Economic valuation of cultivated lands as nitrogen removal/effusion sites by newly proposed replacement cost method

To valuate the multifunctionality economically is effective to make it possible to realize the value for the nation and to compare functionalities among countries of the world. In this paper, the external economies of paddy fields and fallow paddy fields including wetlands as N removal function sites, and of upland fields and orchards as pollution sites are valuated by the newly proposed replacement cost method, by replacing them with construction costs of water quality improvement facilities. In addition, we discuss an agricultural land-use scenario in which cultivated land has no net negative economic effect on the water environment. The results showed that (1) paddy fields and fallow paddy fields including wetlands were respectively valued at 1.2×10³ and 2.81×10³ JPY m⁻² on average as the N removal sites, (2) upland fields had 0.32×10³ JPY m⁻² on average of economic value, and suggested that paddy fields have an external economic value that compensates for the negative external economic value of upland fields 3.65 times their size.     

Export rate of dissolved organic matter from paddy fields during cultivation-activity events

The aim of this study is to quantify the dissolved organic carbon (DOC) of drainage water from paddy fields in agricultural areas of Tottori prefecture, Japan. In four experimental paddy fields, DOC concentration varied much from 1.1 to 10.1 mg C l⁻¹, and was the highest during heavy runoff that occurred in April when there was a non-agricultural period. However, variation in DOC concentration did not always correspond to rainfall, but depended more on cultivation-activity events such as tilling, planting, draining in summer, and final draining in autumn. The water discharge rate from each experimental field was estimated by using a hydrologic model (the Tank Model and a genetic algorithm). Daily DOC export rate per unit area of three experimental paddy fields was calculated to be 0.0074, 0.0052, and 0.0081 kg a⁻¹ day⁻¹, respectively. The daily DOC export rate showed large seasonal variation with the highest value in May and June. It can be concluded that DOC export from paddy fields can be a substantial source of DOC in receiving waters, and the export rate depends much on cultivation method practice. It might be suggested that DOC export from paddy fields can be controlled by a better water management practice of farmers.     

Long-term evaluation of the groundwater recharge function of paddy fields accompanying urbanization in the Nobi Plain, Japan

The groundwater recharge function, one example of the multifunctionality of agriculture, is closely related to hydrogeological phenomena and socioeconomic factors such as pumpage and land use. A long-term evaluation of the groundwater recharge function is necessary to understand its role among the multiple functions of agriculture. The Nobi Plain, one of the largest coastal plains in Japan, was selected as the study area because it has experienced typical socioeconomic changes. We conducted a long-term evaluation of the groundwater recharge function based on simple water-balance equations using long-term data on groundwater levels and river flows. Leakage recharge from paddy fields in 1975 was about 2.8×10⁸ m³/year, decreased to 0.6×10⁸ m³/year in 1984, and ceased in 1985. Its monetary value of the function in 1975 was estimated by the replacement cost method, was about $56 million for 20 ha×10³ ha of paddy fields. The value per unit area of paddy fields was calculated as $2820/ha and that in Japan was calculated as $400/ha. Paddy fields in suburbs of big cities have a higher value than the average paddy field in Japan. However, this recharge value is no longer produced because no leakage recharge occurs at present owing to socioeconomic changes.     

A grid-based rainfall-runoff model for flood simulation including paddy fields

A grid-based, KIneMatic wave STOrm Runoff Model (KIMSTORM) is described. The model adopts the single flow-path algorithm and routes the water balance during the storm period. Manning’s roughness coefficient adjustment function of the paddy cell was applied to simulate the flood mitigation effect of the paddy fields for the grid-based, distributed rainfall-runoff modeling. The model was tested in 2296 km² dam watershed in South Korea using six typhoon storm events occurring between 2000 and 2007 with 500 m spatial resolution, and the results were tested through the automatic model evaluation functions in the model. The average values of the Nash–Sutcliffe model efficiency (ME), the volume conservation index (VCI), the relative error of peak runoff rate (EQ_p), and the absolute error of peak runoff (ET_p) were 0.974, 1.016, 0.019, and 0.45 h for calibrated storm events and 0.975, 0.951, 0.029, and 0.50 h for verified storm events, respectively. In the simulation of the flood mitigation effect of the paddy fields, the average values of the percentage changes for peak runoff, total runoff volume, and time to peak runoff were only −1.95, −0.93, and 0.19%, respectively.     

Microorganism repair after UV-disinfection of secondary-level effluent for agricultural irrigation

A pilot study of microorganism repair after UV disinfection was performed for agricultural reuse of secondary-level effluent in paddy rice fields in Korea. Effluent from the bio-filter of a 16-unit apartment was used in a flow-through type UV-disinfection system. The average concentration of suspended solids (SS) and biochemical oxygen demand (BOD) were 3.4 and 5.9 mg L⁻¹, respectively. The mean total coliform level was in the range of 1.5 × 10⁴ MPN 100 mL⁻¹. Photoreactivation and dark repair were apparent at a low UV dose (6 mW s cm⁻²). In low-dose UV disinfection, microorganisms increased within 12 h by approximately 5 and 1% due to photoreactivation and dark repair, respectively. This increase was not significant at a high UV dose (16 mW s cm⁻²). The repaired microorganisms were further inactivated, rather than reactivated, by solar irradiation, and numbers decreased to non-detectible levels after 4 h of exposure to solar irradiation. Based on UV disinfection and repair studies, a UV dose of 30 mW s cm⁻² is recommended as sufficient to produce reclaimed water virtually free of pathogens and may be adequate for disinfection of secondary effluent for agricultural irrigation in paddy rice culture.     

Surface and subsurface losses of N and P from salt-affected rice paddy fields of Saemangeum reclaimed land in South Korea

The present study was carried out to evaluate nutrient losses that occur during the course of agricultural activity from rice paddy fields of reclaimed tidal flat. For this study, we chose a salt-affected rice paddy field located in the Saemangeum reclaimed tidal area, which is located on the western South Korean coasts. The plot size was 1,000 m² (40 m × 25 m) with three replicates. The soil belonged to the Gwanghwal series, i.e., it was of the coarse silty, mixed, mesic type of Typic Haplaquents (saline alluvial soil). The input quantities of nitrogen and phosphorus (as chemical fertilizer) into the experimental rice paddy field were 200 kg N ha⁻¹ and 51 kg P₂O₅ ha⁻¹ per annum, and the respective input quantities of each due to precipitation were 9.3–12.9 kg N ha⁻¹ and 0.4–0.7 kg P ha⁻¹ per annum. In terms of irrigation water, these input quantities were 4.5–8.2 kg N ha⁻¹ and 0.3–0.9 kg P ha⁻¹ per annum, respectively. Losses of these nutrients due to surface runoff were 22.5–38.1 kg N ha⁻¹ and 0.7–2.2 kg P ha⁻¹ for the year 2003, and 26.8–29.6 kg N ha⁻¹ and 1.6–1.9 kg P ha⁻¹ for the year 2004, respectively. Losses of these nutrients due to subsurface infiltration during the irrigation period were 0.44–0.67 kg N ha⁻¹ and 0.03–0.04 kg P ha⁻¹ for the year 2003, and 0.15–0.16 kg N ha⁻¹ and 0.05–0.06 kg P ha⁻¹ for 2004. When losses of nitrogen and phosphorus were compared to the amount of nutrients supplied by chemical fertilizers, it was found that 11.3–19.1% of nitrogen and 0.5–1.7% of phosphorus were lost via surface runoff, whereas subsurface losses accounted to 0.2–0.8% for nitrogen and only 0.02–0.04% for phosphorus during the 2-year study period.     

Application of system of rice intensification practices in the arid environment of the Timbuktu region in Mali

Cereal production is chronically deficit in the Timbuktu region of Mali, sufficient for only 4.5 months of annual household consumption. Small-scale, village-based irrigation schemes, usually 30–35 ha in size, irrigated by a diesel motor pump, have become important to improve food security in this arid region. The NGO Africare has worked during the past 12 years with farmers in Goundam and Dire circles to establish irrigation schemes and provide them with technical assistance. In 2007, Africare undertook a first test of the System of Rice Intensification (SRI) in Goundam circle. After farmers observed a yield of 9 t ha⁻¹ of paddy compared to 6.7 t ha⁻¹ in the control plot there was interest in larger scale testing of the SRI system. In 2008, Africare, in collaboration with the local Government Agriculture Service and with support from the Better U Foundation, implemented a community-based evaluation of SRI with 60 farmers in 12 villages. Farmers in each village selected five volunteers, who each installed both SRI and control plots, side by side, starting the nurseries on the same day and using the same seed. For SRI plots, seedlings were transplanted one plant hill⁻¹ at the two-leaf stage (on average, 11.6 days old), with spacing of 25 cm × 25 cm between hills and aligned in both directions. This allowed farmers to cross-weed with a cono-weeder, on average 2.4 times during the season. In the control plots, farmers planted 3 plants hill⁻¹ with seedlings 29.4 days old and spaced on average 23.7 cm, not planted in lines. Weeding was done by hand. 13 t ha⁻¹ of organic matter was applied under SRI management, and 3 t ha⁻¹ in the control plots. Fertilizer use was reduced by 30% with SRI compared to the control. Although alternate wetting and drying irrigation is recommended for SRI, this was not optimally implemented due to constraints on irrigation management within the scheme; thus water savings were only 10% compared to the control. Average SRI yield for all farmers reached 9.1 t ha⁻¹, with the lowest being 5.4 t ha⁻¹ and highest being 12.4 t ha⁻¹. SRI yields were on average 66% higher than the control plots at 5.5 t ha⁻¹, and 87% higher than the yields in surrounding rice fields at 4.9 t ha⁻¹. Number of tillers and panicles hill⁻¹, number of tillers and panicles m⁻², and panicle length and number of grains panicle⁻¹ were clearly superior with SRI compared to control plants. Farmers tested five varieties, all of which produced better under SRI. The SRI system allowed for a seed reduction of 85–90%: from 40–60 kg ha⁻¹ for the control plots to 6.1 kg ha⁻¹ under SRI. Although production costs per hectare were 15% higher for SRI, revenue was 2.1 times higher than under the control. Farmers were very satisfied with these results. In 2009/2010, Africare and the Government’s agriculture service worked with over 270 farmers in 28 villages to scale up SRI practices and to test innovations, including composting techniques, optimization of irrigation, and techniques to reduce labor requirements and production costs. The good crop performance along with other advantages was confirmed in this third year with SRI yields of 7.7 t ha⁻¹ (n = 130 farmers) compared to 4.5 t ha⁻¹ in farmers’ fields.     

Appraisal of affordable green subsidy of rice paddy in Taiwan

The study synthesizes the spatiotemporal changes of the multifunctionality and benefit of Taiwanese paddy. The internal and external economic values of the paddy are quantitatively determined. Nationwide as well as regional variation of multifunctionality and benefits from 1999 to 2007 were considered. The substitution cost method was adopted to quantify the external economical values of rice paddy. Moreover, the compensating variation concept was applied to appraise the rational green subsidy of rice paddy in Taiwan. The result shows that the multifunctional benefits of rice paddy from 1999 to 2007 reduce 55, 18, 31, 13, and 28% in north, center, south, east regions, and nationwide of Taiwan, respectively. The reduction is mainly attributable to the significant decrease of rice-planting area. The external benefit may be further diminished if the fallow area increases continuously. In order to maintain the multifunctionality of rice paddy, we appraise a reasonable green subsidy to the cultivated paddy farmers. According to the results of the amount of green subsidy evaluated by the compensating variation concept, the estimated green subsidy is 21,000 NT$/ha for the nationwide paddy farmers. The government may consider to award the appraised green subsidy to paddy farmers directly for the sustainable management of rice paddy in Taiwan.     

Evaluation of the management practice for controlling herbicide runoff from paddy fields using intermittent and spillover-irrigation schemes

Two water management practices, an intermittent irrigation scheme using automatic irrigation system (AI) and a spillover-irrigation scheme (SI), were compared for the fate and transport of commonly used herbicides, mefenacet (MF) and bensulfuron-methyl (BSM) in experimental paddy plots. Maximum mefenacet concentrations in paddy water were 660 and 540 μg L⁻¹ for AI and SI plot, respectively. The corresponding values for bensulfuron-methyl were 46.0 and 42.0 μg L⁻¹. Dissipation of the herbicides in paddy water appeared to follow the first-order kinetics with half-lives (DT₅₀) of 1.9–4.5 days and DT₉₀ (90% mass dissipation) of 7.8–11.3 days. The AI plot had no surface drainage, hence no herbicide was lost through paddy-water discharge. However, SI plot lost about 38 and 49% of applied mefenacet and bensulfuron-methyl, respectively. The intermittent irrigation scheme using automatic irrigation system with a high drainage gate was recommended to be a best management practice for controlling the herbicide losses from paddy fields. The paddy field managed by spillover-irrigation scheme may cause significant water and herbicide losses depending on the volume of irrigation and precipitation. The water holding period after herbicide application was suggested to be at least 10 days according to the DT₉₀ index.     

Nitrous oxide emissions from paddy fields under different water managements in southeast China

Water management is recognized as one of the most important factors in regulating nitrous oxide (N₂O) emissions from paddy fields. In China, controlled irrigation (CI) is widely applied because it has been proved highly effective in saving water. During the rice-growing season, the soil in CI paddy fields remains dry 60–80% of the time compared with soil irrigated by traditional methods. This study aims to assess N₂O emissions from paddy fields under CI, with traditional irrigation (TI) as the control. The cumulative N₂O emission from CI paddy fields was 2.5 kg N ha⁻¹, which was significantly greater than that from TI paddy fields (1.0 kg N ha⁻¹) (P < 0.05). Soil drying caused substantial N₂O emissions. The majority (73.9%) of the cumulative N₂O emission from CI paddy fields was observed during the drying phase, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the drying phase. More and significantly higher peaks of N₂O emissions from CI paddy fields (P < 0.05) were also detected. These peaks were observed ~8 days after fertilizer application at water-filled pore spaces (WFPS) ranging from 78.0 to 83.5%, soil temperature ranging from 29.1 to 29.4°C, and soil redox potential (Eh) values ranging from +207.5 to +256.7 mV. The highest N₂O emission was measured 8 days after the application of base fertilizer at a WFPS of 79.0%, soil temperature of 29.1°C, and soil Eh value of +207.5 mV. These results suggest that N₂O emissions may be reduced obviously by keeping the WFPS higher than 83.5% within 10 days after each fertilizer application, especially when the soil temperature is suitable.     

The economic impacts to commercial farms from invasive monkeys in Puerto Rico

Beginning in the 1930s and continuing through the 1970s, rhesus macaques and patas monkeys were introduced to presumed secure locations, primarily coastal islets, in Puerto Rico. Escapes into the wild began almost immediately after introduction. Today the combined range of the two species covers approximately 600 km² of southwestern Puerto Rico, where serious conflicts with agricultural interests have resulted. The Puerto Rico Department of Agriculture surveyed about 90% of commercial farmers in the range of the monkeys to begin quantifying damage by monkeys and the associated economic losses during the years 2002–2006. During that time, total economic losses by commercial farmers to monkeys increased from $1.13 million USD to over $1.46 million per year. Of these amounts, the economic losses due to farmers avoiding monkey damage by switching from fruit and vegetable crops to less rewarding land use (primarily hay or pastureland) increased from $490,000 to $1.33 million per year. The losses reported from the survey represent only a portion of economic losses to the invasive monkeys. Subsistence and other smaller farms and agriculture were not included in the survey. We also discuss many other economic issues surrounding the impacts of the invasive monkeys, but for which sufficient data are not available for economic analyses. These include concerns such as destruction of native (especially endangered) wildlife, threat of disease spread, and property damage, all of which would also have to be considered to fully evaluate invasive monkey economic impacts in Puerto Rico.     

Spatial variation of infiltration rate and compactness in paddy fields

Percolation loss of water in rice fields is a major cause of low water use efficiency. Variation of infiltration rate and soil compactness in four paddy fields (with clay, silty clay, clay loam, and loam textures) was investigated in northern Iran. In each field, in longitudinal and transverse directions, points located 0.5, 2.5, 6.5, 12.5, … m from the bunds were selected and water infiltration rate and resistance to penetration of a pocket penetrometer were measured. The results showed that in clay soil, average final infiltration rate (f _c) in longitudinal direction, transverse direction, and center of the field was 0.216, 0.136, and 0.08 cm day⁻¹, respectively. The f _c for loamy soil was 2.77, 2.32, and 0.409 cm day⁻¹, respectively. Similar differences were observed in the other two soil textures. In general, effect of direction of the field for measuring infiltration rate was not statistically significant. Loam and clay loam soils, with resistance to penetration of 0.37 and 0.33 kg cm⁻², were not significantly different. But, clay and silty clay soils with resistance to penetration of 0.25 and 0.14 kg cm⁻² were significantly different (P < 0.05). Resistance to penetration of the penetrometer was not affected significantly (P < 0.05) by direction of measuring this parameter in the field. The conclusion is that if measured soil physical properties in a paddy field are going to be representative of the whole field, they should be measured at different locations, especially near the bunds. Another strategy for obtaining a representative infiltration rate or compactness for a paddy field is uniform puddling of the field.     

Policy measures to promote mid-summer drainage in paddy fields for a reduction in methane gas emissions: the application of a dynamic,spatial computable general equilibrium model

Rice production is affected by climate change, while climate change is simultaneously accelerated by methane gas (CH₄) emissions from paddy fields. The rice sector must take suitable mitigation measures, such as prolonging mid-summer drainage (MSD) before the rice flowering period. To propose a mitigation policy, this study aims to demonstrate the environmental and economic effects of MSD in Japanese paddy fields by using a dynamic, spatial computable general equilibrium (CGE) model and crop model; the study also considers environmental subsidies with a carbon tax scheme to promote MSD measures. The results demonstrate that climate change under the 8.5 representative concentration pathway (RCP) scenario will reduce rice prices and rice farmers’ nominal income due to bumper harvests until the 2050s. Promoting MSD in paddy fields can prevent a decrease in farmers’ nominal income and effectively reduce CH₄ emissions if all farmers adopt this measure. However, some farmers can potentially increase their own yield by avoiding MSD under high rice prices, which would be maintained through other farmers’ participation. A strong motivation exists for some farmers to gain a “free ride,” and an environmental subsidy with a carbon tax can help motivate farmers to adopt MSD. Therefore, the policy mix of prolonging MSD and environmental subsidies can increase all farmers’ incomes by preventing “free rides” and decrease greenhouse gas emissions with a slight decrease in Japan’s GDP.

     

Comparative analysis of temporal changes of multifunctionality benefit of two major rice paddy plains in Taiwan

Recently, free trade of farm land, changes of agricultural policy and global climate changes have resulted a significant reduction of rice planting area and the multifunctionality values of paddy field in Taiwan. This study aims to evaluate the temporal changes of multifunctionality benefit of two major rice paddy plains in Taiwan. The main agricultural production regions of the Chou-Shui river alluvial fan and Ping-Tung plain are selected for the comparative study. The replacement method is adopted to quantify the multifunctionality of the paddy field. The results show that percentage of cultivated paddy to the total paddy gradually decreases from 92 to 80% and the external value remains from 572,000 to 668,000 NT$/ha in the Chou-Shui river alluvial fan. Whereas, the percentage of area of cultivated paddy to the total paddy markedly decreases from 37 to 23% from 1999 to 2006 and resulting the external values of paddy only ranges from 156,000 to 258,000 NT$/ha in the Ping-Tung plain. To maintain the sustainable agriculture in the paddy field, government needs to formulate incentive policy to conserve the paddy farming, promote, and transmit the general understanding of the environmental and living-hood multifunctionality values to the people.     

Assessment of nitrogen contamination of groundwater in paddy and upland fields

This study aims to assess the nitrogen contamination of groundwater in paddy and upland fields. A reactive chemical transport model PHREEQC and a variable saturated groundwater flow and transport model FEMWATER were used to evaluate the vertical transport of nitrogen compound in various soil types of paddy and upland. The shallow groundwater quality monitoring data of 2003, 2006, 2009 in the Choushui river alluvial fan, the major agriculture production area in Taiwan, were applied to support the validity of the numerical simulation findings. Results from PHREEQC and FEMWATER simulations showed that the organic-rich impermeable plow sole layer underneath the muddy layer of rice paddy can effectively reduce NO₃ ⁻ and N₂ to NH₄ ⁺ and retard the movement of NH₄ ⁺. However, in the upland field which has no plow sole layer, the NH₄ ⁺ can move easily to the shallow aquifer and contaminate the groundwater. The spatiotemporal distribution of NO₃ ⁻–N and NH₄ ⁺–N in the Choushui river alluvial fan revealed that high nitrate–N contamination areas were located mainly in the upland field of the proximal fan, where the granular unconfined aquifer was vulnerable to surface contaminants. Moreover, the unconfined nature of the aquifer allows the oxidization of NH₄ ⁺ to NO₃ ⁻ and accelerates the plume movement. High ammonium–N concentration areas were mostly dispersed in the distal-fan area where upland planting and aquacultural farming were prevailed. The high NH₄ ⁺–N found in the northern Choushui river alluvial fan was attributed to the alternative planting of rice and upland crops, and the plow sole layer was broken to maintain the quick drainage upland crop needs.     

Fertilization management of paddy fields in Piedmont (NW Italy) and its effects on the soil and water quality

The fertilization management of the rice crop in Piedmont was analyzed at a regional scale, and the agronomic and environmental sustainability of the actual fertilization strategy of rice was evaluated through the analysis of its effect on the soils and waters quality. On average, a total amount of 127 kg ha⁻¹ of N, 67 kg ha⁻¹ of P₂O₅ and 161 kg ha⁻¹ of K₂O were supplied to the rice crop. In most cases N and P fertilization was rather well balanced with crop removal. The N balance was in the range ±50 kg for 77% of the surface. The low concentration of N in the groundwater reflected the small N surplus. P fertilization resulted to be smaller than removal for 53% of the surface. Nevertheless, the soil extractable P was very high, probably because of former higher P inputs. This resulted in a high concentration in water courses and aquifers. The K fertilization was excessive (surplus >100 kg ha⁻¹) for 53% of the surface, but most soils showed a low K content. K is probably contributing to nutrient leaching to a great extent. The average soil organic matter (SOM) content of paddy fields was higher than that of normally-cultivated soils in Piedmont, and the C/N was higher, owing to the low mineralization rate in waterlogged conditions. The SOM content was in relation with the management of the crop residues, as the tradition of burning straw after harvest was still widespread on 65% of the paddy surface.     

Multifunctionality of paddy fields in Taiwan

Paddy rice is the staple food in Taiwan, where rice farming always plays an important role in agricultural activities. The paddy fields and irrigation activities hold diversified functions, such as production, eco-environmental and living-associated functions. This paper is to provide information regarding the potential magnitude and monetary value of seven functions of paddy fields in Taiwan, including flood mitigation, fostering water resources, preventing soil erosion, purifying water, cooling air temperature, refreshing atmosphere and recreation. For quantification of the above values, replacement cost method (RCM), contingent valuation method (CVM), and the travel cost method (TCM) are adopted. In addition, the ratio of monetary value and their rice production commodity value (R) was also estimated. The results indicated that the flood mitigation function had a monetary value of US$ 389 million each year, and the ratio to the rice production value R was estimated at 37%. Water resource fostering function was US$ 501 million and R at 47%; soil erosion reduction function was US$ 433 million and R at 41%; water quality purification function was US$ 3 million and R at 0.3%; cooling air temperature function was US$ 961 million and R at 91%; refreshing air function was US$ 196 million and R at 19%, health and recreation function was US$ 987 million and R at 93%, respectively. Due to the significant importance of these externalities, it is recommended that the government should properly take into account the multifunctionalities in policy making to ensure sustainable development of agriculture.     

Converting rice paddy to dry land farming in the Tai Lake Basin,China: toward an understanding of environmental and economic impacts

Water pollution is a well-known major problem in the Tai Lake Basin, China. Compared to industries and domestic sewage, non-point pollution from agriculture is more difficult to detect, measure, and control. Therefore, a range of policies has been formulated, among which is that of ‘adjustment of the planting structure.’ However, this policy during implementation has been used to simply convert paddy fields to dry land and food crops to cash crops. More surprisingly, to date, no research has provided evidence that such an agricultural land-use change contributes to the reduction of agricultural nutrient pollution. Based on an extensive farm survey, this research finds that conversion of rice paddy to dry land farming has not generated a positive effect on nutrient pollution control. It is estimated that nitrogen runoff from agricultural land has increased by 11 %, while phosphorus runoff has increased more than two times since land-use patterns changed, as farmers are inclined to apply more fertilizer on dry land than in paddy fields. However, this agricultural land-use change is economically effective as land-use conversion increases the net profits of farming in a significant way. It is demonstrated that, compared to environmental concerns, economic considerations are seen to have greater benefits after such an adjustment in the planting structure. These findings have important implications for policy making by local authorities in their efforts to improve environmental management and pollution control in their territories.     

The methods to consolidate scattered tenanted lots into large rice paddy lots by the land consolidation projects in Japan

Today in Japan, agricultural productivity of rice cropping farmers is low. In order to get sufficient agricultural productivity, Japanese government is encouraging enlarging core farmers' farm sizes to 10–20 ha by borrowing farm lots from retiring farmers of small farms and carrying out the land consolidation projects to construct large rice paddy lots. In order to realize large rice paddy lots of more than several hectares, it is necessary to consolidate small scattered leased farm lots of core tenant farmers, but it is supposed to be very difficult. In order to clarify how to consolidate those leased lots into large rice paddy lots, I investigated five land consolidation project areas in which large rice paddy lots of more than several hectares were constructed for core tenant farmers. The result shows that (1) large rice paddy lots for core tenant farmers were settled in relatively inferior areas of the project areas, for instance, far from the land owners' residence area. (2) Basically land lenders do not accept their substitute lots settled into large rice paddy lots in such inferior areas, (3) but some land lenders who were eager to lend their farmland to core farmers accepted their substitute lots in such inferior areas. (4) Even in cases that tenant farmers could not consolidate substitute lots of their tenant land into large rice paddy lots, they could consolidate their cultivating lots by adjusting user rights, that is, exchange of user rights of lots between land lenders whose substitute lots were located outside of a large rice paddy lot area and owner farmers whose substitute lots were located in the area. (5) Owner farmers accepted this adjustment on their farmland as they could cultivate superior lots, consolidate their scattered cultivating lots into one place and so on.     

Convective velocity of ponded water in the vegetated paddy lysimeter

Ponded water convection kinetics should be altered by growth stages of rice plants. We investigated the convective velocity of ponded water in a vegetated paddy field. The convective velocity was measured using the equipment through use of the principle of a hot-wire anemometer, and the temperature profile of the ponded water was measured using lysimeters with and without paddy rice vegetation. The maximum convective velocity in a vegetated plot was 0.7 mm s⁻¹, slower than the maximum velocity in an unvegetated plot, which was 1.6 mm s⁻¹. The convective velocity in a vegetated plot increased slightly when the temperature of the surface water was higher than that near the soil, between 09:00 and 17:00.