Mass Loss Of Straw Research Articles

Taxon-specific ability of saprophagous soil macrofauna to reintegrate carbon from agricultural waste into soil

Saprophagous soil macroinvertebrates may potentially degrade agricultural wastes. However, it is not known, to what extent and representatives of which taxa may help reintegrating carbon from crop residues back into soil without triggering massive carbon release into the atmosphere. To tackle this problem, we conducted a three-month-long microcosm experiment with 21 different species of macrofauna (each treatment replicated four times) belonging to 13 families to test their ability to degrade wheat straw. Simultaneously CO2 release from the microcosms was measured. Five species did not survive under experimental conditions. Among the remaining 16 species, three significantly increased wheat straw decomposition with Oryctes nasicornis larvae having inflicted the highest straw mass loss (64%) in comparison with the control, where no animals were added (29%). None of the tested species increased cumulative CO2 evolution from the microcosms, while two species significantly reduced it. The reduction of carbon loss with aerobic respiration was recorded for Cetonia aurata larvae and the earthworm Dendrobaena veneta (respectively 2.5 and 2-fold in relation to the control – 53.8±4.6 mg CO2-C g−1 soil dry weight during the entire experiment). The original integrative Carbon Sequestration Index by Macrofauna (CSIM) calculated for both of the measured parameters suggests that the woodlouse Armadillidium vulgare and to a smaller extent the earthworm D. veneta appear to be the most promising organisms for industrial climate-friendly organic waste recycling in terms of survival, straw processing and simultaneous reduction of CO2 emissions from soil. Our results proved that the engagement of saprophagous macrofauna in crop residue decomposition is a viable technique of carbon reincorporation into the soil. It is accompanied with CO2 release mitigation into the atmosphere.

Key decomposers of straw depending on tillage and fertilization

Crop straw is often incorporated into soil, but how agricultural practices affect straw decomposition and the involved biological mechanisms are not fully understood. We conducted a half-year straw decomposition assay in a 16-year experiment with tillage (conventional tillage or no-tillage) and fertilization (single or combined nitrogen, phosphorus and/or cow manure addition) regimes in a dryland agroecosystem. Straw decomposition and extracellular enzyme activities as well as bacterial, fungal, protistan and metazoan communities in the straw residues were analyzed. Straw mass loss was accelerated by tillage, whereas it was slowered by all but not single nitrogen fertilization treatments and correlated negatively with soil fertility. Enzyme activities were sensitive to tillage and fertilization but not correlated with straw decomposition. Straw mass loss was positively correlated with the relative abundances of a dominant saprotrophic fungus (related to Apodus deciduus) and an ecological cluster of the inter-kingdom co-occurrence network, whose abundances were increased by tillage and decreased with increasing soil fertility. This study shows strong effects of agricultural practices on straw decomposition, and highlights the importance of key decomposers and inter-kingdom interactions in regulating straw decomposition. We propose that straw incorporation should be applied with appropriate tillage and reduced fertilizers in dryland agroecosystems.

Laccase-Based Self-Amplifying Catalytic System Enables Efficient Antibiotic Degradation for Sustainable Environmental Remediation.

Antibiotic contamination poses potential risks to ecosystems and human health. Laccase (LAC) has emerged as a promising biocatalyst for the oxidation of environmentally toxic contaminants with high catalytic efficiency; however, its large-scale application is hindered by enzyme costs and dependency on redox mediators. Herein, a novel self-amplifying catalytic system (SACS) for antibiotic remediation that does not require external mediators is developed. In SACS, a natural mediator-regenerating koji with high-activity LAC, derived from lignocellulosic waste, initiates the chlortetracycline (CTC) degradation. Subsequently, an intermediate product, CTC327, identified as an active mediator for LAC via molecular docking, is formed and then starts a renewable reaction cycle, including CTC327-LAC interaction, stimulated CTC bioconversion, and self-amplifying CTC327 release, thus enabling highly efficient antibiotic bioremediation. In addition, SACS exhibits excellent performance in producing lignocellulose-degrading enzymes, highlighting its potential for lignocellulosic biomass deconstruction. To demonstrate its effectiveness and accessibility in the natural environment, SACS is used to catalyze in situ soil bioremediation and straw degradation. The resulting CTC degradation rate is 93.43%, with a straw mass loss of up to 58.35% in a coupled process. This mediator regeneration and waste-to-resource conversion in SACS provides a promising route for environmental remediation and sustainable agricultural practices.

Maize/peanut intercropping has greater synergistic effects and home-field advantages than maize/soybean on straw decomposition.

The decomposition of plant litter mass is responsible for substantial carbon fluxes and remains a key process regulating nutrient cycling in natural and managed ecosystems. Litter decomposition has been addressed in agricultural monoculture systems, but not in intercropping systems, which produce species-diverse litter mass mixtures. The aim here is to quantify how straw type, the soil environment and their combined effects may influence straw decomposition in widely practiced maize/legume intercropping systems. Three decomposition experiments were conducted over 341 days within a long-term intercropping field experiment which included two nitrogen (N) addition levels (i.e. no-N and N-addition) and five cropping systems (maize, soybean and peanut monocultures and maize/soybean and maize/peanut intercropping). Experiment I was used to quantify litter quality effects on decomposition; five types of straw (maize, soybean, peanut, maize-soybean and maize-peanut) from two N treatments decomposed in the same maize plot. Experiment II addressed soil environment effects on root decomposition; soybean straw decomposed in different plots (five cropping systems and two N levels). Experiment III addressed 'home' decomposition effects whereby litter mass (straw) was remained to decompose in the plot of origin. The contribution of litter and soil effects to the home-field advantages was compared between experiment III ('home' plot) and I-II ('away' plot). Straw type affected litter mass loss in the same soil environment (experiment I) and the mass loss values of maize, soybean, peanut, maize-soybean, and maize-peanut straw were 59, 77, 87, 76, and 78%, respectively. Straw type also affected decomposition in the 'home' plot environment (experiment III), with mass loss values of maize, soybean, peanut, maize-soybean and maize-peanut straw of 66, 74, 80, 72, and 76%, respectively. Cropping system did not affect the mass loss of soybean straw (experiment II). Nitrogen-addition significantly increased straw mass loss in experiment III. Decomposition of maize-peanut straw mixtures was enhanced more by 'home-field advantage' effects than that of maize-soybean straw mixtures. There was a synergistic mixing effect of maize-peanut and maize-soybean straw mixture decomposition in both 'home' (experiment III) and 'away' plots (experiment I). Maize-peanut showed greater synergistic effects than maize-soybean in straw mixture decomposition in their 'home' plot (experiment III). These findings are discussed in terms of their important implications for the management of species-diverse straw in food-production intercropping systems.

Where the straw-derived nitrogen gone in paddy field subjected to different irrigation regimes and straw placement depths? Evidence from 15N labeling

Straw-derived N is an organic N source, that plays an important role in agroecosystems. However, quantitatively tracing the release and fate of exogenous straw-derived N in a rice-soil system amended by irrigation regime and straw placement depth is poorly understood. The objectives of this study were to determine the release and fate of straw-derived N in the rice-soil system under different irrigation regimes and straw placement depths. 15N-labeled rice straw was used for two consecutive years in a field experiment in Northeast China, and four treatments were established: (i) controlled irrigation + shallow straw return (5 cm depth, CSD1); (ii) controlled irrigation + deep straw return (15 cm depth, CSD2); (iii) flooded irrigation + shallow straw return (5 cm depth, FSD1); and (iv) flooded irrigation + deep straw return (15 cm depth, FSD2). We found that the temporal patterns of straw N release were best described by the one-pool model, which was helpful to predict the straw-derived N fluxes during straw decomposition under different irrigation regimes and straw placement depths. Controlled irrigation and shallow straw placement depth increased the straw N release rate, which was consistent with their effects on straw mass loss, especially in the first rice season, showing a decreasing order of CSD1 > CSD2 > FSD1 > FSD2. Irrigation regime and straw placement depth significantly affected the fate of straw-derived N in the rice-soil system. Controlled irrigation will not only increase plant utilization rates of straw-derived N at different straw placement depths but also promote soil sequestration of straw-derived N and reduce the loss of straw-derived N. Additionally, we also found that placing straw at a shallower depth can also increase straw-derived N utilization by plants. Coupling controlled irrigation and placing straw at a shallower depth (CSD1) resulted in the highest utilization of straw-derived N by plants. However, it is worth noting that placing straw at a shallower depth also increases the loss of straw-derived N, which may increase the risk of environmental pollution in a soil-rice system. This study expanded the theory of straw N release and effective utilization in agroecosystems, which is helpful to better predict gross N fluxes and fates of straw-derived N in the agroecosystem to formulate a scientific and reasonable mode of field management with straw return.

Enchytraeids simultaneously stimulate rice straw degradation and mitigate CO2 release in a paddy soil

The contribution of soil enchytraeids (potworms) to carbon cycling is often considered marginal and is therefore rarely quantified. In our experiment we aimed at evaluating the impact of the model enchytraeid species Enchytraeus buchholzi Vejdovsky, 1879 on rice straw degradation and associated CO2 release from soil. We filled 48 microcosms with soil collected in rice paddies of the Republic of Kalmykia, Russia, at 75% water holding capacity and added 0.5 g dry rice straw sealed in litterbags to each of them. Half of the microcosms were inoculated with 100 potworms. On days 3, 6, 9, 14, 21 and 31 after the start of the experiment, we measured CO2 emissions from soil. In addition, we terminated four microcosms with and four without enchytraeids at each of these dates to measure both rice straw mass loss and enchytraeid recovery rates. E. buchholzi significantly accelerated the relative rice straw mass loss (10.2 ± 1.4 and 14.2 ± 2.0%, respectively). It also significantly reduced CO2 emissions by 35% on average across the whole observation period. Though the number of potworms extracted dropped by 61% of the initial density up to day 9, it then consistently increased and reached a mean density of 365 individuals per microcosm at the end of the experiment. Considering both the rapid reproduction of E. buchholzi and the efficient mitigation of CO2 release, the promotion of enchytraeid activity may be a promising management measure for stabilizing carbon in paddy soils amended with rice straw. This opens up innovative perspectives for further research on exploiting the potential of the soil fauna for sustainable recycling of rice crop residues.

Temperature and Straw Quality Regulate the Microbial Phospholipid Fatty Acid Composition Associated with Straw Decomposition

Variations in temperature and moisture play an important role in soil organic matter (SOM) decomposition. However, relationships between changes in microbial community composition induced by increasing temperature and SOM decomposition are still unclear. The present study was conducted to investigate the effects of temperature and moisture levels on soil respiration and microbial communities involved in straw decomposition and elucidate the impact of microbial communities on straw mass loss. A 120-d litterbag experiment was conducted using wheat and maize straw at three levels of soil moisture (40%, 70%, and 90% of water-holding capacity) and temperature (15, 25, and 35 °C). The microbial communities were then assessed by phospholipid fatty acid (PLFA) analysis. With the exception of fungal PLFAs in maize straw at day 120, the PLFAs indicative of Gram-negative bacteria and fungi decreased with increasing temperatures. Temperature and straw C/N ratio significantly affected the microbial PLFA composition at the early stage, while soil microbial biomass carbon (C) had a stronger effect than straw C/N ratio at the later stage. Soil moisture levels exhibited no significant effect on microbial PLFA composition. Total PLFAs significantly influenced straw mass loss at the early stage of decomposition, but not at the later stage. In addition, the ratio of Gram-negative and Gram-positive bacterial PLFAs was negatively correlated with the straw mass loss. These results indicated that shifts in microbial PLFA composition induced by temperature, straw quality, and microbial C sources could lead to changes in straw decomposition.

The role of UV-B radiation and precipitation on straw decomposition and topsoil C turnover

In arid and semi-arid area, ultraviolet-B (UV-B) radiation plays a mainly positive role in litter decomposition. In subtropical area, however, the role of UV-B radiation remains uncertain due to the interference of precipitation. To evaluate the potential contribution of precipitation to the role of UV-B radiation, we exposed 84 bags of rice straw to ambient and reduced UV-B radiation, with and without water addition after each precipitation event, on the roof of a building at Huazhong Agricultural University (Wuhan, China). Additionally, the indirect effects of UV-B radiation on soil dissolved organic carbon (DOC) were investigated by placing 70-g soil samples beneath 5-g straw bags with precipitation treatments. Mass loss, DOC and water extractable phenols (WEP) were monitored over 228 days. Subsequently, microbial facilitation was studied, by incubating straw and soil samples exposed for the longest period (228 days) in the laboratory at 25 °C, and by afterwards analyzing their CO2–C emission. Our results demonstrated that UV-B radiation did not significantly affect straw mass loss, but induced an increase in straw DOC, WEP and CO2–C emission by 20.6%, 10.7% and 20.4%, respectively, under dry conditions. Whereas, combined with precipitation, the effects of UV-B radiation on straw DOC, WEP and CO2–C emission were negligible. Only a small decrease in soil DOC (9.9%) and CO2–C (4.0%) was observed. Furthermore, UV-B radiation interacted significantly with precipitation during straw decomposition. These results indicate that for dry conditions UV-B radiation accelerates straw decomposition by increasing DOC content. For wet conditions, however, the effects of UV-B radiation on straw decomposition are balanced out and even negative on topsoil C turnover.

Decomposition rate of cereal straw as affected by soil placement

Decomposition rates for crop residues have generally been estimated based on data obtained using buried litter bags. Because of limited soil–residue contact, the litter bag technique may not adequately simulate decomposition when residues are mixed through the soil. In field microplots, decomposition of wheat (Triticum aestivum) and barley (Hordeum vulgare) straw (autumn-incorporated at a rate of 7 t/ha) mixed through the 0–0.20 m soil layer was compared with straw decomposition in fibreglass bags (4-mm mesh) buried at a depth of 0.20 m. A surface-placed straw treatment and a no-straw control were included for comparison. Emissions of CO2 were monitored from the incorporated straw treatments and undecomposed straw was recovered after 158 days (mean soil temperature during the trial period was 8°C at 0.10 m). Emissions of CO2 from the soil‐mixed straw treatment were generally greater than from the buried bag treatment in the 2 months following incorporation. Output of CO2-C over the first 73 days averaged 83 g/m2 for the soil-mixed straw treatment compared with 61 g/m2 for the litter bag treatment and 34 g/m2 for the no-straw control. Over the entire trial, CO2-C attributable to straw (CO2-C output from straw-treated plots minus CO2-C emitted from the control) was 66% greater for soil‐mixed straw than for litter bag straw, indicating that within soil placement can have a strong and persistent effect on straw decomposition. Straw type had a small but significant (P < 0.05) effect on CO2 output (barley > wheat). Straw mass loss during the trial averaged 66% for soil-mixed straw, 32% for litter bag straw, and 13% for straw placed on the soil surface. The low recovery of soil‐mixed straw is partly due to difficulty of extracting small (<2 mm) residue fragments from the soil; however, such fragments could legitimately be considered part of the soil organic matter. The results confirm that straw that is well distributed through the soil may decompose more rapidly than would be anticipated from litter bag measurements.

Suitability of wheat straw decomposition, cotton strip degradation and bait-lamina feeding tests to determine soil invertebrate activity

The activities of earthworms, springtails and mites in the decomposition of different substrates were examined by applying three different test methods: wheat straw degradation, the cotton-strip assay and the bait-lamina test. The main aim was to determine the potential of these three methods to describe the (direct and indirect) contribution of soil invertebrates to decomposition processes in soil. Animals were introduced at different densities to mesocosms consisting of intact soil cores taken from grassland. Wheat straw mass loss, determined after 27 days, and cotton tensile strength loss, measured after 14 days, did not significantly differ for the different densities of earthworms, springtails and mites. These findings indicate that cellulose degradation and wheat straw decomposition are more dependent on microbial activity, rather than on the abundance and activity of soil invertebrates. Soil microbial activity, measured as dehydrogenase activity at the end of the 75-day incubation period, did not show any correlation with animal density. Bait-lamina consumption rate was highest for the mesocosms containing earthworms, and increased with increasing earthworm density. Bait-lamina consumption in the mesocosms inoculated with springtails or mites only was not significantly different from that in the controls without animals. In the case of the mites this might at least partly be explained by the low densities used in this experiment. It may be concluded that whilst the bait-lamina test gives the best reflection of the biological activity of soil animals, in particular earthworms, wheat straw and cotton strip decomposition rates are more indicative of microbial activity in the soil.

Decomposition of straw in relation to tillage, moisture, and arthropod abundance in a semi-arid tropical Alfisol

The decomposition of rice straw was studied in relation to straw moisture and the abundance of soil arthropods, such as Acarina, Collembola, and miscellaneous groups dominated by termites [Odontotermes obesus (Rambur) and Microtermes obesi Holmgren], across tillage treatments (no tillage, shallow tillage, and deep tillage) in Alfisols of the semi-arid tropics in India from August 1989 to July 1990. In the straw, across the treatments, Acarina were dominant (>70% of the total arthropods), and Collembola were a minor component. O. obesus and M. obesi foraged straw together under the cover of an earthern sheet. A larger number of arthropods was recorded during the rainy season, but they were either negligible or absent during the dry season. The abundance of arthropods and mass loss of straw was greater in coarse-mesh bags than in the fine-mesh bags. Their abundance was significantly affected by tillage treatments and season (P<0.01). In the beginning, it was significantly greater in the no-tillage and shallow-tillage than in the deep-tillage treatment. The mass loss was 46% of the initial mass during the first 60 days, and more than 90% after 330 days of decomposition. Tillage had a significant effect on mass loss, particularly after 330 days, and the no tillage treatment led to a greater mass loss. Multiple linear regression analysis revealed that the moisture content of the straw and the abundance of arthropods had significantly affected the mass loss in both fine-and coarse-mesh bags across the tillage managements.