Simulation Model for Composting Cellulosic (Bagasse) Substrates

A dynamic model of aerobic composting with solid substrates was developed as a first step to predict the rate of decomposition of cellulosic materials. The model was based on heat and mass transfer principles and reaction kinetics of biological processes. The relations describing the rates of reaction and the degradability potential of the substrates were determined based on laboratory-scale experiments. The model was developed using a graphical software package, Stella II® (which was able to solve feedback loops encountered in actual composting processes.

The model was validated with temperature, oxygen distribution and mass degradation accompanying the composting of bagasse. Experimental setups consisted of 30 gallon drum reactors, continuously aerated. Temperature and oxygen in exhaust gases were monitored on an hourly basis and measurements of moisture content, pH and volatile solids were done on a weekly basis.

The data fit with the model was excellent for mass degraded and temperatures for the first 10 days. From day 10 to 14, the deviations between model predictions (as solved with Stella II®) and actual measurements did not exceed 2.6 percent. The concentrations of oxygen in outlet gases showed fair agreement between predicted and experimental values. Simulating the model with varying airflow rates showed that the maximum mass breakdown rates occurred for airflow rates of 0.12 kg dry air/(kg dry compost.hr) while maintaining the temperatures below 50°C, through a temperature feedback control strategy.     

Calculating the density of loamy sandy soddy-podzolic soils from penetration resistance diagrams

The possibility for the calculation of the soil bulk density from two-dimensional penetration resistance diagrams drawn using a penetrometer during the vertical sounding of the soil has been discussed. A method has been proposed for calculating the bulk density of loamy sandy soddy-podzolic soils from the soil penetration test diagrams. The model for the calculation of the soil bulk density is based on the general physical concepts with the involvement of similarity theory methods. The adequacy and quality of the model have been studied statistically. The model has been found to be suitable for calculating the bulk density of loamy sandy and sandy podzolic soils.     

Changes in the pore space of soil constructions in physical laboratory models

The dynamics of pore space structure in different filled soil constructions during water infiltration and wetting–drying processes is studied. Model laboratory experiments in columns physically simulate water infiltration after penetration at a rate of 600 mm with free outflow from the lower end of the column followed by multiple drying of soil constructions composed by alternating layers of sand, peat, and A and В horizons of soddy-podzolic soil. In two- and three-dimensional tomographic images, changes in the pore space and the interpenetration of solid phase at the boundaries between individual horizons of soil constructions are analyzed.     

Site-Specific Nitrogen Management in Rice Using Remote Sensing and Geostatistics

Proper doses of nitrogenous fertilizer are most important for rice production system because a large part of the nitrogen may be lost if it is not applied judiciously. A study was conducted covering five blocks of Balasore and two blocks of Bhadrak districts. Soil samples were collected randomly, and field visit was conducted during peak vegetative stage of rice. Two approaches have been used in this study for estimating the site-specific nitrogen (N) requirement in the study area. In one approach, geostatisical analysis and kriging was used to develop the soil test–based N recommendation map by which a minimum of 72 kg N ha^?1 and maximum of 94 kg N ha^?1 were recommended. In a second approach, remote sensing was used and N recommendation map was developed using the moderate-resolution imaging spectroradiometer (MODIS) leaf area index (LAI) and normalized difference vegetation index (NDVI) satellite data, and a minimum requirement of 60 kg N ha^?1 and maximum of 120 kg N ha^?1 was estimated through this approach.     

The Compostable Plastic Poly(lactic) Acid Causes a Temporal Shift in Fungal Communities in Maturing Compost

The compostable biopolymer, poly(lactic) acid (PLA), is increasingly being used as an alternative to conventional plastics for short shelf-life products, disposable bags and packaging, and in agriculture. Despite the increase in the amount of PLA entering composting systems, few studies have examined the impact of PLA degradation on the compost microbial community. Thermophilic fungi play an import role in the composting process as they secrete hydrolytic enzymes capable of breaking down an array of complex natural polymers. In this study, the impact of PLA hydrolysis on the compost fungal community was examined by terminal restriction fragment length polymorphism and 454 sequencing. At 25°C, the effect of PLA on the surrounding compost community was relatively small and no physical changes were observed to the PLA films. However, when incubated at 50°C, where physical disintegration of PLA was occurring, a clear divergence between the compost populations in the presence and absence of PLA was evident after 2 months but became closer to the population in the absence of PLA after 4 months indicating that, after causing an initial perturbation after 2 months, the population began to return to that seen in the absence of PLA. The only exception was in the population containing 50% (w/w) PLA film, which remained divergent after 4 months and was associated with a marked acidification of the compost. Thus, 454-pyrosequencing revealed that the presence of PLA caused a strong selection for a Thermomyces sp. that was present only at low abundance in the absence of PLA.     

Patterns of SSR variation in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) seeds under ex situ genebank storage and accelerated ageing

Maintaining seed viability and germplasm integrity is a challenging task in conservation of plant genetic resources, as seeds under storage will lose viability and genetic changes will occur. Attempt was made to analyze the patterns of genetic changes in wheat germplasm under ex situ genebank storage and accelerated ageing treatments. A set of 16 naturally aged wheat accessions under ex situ genebank storage since 1994 were sampled. Four recently regenerated wheat accessions were selected, four random seed samples were chosen from each accession, and three of them were exposed to three different accelerated ageing treatments. These 32 seed samples in two germplasm sets displayed a range of germination rates from 4 to 98 %. Thirty-seven microsatellite markers representing 21 wheat chromosomes were applied to screen 12 seeds of each sample and 449 SSR alleles were scored. Large SSR variation was found in each germplasm set. There was 73.1 % of the total SSR variation present among the naturally aged samples and 78.2 % present among the accelerated ageing samples. Several analyses for genetic association consistently revealed no clear genetic separations among samples of high or low germination rates in both germplasm sets. Samples under different accelerated ageing treatments did not show much genetic differentiations from the original sample of each accession. Mantel tests revealed non-significant associations between SSR variability and sample germination rates for both germplasm sets. These findings are useful for understanding seed deterioration under different ageing conditions and suggest that genome-wide SSR variability may not provide sensitive markers for the monitoring of wheat seed viability.     

A Greener UV and Peroxide-Based Chemical Oxygen Demand Test

Water quality assessment typically includes the determination of chemical oxygen demand (COD) by oxidation of organic matter with Cr(VI) in an acidic medium followed by digestion. Unfortunately, the required reagents are harmful and the reaction times are rather long. We investigated earlier the use of H₂O₂ as a more environmentally friendly oxidizing agent to replace the hazardous chromates. In the present study, we have furthered this possibility by incorporating the use of H₂O₂ in the presence of UV light. A protocol has been devised and tested with standards and real samples that replaces toxic Cr(VI), halves the amount of silver sulfate required, and greatly reduces the necessary reaction time, thus yielding a faster and more environmentally sound method.     

Soils of mountainous forest-steppe in the southwestern part of Khentei Ridge (Mongolia)

The study of soil cover in the mountainous forest-steppe on the southwestern macroslope of Khentei Ridge has shown that the spatial distribution of soils is controlled by the ruggedness of topography, slope aspects, geocryological conditions, and the thickness of loose deposits. The soils belong to the orders of lithozems and organo-accumulative soils (Mollic Leptosols) of the postlithogenic trunk of pedogenesis. Dark-humus and mucky–dark-humus horizons of the organic matter accumulation are characteristic features of these soils. The investigated area is differentiated according to the soil moistening conditions on the slopes of different aspects. Favorable growth conditions for dwarf birch and Siberian larch at the southern boundary of the boreal forests in Mongolia are explained by the relatively high moistening of mucky–darkhumus lithozems and mucky–dark-humus soils developed on windward northern slopes and on mountain terraces in places of the local snow accumulation by wind. An important role in preservation of forest vegetation belongs to permafrost in small cirque-like depressions.     

Characteristics of Nitrogen Loss through Surface-Subsurface Flow on Red Soil Slopes of Southeast China

Soil nitrogen (N) loss related to surface flow and subsurface flow (including interflow and groundwater flow) from slope lands is a global issue. A lysimetric experiment with three types of land cover (grass cover, GC; litter cover, LC; and bare land, BL) were carried out on a red soil slope land in southeast China. Total Nitrogen (TN) loss through surface flow, interflow and groundwater flow was observed under 28 natural precipitation events from 2015 to 2016. TN concentrations from subsurface flow on BL and LC plots were, on average, 2.7–8.2 and 1.5–4.4 times greater than TN concentrations from surface flow, respectively; the average concentration of TN from subsurface flow on GC was about 36–56% of that recorded from surface flow. Surface flow, interflow and groundwater flow contributed 0–15, 2–9 and 76–96%, respectively, of loss load of TN. Compared with BL, GC and LC intercepted 83–86% of TN loss through surface runoff; GC intercepted 95% of TN loss through subsurface flow while TN loss through subsurface flow on LC is 2.3 times larger than that on BL. In conclusion, subsurface flow especially groundwater flow is the dominant hydrological rout for N loss that is usually underestimated. Grass cover has the high retention of N runoff loss while litter mulch will increase N leaching loss. These findings provide scientific support to control N runoff loss from the red soil slope lands by using suitable vegetation cover and mulching techniques.