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The biochemical reactions of aerobic microbial respiration (AMR) suggest that silage temperature (Tsi) rise, oxygen (O2) consumption and carbon dioxide (CO2) emission may be equally useful as indicators of silage deterioration during feed-out, but only temperature has been used extensively to assess aerobic stability. Here we extend the study of aerobic stability to incorporate AMR of silage by developing a novel experimental cell integrated with multiple sensors. Silage samples, ensiled from a triticale crop, were made in twelve air-tight barrels (60 L), packed to bulk densities of 190 or 250 kg m−3 dry matter (DM). Tsi and O2 measurements were co-located at 15- and 30-cm behind the working face. CO2 was measured as flux across the working face. The experimental period of aerobic exposure was 7 days. We provide the first reports of: (i) distinct aerobic responses of these parameters, showing that Tsi varied with CO2 in phase but with O2 out-of phase; (ii) CO2 flux was dominated initially by anaerobic discharge and subsequently by aerobic products; (iii) linear relationships between aerobic reheating and both O2 consumption (0.994 ≥ R2 ≥ 0.815, P

Silage is an essential global feedstuff and an emitter of greenhouse gases. However, few studies have examined the formation of carbon dioxide (CO

The microbiome in silage may vary substantially from the onset to the completion of fermentation. Improved additives and inoculants are being developed to accelerate the ensiling process, to enhance fermentation quality, and to delay spoilage during feed-out. However, current methods for preselecting and characterizing these amendments are time-consuming and costly. Here, we have developed a multi-sensor mini-bioreactor (MSMB) to track microbial fermentation in situ and additionally presented a mathematical model for the optimal assessment among candidate inoculants based on the Bolza equation, a fundamental formula in optimal control theory. Three sensors [pH, CO2, and ethanol (EtOH)] provided data for assessment, with four additional sensors (O2, gas pressure, temperature, and atmospheric pressure) to monitor/control the fermentation environment. This advanced MSMB is demonstrated with an experimental method for evaluating three typical species of lactic acid bacteria (LAB), Lentilactobacillus buchneri (LB) alone, and LB mixed with Lactiplantibacillus plantarum (LBLP) or with Enterococcus faecium (LBEF), all cultured in De Man, Rogosa, and Sharpe (MRS) broth. The fermentation process was monitored in situ over 48 h with these candidate microbial strains using the MSMB. The experimental results combine acidification characteristics with production of CO2 and EtOH, optimal assessment of the microbes, analysis of the metabolic sensitivity to pH, and partitioning of the contribution of each species to fermentation. These new data demonstrate that the MSMB associated with the novel rapid data-processing method may expedite development of microbial amendments for silage additives.

The aim of this study was to develop a new experimental setup to determine parallel the emissions of greenhouse gases (GHG) and volatile organic compounds (VOCs) from silage during the opening as well as the subsequent aerobic storage phase of the complete bale without wrapping film. For this purpose, a special silage respiration chamber was used in which a silage bale could be examined. The gas analysis (CO2, methanol, ethanol, ethyl acetate) of inlet, ambient and outlet air of the silage respiration chamber was carried out by photoacoustic spectroscopy. The gas samples taken inside the bale were analysed by gas chromatography for CO2, O2, CH4, and N2O. Three silage bales (grass and lucerne) as the smallest silage unit commonly used in practice were examined. The emission behaviour of the bales was recorded during experimental periods up to 55 days. The results allow a differentiation of the outgassing processes. On the one hand, gases produced during the anaerobic ensiling process (CO2, CH4, N2O) are released once in a large amount during the first experimental hours after opening the silage. On the other hand, a continuous outgassing process takes place, which is particularly true for the VOCs ethanol, methanol, and ethyl acetate, whereby VOC emissions increase with rising ambient air temperatures. In this study, the emissions during the first 600 experimental hours from the grass silage bale and lucerne silage bale were 2313 g and 2612 g CO2, 17.6 g and 145.2 g methanol, 132.3 g and 675.9 g ethanol, 55.1 g and 66.2 g ethyl acetate, respectively. Nevertheless, the focus of this study was on the technical recording of gas concentrations inside the silage bale itself and the emissions in the ambient air of the bale. For a better interpretation of the data, additional factors should be considered in further investigations.

In situ measurement oxygen (O2) and temperature (Tsi) for silage production.Simultaneously tracking O2 diffusion and Tsi dynamics with three packed densities.Evaluating accuracy/feasibility of Pitt-Muck model to advance silage management. Aerobic deterioration is a major concern for silage production and quality change in unloading phase. To simulate silage aerobic deterioration relative to an exposure surface of bunker silo, a partial differential equation system model including oxygen (O2) concentration, silage temperature (Tsi) rise and microbial activity was presented. There is still a need to assess the predictability of the developed model at different bulk densities (BDs). For this study, the Clark oxygen electrodes (COE) was employed for the in situ simultaneous measurements of O2 and Tsi within maize silage samples, which were packed into twelve barrels (i.d.: 35.7cm, length: 60cm, vol. 60L) at three BD levels (low: 520550kgm3; medium: 660730kgm3; high: 860950kgm3). To assure the COE to be insensitive to CO2, a cross calibration for O2 concentrations (020% vol.) was made at 15% vol. of CO2 in advance of performing the experiment. For each barrel, two of the COEs were installed at 10cm and 40cm behind the exposure surface, respectively. The model was computed taking the in situ measurements of O2 and Tsi to be targets. Our study showed general well-agreements between the model simulations and the in situ measurements of O2 and Tsi for all BD levels. Some uncertainties and relevant reasons were also addressed. Based on these results, we concluded that the model has sufficient ability to predict aerobic deterioration in silage for bunker silos being unloaded.

Context Knowledge of the nutrient requirements of dairy cows, and the nutritional composition and physical form of the feed resources used to prepare the total mixed ration (TMR) of basic and concentrated feeds, is essential to achieving high milk yields, health and welfare in modern commercial herds. Grass and maize silage components can vary widely in composition depending on harvesting intervals and weather; thus, the distribution of dry matter (DM) and nutrients in silos may vary greatly, resulting in serious errors during sampling and analysis. In addition, the flow of information from the stored silage stops once the forages are stored in the silo. Aims The objective of this study was to develop a practical approach for measuring variations in DM and silage quality parameters (crude protein, fibre, ash and fat) during the feed-extraction process from a bunker silo by a self-propelled feed mixer, which would ultimately help farmers to optimise the TMR. Methods Near-infrared spectroscopy (NIRS) technology was used to estimate fodder DM and nutrient contents in the material flow. Wet chemical analyses were used for preliminary evaluation of grass and maize silage samples. A portable NIRS was developed to record the spectra of various silage samples. Key results The spans of calibration of sample DM content were 21.3–59.2% for grass and 26–46.7% for maize. Crude protein content had span values of 11.4–18.3% for the grass silage and 5.4–10.8% for the maize silage models. Conclusions NIRS technology was used successfully to estimate the DM and nutrient contents of the fodder. The location for the functional unit on the self-propelled feed mixer may need to be modified for series production because it is not fully accessible. Implications NIRS is a suitable method for measuring DM and nutrient contents continuously during feed extraction from the bunker silo and can be used to help farmers to optimise the TMR.

Context Knowledge of the nutrient requirements of dairy cows, and the nutritional composition and physical form of the feed resources used to prepare the total mixed ration (TMR) of basic and concentrated feeds, is essential to achieving high milk yields, health and welfare in modern commercial herds. Grass and maize silage components can vary widely in composition depending on harvesting intervals and weather; thus, the distribution of dry matter (DM) and nutrients in silos may vary greatly, resulting in serious errors during sampling and analysis. In addition, the flow of information from the stored silage stops once the forages are stored in the silo. Aims The objective of this study was to develop a practical approach for measuring variations in DM and silage quality parameters (crude protein, fibre, ash and fat) during the feed-extraction process from a bunker silo by a self-propelled feed mixer, which would ultimately help farmers to optimise the TMR. Methods . Near-infrared spectroscopy (NIRS) technology was used to estimate fodder DM and nutrient contents in the material flow. Wet chemical analyses were used for preliminary evaluation of grass and maize silage samples. A portable NIRS was developed to record the spectra of various silage samples. Key results The spans of calibration of sample DM content were 21.3–59.2% for grass and 26–46.7% for maize. Crude protein content had span values of 11.4–18.3% for the grass silage and 5.4–10.8% for the maize silage models. Conclusions NIRS technology was used successfully to estimate the DM and nutrient contents of the fodder. The location for the functional unit on the self-propelled feed mixer may need to be modified for series production because it is not fully accessible. Implications NIRS is a suitable method for measuring DM and nutrient contents continuously during feed extraction from the bunker silo and can be used to help farmers to optimise the TMR.

Abnormal rise of temperature in silage is regarded as a signal of aerobic deterioration caused by the permeation of atmospheric oxygen into the silage, which indicates the growth of lactate-assimilating yeasts and energy release. Although baled silage has distinct advantages over other forms of silage, the high surface-area to volume ratio of the bale leads to a high risk of aerobic deterioration due to plastic cover damage. With an objective to spatially assess any aerobic deterioration within round-bales silage, we modified a bale-penetrometer that is capable of profiling temperature distribution. For each tested bale having a cylindrical volume of 2.154 m 3 , 72 path profiles including 504 stepwise measurements were made. Furthermore, two paths were re-profiled to check if the proposed invasive method has a significantly contaminative effect on the internal temperature field. The resulting R 2 = 0.9978 between the profiling data and the re-profiling data verified that the contamination due to the invasion of ambient air following the temperature probe penetration could be negligible. We presented two mapping methods, one for two-dimensional (2D) cross-sections and one for three-dimensional (3D) volumes. To demonstrate the applicability of the proposed method, six representative samples of round bales with varied damage to plastic covers were tested. All temperature patterns, generated in both 2D- and 3D-space, were informative and clearly interpretable. Therefore, we conclude that the tested measurement method can benefit advance of bale silage research and production.

Ensiling and compaction of silage crops in bags is a well proved method to store fodder anaerobically to feed animals throughout the year. The essential process principle is to compact the silage substrate using a rotor into a press tunnel and the connected plastic bag to generate an oxygen-free environment. The objective of this study was to develop an automatic pressure-controlling system for the compaction process. The automatic system controls elongation of the bag film calculated based on the circumference during ensiling. Due to the different physical composition of pasture grass and maize substrates, only 2% of values in the case of maize silage deviated from the specified tolerance range (9.5 ± 0.5% elongation) while over 50% of the values with grass silage deviated from the tolerance range (8.5 ± 0.5% elongation). To determine the effect on crop density and stability of silage, investigations were made during feed-out. Accordingly, the identified storage density of the maize and grass silage varied between 179.0 and 280.8 kg DM m−3, and 89.3 and 197.7 kg DM m−3, respectively. Basically, the automated pressure control of silo bagging press machines is possible, and the machine operator can be relieved. However, the homogeneity of the silo bag contours is highly dependent on the stored ensiled material.

Making silage involves a complicated biochemical process where oxygen (O2) is rapidly consumed within the sealed environment leading to fermentation and stable storage of the biomass. Reintroduction of the oxygen from a leak or the feed-out process results in silage degradation. Monitoring silage O2 concentration and temperature (Tsi) can provide critical insight regarding silage quality. Thus, an in situ biosensor for simultaneous monitoring of O2 and Tsi to track silage aerobic deterioration has long been needed but was unavailable. Although the Clark oxygen electrode (COE) is traditionally applied for O2 concentration dissolved in liquids, we extended its use to the gaseous phase of silage based on Henry's law. This study tested COE's using two trials, where trial-1 explored the initial-aerobic/ensiling phase and trial-2 examined the silage feed-out phase. The experimental results of both trials demonstrated that the COE can be an important monitoring tool for assessing the O2 dynamics throughout the silage lifecycle.

Silage is a critical global feedstock, but is prone to aerobic deterioration. The dominant mechanism of O2 transport into silage remains unresolved. Here, multiple sensors tracked O2 and CO2, gas pressure (ΔP) between internal silage and ambient air, pH and silage temperature (Tsi) during the ensilage of maize and ryegrass. We report the first observation that CO2 produced from microbial respiration was partially dissolved in silage water, with evidence of negative or positive ΔP depending on the changing balance between CO2 production and dissolution. The ΔP 2 production was much greater in anaerobic fermentation stage than in initial aerobic phase or later aerobic feed-out phase. O2 transport into silage is intimately linked to the dynamics of net CO2, ΔP, microbial activity, pH and Tsi. These results suggested that both gas diffusion (based on Fick’s law) and advective transfer (Darcy’s law) play equally important roles in governing the complex temporal progression of inward and outward gas fluxes to and from the silage interior. Even though low pH suppressed microbial activity and supported aerobic stability, the negative ΔP increased the risk of O2 entry and aerobic deterioration during feed-out phase.

Silage quality and aerobic stability are sometimes insufficient. If management requirements are not met, or to improve silage quality, additives are often used. The objective of this study is to investigate the effects of different factors on silage during aerobic conditions. Whole-crop forage maize was harvested and 24 buckets (65 L) were filled and assigned to one of four treatment groups: (1) control (no treatment); (2) chemical additive (sodium benzoate, potassium sorbate, sodium acetate); (3) a mixed biological inoculant containing Lactobacillus buchneri, L. plantarum, and Pediococcus acidilacti; and (4) a mixed biological inoculant containing L. buchneri, L. plantarum, and L. rhamnosus. An untreated variation was also ensiled. Two different densities were adjusted during ensiling. After opening, the temperature was measured for seven days and O2 and CO2 concentrations were analysed. The findings show that the chemical additive very effectively prevented silage from reheating and deteriorating. Aerobic reheating of silage was also successfully inhibited through biological additives and high density.

Biogas plants are the most complex systems and are heavily studied in the field of renewable energy. A biogas system is mainly influenced by biological and technical parameters that strongly interact with each other. One recommended practice when operating a biogas plant is the recirculation of the substrate from the second fermenter into the first fermenter, which extends the recirculation amount (RA) and, in turn, the recirculation rate (RR). This technique should be applied to support and secure the biogas process. In this investigation, the RA was varied, starting with the recommended “best practice” of 10.0 m3/d (RR 40%). Every ten days, the RA was reduced in steps of 1.5 m3/d, with 5.5 m3/d (RR 27%) being the final value. The basic question to be addressed concerns to what extent the RR influences the methane yield and thereby influence the efficiency of a manure-based biogas plant in practice. Diverting the “best practice” to a RR of 27% stabilised the fermentation process and lead to significantly higher methane yields with smaller standard deviations. In addition, with a reduced RR, the standard optimal acid concentration within the biogas substrate was approximately reached.

Carbon dioxide (CO2) is a principal byproduct of various chemical, biological and biochemical processes. CO2 has been measured using various advanced sensors, but a limiting technical challenge has been resolving independent streams of CO2 produced by processes occurring simultaneously. The magnitude and kinetics of each stream may be chemically, biologically or/and physically informative, but such partitioning has received little attention and successful case studies remain rare. In silage production, CO2 flux, an important indicator of aerobic deterioration, microbial activity or oxidative rate of silage, derives from two different pools: gas accumulated in the pores during the early anaerobic phase, and current real-time production of CO2 as oxygenated air enters the silage across the exposed face after opening for feed-out. The former is regarded as a noise confounding the signal and the latter reflects current degradation of the silage. Using a self-developed automatic sensor system with novel signal decomposition, we successfully partitioned CO2 flux into two independent streams derived from the two distinct pools in maize silage, following two independent processes: a physical venting of stored gas through a tortuous diffusive pathway, and a biochemical process generating gas in real time. Three silage samples, treated with a chemical or a biological additive, or left untreated, were tested. The signal decomposition found two best-fit functions (0.8034 ≤ R2 ≤ 0.9036), a quadratic CO2 discharge function and an exponential CO2 production function, for characterizing these distinct processes. These results demonstrate chemical sensor with powerful data-processing capability to resolve the complexity of dual-pool CO2 emission.

To ensure penetration results that are comparable under various experimental conditions, cone penetrometers specified by ASABE Standards have been suggested for many years. Elastic-plastic properties are typical of most agricultural materials, so the material being penetrated by a cone penetrometer may contact the penetrometer shaft, and friction on the shaft may affect the penetration force data. Development of a method for quantifying this friction force is expected to improve the accuracy of cone penetrometer data. The objectives of this study were: (1) to evaluate a method for determining friction force on the shaft of a cone penetrometer while penetrating sand and clay soils packed in a specific cylinder, (2) to verify the penetration friction component (PFC) that may significantly influence penetration resistance (PR) measurements for various densities of chopped maize, and (3) to assess the effectiveness of a proposed filter method for adjusting friction on the penetrometer shaft. With these intentions, we embedded strain gauges into an ASABE Standard small cone. The tip was free from the shaft friction, so the output of this sensor was used as a reference in this study. We found the ASABE Standard small cone suitable for a broad range of soil textures, as little PFC was observed from the sand or the clay soil samples. However, considerable friction from penetrating chopped maize was observed at three levels of packed density using the cylinder method. In this situation, with the reference of the sensor output inside the tip, a pair of coefficients (C 1 = 2329, C 2 = 2120) were optimized to filter the PFC out of the PR measurement. The adjusted data agreed well with those of the reference sensor (R 2 = 0.968; RMSE = 6.521 N). Thus, ASABE Standard penetrometers can also be used for silage materials without mechanical modification.

For silage production, high bulk density (BD) is critical to minimize aerobic deterioration facilitated by oxygen intrusion. To precisely assess packing quality for bunker silos, there is a desire to visualize the BD distribution within the silage. In this study, a penetrometer-based mapping system was developed. The data processing included filtering of the penetration friction component (PFC) out of the penetration resistance (PR), transfer of the corrected penetration resistance (PRc) to BD, incorporation of Kriged interpolation for data expansion and map generation. The experiment was conducted in a maize bunker silo (width: 8 m, middle height: 3 m). The BD distributions near the bunker silo face were represented using two map groups, one related to horizontal- and the other to vertical-density distribution patterns. We also presented a comparison between the map-based BD results and core sampling data. Agreement between the two measurement approaches (RMSE = 19.175 kg·m(-3)) demonstrates that the developed penetrometer mapping system may be beneficial for rapid assessment of aerobic deterioration potential in bunker silos.

Penetration resistance (PR) has been regarded as a common measure for characterizing the density profile of soil and biological materials in agricultural engineering. Due to diversity of agricultural materials associated with different elastic–plastic properties, a prerequisite for a reasonable measurement is to preclude the effect of penetration friction component (PFC) between the penetration shaft and surrounding material during a penetration process, otherwise an additional error may be significantly induced relating to the cone penetration depth. In this study, a bi-directional penetration method was proposed to determine PFC using a specially designed cylinder with tests of two types of agricultural materials (silty–clay loam and chopped maize). No significant PFC was observed from the soil sample, whereas significant PFC was observed to be strongly dependent on penetration depth from the chopped maize. Thus, a mathematical filter was developed to correct the friction-induced error of the PR measurements.

There is an increasing desire to have an insight into the density distribution of silage bales because a low initial air content can significantly reduce the risk of temperature rise and the loss of sugar content. In addition, biomass moisture also plays a determinant role in the risk of temperature rise of bale and biomass degradation. For the visual assessment of the bale density, @c-ray scanner is regarded as an accurate and reliable technique but has potential risk of exposure to radiation. This study proposed a practical technique using a dual-sensor penetrometer for the simultaneous measurements of penetration resistance (PR) and moisture content (MC) in conjunction with image-based analysis. Four round bales made by two types of balers were prepared for the test. During a measurement process, both MC and PR data were collected following the signal of a penetrating depth transducer in-phase. Each bale included 72 penetration measurements that were transformed into an image referring to either PR or MC, respectively. With the reference to the two-dimensional (2D) results obtained from a @c-ray scanner, the dual-sensor images revealed the similar discrepancies of the baled density. Moreover, the proposed dual-sensor penetrometer method could discover the density discrepancies from the different sections of the measured bale so that the visualizations in three-dimensional (3D) space were also feasible. In contrast, the MC sensor seemed more reliable since the PR measurements were relatively susceptible to the interference from the penetrating friction between the shaft wall and material.

Oxygen (O2) concentration inside the substrate is an important measurement for silage-research and-practical management. In the laboratory gas chromatography is commonly employed for O2 measurement. Among sensor-based techniques, accurate and reliable in situ measurement is rare because of high levels of carbon dioxide (CO2) generated by the introduction of O2 in the silage. The presented study focused on assessing three types of commercial O2 sensors, including Clark oxygen electrodes (COE), galvanic oxygen cell (GOC) sensors and the Dräger chip measurement system (DCMS). Laboratory cross calibration of O2 versus CO2 (each 0–15 vol.%) was made for the COE and the GOC sensors. All calibration results verified that O2 measurements for both sensors were insensitive to CO2. For the O2 in situ measurement in silage, all O2 sensors were first tested in two sealed barrels (diameter 35.7 cm; height: 60 cm) to monitor the O2 depletion with respect to the ensiling process (Test-A). The second test (Test-B) simulated the silage unloading process by recording the O2 penetration dynamics in three additional barrels, two covered by dry ice (0.6 kg or 1.2 kg of each) on the top surface and one without. Based on a general comparison of the experimental data, we conclude that each of these in situ sensor monitoring techniques for O2 concentration in silage exhibit individual advantages and limitations.