Influence of Aeration Method on Gaseous Emissions and the Losses of the Carbon and Nitrogen during Cow Manure Composting

The objective of this research was to explore the effects of different aeration methods on NH3 and greenhouse gas (GHG) emissions and the losses of carbon and nitrogen from composting of cow manure and corn stalks in the laboratory-scale reactors. Here, we designed three treatments, including continuous aerated treatment C1 (aeration rates 0.21 L·kg−1 dry matter (DM)·min−1) and intermittent aerated treatments I1 (aeration rates 0.42 L·kg−1 DM·min−1; aerate 10 min, stop 10 min) and I2 (aeration rates 0.84 L·kg−1 DM·min−1; aerate 5 min, stop 15 min). The results showed that the physicochemical parameters (temperature, pH values, and germination index) of composting products met the requirements of maturity and sanitation. Compared with continuous aerated treatment C1, the cumulative NH3 emissions of I1 and I2 treatments decreased by 24.37% and 19.27%, while the cumulative CO2 emissions decreased by 13.01% and 20.72%. On the contrary, the cumulative N2O emissions of I1 and I2 treatments increased by 22.22% and 43.14%. CO2 emission was the principal pathway for the TOC losses, which comprised over 65% of TOC losses. C1 treatment had the highest TOC losses due to its highest cumulative CO2 emissions. The TN losses of I1 and I2 treatments reduced 9.07% and 6.1% compared to C1 treatment, so the intermittent aerated modes could reduce the TN loss. Due to the potential for mitigation of gaseous emissions, I1 treatment was recommended to be used in aerobic composting of cow manure

Influence of Aeration Method on Gaseous Emissions and the Losses of the Carbon and Nitrogen during Cow Manure Composting

The objective of this research was to explore the effects of different aeration methods on NH3 and greenhouse gas (GHG) emissions and the losses of carbon and nitrogen from composting of cow manure and corn stalks in the laboratory-scale reactors. Here, we designed three treatments, including continuous aerated treatment C1 (aeration rates 0.21 L·kg−1 dry matter (DM)·min−1) and intermittent aerated treatments I1 (aeration rates 0.42 L·kg−1 DM·min−1; aerate 10 min, stop 10 min) and I2 (aeration rates 0.84 L·kg−1 DM·min−1; aerate 5 min, stop 15 min). The results showed that the physicochemical parameters (temperature, pH values, and germination index) of composting products met the requirements of maturity and sanitation. Compared with continuous aerated treatment C1, the cumulative NH3 emissions of I1 and I2 treatments decreased by 24.37% and 19.27%, while the cumulative CO2 emissions decreased by 13.01% and 20.72%. On the contrary, the cumulative N2O emissions of I1 and I2 treatments increased by 22.22% and 43.14%. CO2 emission was the principal pathway for the TOC losses, which comprised over 65% of TOC losses. C1 treatment had the highest TOC losses due to its highest cumulative CO2 emissions. The TN losses of I1 and I2 treatments reduced 9.07% and 6.1% compared to C1 treatment, so the intermittent aerated modes could reduce the TN loss. Due to the potential for mitigation of gaseous emissions, I1 treatment was recommended to be used in aerobic composting of cow manure

Maize Straw Return and Nitrogen Rate Effects on Potato (Solanum tuberosum L.) Performance and Soil Physicochemical Characteristics in Northwest China

The average yield of fresh potato tubers per hectare is relatively low in China, partly due to poor nutrient management. Chronic inorganic N enrichment leads to soil acidification, which deteriorates soil fertility. Straw residues are removed from the field or burnt during land preparation, resulting in nutrient depletion and air pollution. However, these residues can be returned to the soil to improve its fertility. Therefore, a two–year experiment was conducted in an existing field with five years of different inorganic nitrogen (N) rate to determine the effects of straw return and N rate on potato growth, tuber yield, and quality, profit margin, and soil physicochemical properties. The experiment consisted of four N rates: 0 (control, CK), 75 (low N rate, LN), 150 (medium N rate, MN), and 300 (high N rate, HN) kg N ha−1 with and without straw (9 t ha−1) return. The results showed that straw with N enrichment improved soil fertility, which increased tuber yield and quality. Compared to the control, MN + straw treatment stimulated economic tuber yield (34.73% and 38.34%), profit margin (55.51% and 63.03%), and protein content (20.04% and 25.46%) in 2018 and 2019, respectively. Nitrogen enrichment after straw return is a sustainable practice for stimulating potato tuber yield, profit margin, and improving soil fertility to promote sustainable agriculture development

Moisture-Induced Effects on Lignocellulosic and Humification Fractions in Aerobically Composted Straw and Manure

Humic substances affect compost stability and maturation. However, the intricate structure of lignocellulosic materials hinders the biodegradation of cellulose, hemicellulose, and lignin, often promoting the use of synthetic additives which results in microbial inactivation and death. Therefore, this study examined the effects of optimal moisture levels (MC1 = 45%, MC2 = 55%, and MC3 = 65%) on lignocellulosic and humification fractions in aerobically composted straw and manure. The study showed that 65% moisture content was more efficient in decomposing cellulose, hemicellulose, and lignin, with hemicellulose (115.3% w/w ≈ 47.1%) degrading more than cellulose (76.0% w/w ≈ 39.5%) and lignin (39.9% w/w ≈ 25.9%). However, in compost heaps with 45% moisture, the humic acid concentration increased significantly by 12.4% (3.1% w/w) and 17.3% (4.3% w/w) compared with 55% and 65% moisture, respectively. All moisture levels increased the mineralization of humic substances, but the index measured was highest at 65% MC (23.8% w/w) and lowest at 45% MC (18% w/w). In addition, the humification rate showed the trend: 0.083% w/w > 0.087% w/w > 0.100% w/w for MC1, MC2, and MC3, respectively. Overall, the results indicate that an initial moisture content of 65% is aerobically efficient for the conversion of corn straw and cow manure into stable and mature compost

Divergent Accumulation of Microbial Residues and Amino Sugars in Loess Soil after Six Years of Different Inorganic Nitrogen Enrichment Scenarios

Amino sugars are key microbial biomarkers for determining the contribution of microbial residues in soil organic matter (SOM). However, it remains largely unclear as to what extent inorganic nitrogen (N) fertilization can lead to the significant degradation of SOM in alkaline agricultural soils. A six-year field experiment was conducted from 2013 to 2018 to evaluate the effects of chronic N enrichment on microbial residues, amino sugars, and soil biochemical properties under four nitrogen (urea, 46% N) fertilization scenarios: 0 (no-N, control), 75 (low-N), 225 (medium-N), and 375 (high-N) kg N ha−1. The results showed that chronic N enrichment stimulated microbial residues and amino sugar accumulation over time. The medium-N treatment increased the concentration of muramic acid (15.77%), glucosamine (13.55%), galactosamine (18.84%), bacterial residues (16.88%), fungal residues (11.31%), and total microbial residues (12.57%) compared to the control in 2018; however, these concentrations were comparable to the high-N treatment concentrations. The ratio of glucosamine to galactosamine and of glucosamine to muramic acid decreased over time due to a larger increase in bacterial residues as compared to fungal residues. Microbial biomass, soil organic carbon, and aboveground plant biomass positively correlated with microbial residues and amino sugar components. Chronic N enrichment improved the soil biochemical properties and aboveground plant biomass, which stimulated microbial residues and amino sugar accumulation over time