Biochar alters hydraulic conductivity and impacts nutrient leaching in two agricultural soils

Biochar is purported to provide agricultural benefits when added to the soil, through changes in saturated hydraulic conductivity (Ksat) and increased nutrient retention through chemical or physical means. Despite increased interest and investigation, there remains uncertainty regarding the ability of biochar to deliver these agronomic benefits due to differences in biochar feedstock, production method, production temperature, and soil texture. In this project, a suite of experiments was carried out using biochars of diverse feedstocks and production temperatures, in order to determine the biochar parameters which may optimize agricultural benefits. Sorption experiments were performed with seven distinct biochars to determine sorption efficiencies for ammonium and nitrate. Only one biochar effectively retained nitrate, while all biochars bound ammonium. The three biochars with the highest binding capacities (produced from almond shell at 500 and 800 ∘C (AS500 and AS800) and softwood at 500 ∘C (SW500)) were chosen for column experiments. Biochars were amended to a sandy loam and a silt loam at 0 % and 2 % (w/w), and Ksat was measured. Biochars reduced Ksat in both soils by 64 %–80 %, with the exception of AS800, which increased Ksat by 98 % in the silt loam. Breakthrough curves for nitrate and ammonium, as well as leachate nutrient concentration, were also measured in the sandy loam columns. All biochars significantly decreased the quantity of ammonium in the leachate, by 22 % to 78 %, and slowed its movement through the soil profile. Ammonium retention was linked to high cation exchange capacity and a high oxygen-to-carbon ratio, indicating that the primary control of ammonium retention in biochar-amended soils is the chemical affinity between biochar surfaces and ammonium. Biochars had little to no effect on the timing of nitrate release, and only SW500 decreased total quantity, by 27 % to 36 %. The ability of biochar to retain nitrate may be linked to high micropore specific surface area, suggesting a physical entrapment rather than a chemical binding. Together, this work sheds new light on the combined chemical and physical means by which biochar may alter soils to impact nutrient leaching and hydraulic conductivity for agricultural production.

Soil macroporosity, physical properties and nutrient leaching after forest conversion to rubber and oil palm plantation in an Acrisol of Jambi, Indonesia

Soil degradation is expected to continue as forest conversion into other land uses increases significantly. In Indonesia, Jambi is one of the main areas for the development of oil palm and rubber, whichare mainly converted from the forest. As a base for better management, we attempted to study macro-porosity in rubber and oil palm plantation, in comparison to secondary forests. Four landuse systems (secondary forest, jungle rubber, rubber plantation and oil palm plantations) in Bukit Duabelas, Sarolangun District, Jambi Province, Sumatera, were selected for this study. The number of macropores in vertical or horizontal planes and their related factors (root mass, litter thickness, % organic C, bulk density, water content at pF 0 and pF 2.54, aggregate stability) were measured within the soil profiles. Forest conversion to jungle rubber, rubber and oil palm plantation led to a decrease of macro-porosity in the soil profile, especially in the upper 50 cm. Macropores, both at vertical and horizontal planes in the secondary forest was significantly higher than other landuses. Horizontal macropores in jungle rubber were higher than rubber and oil palm plantation, but not the vertical macropores. Among the soil properties measured, litter thickness, coarse root dry mass (Ø >2 mm), mesopores and aggregate stability were closely associated with soil macro-porosity. However, macro-porosity in the soil profile was insignificantly correlated to soil bulk density and % organic C. Increasing the number of horizontal macropores resulted in higher nutrient leaching, especially K and Na.

Nutrient Leaching in Extensive Green Roof Substrate Layers With Different Configurations

Due to substrate layers with different substrate configurations, extensive green roofs (EGRs) exhibit different rainfall runoff retention and pollution interception effects. In the rainfall runoff scouring process, nutrient leaching often occurs in the substrate layer, which becomes a pollution source for rainwater runoff. In this study, six EGR devices with different substrate layer configurations were fabricated. Then, the cumulative leaching quantity (CLQ) and total leaching rate (TLR) of NH4+, TN and TP in the outflow of nine different depth simulated rainfall events under local rainfall characteristics were evaluated and recorded. Furthermore, the impact of different substrate configurations on the pollution interception effects of EGRs for rainfall runoff was studied. Results show that a mixed adsorption substrate in the EGR substrate layer has a more significant rainfall runoff pollution interception capacity than a single adsorption substrate. PVL and PVGL, as EGRs with layered configuration substrate layers, exhibited good NH4+-N interception capacity. The CLQ and TLR of NH4+-N for PVL and PVGL were -114.613 mg and -63.43%, -121.364 mg and -67.16%, respectively. Further, the addition of biochar as a modifier significantly slowed down the substrate layer TP leaching effect and improved the interception effect of NH4+-N and TN. Moreover, although polyacrylamide addition in the substrate layer aggravated the nitrogen leaching phenomenon in the EGRs outflow, but the granular structure substrate layer constructed by it exhibited a significantly inhibited TP leaching effect.

Examination of nutrient leaching dynamics of Solidago virgaurea in Hévíz Lake and Hévíz canal

The different nitrogen and phosphorus elements are prime constituents of the ecosystem and can exert a major effect on aquatic species and the overall ecological cycle. During our investigation we examined the nutrient leaching dynamics in decomposing leaf litter (stem and leaf blades) of Solidago virgaurea. We chose four different sampling sites during the winter period with different water temperatures in the Hévíz Lake and Hévíz canal. The bottles containing the plant material and water were incubated at natural temperatures and the fluid was removed at particular times. Water parameters such as pH level, conductivity, nutrients (ammonium and phosphates) were measured. In the case of Solidago leaf, we obtained higher values ​​for all parameters compared to the stem ones.

Biochar alters hydraulic conductivity and inhibits nutrient leaching in two agricultural soils

Biochar is purported to provide agricultural benefits when added to the soil, through changes in soil water hydraulic conductivity (Ksat), and increased nutrient retention through chemical or physical means. Despite increased interest and investigation, there remains uncertainty regarding the ability of biochar to deliver these agronomic benefits due to differences in biochar feedstock, production method, production temperature and soil texture. In this project, a suite of experiments was carried out using biochars of diverse feedstocks and production temperatures, in order to determine the biochar parameters which may optimize agricultural benefits. Sorption experiments were performed with seven distinct biochars to determine sorption efficiencies for ammonium and nitrate. Only one biochar effectively retained nitrate, while all biochars bound ammonium. The three biochars with the highest binding capacities (produced from almond shell at 500 and 800 °C (AS500 and AS800) and softwood at 500 °C (SW500)) were chosen for column experiments. Biochars were amended to a sandy loam and a silt loam at 0 and 2 % (w/w) and saturated hydraulic conductivity (Ksat) was measured. Biochars reduced Ksat in both soils by 64–80 %, with the exception of AS800, which increased Ksat by 98 % in the silt loam. Breakthrough curves for nitrate and ammonium, as well as leachate nutrient concentration, were also measured in the sandy loam columns. All biochars significantly decreased the quantity of ammonium in the leachate, by 22 to 78 %, and slowed its movement through the soil profile. Ammonium retention was linked to high cation exchange capacity and a high oxygen to carbon ratio, indicating that the primary control of ammonium retention in biochar-amended soils is the chemical affinity between biochar surfaces and ammonium. Biochars had little to no effect on the timing of nitrate release, and only SW500 decreased total quantity, by 27 to 36 %. The ability of biochar to retain nitrate may be linked to high surface area, suggesting a physical entrapment rather than a chemical binding. Together, this work sheds new light on the combined chemical and physical means by which biochar may alter soils to impact nutrient leaching and hydraulic conductivity for agricultural production.

Biochar and Its Broad Impacts in Soil Quality and Fertility, Nutrient Leaching and Crop Productivity: A Review

Biochar is gaining significant attention due to its potential for carbon (C) sequestration, improvement of soil health, fertility enhancement, and crop productivity and quality. In this review, we discuss the most common available techniques for biochar production, the main physiochemical properties of biochar, and its effects on soil health, including physical, chemical, and biological parameters of soil quality and fertility, nutrient leaching, salt stress, and crop productivity and quality. In addition, the impacts of biochar addition on salt-affected and heavy metal contaminated soils were also reviewed. An ample body of literature supports the idea that soil amended with biochar has a high potential to increase crop productivity due to the concomitant improvement in soil structure, high nutrient use efficiency (NUE), aeration, porosity, and water-holding capacity (WHC), among other soil amendments. However, the increases in crop productivity in biochar-amended soils are most frequently reported in the coarse-textured and sandy soils compared with the fine-textured and fertile soils. Biochar has a significant effect on soil microbial community composition and abundance. The negative impacts that salt-affected and heavy metal polluted soils have on plant growth and yield and on components of soil quality such as soil aggregation and stability can be ameliorated by the application of biochar. Moreover, most of the positive impacts of biochar application have been observed when biochar was applied with other organic and inorganic amendments and fertilizers. Biochar addition to the soil can decrease the nitrogen (N) leaching and volatilization as well as increase NUE. However, some potential negative effects of biochar on microbial biomass and activity have been reported. There is also evidence that biochar addition can sorb and retain pesticides for long periods of time, which may result in a high weed infestation and control cost.

Biochar-Swine Manure Impact on Soil Nutrients and Carbon Under Controlled Leaching Experiment Using a Midwestern Mollisols

Biochar application to the soil can improve soil quality and nutrient leaching loss from swine manure adapted soils. Our working hypothesis was that the biochar-incubated with manure could be a better soil amendment than conventional manure application. The manure-biochar application to the soil would decrease nutrient leaching from manure and increase plant-available nutrients. The study objectives were to 1) assess the physicochemical properties of the manure-biochar mixture after lab incubation and 2) evaluate the impact of biochar-treated swine manure on soil total C, N, and other major and minor nutrients in comparison to conventional manure application to soil. Three biochars 1) neutral pH red-oak (RO), 2) highly alkaline autothermal corn (Zea mays) stover (HAP), and 3) mild acidic Fe-treated autothermal corn stover (HAPE) were incubated with swine manure for a month. The biochar-manure mixture was applied in triplicate to soil columns with an application rate determined by the P2O5-P content in manure or manure-biochar mixtures after the incubation. The ammonium (NH4+), nitrate (NO3‒), and reactive P concentrations in soil column leachates were recorded for eight leaching events. Soil properties and plant-available nutrients were compared between treatments and control manure and soil. Manure-(HAP&HAPE) biochar treatments significantly increased soil organic matter (OM), and all biochar-manure mixture increased (numerically) soil total C, N, and improved soil bulk density. Concentrations of NH4+ and NO3‒ significantly increased in MHAPE column leachates during this 4-week study and the KCl-extractable NH4+ and NO3‒ in the soil at the end of the experiment. A significant reduction in soil Mehlich3 Cu was also observed for the manure-HAPE mixture compared with the manure control. The manure-red oak biochar significantly increased the soil Mn availability than other manure-biochar treatments or manure control. Overall, the manure-biochar incubation enabled biochar to stabilize the C and several nutrients from manure. The subsequent manure-biochar mixture application to soil improved soil quality and plant nutrient availability compared to conventional manure application. This proof-of-the-concept study suggests that biochars could be used to solve both environmental and agronomic challenges and further improve the sustainability of animal and crop production agriculture.

How nutrient rich are decaying cocoa pod husks? The kinetics of nutrient leaching

Aim Recycling of cocoa pod husks has potential to contribute to mineral nutrition of cocoa. Yet little is known of the nutrient content and nutrient release patterns from the husks. The potassium (K) rich husks are usually left in heaps in cocoa plantations in Africa. We aimed to understand and quantify release patterns of K and other nutrients from husks under varying rainfall regimes and assessed the effects of partial decomposition and inundation on nutrient leaching rates. Methods We incubated chunks of cocoa pod husks to assess decomposition rates and we measured nutrient leaching rates from two sets of husk chunks: one set was placed in tubes that were submitted to simulated scheduled rainfall events while the second set was continuously inundated in beakers. Results Decomposition of husks followed a second-order exponential curve (k: 0.09 day−1; ageing constant: 0.43). Nutrient losses recorded within 25 days were larger and more variable for K (33%) than for other macronutrients released in this order: Mg > Ca ≈ P > N (less than 15%). Potassium leaching was mainly driven by rainfall frequency (P < 0.05) and reinforced by intense rainfall, especially at lower frequency. Under water-saturated conditions, 11% of K was leached out within 48 h from fresh husks compared with 92% from partially decayed husks. Conclusion Some initial decomposition of cocoa pod husks is required to expose K to intense leaching. As decomposition progresses, abundant K losses are to be expected under frequent and/or intense rainfall events.

The influence of biochar on nutrient leaching and hydraulic conductivity in two California soils

&lt;p&gt;The unique chemical and physical properties of biochars typically include low bulk density, high porosity, high surface area, reactive surface functional groups, and variable particle size distribution. These attributes make biochar a promising material for amendment to agricultural soils, as biochar may help improve soil water holding capacity, hydraulic conductivity (K&lt;sub&gt;sat&lt;/sub&gt;), and nutrient retention through chemical or physical means. Despite increased interest and investigation, there remains uncertainty regarding the ability of biochar to alter soils to deliver these agronomic benefits, due to differences in biochar feedstock, production method, production temperature and soil texture. In this project, a suite of experiments was carried out using biochars of diverse feedstocks and production temperature, in order to determine the biochar parameters which may optimize agricultural benefits. Sorption experiments [SJP1]&amp;#160;were performed with seven distinct, commercially available biochars to determine sorption efficiencies for ammonium and nitrate. Only one biochar effectively retained nitrate, while all biochars bound ammonium. The three biochars with the highest nitrate and/or ammonium binding capacity (produced from almond shell at 500 and 800 &amp;#176;C (AS500 and AS800) and softwood at 500 &amp;#176;C (SW500)), were chosen for a series of column experiments. These biochars were amended to a sandy loam and a silt loam at 0 and 2% (w/w) and saturated hydraulic conductivity (K&lt;sub&gt;sat&lt;/sub&gt;) was measured. The biochars reduced K&lt;sub&gt;sat&lt;/sub&gt; in both soils by 64-80%, with the exception of AS800, which increased K&lt;sub&gt;sat &lt;/sub&gt;by 98% in the silt loam. Breakthrough curves for nitrate and ammonium, as well as concentrations of nutrients in the leachate, were also measured in the sandy loam columns. &amp;#160;Biochars significantly reduced the quantity of ammonium in the leachate, and significantly slowed its movement through the soil profile. Biochars had little to no effect on the timing and quantity of nitrate release. In this presentation, we present results from each experiment, and show images from our current work using x-ray micro-computed tomography on these soils and biochars to quantify porosity, pore size, and pore connectivity. Together, this work sheds new light on the chemical and physical means by which biochar alters soils to impact nutrient leaching and hydraulic conductivity.&lt;/p&gt;