Maturity and Stability Evaluation of Composted Yard Trimmings

The objective of this research was to evaluate a variety of stability and maturity indices for yard trimmings compost produced in the Puget Sound region of western Washington State. Compost samples were collected periodically during a 133-d composting cycle at a commercial composting facility, showing that indices of compost respiration rate were sensitive indicators of compost quality. All respiration rate indices identified a period of high respiration rates during active composting (first 27 d), and a period of relatively stable respiration rates during the latter part of curing (70 to 133 d). Chemical tests of compost solids showed less promise as maturity indicators, but provided valuable information on final compost quality. Mature yard trimmings compost had a C:N of 12, an NH₄-N to NO₃-N ratio of less than 4, a cation exchange capacity (CEC) of 400 cmol per kg of compost-C, and a pH between 6.5 and Seed germination tests and sensory tests (color and odor) were of limited value in assessing compost maturity. Fully-cured compost produced with forced aeration had a Solvita CO₂ test value of 6 to 7 and a respiration rate via the alkaline trap method of 2 mg CO₂-C g compost-C^?1 d^?1. It reheated less than 2°C in an insulated Dewar flask in a 7 d incubation. Further evaluation and calibration of respiration test protocols for compost quality assurance testing programs are recommended.     

Stability Evaluation of Mixed Food Waste Composts

As interest in food waste composting grows, so does the need for proven composting methods. Stability testing has been proposed as a compost quality assurance tool. We conducted this study to: (i) to evaluate the efficacy of simple outdoor composting methods in producing a compost with a low, stable decomposition rate, and (ii) to determine the reliability of simple, 4-h compost stability evaluation methods. Composting was conducted outdoors in winter and spring in Eugene, Oregon without moisture addition. Mixed food waste was combined with screened dairy solids and ground yard trimmings. Sawdust was used to cover windrows for the first 27 d of composting. Compost windrow temperatures remained above 55°C for 30+ d. Carbon dioxide evolved with several 4-h test methods was strongly correlated (r² > 0.7) with CO₂ evolved using a 48-h test. A limited-turn windrow (LTW) composting system produced compost with slightly greater stability than a passively aerated windrow (PAW) composting system. Food waste compost samples had a low CO₂ evolution rate after 71 to 99 d using either composting system. Compost CO₂ evolution rate at 25°C decreased with composting time, reaching approximately 1 to 4 mg CO₂-C g compost C^?1 d^?1 for the PAW method and 0.5 to 2 mg CO₂-C g compost C^?1 d^?1 for the LTW method. Putrescible organic matter in food waste was effectively decomposed in outdoor windrows using composting methods that did not employ forced aeration, self-propelled windrow turners, or manufactured composting vessels. Several 4-h stability tests showed promise for implementation as quality assurance tools.     

Relating Compost Measures of Stability And Maturity to Plant Growth

Assessment of compost maturity is important for successful use of composts in agricultural and horticultural production. We assessed the “maturity” of four different sawdust-based composts. We composted sawdust with either cannery waste (CW), duck manure (DM), dairy (heifer) manure (HM) or potato culls (PC) for approximately one year. Windrows were turned weekly for the first 60 days of composting, covered for four winter months and then turned monthly for six more months. We measured compost microbial respiration (CO₂ loss), total C and N, C:N ratio, water soluble NO₃-N and NH₄-N, dissolved organic carbon (DOC), pH and electrical conductivity at selected dates over 370 days. Compost effects on ryegrass biomass and N uptake were evaluated in a greenhouse study. We related compost variables to ryegrass growth and N uptake using regression analysis. All composts maintained high respiration rates during the first 60 days of composting. Ammonium-N concentrations declined within the first 60 days of composting, while NO₃-N concentrations did not increase until 200+ days. After 250+ days, DM and PC composts produced significantly more ryegrass biomass than either CW or HM composts. Total C, microbial respiration and water-extractable NO₃-N were good predictors of compost stability/maturity, or compost resistance to change, while dissolved organic carbon, C:N ratio and EC were not. The compost NO₃-N/CO₂-C ratio was calculated as a parameter reflecting the increase in net N mineralization and the decrease in respiration rate. At ratio values >8 mg NO₃-N/mg CO₂-C/day, ryegrass growth and N uptake were at their maximum for three of the four composts, suggesting the ratio has potential as a useful index of compost maturity.     

Effect of Feeding Regime on Composting in Bins

Composting in bins is one of the most practical home composting methods. There is currently a need for greater information to improve the management of the composting process and to create home composting programs, which ensure sustainable production of high quality compost. This study investigates how two aspects of the bin feeding regime—the feeding frequency and the amount of waste applied at each feed—influence the process's evolution and the quality of the compost. Compost bins were assayed after introducing the same amount of kitchen and garden waste according to three different frequencies: in a single batch, weekly, or every 3 weeks. A fourth treatment was applied to calculate the potential waste reduction achieved by the composting process, filling the bins to the brim on a weekly basis. Temperature, mass, and volume changes; the microbial diversity (by Biolog); and gas emissions (CO₂, CH₄, N₂O, and NH₃) were all determined during the process. At the end of the experiment, all of the composts were weighed and characterized. Results show that the main differences were very dependent on the quantity of waste provided. Large amounts of waste were added increasing the compost's temperature and maturity during the process, while slightly affecting the salinity and phytotoxicity of the final compost but without any clear effects on microbial diversity and gas emission. Therefore, from a technical point of view, the shared use of compost bins among several households (community composting) is preferable to individual use.     

MSW Compost Reduces Nitrogen Volatilization During Dairy Manure Composting

Manures lose N through volatilization almost immediately after deposit. Attempts to control losses include the addition of a C source to stimulate nitrogen immobilization. Composting is a treatment process that recommends the addition of carbonaceous materials to achieve a C:N ratio of 30:1 to stimulate degradation and immobilize nitrogen. Dairies near cities may be able to reduce N loss from manures by composting with urban carbonaceous residues such as municipal solid waste (MSW) or MSW compost that, by themselves, have little agronomic value. Studies were conducted using a self-heating laboratory composter where dairy solids were mixed with MSW compost to determine the reduction of N loss during composting. One-to-one mixtures (v/v) of dairy manure solids and MSW compost were composted and NH₃ volatilization, CO₂ evolution and temperatures were compared to composting of manure alone. Addition of MSW compost resulted in increased CO₂ evolution and reduced N loss. Nitrogen loss from composting dairy manure alone was four to ten times greater than that from composting dairy manure mixed with MSW compost. Adjustment of the C:N ratio to 25 by adding MSW compost to manure appeared to be the major factor in reducing N losses.     

Chemical and microbiological parameters for the characterisation of the stability and maturity of pruning waste compost

Composting of pruning waste, leaves and grass clippings was monitored by different parameters. A windrow composting pile, having the dimensions 2.5 m (height) x 30 m (length) was establish. The maturation of pruning waste compost was accompanied by a decline in NH₄ ⁺-N concentration, water soluble C (WSC) and an increase in NO₃ ^–-N content. Both organic matter (OM) content and total N (TN) losses during composting followed a first-order kinetic equation. These results were in agreement with the microbiological activity measured either by the CO₂ respiration or dehydrogenase (DH-ase) activity during the process. Statistically significant correlations were found between DH-ase activity, easily biodegradable organic C forms, NH₄ ⁺-N and NO₃ ^–-N concentrations and organic matter content and N losses. For this reason, DH-ase activity and the CO₂ evolution could be used as good indicators of pruning waste compost maturity. In contrast, humification parameters data from the organic matter fractionation did not agree with the initially expected values and did not contribute to the assessment of compost maturity. Neither the cation exchange capacity nor the germination index showed a clear tendency during the composting time, suggesting that these parameters are not suitable for evaluating the dynamics of the process.     

Feedstock Carbon Influence on Compost Biochemical Stability and Maturity

Quantity and quality of readily degradable carbon influences the composting process especially for compost mixture high in lignocellulotic material. Effects of carbon source on stability and maturity of compost from in-vessel systems are poorly understood. Research was conducted to investigate the effects of carbon composition of feedstock on the evolution of stability indices and reliability of maturity tests for accelerated vessel composting systems. Rice straw, sugarcane bagasse, and coffee hulls were composted in a modified rotary in-vessel composter amended with either cattle or sheep manure. Distinct evolution patterns were observed across carbon sources for temperature, with the sugarcane compost never attaining thermophilic temperatures. Time to peak temperature and return to ambient were significantly different between the rice and coffee compost. Comparatively, organic matter degradation followed a similar pattern for all carbon sources, although rice straw showed the faster degradative rate and coffee hulls the greatest overall loss. Both pH and electrical conductivity were inappropriate stability indices across carbon sources, while the NH₄⁺/NO₃^? ratio was lower than the threshold from week 1. The Solvita® maturity test was the best suited quality indicator and was related to compost respiration. The rice compost at week 12 was the only mature compost with an index value of 7. However, the coffee compost was in the curing stage with a value of 6. In vitro phytotoxicity assays on hot pepper contrasted the Sovita® interpretation for rice compost, which showed the lowest germination index. All compost had a stimulatory effect on cucumber seeds. In vivo seeding assays corroborated in vitro results with rice compost showing the greatest negative effect, augmented at 100% compost inclusion. Carbon source significantly influenced compost stability and maturity indices, which suggests that greater attention should be directed to quality indices in relation to feedstock composition.     

Physical,Chemical and Biological Properties of an Accelerated Cassava Based Compost Prepared Using Different Ratios of Cassava Peels and Poultry Manure

Monitoring the physical, chemical and biological properties during accelerated composting enables concise determination of its stability and maturity. Determination of physical parameters such as pH, moisture and temperature, chemical parameters such as total nitrogen (N), phosphorus (P), potassium (K), organic matter and humic acid as well as biological parameters such as microbial count and carbon dioxide (CO₂) evolution was carried out during a four (4) week composting period, The trend observed for pH showed the mesophilic and thermophilic phases and a similar trend was observed for the compost temperature. Intermittent increase and decrease was observed for total N, P, K as well as for the fungal and bacterial population. A direct relationship was observed among the bacterial population, CO₂ evolution and humic acid. However, composting for four (4) weeks produced a stable compost, which was evident through the physical observation of the final product and the results obtained for the chemical and biological parameters.     

Chemical,Physical and Biological Criteria for Maturity in Composts for Organic Farming

Properties of organic farming composts were examined during the composting process: pH, electrical conductivity, C/N ratio, total N content, NH₄₊ content, NO_3?content, ash content, and organic matter content. In addition to these properties the respiration rate, microbial population counts, hydrolysis of Fluorescein Diacetate (FDA) and the activity of the enzyme amidase were studied. Composts at several stages of maturity were incubated in soil, and their N mineralization rates were measured. The end of the thermophilic stage was characterized by irreversible decrease in pile temperature to under 55°C, followed by stabilization of the chemical properties. This stage in the composting process is also characterized by decrease in CO₂ evolution rate, changes in microbial populations and specific patterns in FDA hydrolysis and amidase activity. Based on this evidence, we suggest that biological parameters can be considered as indicators for compost maturity.     

Assessment of the Reliability of a Commercial Maturity Test Kit for Composted Manures

Stability significantly affects the potential for beneficial utilization of composts but is difficult to measure by farmers and compost producers. A simple four hour test (the Solvita® maturity test) that measures CO₂ evolution and ammonia emission from compost samples was compared to a traditional three-day, 25°C, CO₂ evolution rate procedure and to measurements of ammoniacal nitrogen concentrations in manure composts to assess the reliability of this test. Three composts — 1) Dairy manure amended with wheat straw, 2) The same dairy manure but amended with sawdust and 3) Swine manure amended with sawdust and ground wood pallets — were composted in windrows for 120 days. Samples were removed weekly to biweekly. CO₂ evolution rates of the three composts decreased from initial means (n=6) of 3.41, 3.42 and 9.35 to 0.63, 0.76 and 0.31 mg CO₂-C g^?1 VS day^?1, for the dairy manure-straw, dairy manure-sawdust, hog manure composts, respectively. The corresponding mean Solvita CO₂ test values for these composts increased from 3.4, 3.0 and 3.2 to 6.8, 6.5 and 7.0, respectively. Correlation analysis between CO₂ evolution rates and Solvita CO₂ test values gave linear correlation coefficients (r) of ?0.82, ?0.78, and ?0.87 for the straw-amended dairy manure, the sawdust-amended dairy and the hog manure composts, respectively. The Solvita NH₃ test gave highly significant correlations (p<0.0001) with ammoniacal-N concentrations (correlation coefficients (r) = ?0.43, ?0.64 and ?0.65, respectively). The Solvita® maturity index, a combination of Solvita CO₂ and NH₃ values, correlated significantly with both CO₂ evolution rate and ammoniacal-N concentrations. However, the Solvita CO₂ index alone was the best predictor of compost CO₂ evolution rate or stability. The Solvita Maturity test, which combines the Solvita CO₂ and NH₃ tests, provided useful information about the potential for the development of a toxic response in plants due to excessive concentrations of ammoniacal-N present in some stable compost samples that would not have been detected if the CO₂ stability test were used by itself. We conclude that the Solvita maturity test provided a simple, inexpensive relative test of compost stability and NH₃ emission for diverse samples of composted manures. Even so, it did not accurately predict their CO₂ evolution rates measured by respirometry nor their ammoniacal-N concentrations. The test would be most useful for on-farm applications.     

Decomposition of peat,biogenic municipal waste compost,and shrub/grass compost added in different rates to a silt loam

An incubation experiment was carried out to test the effects of biogenic municipal waste (compost I) and shrub/grass (compost II) composts in comparison to peat on respiration and microbial biomass in soil. The amounts of these three substrates added were linearly increased in the range of field application rates (0.5%, 1.0%, 1.5%, 2.0%). The sum of CO₂ evolved during the incubation was markedly raised by the three substrates and increased with the rate of substrate concentration. However, the percentage of substrate mineralized to CO₂ decreased with the addition rate from 103 to 56% for compost I, from 81 to 56% for compost II, and from 21 to 8% for peat. During the first 25 days of incubation, compost I enlarged the biomass C content, which remained constant until the end. In contrast, compost II did not raise biomass C initially. But at the end of the incubation, the biomass C content of all 4 compost II treatments almost reached the level of the respective compost I treatment. The increase was significantly larger the more of the two composts was added. In contrast to the two composts, the addition of peat did not have any significant effect on microbial biomass C. The average qCO₂ values at day 25 declined in the order compost I > compost II > peat, at day 92 the order was changed to compost II > peat > compost 1. This change in the order was caused by a significant decrease in qCO₂ values of the compost I treatments, a significant increase in qCO₂ values of the peat treatments and constant qCO₂ values in the compost II treatments.     

Effect of lignite humic acid treatment on the rate of decomposition of wheat straw

Comparisons were made between the rates of microbial respiration during the incubation of milled wheat straw in the presence or absence of a dispersal of lignite humic acids. Lignite treatment significantly reduced both the rate of O₂ consumption and CO₂ evolution from the straw substrate over a 4-week period. In view of this observed inhibitory effect, additions of exogenous humic acids from lignite during composting might have a practical application as a means of increasing the microbial stability of horticultural composts derived from plant waste materials.     

A comparison of the properties of manufactured soils produced from composting municipal green waste alone or with poultry manure or grease trap/septage waste

Manufactured soil for landscaping purposes was produced by composting for 6 weeks (1) municipal green waste alone, (2) green waste amended with 25% v/v poultry manure, or (3) green waste immersed in, and then removed from, a mixture of liquid grease trap waste/septage. Composting temperatures increased most rapidly and reached highest values (78oC) in the grease trap/septage-amended green waste. In comparison with green waste alone, addition of poultry manure prolonged the period of elevated temperatures and increased the maximum temperature attained from 52oC to 61oC. Following composting, each of the materials was split into (1) 100% compost, (2) 80% compost plus 20% v/v soil, and (3) 70% compost plus 20% soil plus 10% coal fly ash. Addition of poultry manure or grease trap/septage to green waste prior to composting increased bulk density and reduced total porosity of the composted product. Addition of soil, or soil and ash, to composts increased bulk density, reduced total porosity, decreased percentage macropores, and increased percentage mesopores and available water-holding capacity. Bicarbonate-extractable P, exchangeable NH₄⁺ and NO₃⁻, electrical conductivity (EC), soluble C, soluble C as a percentage of organic C, basal respiration, and metabolic quotient were all markedly greater in the grease trap/septage-amended than poultry manure-amended or green waste alone treatments. Values for extractable P and EC were considered large enough to be damaging to plant growth and germination index (GI) of watercress was less than 60% for all grease trap/septage composts. Extractable P and EC were also high, and GI was <100%, in the green waste alone and poultry manure-amended green waste alone treatments. Addition of soil or soil and ash to these composts resulted in GI values >100%.     

Estimating Soil Carbon,Nitrogen, and Phosphorus Mineralization from Short‐Term Carbon Dioxide Respiration

The measurement of soil carbon dioxide (CO₂) respiration is a means to gauge biological soil fertility. Test methods for respiration employed in the laboratory vary somewhat, and to date the equipment and labor required have limited more widespread adoption of such methodologies. A new method to measure soil respiration was tested along with the traditional alkali trap and titration method. The new method involves the Solvita gel system, which was originally designed for CO₂ respiration from compost but has been applied in this research to soils with treatments of increasing dairy manure compost. The objectives of this research are to (1) examine the relationship between the CO₂ release after 1 day of incubation from soils amended with dairy manure compost that have been dried and rewetted as determined using the titration method and the Solvita gel system, and (2) compare water‐soluble organic nitrogen (N), as well as carbon (C), N, and phosphorus (P) mineralization after 28 days of incubation with 1‐day CO₂ release from the titration method and Solvita gel system. One‐day CO₂ from both titration and the Solvita gel system were highly correlated with cumulative 28‐day CO₂ as well as the basal rate from 7–28 days of incubation. Both methods were also highly correlated with 28‐day N and P mineralization as well as the initial water‐extractable organic N and C concentration.

The data suggest that the Solvita gel system for soil CO₂ analysis could be a simple and easily used method to quantify soil microbial activity and possibly provide an estimate of potential mineralizable N and P. Once standardized soil sampling and laboratory analysis protocols are established, the Solvita method could be easily adapted to commercial soil testing laboratories as an index of soil microbial activity.     

A Newly Isolated Thermophilic Bacterium,Bacillus Licheniformis HA1 to Accelerate the Organic Matter Decomposition in High Rate Composting

Efficacy of various compost starter cultures was tested in a bench-scale composting system utilizing a ceiling process temperature of 60°C. Variables tested with time were CO₂ and NH₃ evolution, conversion of carbon and the succession of microorganisms in the compost. When an initial compost pH of 7.0 was used, a laboratory produced starter culture (Culture A) was much less effective than a commercial culture (Culture B). Low activity in the experiment with Culture A was due to a low pH(<5.5) that developed within 30 h after inoculation. Inoculation of Culture A with a thermophilic strain (HA1) of Bacillus licheniformis isolated from Culture B prevented the decrease in pH and significantly increased the rate of decomposition. It also enhanced populations of other thermophilic bacterial groups during the process.     

Compost Maturity Effects on Nitrogen and Carbon Mineralization and Plant Growth

Improved predictive relationships between compost maturity and nitrogen (N) availability are needed. A total of 13 compost samples were collected from a single windrow over a 91 d period. Compost stability and maturity were assessed using both standard chemical analyses (total C and N, mineral N, total volatile solids) and other methods (CO₂ evolution, commercial maturity kits, and neutral detergent fiber, and lignin). Compost N and carbon (C) were evaluated during a 130 d aerobic incubation in a sandy loam soil after each compost was applied at 200 mg total kg^?1 soil. The effect of compost maturity on plant growth was evaluated by growing two ryegrass (Lolium perenne L.) crops and one barley (Hordeum vulgare L.) crop in succession in compost-amended soil under greenhouse conditions. Potential phytotoxicity from compost was assessed by growing tomato (Lypersicum esculentum L.) seedlings in compost-amended soil. Regression and correlation analyses were used to evaluate the relationship between compost maturity parameters, the rate and extent of net N and C mineralization, plant yield and N uptake, and phytotoxicity. Commonly used maturity parameters like total C, total N, and C:N ratio were poorly correlated with the rate and extent of mineralization, and with plant growth parameters. The N mineralization rate during the first 48 d of aerobic incubation was strongly correlated (r= ?0.82 to ?0.86) to compost fiber and lignin concentration, and to the Maturity Index (r=0.85). Trends in C mineralization were similar. There were few differences in C mineralization between composts after 48 d of aerobic incubation in soil. Ryegrass harvested 35 and 70 d after compost application was not strongly affected by compost maturity, and relatively immature composts were phytotoxic to tomato seedlings. Methods of characterizing compost maturity and stability that more realistically reflect the composting process are better predictors of N release and potential plant inhibition after incorporation into soil.     

Application of respiration and FDA hydrolysis measurements for estimating microbial activity during composting processes

Olive-tree leaves (OL) were mixed with olive press cake (OPC) and extracted olive press cake (EPC) at 1:1 dw/dw ratios to prepare two composting mixtures (OL+OPC and OL+EPC). Both CO₂–C evolution and fluorescein diacetate (FDA) hydrolysis, determined as estimates of the microbial activity during composting, were related to temperature fluctuations in the compost piles, showing greater values at the temperature peaks, compared to the end, of each thermophilic phase. This, however, was only shown after handling and incubating samples at the temperatures of the compost mixtures at the sampling times and not at a low standard temperature. Incubating samples from thermophilic phases at low standard temperatures resulted in underestimation of the microbial activity occurring during composting. The effect of incubation temperature was less dramatic for FDA hydrolysis compared to CO₂–C evolution measurements, probably reflecting the reduced dependence of enzymes involved in FDA hydrolysis on the respective temperatures. However, FDA hydrolysis was a less sensitive indicator of microbial activity, probably due to extracellular cleavage of fluorescein by persistent esterases, at lowered microbial activity phases. Total microbial biomass, estimated by the fumigation–extraction method, was not consistently related to temperature fluctuations during composting and showed a clear increase at the end of composting, probably resulting from a large slow-growing mycelial community colonising the end products. Since high temperatures did not induce significant non-microbial CO₂–C release and FDA degradation, we propose the performance of microbial activity measurements during thermophilic composting phases at the actual temperatures evolving in the composts.     

Yard Waste Composting: Studies Using Different Mixes of Leaves and Grass in a Laboratory Scale System

Composting has become a widely used method of recycling yard wastes such as leaves and grass. However, very little information is available on the chemical changes that occur during the composting of different mixtures of leaves and grass. In this study, three different mixes of leaves and grass were composted at approximately 60% moisture in a temperature controlled laboratory scale system. The mixes, which consisted of all leaves (Mix 1); 2/3 leaves + 1/3 grass (Mix 2); and 1/3 leaves + 2/3 grass (Mix 3), had initial C:N ratios of 48, 30 and 22, respectively. The compost process was monitored by measuring the rate of CO₂ evolution, pH, stability, the degree of humification and changes in polysaccharide, carbon, nitrogen and organic matter content. Results showed that the greater the grass content of the mix, the higher the initial pH and the faster the rate of CO₂ evolution, organic matter loss and nitrogen loss. After 43 days of composting, Mixes 1, 2 and 3, lost, respectively 61%, 74% and 78% of the cellulose, 57%, 79% and 82% of the hemicellulose and 40%, 49% and 42% of the acid-insoluble organic matter. Humification indices and stability tests indicated that composts produced from the three mixes were well humified and stable.     

Fluorescein diacetate hydrolysis,respiration and microbial biomass in freshly amended soils

The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of soil microflora, measured by the microbial biomass C (B _C) and CO₂ evolution, respectively. Three different composting mixtures at different phases of the composting process were added to a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately increased B _C and both measures of microbial activity (FDA and CO₂ evolution). Highly significant correlations were found between FDA hydrolysis and B _C for soil amended with the three composting mixtures (r = 0.81–0.96; P < 0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely to CO₂ evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass in freshly amended soils, despite the disturbance caused by the exogenous organic matter.     

Impact of a biochar or a biochar-compost mixture on water relation, nutrient uptake and photosynthesis of Phragmites karka

Soil water and nutrient status are both of major importance for plant appearance and growth performance. The objective of this study was to understand the effect of biochar (1.5%) and a biochar-compost mixture (1.5% biochar + 1.5% compost) on the performance of Phragmites karka plants grown on a synthetic nutrient-poor sandy clay soil (50% sand, 30% clay, and 20% gravel). Indicators of plant performance, such as growth, lignocellulosic biomass, water status (leaf water potential, osmotic potential, and turgor potential), mineral nutrition status, leaf gas exchange, and chlorophyll fluorescence, and soil respiration (carbon dioxide (CO₂) flux) were assessed under greenhouse conditions. Biochar-treated plants had higher growth rates and lignocellulosic biomass production than control plants with no biochar and no compost. There was also a significant increase in soil respiration in the treatments with biochar, which stimulated microbial interactions. The increase in soil water-holding capacity after biochar amendment caused significant improvements in plant water status and plant ion (K⁺, Mg²⁺, and Ca²⁺) contents, leading to an increase in net photosynthesis and a higher energy-use efficiency of photosystem II. Biochar-treated plants had lower oxidative stress, increased water-use efficiency, and decreased soil respiration, and the biochar-compost mixture resulted in even greater improvements in growth, leaf turgor potential, photosynthesis, nutrient content, and soil gas exchange. Our results suggest that biochar and compost promote plant growth with respect to nutrient uptake, water balance, and photosynthetic system efficiency. In summary, both the soil amendments studied could increase opportunities for P. karka to sequester CO₂ and produce more fodder bio-active compounds and biomass for bio-energy on nutrient-poor degraded soils.