Effects of rice husk biochar and soil moisture on the accumulation of organic and inorganic nitrogen and nitrous oxide emissions during the decomposition of hairy vetch (Vicia villosa) mulch. Issue 4 (4th July 2019)

• Record Type: Journal Article
• Authors: Uchida, Yoshitaka; Moriizumi, Mihoko; Shimotsuma, Moe
• Is Part Of: Soil science and plant nutrition. Volume 65:Issue 4(2019)
• Page Start: 409
• Page End: 418
• Publication Date: 2019-07-04
• Subjects: Soil amendments -- organic chemistry; Soil science -- Periodicals; Plants -- Nutrition -- Periodicals; 631.4
• DOI: 10.1080/00380768.2019.1624139
• Languages: English
• ISSNs: 0038-0768

Abstract

ABSTRACT: Hairy vetch ( Vicia villosa Roth ssp. dasycarpa ) mulch is widely used as green manure. This mulch decomposes in the soil and produces nitrous oxide (N2 O) emissions. Although rice husk charcoal can be used as a soil conditioner to reduce N2 O emissions, the effects of charcoal on the decomposition of vetch mulch and consequent N2 O emissions have not been well studied. We conducted an incubation experiment to examine how the decomposition of vetch mulch, charcoal amendments and two soil moisture regimes (field capacity and at a slightly drier moisture regime) affect the mineralisation of N during decomposition. We applied high-performance size-exclusion chromatography and chemiluminescent N detection to quantify soluble organic-N compounds of various molecular sizes. Changes over time in inorganic-N, soluble organic-N fractions and N2 O fluxes were measured in soils . We found that vetch mulch induced the accumulation of small-molecular-size soluble organic-N compounds in the early phase during decomposition; however, in wet soils with charcoal, the small-molecular-weight N fraction was depleted earlier than in wet soils without charcoal, suggesting more rapid mineralisation in wet soils. Charcoal in wet soils resulted in earlier and sharper N2 O peak emissions and did not reduce cumulative N2 O emissions in vetch mulch treatments, suggesting that previously reported N2 O emission reductions due to charcoal do not occur in the soils . The rates of N2 O emission did not correlate with the concentrations of soluble organic N and inorganic N, indicating that other factors control the N2 O emission rates during the decomposition of vetch mulch. Our results indicated that the incorporation of charcoal does not reduce N2 O emissions in soils where vetch mulch is applied. The depletion of nitrate-N in wet soils with charcoal demonstrates that adding charcoal can reduce nitrate-N leaching from soils.