Experiments to document the long-term effects of clipping management on N requirements, soil organic carbon (SOC), and soil organic nitrogen (SON) are difficult and costly and therefore few. The ...CENTURY ecosystem model offers an opportunity to study long-term effects of turfgrass clipping management on biomass production, N requirements, SOC and SON, and N leaching through computer simulation. In this study, the model was verified by comparing CENTURY-predicted Kentucky bluegrass (Poa pratensis L.) clipping yields with field-measured clipping yields. Long-term simulations were run for Kentucky bluegrass grown under home lawn conditions on a clay loam soil in Colorado. The model predicted that compared with clipping-removed management, returning clippings for 10 to 50 yr would increase soil C sequestration by 11 to 25% and nitrogen sequestration by 12 to 28% under a high (150 kg N ha−1 yr−1) nitrogen (N) fertilization regime, and increase soil carbon sequestration by 11 to 59% and N sequestration by 14 to 78% under a low (75 kg N ha−1 yr−1) N fertilization regime. The CENTURY model was further used as a management supporting system to generate optimal N fertilization rates as a function of turfgrass age. Returning grass clippings to the turf–soil ecosystem can reduce N requirements by 25% from 1 to 10 yr after turf establishment, by 33% 11 to 25 yr after establishment, by 50% 25 to 50 yr after establishment, and by 60% thereafter. The CENTURY model shows potential for use as a decision-supporting tool for maintaining turf quality and minimizing negative environmental impacts.
The objective of this study was to evaluate the chemical, physicochemical, and functional properties of agrowastes derived from okara (Glycine max), corn cob (Zea mays sp.), wheat straw (Triticum ...sp.), and rice husk (Oryza sativa) for potential applications in foods. The fibrous materials (FM) were treated with alkali to yield fibrous residues (FR). Rice husk contained the highest ash content (FM, 8.56%; FR, 9.04%) and lowest lightness in color (FM, 67.63; FR, 63.46), possibly due to the abundance of mineral constituents. Corn cob contained the highest amount of soluble dietary fiber (SDF), whereas okara had the highest total dietary fiber (TDF). The high dietary fiber fractions of corn cob and okara also contributed to the highest water- and oil-holding capacities, emulsifying activities, and emulsion stabilities for both FM and FR samples. These results indicate that these agrowastes could be utilized as functional ingredients in foods.
Emissions of N2O were measured following addition of 15N-labelled (2.6-4.7 atom% excess 15N) agroforestry residues (Sesbania sesban, mixed Sesbania/Macroptilium atropurpureum, Crotalaria grahamiana ...and Calliandra calothyrsus) to a Kenyan oxisol at a rate of 100 mg N kg soil(-1) under controlled environment conditions. Emissions were increased following addition of residues, with 22.6 mg N m(-2) (124.4 mg N m(-2) kg biomass(-1); 1.1 mg 15N m(-2); 1.03% of 15N applied) emitted as N2O over 29 d after addition of both Sesbania and Macroptilium residues in the mixed treatment. Fluxes of N2O were positively correlated with CO2 fluxes, and N2O emissions and available soil N were negatively correlated with residue lignin content (r = -0.49; P < 0.05), polyphenol content (r = -0.94; P < 0.05), protein binding capacity (r = -0.92; P < 0.05) and with (lignin + polyphenol)-to-N ratio (r = -0.55; P < 0.05). Lower emission (13.6 mg N m(-2) over 29 d; 94.5 mg N m(-2) kg biomass(-1); 0.6 mg 15N m(-2); 0.29% of 15N applied) after addition of Calliandra residue was attributed to the high polyphenol content (7.4%) and high polyphenol protein binding capacity (383 microgram BSA mg plant(-1)) of this residue binding to plant protein and reducing its availability for microbial attack, despite the residue having a N content of 2.9%. Our results indicate that residue chemical composition, or quality, needs to be considered when proposing mitigation strategies to reduce N2O emissions from systems relying on incorporation of plant biomass, e.g. improved-fallow agroforestry systems, and that this consideration should extend beyond the C-to-N ratio of the residue to include polyphenol content and their protein binding capacity.
Hemicelluloses from oil palm frond (OPF) were extracted using 3 M potassium hydroxide (KOH) for 4 h at 40 °C with stirring at 400 rpm to obtain hemicelluloses A and B. The total yield of the ...hemicellulose isolated from OPF was 33% (dry weight). Both hemicelluloses A and B were then subjected to hydrothermal treatment at 121 °C and 1.03 × 105 Pa for 10, 30, and 50 min. Physicochemical characterizations of hydrothermally treated hemicelluloses, such as Klason lignin content and reducing sugar content, were performed to study the effect of autohydrolysis processing on OPF-derived hemicelluloses. It was shown that Klason lignin content in hemicellulose A was higher than that in hemicellulose B and decreased after hydrothermal treatment. Hydrothermal treatment enhanced the solubility of hemicelluloses, which reflects their higher reducing sugar content. Monosaccharide analysis using HPLC showed that xylose was the predominant monosaccharide for both hemicelluloses A and B.
Harvest residue management can affect the dynamics of soil carbon (C) and nutrient pools and associated soil microbial processes. A field experiment was conducted to investigate the impacts of ...harvest residue management practices on soil C and nitrogen (N) pools in a slash pine plantation grown on a sandy soil of subtropical Australia. Results showed that harvest residue retention significantly enhanced accumulation of soil total C and N compared with residue removal. The NH
4
+-N was the predominant form of soil mineral N, and there were no significant impacts of residue management practices on concentrations of soil NH
4
+-N measured at the time of sampling. Concentrations of water-soluble and hot water extractable organic C and total N tended to be higher in soil with residue retention compared with residue removal, but this trend was only significant for hot water extractable organic C (HWEOC) in surface soil (0–10
cm). Residue retention also tended to increase soil microbial biomass C and N, but did not significantly affect soil respiration and metabolic quotient (
qCO
2). Direct C and N inputs into soil from the residue layer and moderation of the variation of soil moisture and temperature over the seasons by harvest residue cover might have contributed to the accumulation of soil C and N and microbial biomass with the residue retention treatments. The lack of statistically significant differences in some of soil microbial properties (e.g. microbial biomass C, respiration, etc.) might have been related to a large spatial variability among replicate plots at the experimental site.
The antioxidant effects of tocols (α-tocopherol and α-tocotrienol) and Rosa mosqueta shell extract added to antioxidant-stripped canola oil (TCO) were evaluated and compared with the non-stripped oil ...(CO) under the same conditions. Seven oil systems were subjected to thermal treatment at 180
°C for 18
h. Polar compounds formation, degradation of tocols and carotenoid pigments were studied. The addition of Rosa mosqueta shell extract gave a great stability to TCO, similar to CO, with a low polar compound formation and a high retention of α-tocopherol compared with other TCO samples, which suggested the protective action of the minor components present in the extract. Alpha-tocopherol showed a higher effectiveness than α-tocotrienol at high temperature. However, an increase in the level of α-tocopherol did not improve its action.
The citrus seeds are one of the principal residues in the juice industry and their utilization can decrease significantly the problems of their final disposal. In this work the thermal degradation of ...three Mexican citrus seeds: orange (
Citrus sinensis), lemon (
Citrus Limon) and grapefruit (
Citrus paradisi) was studied in nitrogen atmosphere. The two components (embryo and husk) of the seeds were characterized separately. The results showed that the thermal effects are very similar between the three embryos and the three husks. The embryos show higher degradability, superior content of nitrogen and higher heating value than the husks. The thermal degradation of the components of the three seeds is completed at 600
°C and it is considered to be a global process derived from the decomposition of their principal components (cellulose, hemicellulose and lignin). The results suggest that mixing the three entire seeds will not lead to a severe deviation from their individual thermal behavior and that the industry could apply them for carbonization purposes.
We studied the effects of long-term organic and mineral fertilization on soil microarthropods and soil chemical parameters in a field experiment under semi-arid conditions in Central Spain. Two ...different regimes of organic manuring, i.e. farmyard manure applied once in 3 years versus annual manuring with crop residues were compared. Soil carbon and nitrogen contents were increased markedly by farmyard manure, whereas straw and green manure had no significant effect. In contrast, the abundance of soil microarthropods was increased by annual application of straw and green manure, but not by farmyard manure last applied 2.5 years before sampling. We conclude that in the field experiment under study the abundance of soil microarthropods was influenced by the immediate food supply rather than by soil chemical parameters, such as carbon and nitrogen content or the pH. Biodiversity of soil microarthropods, as estimated by the Shannon index, was not affected significantly by straw and green manure. Obviously, other management practices, especially tillage, are limiting the species composition of soil microarthropods and thereby overshadow possible effects of fertilization on diversity.
Predicting carbon (C) and nitrogen (N) mineralization of plant residues returned to soils is vital for foreseeing carbon dioxide (CO ₂) emissions into the atmosphere and soil nitrogen availability. ...Similarly, dissolved organic matter (DOM) is an important factor in forecasting microbial degradation of organic inputs as it represents the most active organic fraction, both biologically and chemically. In this study, an incubation experiment was conducted to investigate C and N mineralization and DOM potentials of residues of peanut (green manure, GM) and rice (rice straw, RS) at moisture regimes 50% (W1) and 100% (W2) of water holding capacity and temperature T1 (25°C) and T2 (35°C). The incorporation of plant residues significantly (P < 0.05) increased the mineralization and DOM, compared to controls. We observed that though GM residue had high carbon and nitrogen and DOM potential, but because of low C:N ratio and lignin, cellulose, and hemicelluloses compounds were vulnerable to easy decomposition with the increase in temperature, which led to more CO ₂ emission, fast mineralization, and less net OM in the soil. Conversely, RS residue, due to high C:N ratio, lignin, cellulose, and hemicelluloses compounds was resistant to decompose with the increase in temperature and possessed slow mineralization and eventually low CO ₂ emission. The moisture regimes (W1 and W2) and temperature (T1 and T2) had significant (P < 0.05) effect on mineralization and DOM potentials of both plant residues. The significant decrease and increase in the mineralization and DOM potential of both plant residues was observed with the increase in moisture and temperature. Our results suggest that plant residues with high C:N ratio, lignin, cellulose, and hemicelluloses compounds like RS are resistant to decompose with the increase in temperature, as a result possessed slow decomposition and mineralization, and can be used as an eco-friendly organic amendment, to get enduring benefits, and to mitigate the problem of carbon losses and CO ₂ emission from soil to atmosphere.
A new biorefining process is presented that embodies green processing and sustainable development. In the spirit of a true biorefinery, the objective is to convert agricultural residues and other ...biomass feedstocks into value-added products such as fuel ethanol, dissolving pulp, and lignin for resin production. The continuous biomass fractionation process yields a liquid stream rich in hemicellulosic sugars, a lignin-rich liquid stream, and a solid cellulose stream. This paper generally discusses potential applications of the three streams and specifically provides results on the evaluation of the cellulose stream from corn stover as a source of fermentation sugars and specialty pulp. Enzymatic hydrolysis of this relatively pure cellulose stream requires significantly lower enzyme loadings because of minimal enzyme deactivation from nonspecific binding to lignin. A correlation was shown to exist between lignin removal efficiency and enzymatic digestibility. The cellulose produced was also demonstrated to be a suitable replacement for hardwood pulp, especially in the top ply of a linerboard. Also, the relatively pure nature of the cellulose renders it suitable as raw material for making dissolving pulp. This pulping approach has significantly smaller environmental footprint compared to the industry-standard kraft process because no sulfur- or chlorine-containing compounds are used. Although this option needs some minimal post-processing, it produces a higher value commodity than ethanol and, unlike ethanol, does not need extensive processing such as hydrolysis or fermentation. Potential use of low-molecular weight lignin as a raw material for wood adhesive production is discussed as well as its use as cement and feed binder. As a baseline application the hemicellulosic sugars captured in the hydrolyzate liquor can be used to produce ethanol, but potential utilization of xylose for xylitol fermentation is also feasible. Markets and values of these applications are juxtaposed with market penetration and saturation.
