Mitigation of Impact of Nitrogen Cycling Associated with Agriculture and Food Consumption on Regional Environments

Session 2: Nitrogen, Green House Gasses and Agricultur

Effect of different moisture content on nitrous oxide production in aggregated soil of Shintoku, Japan

Agricultural soils are the major source of the potent greenhouse gas and ozone-depleting substance, N2O. An incubation study was carried out using the volcanic ash fine textured soil of Shintoku. Soil samples used in this study were taken from managed grassland at Shintoku Experimental Livestock Farm of Hokkaido University in Southern Hokkaido, Japan (N43º05′, E142º51′). Soil aggregates were air-dried, and sieved with 4.5 mm and 2 mm and adjusted the soil moisture of 60% and 80% of field water capacity (FWC). Just after the moistening, the aggregates were incubated for 9 days under a temperature of 20°C. Just after starting the incubation, the flush of N2O production was observed. Similar flushes of carbon dioxide (CO2) and nitric oxide (NO) productions were also observed. All of the gas productions were higher in larger aggregates with 80% of field water capacity. The concentrations of Water Extractable Organic Carbon (WEOC), NH4+-N, pH and total N were significantly different before and after incubation. Shintoku soil showed a significant correlation between before and after incubation for all soil chemical properties except pH. Especially WEOC and NH4+-N changed immediately after the addition of water and this situation continued during the incubation. Larger aggregates showed higher amounts of NH4+-N and NO3-–N and were responsible for higher N2O production compared to smaller aggregates. In Shintoku the results of N2O-N/NO-N ratio in both moisture contents indicated nitrification as a main process of N2O production. It is very well known that N2O is produced more from the denitrification process than nitrification. Poor aeration and less diffusion of NO3-N and WEOC from the aerobic area to the anaerobic area reduce N2O production in the denitrification process of fine textured Shintoku soil. Int. J. Agril. Res. Innov. Tech. 14(2): 99-110, December 202

Effect of different moisture content on nitrous oxide production in aggregated soil of Shintoku, Japan

Agricultural soils are the major source of the potent greenhouse gas and ozone-depleting substance, N2O. An incubation study was carried out using the volcanic ash fine textured soil of Shintoku. Soil samples used in this study were taken from managed grassland at Shintoku Experimental Livestock Farm of Hokkaido University in Southern Hokkaido, Japan (N43º05′, E142º51′). Soil aggregates were air-dried, and sieved with 4.5 mm and 2 mm and adjusted the soil moisture of 60% and 80% of field water capacity (FWC). Just after the moistening, the aggregates were incubated for 9 days under a temperature of 20°C. Just after starting the incubation, the flush of N2O production was observed. Similar flushes of carbon dioxide (CO2) and nitric oxide (NO) productions were also observed. All of the gas productions were higher in larger aggregates with 80% of field water capacity. The concentrations of Water Extractable Organic Carbon (WEOC), NH4+-N, pH and total N were significantly different before and after incubation. Shintoku soil showed a significant correlation between before and after incubation for all soil chemical properties except pH. Especially WEOC and NH4+-N changed immediately after the addition of water and this situation continued during the incubation. Larger aggregates showed higher amounts of NH4+-N and NO3-–N and were responsible for higher N2O production compared to smaller aggregates. In Shintoku the results of N2O-N/NO-N ratio in both moisture contents indicated nitrification as a main process of N2O production. It is very well known that N2O is produced more from the denitrification process than nitrification. Poor aeration and less diffusion of NO3-N and WEOC from the aerobic area to the anaerobic area reduce N2O production in the denitrification process of fine textured Shintoku soil

Nitric Oxide Fluxes from Upland Soils in Central Hokkaido, Japan

Symposium Pape

Comparison of Nitrogen Budgets in Agricultural Watersheds

Poster Sessio

Variations of soil properties and soil surface loss after fire in rotational shifting cultivation in Northern Thailand

Since fire is still necessary for rotational shifting cultivation (RSC), the vertical distribution and slope effect on soil properties and soil surface loss after a fire remain unclear. To address these research gaps, the study aims to achieve the following objectives: 1) investigating post-fire soil properties and soil surface loss in RSC, and 2) assessing the vertical distribution and slope effect on soil properties and soil surface loss in RSC. Soil samples were collected from two stages of RSC: 6 years (RSC-6Y) and 12 years (RSC-12Y), located in Chiang Mai Province, Northern Thailand. A continuous 15-year left fallow field (CF-15Y) was used as the reference site. Soil samples were collected from the upper, middle, and lower slopes at depths of 0–5, 5–10, 10–20, and 20–30 cm at five different time points: before burning, 5 min, 3 months, 6 months, and 9 months post-fire. The results indicated that older fallow fields had a tendency to accumulate more soil organic carbon (SOC) and soil organic nitrogen (STN). The color of the ash was altered by the fire, resulting in dark reddish-brown ash with higher levels of pH, organic matter (OM), electrical conductivity, total nitrogen, and soil nutrients when compared to gray and white ashes. The combustion of OM during the fire was found to release soil nutrients, which could explain the increase after burning. SOC stock increased at deeper layers (5–10 cm) with higher values than pre-burning levels, especially at lower slope positions, while STN stock decreased at the surface soil post-fire but increased in deeper layers at all slope positions. The average soil surface loss ranged from 1.6 to 3.1 cm, with the highest loss observed 9 months after the fire (during the rainy season) at the upper slope. In terms of the impact of slope on soil properties following the fire event, our study indicated a significant correlation between lower slopes and variables including SOC, STN, electrical conductivity, nitrate–nitrogen (NO3-N), ammonium nitrogen (NH4-N), exchangeable calcium, and exchangeable magnesium. Further study is required to investigate and develop appropriate post-fire management strategies to effectively reduce nutrient loss and minimize soil surface erosion

Biophysical Characteristics of Tropical Peatland

Based on Jenny’s equation (1941) of soil forming factors i.e. S = f(C, R, B, P, T) with the five soil forming factors, the biotic (B) factor of soil formation is the most multifaceted among them. The biotic factor can be grouped into vegetation, microorganisms, animals and human activities. Vegetation is considered to be the most important facet of the biotic factor. Efforts to explain soil characteristics in terms of the influence of biota are best facilitated by biosequence studies. These studies contain a series of soil profiles across which the biotic soil forming factor varies while other soil forming factors remain constant. Within the context of a biosequence, the effect of changing biotic factor upon any soil property can be assessed quantitatively. For tropical peat, vegetation is both a biotic and parent material for soil forming factors. The elemental composition of soil differs from that of geologic materials in its striking enrichment of carbon and nitrogen compounds relative to most rocks. The organic compounds of the plants are the ultimate sources of this C and N. Plants contribute organic compounds to the soil in a variety of ways, including the senescence or necrosis of tissue, exudation or respiration from the roots, and the liberation of reproductive tissues such as pollen, seeds and fruits. Thus plants that live on the soil both influence soil properties and are influenced by soil properties. And these have been observed on the tropical peat of Sarawak whereby there is an existence of biosequence in each peat basin i.e. different forest types on a peat basin means different soil characteristics caused by different biophysical characteristics of the peat. This biosequence in the peat swamps of Peninsular Malaysia is less highly developed than those in Sarawak (Anderson, 1964). Therefore the objective of this paper is to describe the physical characteristics of the peat in relation to the forest types and its implication to agriculture development especially oil palm cultivation on tropical peat

Integrated Evaluation of Soil Carbon Budget by Manure Application on Forage Production

Grasslands and forage crop fields produce forages and also have many services and functions such as repositories of biodiversity, climate regulation and soil conservation (Sala and Paruelo, 1997). Carbon budget is one of these important ecosystem services by high levels of carbon sequestration below ground (Hungate et al., 1997). Manure application increases carbon budget and also affects forage production, NO3- leaching to underground water and N2O emission to atmosphere. Integrated evaluation of these various environmental impacts is important to find optimum condition for forage production and environmental impacts. LIME2 (Life-cycle Impact assessment Method based on Endpoint modeling 2, Itsubo and Inaba, 2010) is one of the methods to evaluate environmental impacts and to integrate them into a single index of environmental damages with the unit of Japanese yen. By comparing this index to economic benefit of forage production, integrated evaluation of environmental damages and profit of farmers is achieved. In this study, the effects of manure application to forage production, carbon budget, NO3- leaching and N2O emission were evaluated and optimum level of manure application level was estimated with LIME2 integration factors

Post-fire recovery of soil organic carbon, soil total nitrogen, soil nutrients, and soil erodibility in rotational shifting cultivation in Northern Thailand

The hill tribes in Thailand traditionally depend on rotational shifting cultivation (RSC). However, insufficient understanding remains on post-fire soil properties and soil erodibility (k-values) with fallow years. To address this gap, the levels of soil organic carbon (SOC), soil total nitrogen (STN), soil nutrients, and soil erodibility after fire in RSC were investigated. Topsoil (0–10 cm) samples from sites with 4 (RSC-4Y), 5 (RSC-5Y), and 7 (RSC-7Y) fallow years in Chiang Mai Province, northern Thailand, were taken at four time points: before burning, 5 min after burning, 9 months after burning, and 2 years after burning. Soil pH, electrical conductivity, and soil nutrient (available P, K, and Ca) levels were increased after burning and remained higher than the pre-burning levels for at least 2 years. The SOC stock decreased after burning in all fallow fields. At 2 years after burning, the SOC stock in RSC-4Y was higher than before burning, whereas in RSC-5Y and RSC-7Y, the levels had not reached the pre-fire levels. The STN stocks of all studied fields significantly decreased after burning and had not reached the pre-burning levels after 2 years. After burning, the topsoil of RSC-4Y was most susceptible to erosion. However, only in RSC-4Y, the k-value was unchanged at 2 years after burning. Three different approaches are recommended for post-fire land management: 1) farmers should not cut and remove the weeds and grasses at the soil surface, 2) burning should be performed around late winter or early summer (November–February) to inhibit complete combustion, and 3) contour-felled log erosion barriers should be made by using the trunks remaining after the fire to trap the sediment and slow down surface runoff