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Rice–duck farming is a sustainable food system that provides rice and duck meat and eggs. Excessive application of commercial feedstuff for ducks weakens the sustainability of rice–duck farming. This study aims to investigate green forage (Lolium multiflorumLam.) as a substitute for commercial grain mix, to attain a maximum economic benefit and pollution-free production in rice–duck farming. The effects of a mixed feedstuff of green forage and commercial grain mix with a stable ratio of 1:4 (MFSR), mixture feedstuff of green forage and commercial grain mix with dynamic ratios (MFDR), and full commercial grain mix (FCGM) were studied. Results showed that Cherry Volley and hybrid ducks were more adaptable to mixed feedstuff than Mud ducks. Growth of ducks was classified into rapid, slow and steady-growth stages. The weight, body length, neck length, and chest circumference of ducks that were fed MFDR were only slightly decreased. The carcass weight, eviscerated weight, and semi-eviscerated weight of ducks fed MFDR were similar to those fed FCGM. MFDR significantly decreased duck fat accumulation. MFDR did not have negative impacts on the agronomic traits of rice yields. Duck profits per 667 m2were calculated as CNY (Chinese Yuan) 254.91 (MFSR), CNY309.27 (MFDR), and CNY39.36 (FCGM). MFDR effectively improved the rice–duck farming. [ABSTRACT FROM PUBLISHER]

Acid rain is one of the most serious ecological and environmental problems worldwide. This study investigated the impacts of simulated acid rain (SAR) upon leaching of trace metals and aluminum (Al) from a soil. Soil pot leaching experiments were performed to investigate the impacts of SAR at five different pH levels (or treatments) over a 34-day period upon the release of trace metals (i.e., Cu, Ni, Pb, Zn, and Fe) and Al from the Latosol (acidic red soil). The concentrations of trace metals in the effluent increased as the SAR pH level decreased, and were highest at the SAR pH = 2.0. In general, the concentrations of Cu, Pb, Fe, and Al in the effluent increased with leaching time at the SAR pH = 2.0, whereas the concentrations of Zn, Fe, and Al in the effluent decreased with leaching time at the SAR pH ≥ 4.0. The increase in electrical conductivity (EC) with leaching time at five different SAR pH levels was primarily due to the concentrations of Al and Fe in the effluent. There were good linear correlations between the effluent Al concentrations and the effluent pH at the SAR pH = 2.0 (R2= 0.87) and pH = 3.0 (R2= 0.83). More soil trace metals and Al were activated and released into the soil solution as the SAR pH level decreased. [ABSTRACT FROM PUBLISHER]