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Effects of the application of digestates from wet and dry anaerobic fermentation to Japanese paddy and upland soils on short-term nitrification.

Sawada K, Toyota K - Microbes Environ. (2015)

Bottom Line: Wet and dry anaerobic fermentation processes are operated for biogas production from organic matter, resulting in wet and dry digestates as by-products, respectively.Therefore, we herein compared the effects of applying wet digestates (pH 8.2, C/N ratio 4.5), dry digestates (pH 8.8, C/N ratio 23.4), and a chemical fertilizer to Japanese paddy and upland soils on short-term nitrification under laboratory aerobic conditions.These results suggest that the immediate effects of applying digestates, especially dry digestates with the highest pH, on nitrate leaching need to be considered when digestates are used as alternative fertilizers.

View Article: PubMed Central - PubMed

Affiliation: Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology.

ABSTRACT
Wet and dry anaerobic fermentation processes are operated for biogas production from organic matter, resulting in wet and dry digestates as by-products, respectively. The application of these digestates to soil as fertilizer has increased in recent years. Therefore, we herein compared the effects of applying wet digestates (pH 8.2, C/N ratio 4.5), dry digestates (pH 8.8, C/N ratio 23.4), and a chemical fertilizer to Japanese paddy and upland soils on short-term nitrification under laboratory aerobic conditions. Chloroform-labile C, an indicator of microbial biomass, was only minimally affected by these applications, indicating that a small amount of labile N was immobilized by microbes. All applications led to rapid increases in NO3 -N contents in both soils, and ammonia-oxidizing bacteria, but not archaea may play a critical role in net nitrification in the amended soils. The net nitrification rates for both soils were the highest after the application of dry digestates, followed by wet digestates and then the chemical fertilizer in order of decreasing soil pH. These results suggest that the immediate effects of applying digestates, especially dry digestates with the highest pH, on nitrate leaching need to be considered when digestates are used as alternative fertilizers.

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K2 SO4 -extractable organic C (EOC) (A and B) and chloroform-labile C (CL-C) (C and D) in paddy and upland soils after 0, 7, 14, and 35 d of incubation. CF indicates chemical fertilizer treatment. Bars indicate standard deviation (n=3). Different letters indicate significant differences between treatments (first uppercase letters) and sampling days (second lowercase letters) (P=0.05).
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f1-30_37: K2 SO4 -extractable organic C (EOC) (A and B) and chloroform-labile C (CL-C) (C and D) in paddy and upland soils after 0, 7, 14, and 35 d of incubation. CF indicates chemical fertilizer treatment. Bars indicate standard deviation (n=3). Different letters indicate significant differences between treatments (first uppercase letters) and sampling days (second lowercase letters) (P=0.05).

Mentions: We arranged for soil to be subjected to 4 treatments in the incubation experiments, including the chemical fertilizer [8:8:8 N/P/K, Asahi Industries, Tokyo, Japan] (CF), the wet and dry digestate treatments, and a control (no addition). Amendments were added at an application rate of ~200 μg NH4 -N g−1 dry soil (equivalent to ~300 kg NH4 -N ha−1 assuming a soil bulk density of 1 g cm−3 up to a depth of 15 cm). The added amounts of wet and dry digestates were 58 and 75 mg g−1 dry soil (equivalent to 87 and 112 Mg ha−1), respectively. Using the NH4 -N content as an index of digestate application rates was a realistic approach since nitrogen is considered to be the main yield-limiting factor (1). Supplemented soil samples were mixed thoroughly with a spatula and weighed 5 g (oven-dried basis, 105°C) into 50 mL glass vials. The vials including soils were covered with aluminum foil and incubated for 0, 7, 14, or 35 d at 27°C. The moisture levels in the vials were maintained at 50% of the maximum water-holding capacity during the incubation with distilled water. K2 SO4 -extractable NO3 -N, organic C (EOC), total N (ETN), and pH, and chloroform-labile C (CL-C) and N (CL-N) as indicators of the soil microbial biomass, as well as AOA and AOB amoA gene copy numbers were analyzed using these vials, which were destructively collected with three replicates per treatment after 0, 7, 14, and 35 d of incubation (although we could not obtain the CL-C and CL-N values after 35 d of incubation for the upland soil because of a technical error [Fig. 1D]). pH (H2 O) was only measured after 0 d of incubation with no replication. Therefore, a total of 296 vials were prepared for two paddy and arable soils, four treatments (control and CF, wet digestate, and dry digestate applications), four sampling times (0, 7, 14, and 35 d), and three analyses (before and after chloroform fumigation and for DNA extraction) in triplicate, plus eight vials for the pH (H2 O) determination. Ammonia volatilization and denitrification were not measured because they were considered to be negligible due to homogeneous mixing of the digestates with soils and the incubation under aerobic conditions, as demonstrated by de la Fuente et al. (7).


Effects of the application of digestates from wet and dry anaerobic fermentation to Japanese paddy and upland soils on short-term nitrification.

Sawada K, Toyota K - Microbes Environ. (2015)

K2 SO4 -extractable organic C (EOC) (A and B) and chloroform-labile C (CL-C) (C and D) in paddy and upland soils after 0, 7, 14, and 35 d of incubation. CF indicates chemical fertilizer treatment. Bars indicate standard deviation (n=3). Different letters indicate significant differences between treatments (first uppercase letters) and sampling days (second lowercase letters) (P=0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356462&req=5

f1-30_37: K2 SO4 -extractable organic C (EOC) (A and B) and chloroform-labile C (CL-C) (C and D) in paddy and upland soils after 0, 7, 14, and 35 d of incubation. CF indicates chemical fertilizer treatment. Bars indicate standard deviation (n=3). Different letters indicate significant differences between treatments (first uppercase letters) and sampling days (second lowercase letters) (P=0.05).
Mentions: We arranged for soil to be subjected to 4 treatments in the incubation experiments, including the chemical fertilizer [8:8:8 N/P/K, Asahi Industries, Tokyo, Japan] (CF), the wet and dry digestate treatments, and a control (no addition). Amendments were added at an application rate of ~200 μg NH4 -N g−1 dry soil (equivalent to ~300 kg NH4 -N ha−1 assuming a soil bulk density of 1 g cm−3 up to a depth of 15 cm). The added amounts of wet and dry digestates were 58 and 75 mg g−1 dry soil (equivalent to 87 and 112 Mg ha−1), respectively. Using the NH4 -N content as an index of digestate application rates was a realistic approach since nitrogen is considered to be the main yield-limiting factor (1). Supplemented soil samples were mixed thoroughly with a spatula and weighed 5 g (oven-dried basis, 105°C) into 50 mL glass vials. The vials including soils were covered with aluminum foil and incubated for 0, 7, 14, or 35 d at 27°C. The moisture levels in the vials were maintained at 50% of the maximum water-holding capacity during the incubation with distilled water. K2 SO4 -extractable NO3 -N, organic C (EOC), total N (ETN), and pH, and chloroform-labile C (CL-C) and N (CL-N) as indicators of the soil microbial biomass, as well as AOA and AOB amoA gene copy numbers were analyzed using these vials, which were destructively collected with three replicates per treatment after 0, 7, 14, and 35 d of incubation (although we could not obtain the CL-C and CL-N values after 35 d of incubation for the upland soil because of a technical error [Fig. 1D]). pH (H2 O) was only measured after 0 d of incubation with no replication. Therefore, a total of 296 vials were prepared for two paddy and arable soils, four treatments (control and CF, wet digestate, and dry digestate applications), four sampling times (0, 7, 14, and 35 d), and three analyses (before and after chloroform fumigation and for DNA extraction) in triplicate, plus eight vials for the pH (H2 O) determination. Ammonia volatilization and denitrification were not measured because they were considered to be negligible due to homogeneous mixing of the digestates with soils and the incubation under aerobic conditions, as demonstrated by de la Fuente et al. (7).

Bottom Line: Wet and dry anaerobic fermentation processes are operated for biogas production from organic matter, resulting in wet and dry digestates as by-products, respectively.Therefore, we herein compared the effects of applying wet digestates (pH 8.2, C/N ratio 4.5), dry digestates (pH 8.8, C/N ratio 23.4), and a chemical fertilizer to Japanese paddy and upland soils on short-term nitrification under laboratory aerobic conditions.These results suggest that the immediate effects of applying digestates, especially dry digestates with the highest pH, on nitrate leaching need to be considered when digestates are used as alternative fertilizers.

View Article: PubMed Central - PubMed

Affiliation: Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology.

ABSTRACT
Wet and dry anaerobic fermentation processes are operated for biogas production from organic matter, resulting in wet and dry digestates as by-products, respectively. The application of these digestates to soil as fertilizer has increased in recent years. Therefore, we herein compared the effects of applying wet digestates (pH 8.2, C/N ratio 4.5), dry digestates (pH 8.8, C/N ratio 23.4), and a chemical fertilizer to Japanese paddy and upland soils on short-term nitrification under laboratory aerobic conditions. Chloroform-labile C, an indicator of microbial biomass, was only minimally affected by these applications, indicating that a small amount of labile N was immobilized by microbes. All applications led to rapid increases in NO3 -N contents in both soils, and ammonia-oxidizing bacteria, but not archaea may play a critical role in net nitrification in the amended soils. The net nitrification rates for both soils were the highest after the application of dry digestates, followed by wet digestates and then the chemical fertilizer in order of decreasing soil pH. These results suggest that the immediate effects of applying digestates, especially dry digestates with the highest pH, on nitrate leaching need to be considered when digestates are used as alternative fertilizers.

Show MeSH