated with saline waters under the application of humic substances. The experiment was conducted under a randomized block design, with six replications in a 6 x 4 x 5 factorial scheme, referring to six electrical conductivities of irrigation water (ECw): 0.5; 1.5; 2.5; 3.5; 4.5 and 5.5 dS m-¹, four humic substances rates (HS) (0; 10; 20 and 30 ml per plant), and five stages of assessment (23, 38, 53, 68 and 83 days after emergency). The characteristics evaluated were: plant height, number of leaves, leaf area, chlorophyll content (a, b and total), stomatal conductance, transpiration, net photosynthesis and CO2 internal concentration, and in the soil, the soil pH and the electrical conductivity of saturated paste extract. The increase of salinity reduced growth, chlorophyll a content, and the stomatal conductance of beet plants. The application rate of 30 ml per plant of humic substances promotes an increase in stomatal conductance. The application of humic substances raises the pH in sandy acidic soils. It is recommended to irrigate table beet plants with water of 0.5 dS m-1 associated with the application of 30 mL per plant of humic substances

Multiple soil factors explain eutrophication signals in the understorey vegetation of temperate forests

AbstractQuestionsVegetation in forest understories is determined by a complex interplay of many different environmental factors, including light, water and nutrient availability. Changes in these conditions, especially changes in nitrogen (N) availability, have been widely discussed to cause shifts in species composition and loss of oligotrophic species. We examined whether nitrogen is the most important factor for the decline of nitrogen‐sensitive species in understorey communities, as measured by average Ellenberg N values and the share and number of nitrogen‐sensitive character species.LocationNine different oligo–mesotrophic types of temperate forest in southwest Germany.MethodsWe combined understorey vegetation and soil data from 135 forest stands. To study the importance of variables in explaining the vegetation gradients, we used random forest analyses and non‐metric multidimensional scaling (NMDS) ordinations combined with fitting of environmental vectors.ResultsWe detected strong differences between three examined forest type groups: eutrophication in the understorey vegetation of broad‐leaved forests on carbonate soils was strongly related to high canopy closure and low soil carbon/phosphorus (C/P) ratio. In broad‐leaved forests on acidic soil, base saturation played a major role, but the vegetation was also influenced by the C/N and C/P ratios. In coniferous forests on acidic soil, soil pH and organic layer depth were important, as were the C/N, C/P and N/P ratios.ConclusionOur results show that eutrophication in understorey forest vegetation is not monocausal. Rather, oligotrophic species of forest communities are reduced at sites with higher N or P availability and/or higher base saturation and soil pH. These conditions favor fast‐growing ubiquitous species in the competition for light and other limiting factors. Since these factors were of varying importance between the forest types examined, differences shaping the forest communities need to be regarded when evaluating the impact of environmental changes, for example through atmospheric nitrogen deposition.

Effects of various phosphorus fertilizers on maize yield and phosphorus uptake in soils with different pH values

ABSTRACT The performance of fertilizers may differ significantly in different soils. Here, we quantify effects of various phosphorus (P) fertilizers on maize yield and P uptake in soils with different pH values, using a pot experiment. Five P fertilizers were used; monoammonium phosphate (MAP), diammonium phosphate (DAP), calcium superphosphate (CSP), calcium magnesium phosphate (CMP) and, ammonium polyphosphate (APP). Two soils were neutral fluvo-aquic soil (pH 7.2) and acidic yellow cinnamon soil (pH 5.0). Generally, acidic soil restricted the root activity, dry matter accumulation, P uptake, and yield of maize. The effects of P fertilizers were inconsistent in the different soils. In neutral soil, the effects were the highest for DAP and lowest for CMP. However, in acidic soil they were highest for CMP, followed by DAP, and lowest for MAP. In neutral soil, DAP treatment showed higher P uptake efficiency (PUpE) and partial factor productivity (PPFP), while CMP treatment showed higher P harvest index (PHI) and utilization efficiency PUtE. In acidic soil, the PUpE and PPFP of CMP and DAP treatments were higher than in other treatments. Therefore, choosing the right P fertilizer based on soil acidity can significantly improve maize yield, P uptake, and P utilization to optimize P management.

Influence of soil properties, temperature and pH on adsorption-desorption of imazamox in Indian aridisols

ABSTRACT As adsorption-desorption behaviour of herbicide plays an important role in determining leachability, release rate and availability to target species, the present study aims to evaluate the influence of soil properties, temperature and ionic state of imazamox on its adsorption-desorption behaviour. The sorption was significantly influenced by above evaluated parameters and Freundlich adsorption coefficient varied from 0.24 × 103 to 7.60 × 103 mg1−1/n kg−1 L1/n. In soils with pH in the range of 6.4–9.5, sorption of imazamox decreased with increase in solution pH while in acidic soil (pH 2.3 to 5.9), adsorption increased with increase in solution pH. At low solution pH adsorption occurs mainly through cationic form while at high solution pH adsorption was predominantly through anionic form. The presence of electrostatic attractive and repulsive forces, ∏→∏ charge transfer, hydrogen bonding and van der waals forces was key mechanism affecting the adsorption of imazamox. Greater adsorption hysteresis was observed in soils having pH in the range of 6.2–9.5 suggesting relatively less adsorption and difficult desorption of imazamox in these soils. Due to irreversible binding in high pH soil, it can be speculated that it may enhance the chances of crop injury in these soils.

Stratification, Scarification and Application of Phytohormones Promote Dormancy Breaking and Germination of Pelleted Scots Pine (Pinus sylvestris L.) Seeds

Seed quality is an important issue in forestry as it is an essential parameter in the production of high quality planting material. Many factors may hinder the harvesting of high quality seeds, including an insufficient number of sunny days, external conditions in temperate climate zones, and fungal pathogens affecting development of seedlings. We undertook to develop a procedure maximizing seed protection and promoting the optimum physiological development of seedlings by examination of the impact of seed pelleting (a general seed protection method) on germination rates and seedling development of Scots pine (Pinus sylvestris L.). Germination of pelleted seeds was examined in relation to substrate (water vs. soil) and LED light spectrum (white vs. red-blue). Several dormancy breaking treatments were applied: stratification/scarification, and growth regulator treatments including gibberellic acid (GA3), indole-3-acetic acid (IAA) and 1-naphthaleneacetic acid (NAA), to stimulate seed germination. Experiments included independent tests for each treatment (stratification/scarification and plant growth regulators), and combinations of both stratification/scarification and phytohormone treatments. The impacts of these treatments and various controlled germination conditions on the fluorescence of chlorophyll were analyzed using the maximum efficiency of photosystem II photochemistry parameter (Fv/Fm). In addition, chlorophyll a and b content in Scots pine seedlings germinated from pelleted seeds, were quantified using high-performance liquid chromatography (HPLC). The combined stratification/scarification and growth regulator treatment was the most effective germination promoting method for pelleted Scots pine seeds. Scots pine seeds are highly likely to be photoblastic. The best germination rate, while maintaining optimal physiological parameters, was achieved in acidic soil (pH 5.0) with white LED light.

The effects of soil incorporation depth of Biodiesel Co-Product (BCP) additions on N leaching losses and on genes involved in soil nitrogen cycling in an acidic Chinese tea soil

The effectiveness of Biodiesel Co-Product (BCP) in decreasing N leaching from an acidic soil (pH 3.7) and effects on greenhouse gas emissions and N functional genes following surface application (0–6-cm depth) of 4.5 mg BCP-C g−1 soil and complete mixing (0–18-cm depth) of 1.5 mg BCP-C g−1 soil, was investigated in a 35-day laboratory lysimeter experiment. The BCP additions significantly decreased AOA and AOB amoA gene copy numbers, especially from the surface BCP application, suggesting both methods therefore inhibited nitrification. Microbial biomass N and C significantly increased following both types of BCP incorporation, particularly with surface mixing, as compared to treatments without BCP. BCP increased nifH genes with both applications. Surface application of BCP produced higher emission rates of N2O and CO2 than complete mixing. Based upon (nirS+nirK)/nosZ ratios, more N2O emissions, caused by denitrification, came from the surface application than complete mixing, in support of the gaseous measurement of N2O. However, complete mixing was more effective than surface BCP application in decreasing N leaching: 2.14% of 15N fertilizer in the leachate from complete mixing, compared to 51% following surface application, and 68% without BCP addition. These findings demonstrate that complete mixing was more effective than surface BCP application in decreasing N leaching and gaseous losses. We conclude that BCP is an effective and biologically safe method to prevent nitrate leaching in this acidic Chinese soil.

Tolerance of F6 Red Rice Lines against Iron (Fe) Stress

Dryland area in Indonesia reaches 108.8 millions ha (69.4%) of the total dry land with the potential to expand the area of food crops reaching 7.1 million ha, which is dominated by ultisol and oxisol soil types. Plant constraint cultivation on ultisol soil types is the acidic soil pH with high Al and Fe levels. One of the efforts that can be made to cultivate plants on ultisol soil is the selection of plants that are tolerant of Fe stress. This study aimed to determine a tolerance level and F6 red rice lines that were tolerant of iron (Fe) stress in ultisol soils. The experimental design used was factorial Completely Randomized Design (CRD) consisting of 2 factors, the first factor consisted of 12 treatments (10 test lines and 2 comparison varieties) and the second factor was iron stress with concentrations (0 ppm and 551,55 ppm). The stress was applied after 3 WAP. The stress resistance test to iron (Fe) should that all lines of red rice F6 on ultisol soils have a score of 1 which indicates the stress tolerance of Fe at a concentration of 551,55 ppm Fe. The 23A-56-30-25-12 and 23A-56-30-25-13 lines were the best lines that were tolerant of 551,55 ppm iron (Fe) stress with the highest growth and yield. The lines tested can be developed on ultisol soils because they are tolerant of Fe.

Responses of greenhouse gas emissions to residue returning in China's croplands and influential factors: A meta-analysis

Climate change is a global issue threatening agricultural production and human survival. However, agriculture sector is a major source of global greenhouse gases (GHGs), especially CH4 and N2O. Crop residue returning (RR) is an efficient practice to sequestrate soil carbon and increase crop yields. However, the efficiency of RR to mitigate climate change and maintain food security will be affected by the response of GHG emissions at both per area-scale and per yield-scale. Therefore, a national meta-analysis was conducted using 309 comparisons from 44 publications to assess the responses of GHG emissions to RR in China's croplands. The results indicated that little response of GWP to RR was observed with conditions under lower nitrogen fertilizer input rates (0–120 kg ha−1), mulch retention, returning one time in double cropping systems, returning with half residue, weakly acidic soil (pH 5.5–6.5), initial SOC contents >20 g kg−1, or mean annual precipitation <1000 mm. In order to mitigate climate change and sustain food security, RR combined with paddy-upland rotation, nitrogen fertilizer input rates of 240–360 kg ha−1, and neutral soil (pH 6.5–7.5) could decrease GWP at per unit of crop yield, which ultimately leads to a lower effect on GHGI and a higher crop production efficiency. In-depth studies should be conducted in the future to explore the interactions between various factors influencing GHG emissions under RR conditions. Overall, optimizing the interactions with management and site-specific conditions, potential for regulating GHGs emissions of RR can be enhanced.

Self-healing of bio-cementitious mortar incubated within neutral and acidic soil

The efficiency of bio self-healing of pre-cracked mortar specimens incubated in sand was investigated. The investigation examined the effect of soil pH representing industrially recognised classes of exposure, ranging from no risk of chemical attack (neutral pH ≈ 7) to very high risk (pH ≈ 4.5). Simultaneously, the soil was subjected to fully and partially saturated cycles for 120 days to resemble groundwater-level fluctuation. Bacillus subtilis with nutrients were impregnated into perlite and utilised as a bacterial healing agent. The healing agent was added to half of the mortar specimens for comparison purposes. Mineral precipitations were observed in both control and bio-mortar specimens, and the healing products were examined by SEM–EDX scanning. The healing ratio was evaluated by comparing (1) the repair rate of the crack area and (2) by capillary water absorption and sorptivity index—before and after incubation. The results indicated that bacteria-doped specimens (bio-mortar) exhibited the most efficient crack-healing in all incubation conditions i.e. different chemical exposure classes. In the pH neutral soil, the average healing ratios for the control and bio-mortar specimens were 38% and 82%, respectively. However, the healing ratio decreased by 43% for specimens incubated in acidic soil (pH ≈ 4) compared with specimens incubated in neutral soil (pH ≈ 7). The study implies that bio self-healing is generally beneficial for concrete embedded within soil; however, aggressive ground conditions can inhibit the healing process.

A case study review of wood ash land application programs in North America

Several regulatory agencies and universities have published guidelines addressing the use of wood ash as liming material for agricultural land and as a soil amendment and fertilizer. This paper summarizes the experiences collected from several forest products facility-sponsored agricultural application programs across North America. These case studies are characterized in terms of the quality of the wood ash involved in the agricultural application, approval requirements, recommended management practices, agricultural benefits of wood ash, and challenges confronted by ash generators and farmers during storage, handling, and land application of wood ash. Reported benefits associated with land-applying wood ash include increasing the pH of acidic soils, improving soil quality, and increasing crop yields. Farmers apply wood ash on their land because in addition to its liming value, it has been shown to effectively fertilize the soil while maintaining soil pH at a level that is optimal for plant growth. Given the content of calcium, potassium, and magnesium that wood ash supplies to the soil, wood ash also improves soil tilth. Wood ash has also proven to be a cost-effective alternative to agricultural lime, especially in rural areas where access to commercial agricultural lime is limited. Some of the challenges identified in the review of case studies include lengthy application approvals in some jurisdictions; weather-related issues associated with delivery, storage, and application of wood ash; maintaining consistent ash quality; inaccurate assessment of required ash testing; potential increased equipment maintenance; and misconceptions on the part of some farmers and government agencies regarding the effect and efficacy of wood ash on soil quality and crop productivity.

Thermomagnesium as a fertilizer for soybean: carbohydrate metabolism, silicon–magnesium fertilizer, and grain yield

Thermomagnesium (TM) or magnesium (Mg) silicate (MgSiO3) is a byproduct of the nickel (Ni) industry. As a fertilizer, TM elevates the pH of acidic soils as well as provides Mg and silicon (Si) to plants. This novel practice can be a pivotal sustainable strategy to enhance soybean [Glycine max (L.) Merrill] development, particularly in tropical environments. Therefore, the present study aimed to evaluate the effects of TM application on the chemical properties of soil; Mg and Si contents in soil and plants; contents of reducing sugars, sucrose, and starch in leaves; and yield of soybean. The experiment was performed under controlled conditions in a greenhouse during the 2016–2017 cropping season. Two soil types (clayey and sandy) and five TM rates (0, 55, 273, 709, and 2,018 mg kg−1 of TM, and 0, 293, 410, 645, and 1,260 mg kg−1 of TM, respectively) with four replicates were used. In both soil types, pH as well as Mg and Si contents increased with increasing TM rates. Similarly, leaf contents of Mg, Si, reducing sugars, and sucrose as well as yield of soybean increased with increasing TM rates. Conversely, leaf starch content decreased with increasing TM rates. Therefore, TM positively affects whole-plant carbohydrate partitioning, thereby improving soybean development, grain filling, and yield.

Soil Organic Matter, Soil Structure, and Bacterial Community Structure in a Post-Agricultural Landscape

Converting forest and wetland landscapes to agriculture has shown to result in a loss of organic matter, structure, and microbial diversity in the converted soil but recovery of post-agricultural soils remains poorly understood. Here we coupled landscape-scale surveys of soil 1) carbon and nitrogen levels, 2) aggregation, and 3) bacterial metagenomes to investigate soil recovery after 30 years in sites with soils ranging from well drained to poorly drained. Sites with no evidence of past agriculture (Reference) served as recovery endpoints. A secondary aim evaluated the role of nitrogen-fixing symbiosis, here associated with alder (Alnus incana) trees, in soil restoration. Soil carbon levels in restored sites (3.5%) were comparable to levels in a present-day farm (3.4%) but much lower than in Reference sites (&amp;gt;7.3%). The same trend occurred with soil nitrogen levels. Sites with alder trees had more acidic soil pH values. Alder trees promoted soil structure with macroaggregates being the largest fraction of bulk soil (75%). Natural abundance of stable nitrogen isotopes suggested extensive decay of organic matter within aggregates. Comparison of total reads from the soil metagenomes indicated the bacterial community in restored sites were more comparable to the present-day farm than Reference sites, except for a well-drained soil with alder. Dissimilarity among sites in terms of gene abundances in soil bacterial community occurred in carbon metabolism, membrane transport, and genetic repair pathways. Soil recovery in post-agricultural landscapes is slow when agriculture caused a large loss of soil organic matter, as is the case in our study, and when the soil bacterial community structure changed markedly, as it did in our study. However, fairly rapid recovery of soil structure, as we noted in our study, is promising, and now we need a better understanding of plant species that improve soil structure for restoration of both well-drained and poorly drained soils.