Tomokazu Haraguchi

Bio: Tomokazu Haraguchi is an academic researcher from Kyushu University. The author has contributed to research in topics: Evapotranspiration & Aquatic plant. The author has an hindex of 7, co-authored 32 publications receiving 153 citations.

Effect of plastic-film mulching on leaching of nitrate nitrogen in an upland field converted from paddy

Abstract: A lysimeter experiment was conducted to examine the effects of plastic film mulching on the leaching rate of nitrate nitrogen (NO3-N) from chemical fertilizer that was applied to an upland field that had been converted from paddy rice production. Leaching was monitored in two lysimeters filled with sandy loam soil, which contained low soil organic matter content, under different surface mulch conditions. One was mulched only on the ridge (ridge-mulch treatment) and another one was mulched fully, including the furrow, with black plastic film (full-mulch treatment). Chemical fertilizer was mixed into the top 0.2 m of soil in the two lysimeters before installing the mulch. After transplanting broccoli, the amount of subsurface discharge water and the NO3-N concentrations in the discharge water were measured every day. Larger NO3-N discharges occurred in the ridge-mulch treatment for three days after heavy rainfalls in which cumulative precipitation exceeded 10 mm, and the daily NO3-N load was twice as large as the full-mulch treatment. The differences in the amount of subsurface discharge water and NO3-N discharged between treatments were not significant when there was no rainfall. Cumulative NO3-N loads for the ridge- and full-mulch treatment during the last month of the experimental period were 0.246 and 0.195 g m−2, respectively. The effect of mulching on the reduction of NO3-N discharge rate was higher for the full-mulch treatment. This result showed that a plastic-film mulching system would be effective as an appropriate fertilizer management to reduce nitrate-leaching losses.

Quantification of soil surface evaporation under micro-scale advection in drip-irrigated fields

Abstract: The objective of this study is to quantify soil surface evaporation under micro-scale advection in drip-irrigated fields. A numerical model for estimating soil surface evaporation under micro-scale advection, assuming drip-irrigated fields, is introduced. Results indicate that the soil surface evaporation changes spatially. Soil surface evaporation at the upwind edge of wet soil portions adjacent to dry soil portions increased abruptly. On the other hand, soil surface evaporation at the upwind edge of dry soil portions adjacent to wet soil portions decreased, and condensation was observed. These phenomena were considered to be due to airflows between differing climates. To verify the accuracy of the model, an experiment using a wind tunnel was conducted. The simulated soil surface evaporation results from the model were consistent with the experimental data. The numerical model introduced here is an effective way to quantify soil surface evaporation under micro-advective conditions.

Observation and simulation of thermal environment in a paddy field

Abstract: This research studied thermal environment in paddy field which the main objective to evaluate it when the water was present in the field by means of observation and simulation. Heat exchange in soil and water, plant and atmosphere were calculated using a two-layer resistance model. The atmospheric boundary layers-thermal, humidity and wind velocity-were assumed horizontally uniform and were arranged in one-dimensional equations. The observed paddy field was located at Kyushu University Experimental Farm in Fukuoka, Japan. In the simulation, fix boundary conditions of wind velocity and humidity, and fluctuating boundary condition of temperature at 100 m height were used over the paddy field with the presence of 5 cm depth of water layer. The simulation was successful in estimating radiation, dissipation of heat fluxes, mechanism of atmospheric thermal changes and the temperature of leaf, air, and water. The results show that most of the available energy dissipates into latent heat, and less into sensible heat.

Plastic mulching in agriculture. Trading short-term agronomic benefits for long-term soil degradation?

Abstract: Plastic mulching has become a globally applied agricultural practice for its instant economic benefits such as higher yields, earlier harvests, improved fruit quality and increased water-use efficiency. However, knowledge of the sustainability of plastic mulching remains vague in terms of both an environmental and agronomic perspective. This review critically discusses the current understanding of the environmental impact of plastic mulch use by linking knowledge of agricultural benefits and research on the life cycle of plastic mulches with direct and indirect implications for long-term soil quality and ecosystem services. Adverse effects may arise from plastic additives, enhanced pesticide runoff and plastic residues likely to fragment into microplastics but remaining chemically intact and accumulating in soil where they can successively sorb agrochemicals. The quantification of microplastics in soil remains challenging due to the lack of appropriate analytical techniques. The cost and effort of recovering and recycling used mulching films may offset the aforementioned benefits in the long term. However, comparative and long-term agronomic assessments have not yet been conducted. Furthermore, plastic mulches have the potential to alter soil quality by shifting the edaphic biocoenosis (e.g. towards mycotoxigenic fungi), accelerate C/N metabolism eventually depleting soil organic matter stocks, increase soil water repellency and favour the release of greenhouse gases. A substantial process understanding of the interactions between the soil microclimate, water supply and biological activity under plastic mulches is still lacking but required to estimate potential risks for long-term soil quality. Currently, farmers mostly base their decision to apply plastic mulches rather on expected short-term benefits than on the consideration of long-term consequences. Future interdisciplinary research should therefore gain a deeper understanding of the incentives for farmers and public perception from both a psychological and economic perspective in order to develop new support strategies for the transition into a more environment-friendly food production.

Soil and Water

Abstract: Soil and Water : Physical Principles and Processes By Daniel Hillel (Physiological Ecology: a Series of Monographs and Treatises) Pp xiv + 288 (Academic: New York and London, January 1971) $14; £655

Plastic film mulch for half growing-season maximized WUE and yield of potato via moisture-temperature improvement in a semi-arid agroecosystem

Abstract: Effects of plastic mulching in ridges and furrows for varying durations on yield and water use efficiency (WUE) in potato were investigated in rainfed areas of north-western China in 2009 and 2010. The experiment comprised four mulched treatments (M50, M65, M80/85, and Mw – indicating plastic film mulch for 50, 65, and 80/85 d after sowing, and whole growth season, respectively – after which mulch in furrows was removed) and a non-mulched control. The results showed that film mulching warmed topsoil and increased topsoil water content. The daily mean topsoil temperature in mulched plots was 2.5–3.2 °C higher than that in controls during the early growing season (sowing–emergence), the difference became less as the plant canopy grew; on some days later in the season, the difference was even negative (i.e. the topsoil temperature in mulched was lower than in control plots). Seedlings under mulching emerged 8.1–11.7 d earlier than those in controls due to the increased topsoil temperature and moisture in the early season. Mulching also prolonged the duration from seedling to maturity by 0.7–15.0 d and significantly increased plant height, leaf area index, and dry matter. Compared to non-mulched plots, yields in mulched plots increased by 33.9–92.5% and 62.9–77.8% in 2009 and 2010, respectively, and corresponding WUEs improved by 41.4–112.6% and 45.9–70.6%. Both tuber yield and WUE were highest in M65. The data indicate that mulching for about 65 d after sowing was ideal to optimize soil moisture and soil temperature and in turn to improve potato productivity and WUE in this semi-arid rainfed region.

The radiation balance of bare soil and vegetation - radiative temperature in the heat balance of natural surfaces

Abstract: A Linke-Feussner radiometer was used to measure the radiative temperature of natural surfaces, with small errors caused by the divergence of radiative flux and by its angular variation. On typical cloudless summer days, the maximum temperature of tall crops and of open water was close to maximum air temperature; a bare soil surface exceeded air temperature by 20°C; short grass was the coldest surface at night. A linear variation of net (total) radiation with net short-wave radiation was established for several tall crops, and the increase in long-wave loss per unit increase of net radiation (heating coefficient) was 0·08. Daily totals of net radiation as a percentage of solar radiation income were: 37 per cent (bare soil), 41 per cent (short grass), 46 per cent (tall crop), and 53 per cent (water). When the aerodynamic character of a crop is known, the effective resistance of the stomata to water-vapour diffusion can be related theoretically to the difference between surface and air temperature. For rough vegetation, estimated stomatal resistance is 0·4 to 0·8 sec cm−1 and the estimated heating coefficient is almost independent of wind speed at about 0·1.

The Palaearctic steppe biome: a new synthesis

Abstract: The Palaearctic steppes range from the Mediterranean basin towards China, forming one of the largest continuous terrestrial biomes. The literature on steppe ecology and conservation is vast but scattered and often not available in English. We provide a review of some key topics based on a new definition of steppes, which includes also Mediterranean steppes and alpine rangelands of the Asian Highlands. Revisiting the terrestrial ecoregions of the world, we estimate that the Palaearctic steppe biome extends over ca. 10.5 million km2. Major chorological regions differ in their macroclimatic niche with a clear distinction between Middle Asia with its winter precipitation and the Central Asian summer-rain regions of the Mongolian plateau and of Tibet. Steppe soils store large amounts of carbon, yet the sequestration potential is debated and depends on land use. Major physiognomic-ecological steppe types include forest-, typical-, desert-, and alpine-steppe, which vary in the importance of grasses, mainly C3 species. The steppes host a specialised fauna, and Middle Asia, Tibet, and especially Mongolia, have large herds of migrating ungulates. The share of pristine and protected sites is low in the steppe regions, with conversion into croplands being the most important land use impact in Europe, Middle Asia, and the Mediterranean, while grazing has a severe impact in some parts of Mongolia and Tibet. There are major gaps in our knowledge on: (1) the effects of climate change on the crucial seasonal patterns; (2) the role of steppe soils in the global carbon budget; and (3) the ecology and distribution of most animal groups except vertebrates.