Evaluation of orange peel waste and its biochar on greenhouse gas emissions and soil biochemical properties within a loess soil.

The environmentally safe disposal of the large quantity of orange peels waste produced each day causes economic and environmental problems, which after conversion into biochar via pyrolysis technique might be used as an effective soil amendment. In this study, a 90-day incubation experiment was conducted to investigate the effects of orange peel waste and waste-derived biochar amendments on greenhouse gas emissions (GHG), soil biochemical properties, and soil enzyme activities. There were five treatments with different amendment levels: control without an amendment (Control), orange waste 1% (W1), orange waste 2% (W2), orange waste biochar 1% (B1), and orange waste biochar 2% (B2). The results showed that, compared with control, the amendments decreased cumulative N2O emissions by 59.2% (B2), 45.2% (B1), 20.6% (W2) and 10.2% (W1), respectively; and increased cumulative CH4 emissions by 81.7% (W1), 84.4% (W2), 75.8% (B1) and 74.9% (B2), respectively. Cumulative CO2 emissions decreased for the B1 (29.3%) and B2 (43.5%) over the waste treatments. While soil pH, SOC, nitrate nitrogen (NO3--N) and enzyme activities (urease and catalase) were significantly increased with the passage of time from the biochar amendments, ammonium nitrogen (NH4+-N) and invertase activities did not show this trend with time. Our study suggests that orange peel waste conversion to biochar should be a viable alternate method of disposal since land application resulted in reduced GHG and improvements in soil fertility.

A user-friendly modified pore-solid fractal model.

The primary objective of this study was to evaluate a range of calculation points on water retention curves (WRC) instead of the singularity point at air-entry suction in the pore-solid fractal (PSF) model, which additionally considered the hysteresis effect based on the PSF theory. The modified pore-solid fractal (M-PSF) model was tested using 26 soil samples from Yangling on the Loess Plateau in China and 54 soil samples from the Unsaturated Soil Hydraulic Database. The derivation results showed that the M-PSF model is user-friendly and flexible for a wide range of calculation point options. This model theoretically describes the primary differences between the soil moisture desorption and the adsorption processes by the fractal dimensions. The M-PSF model demonstrated good performance particularly at the calculation points corresponding to the suctions from 100 cm to 1000 cm. Furthermore, the M-PSF model, used the fractal dimension of the particle size distribution, exhibited an accepted performance of WRC predictions for different textured soils when the suction values were ≥100 cm. To fully understand the function of hysteresis in the PSF theory, the role of allowable and accessible pores must be examined.