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The nitrous oxide (N 2 O) emission of from arable soil following the application of manure is expected to vary by different animal manure types used. This study was conducted to determine the relationship between the type of animal manure used to amend soil and the amount of N 2 O emitted during the cultivation of sweet potato (Ipomoea batatas). An additional objective was to study the characteristics of nitrogen (N) and carbon (C) in different animal manures. Composted manures from chickens, cows, and pigs were applied to the soil at rates of 0, 10, and 20 Mg ha −1 , respectively. The availability and concentration of N and C varied by manure type. The concentration of NH 4 + was greater in pig manure (4638 mg kg −1 ) than in chicken (551 mg kg −1 ) and cow manure (147 mg kg −1 ). The mean cumulative N 2 O emission rate across soil application rates was also the highest with pig manure (11.9 kg ha −1 year −1 ), followed by chicken and cow manure, with emission rates of 10.8 and 10.1 kg ha −1 year −1 , respectively. The majority of N 2 O measured during the sweet-potato-growing season was produced from aerobic nitrification. Dissolved organic carbon (DOC) concentrations in animal manures did not affect cumulative N 2 O emission rates, and no significant relationship was observed throughout the growing season between the concentration of DOC in soil and daily N 2 O emission. Cumulative N 2 O emission rates depended on the type of animal manure and might be governed by NH 4 + concentration, rather than by total N concentration in animal manure type. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

BACKGROUND: Composted animal manure applied to the arable soil for improving soil quality and enhancing crop productivity causes greenhouse gas emissions such as nitrous oxide (N 2 O) by processes of nitrification and denitrification. However, little studies have been conducted on determining effect of application ratio of composted animal manure on N 2 O emission rate and its annual emission pattern from upland soil in South Korea. Therefore, this study was conducted to determine N 2 O emission rate and its annual emission pattern from upland soil supporting for sweet potato. METHODS AND RESULTS: Composted animal manure was applied at the ratio of 0, 10, and 20 Mg/ha to an upland soil supporting for sweet potato (Ipomoea batatas). Nitrous oxide emission was examined during growing season and non-growing season from May 2016 through May 2017. Daily N 2 O fluxes showed peaks right after applications of composted animal manure and inorganic nitrogen fertilizer.

Little is known about the exact mechanism of cadmium (Cd) immobilization by phosphate (P) in arable soil containing low Cd concentration. This study was designed to describe this mechanism in detail. We determined the phosphorus (P) addition rate allowing Cd to precipitate as Cd minerals in Cd-contaminated arable soils and identified the main species of Cd minerals formed by the reaction of Cd and P, using the chemical equilibrium model MINTEQ. To determine the amount of Cd adsorption to soil adsorbed P, 0 –10,000 mgPL−1 of K2HPO4 solution was reacted with soil, then the P adsorbed soil was reacted with a CdCl2 solution (500 mg Cd L−1). Cadmium might not precipitate as Cd minerals such as Cd3(PO4)2 and CdCO3 with a recommended application rate of P fertilizer in field scale. Cadmium might be immobilized by Cd2+ adsorption instead of precipitation under a low P application system. Phosphate adsorption increased the negative charge of soil and Cd adsorption. The contributions of the increase in pH- and P-induced negative charges to the total increase in the soil negative charge were 93.2 and 6.8%, respectively. The increase in Cd adsorption caused by P adsorption was mainly attributed to the increase in pH-induced negative charge.

In a pilot study, we observed cadmium (Cd) immobilization with citric acid (CA) and suggested that mandarin byproducts (MB), which contain CA at ca. 1.65%, can be used as soil amendments that reduce Cd bioavailability. In the present study, we (1) elucidated mechanisms of Cd immobilization by CA and (2) evaluated the use of MB as a soil amendment for Cd immobilization. In Experiment 1, CA was mixed with Cd contaminated soil at 0 and 3.5 mmol kg −1. We then added MB to Cd-spiked soil at 10, 20, and 40 g kg −1. Addition of CA decreased F2 (surface adsorbed Cd fraction) contents by 2.64 mg kg −1 compared with the control but was associated with increases in Cd fractions F1 (bioavailable Cd fraction) and F5 (residual Cd fraction) of 1.04 and 1.49 mg kg −1 , respectively. Addition of CA enhanced the concentration of fraction F5, likely reflecting Cd precipitation from soil solutions with increased HCO 3 − concentrations. However, although this treatment immobilized Cd, it also led to increasing residual and bioavailable Cd fractions. Unlike CA treatments, MB increased non-bioavailable Cd fractions without increasing the bioavailable Cd fraction. Moreover, at 40 g kg −1 , MB decreased F1 contents by 8% compared with the control, but increased F2, F3, and F5 contents by 3.6%, 0.7%, and 4.5%, respectively. Cd may be immobilized by MB through H x CO 3 − mediated precipitation as CdCO 3 following decomposition of CA and concomitant increases in the negative charge of soil due to the organic matter in MB. MB also improved the chemical properties of soils, with increased nutrient concentrations and cation exchange capacities.