Reclaimed Paddy Fields Research Articles

Effects of Rice-Frog Co-Cropping on the Soil Microbial Community Structure in Reclaimed Paddy Fields.

Utilizing and improving the productivity of reclaimed land are highly significant for alleviating the problem of food production shortage in China, and the integrated rice-frog farming model can improve soil fertility. However, there are few studies on the use of integrated rice-frog farming technology to improve the fertility of reclaimed land and increase its efficiency in food production. Therefore, this study was conducted to evaluate the effects of the rice-frog co-cropping mode on the soil fertility and microbial diversity of reclaimed land. A rice monoculture group (SF), low-density rice-frog co-cropping group (SD, 5000 frogs/mu, corresponds to 8 frogs/m2), and high-density rice-frog co-cropping group (SG, 10,000 frogs/mu, corresponds to 15 frogs/m2) were established and tested. The contents of total nitrogen, soil organic matter, available potassium, and available phosphorus of the soil in the SG group were significantly higher than those in the SF group (p < 0.05) in the mature stage of rice. Compared with the SF group, the SD and SG groups improved the soil microbial diversity and changed the structure of the microbial community. This study indicates that compared with the rice monoculture mode, the rice-frog co-cropping pattern can improve the soil fertility, as well as microbial diversity, of reclaimed land.

Effects of Planting Density and Nitrogen Fertilization on the Growth of Forage Rice in Reclaimed and General Paddy Fields.

The purpose of this study is to identify the different effects exerted by planting density and nitrogen fertilization on high-salinity reclaimed paddy fields (RPF) and general paddy fields (GPFs), and to find the amount of fertilization and the planting density suitable for the growth of forage rice in each paddy field. Nitrogen fertilization with high-salt and low-salt soils, an untreated control plot, treatment with 200 kg/ha, 300 kg/ha, and 400 kg/ha, and planting densities of 30 cm × 10 cm and 30 cm × 16 cm, growth, and feed values were investigated. In both experimental locations, there was no significant change in the soil due to N treatment, but in the case of RPF, electrical conductivity (EC) decreased significantly from more than 5 dS/m to up to 2.87 dS/m during the yellow ripe stage due to the influence of floods and concentrated precipitation in the fields. In all soils, as both the amount of N treatment and the planting density increased, there was a proportional relationship in which the number of tillers and the dry weight also increased, with the occurrence of lodging also being increased. The dry weight, as expected, was 1.5 times higher at a planting distance of 10 cm, rather than 16 cm. In addition, in both locations, the N treatment led to an increase in the dry weight, but when N treatment reached 400 kg/ha (2.0), the dry weight decreased instead. Moreover, although there was no clear difference in feed value according to N treatment, in RPF, the neutral detergent fiber (NDF) was higher than 60%, the relative feed value (RFV) was less than 98, and the total digestible nutrient (TDN) was also low, confirming that the quality of rice was higher in GPF.

Assessing nutrient budgets and N2O emission of newly constructed rice-giant freshwater prawn co-culture on reclaimed land

In recent years, newly constructed rice-giant river prawn (Macrobrachium rosenbergii) co-culture has been widely applied on reclaimed land in southeast China. Raising M. rosenbergii in paddy fields can alter nutrient budgets and have environmental impacts. However, the exact impacts remain unclear. Here, a field experiment was conducted using M. rosenbergii and Macrobrachium nipponense in reclaimed paddy fields to assess and compare the nutrient budgets and N2O emissions of the two ecosystems, henceforth referred to as RS1 and RS2, respectively. Each ecosystem was stocked with 150,000 post-larvae per ha and then compared with a rice monoculture system (RM) to evaluate the environmental impacts of rice-shrimp co-culture. In RS1, the main inputs for N and P were fertilizer and artificial feed, accounting for 59.35% and 34.01% of the total N inputs and 53.15% and 41.43% of the total P inputs, respectively. In RS2 and RM, fertilizers dominated the nutrient budget, accounting for more than 79.28% of the total nutrient input. Nutrient exports were dominated by rice (straw+grain) and commercial shrimp in RS1, accounting for 33.44% and 18.66% of N and 55.56% and 20.02% of P, respectively. The wastewater drainage, NH3 volatilization, and N2O emissions contributed to the remainder nutrient budget. Particularly, the N2O emission fluxes in RS1 (2.21 ± 0.32 kg·ha−1·yr−1) were significantly higher than those in RS2 (1.78 ± 0.24 kg·ha−1·yr−1) and RM (1.56 ± 0.17 kg·ha−1·yr−1) over the one-year experiment. Changes in environmental variables (including NH4+-N, NO2--N, DO, pH, SP, etc.) significantly contributed to the enhanced N2O emissions following the conversion from the reclaimed paddy field to RS1. These results implied that RS1 improved the yields of shrimp and rice grains but at the cost of increasing N2O emissions. Considering the wide distribution of reclaimed paddy fields in southeast China, M. rosenbergii could serve as an ideal alternative species in rice-shrimp co-culture systems to increase nutrient utilization efficiency, although N2O emissions still need to be reduced to mitigate the negative environmental impacts.

Dissolved nitrogen in salt-affected soils reclaimed by planting rice: How is it influenced by soil physicochemical properties?

Planting rice is an effective way to reclaim salt-affected soils, but overapplying nitrogen fertilizer has resulted in a large loss in the amounts of soil dissolved nitrogen (SDN) from paddy fields. While the dynamic of SDN and its response to changes in soil physicochemical properties by planting rice are well-studied in non-salt-affected soils, little is known about the relationship between the SDN and soil physicochemical properties in reclaimed salt-affected soils. To fill this knowledge gap, soil samples were collected from bare salt-affected soils and three paddy fields with different reclaimed years (4, 9, 20) in six soil layers. Compared with bare salt-affected soils, soil salinity and sodicity exhibited trends of firstly increasing and then decreasing, whereas organic matter and total nitrogen tended to increase with the extension of the reclamation year. Soil dissolved organic carbon and total dissolved phosphorous showed decreasing trends. The sand content showed an increasing tendency, whereas the silt and clay contents tended to decrease. Ammonium nitrogen concentrations in reclaimed paddy fields were higher than those of bare salt-affected soils, and nitrate nitrogen concentrations in reclaimed paddy fields were smaller than those of bare salt-affected soils. However, the changing trends of dissolved organic nitrogen concentrations were not consistent among paddy fields with different reclamation years. Meanwhile, statistical analysis results revealed significant correlations between SDN and soil physicochemical properties. Moreover, dominant drivers influencing SDN were grouped using principal component analysis, identifying the following factors including soil sodicity, active nutrients, soil texture and water retention. Redundancy analysis also revealed that the soil physicochemical properties explained 69.65% of the variation in SDN and the influenced relationship between soil physicochemical properties and SDN nutrients. This study enhances our understanding of the mechanisms influencing SDN during planting rice and has implications for the management of the nutrient application of reclaimed salt-affected soils.

Changes in profile distribution and chemical properties of natural nanoparticles in paddy soils as affected by long-term rice cultivation

Systematic studies on the genesis, properties, and distribution of natural nanoparticles (NNPs) in soil remain scarce. This study examined a soil chronosequence of continuous paddy field land use for periods ranging from 0 to 1 000 years to determine how NNPs in soil changed at the early stages of soil genesis in eastern China. Soil samples were collected from coastal reclaimed paddy fields that were cultivated for 0, 50, 100, 300, 700, and 1 000 years. Natural nanoparticles were isolated and characterized along with bulk soil samples (< 2-mm fraction) for selected physical and chemical properties. The NNP content increased with increasing soil cultivation age at 60 g m−2 year−1, which was related to decreasing soil electrical conductivity (172–1 297 µS cm−1) and NNP zeta potentials (from –22 to –36 mV) with increasing soil cultivation age. Changes in several NNP properties, such as pedogenic iron oxide and total organic carbon contents, were consistent with those of the bulk soils across the soil chronosequence. Notably, changes in NNP iron oxide content were obvious and illustrated active chemical weathering, pedogenesis, and potential impacts on the microbial community. Redundancy analysis demonstrated that the soil cultivation age was the most important factor affecting NNP properties, contributing 60.7% of the total variation. Cluster and principal component analysis (PCA) revealed splitting of NNP samples into age groups of 50–300 and 700–1 000 years, indicating rapid evolution of NNP properties, after an initial period of desalinization (approximately 50 years). Overall, this study provides new insights into NNP evolution in soil during pedogenesis and predicting their influences on agriculture and ecological risks over millennial-scale rice cultivation.

Long-term submergence of non-methanogenic oxic upland field soils helps to develop the methanogenic archaeal community as revealed by pot and field experiments

The community structure of methanogenic archaea is relatively stable, i.e., it is sustained at a high abundance with minimal changes in composition, in paddy field soils irrespective of submergence and drainage. In contrast, the abundance in non-methanogenic oxic soils is much lower than that in paddy field soils. This study aimed to describe methanogenic archaeal community development following the long-term submergence of non-methanogenic oxic upland field soils in pot and field experiments. In the pot experiment, a soil sample obtained from an upland field was incubated under submerged conditions for 275 d. Soil samples periodically collected were subjected to culture-dependent most probable number (MPN) enumeration, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of archaeal 16S rRNA gene, and quantitative PCR analysis of the methyl-coenzyme M reductase alpha subunit gene (mcrA) of methanogenic archaea. The abundance of methanogenic archaea increased from 102 to 103 cells g−1 dry soil and 104 to 107 copies of mcrA gene g−1 dry soil after submergence. Although no methanogenic archaeon was detected prior to incubation by the DGGE analysis, members from Methanocellales, Methanosarcinaceae, and Methanosaetaceae proliferated in the soils, and the community structure was relatively stable once established. In the field experiment, the number of viable methanogenic archaea in a rice paddy field converted from meadow (reclaimed paddy field) was monitored by MPN enumeration over five annual cycles of field operations. Viability was also determined simultaneously in a paddy field where the plow layer soil from a farmer's paddy field was dressed onto the meadow (dressed paddy field) and an upland crop field converted from the meadow (reclaimed upland field). The number of viable methanogenic archaea in the reclaimed paddy field was below the detection limit before the first cultivation of rice and in the reclaimed upland field. Then, the number gradually increased over five years and finally reached 103–104 cells g−1 dry soil, which was comparable to that in the dressed paddy field. These findings showed that the low abundance of autochthonous methanogenic archaea in the non-methanogenic oxic upland field soils steadily proliferated, and the community structure was developed following repeated and long-term submergence. These results suggest that habitats suitable for methanogenic archaea were established in soil following repeated and long-term submergence.

Periphyton‐induced changes in the phosphorus sorption characteristics of a paddy soil from coastal mudflat reclamation

AbstractSoil phosphorus (P) sorption characteristics critically influence P availability to plants; however, the influence of periphyton on P sorption remains unclear. In this study, the P adsorption and desorption characteristics of soil in a reclaimed paddy field were evaluated after periphyton colonization of different substrates, that is, periphyton only (PO), periphyton with straw addition (PS), and periphyton with biochar addition (PB). The results indicate that the addition of straw to paddy soil increased the periphyton biomass, whereas the addition of biochar decreased the biomass. The P availability in the paddy soil significantly increased in all periphyton treatments. Specifically, the content of NaHCO3‐extractable P and readily available P in the paddy soil increased by 5‐, 6‐, and 7.5‐fold and 3‐, 1.5‐, and 7‐fold, respectively, in the PO, PS, and PB treatments. Compared with the control (no periphyton), the maximal P sorption capacity (qm) and equilibrium P concentration at zero sorption (EPC0) of the paddy soil were enhanced in the PO and PB treatments but reduced in the PS treatment. In contrast, the adsorption constant (KL) and maximum buffer capacity declined in the PO and PB treatments but increased in the PS treatment. In addition, the amount of P desorbed from the soil was higher in all periphyton treatments compared with the control. The P content in the periphyton differed among treatments and ranged from 0.6 to 1.6 mg g−1. These findings demonstrate that paddy periphyton has a great impact on the P sorption characteristics of the paddy topsoil. This study contributes not only to a deep comprehension of P cycling in paddy soil containing periphyton or similar aggregates but also to the regulation of soil P availability by periphyton.

Effects of Reclamation on Soil Nutrients and Microbial Activities in the Huixian Karst Wetland in Guilin

To investigate the effect of reclamation on soil quality in the Huixian Karst Wetland, samples from different soil levels were collected from marsh wetland, reclaimed paddy field, and reclaimed dry farmland, for analyzing soil nutrient (carbon, nitrogen, phosphorous, and potassium) contents, microbial biomass carbon/nitrogen (MBC/MBN), and microbial activity indicators[i.e. basal respiration (BR), potential respiration (PR), microbial quotient (qMB), and metabolic quotient (qCO2)]. The correlations between the soil nutrient contents and soil microbial activity indictors were examined. The results showed that:①Artificial reclamation led to the trend of slight acidity in the soil and a marked loss in soil nutrients, while, the pH value, soil water content (SWC), and the contents of soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), available phosphorus (AP), total potassium (TK), and available potassium (AK) decreased with reclamation. ②Among all the microbes, bacteria were the most numerous, followed by actinomycetes, and fungi were the least numerous. The microbial quantity decreased with the increase in the soil depth on the whole. The proportion of bacteria and actinomycetes were much higher in the paddy field, and that of fungi was the highest in the dry farmland. ③ In total, protease, sucrase, urease, catalase, and polyphenol oxidase activities decreased with the increasing of soil depths. Soil reclamation reduced the soil enzyme activities. ④qCO2 decreased after an initial increase in the marsh wetland, while it rose gradually in the reclaimed paddy field and reclaimed dry farmland. The contents of MBC, MBN, BR, PR, and qMB were the highest in the marsh wetland, followed by those in the reclaimed paddy field, with the lowest contents occurring in the reclaimed dry farmland. The trend of qCO2 contents in the 0-10 cm and 10-20 cm soil layers followed the order of marsh wetland > paddy field > dry farmland, but in the 20-30 cm and 30-40 cm soil layers, it showed the order dry farmland > paddy field > marsh wetland. The continuation of reclamation resulted in the decrease in soil microbial activity, and soil quality as well, especially in the dry farmland. Meanwhile, we should reduce the areas of paddy fields and dry farmlands under reclamation during the process of wetland ecological restoration in future. Conversion of farmlands to wetlands or lakes, to improve and increase the size of wetland ecosystems of nearby lands, should be done gradually.

Effect of gypsum on exchangeable sodium percentage and electrical conductivity in the Daeho reclaimed tidal land soil in Korea—a field scale study

A reclaimed tidal land along the shore has poor soil properties such as high exchangeable sodium percentage (ESP), and electrical conductivity (EC) due to excess sodium (Na) content. Therefore, Na content should be decreased to improve the land productivity, and for this, gypsum has been widely used. The objective of this study was to determine the changes in ESP and EC of the gypsum-treated reclaimed tidal soil in a field scale. For this, gypsum was applied to Daeho reclaimed tidal land (500 ha) in Korea for 5 years (2006 to 2010). The Daeho reclaimed tidal land has been used as reclaimed paddy fields since 1993. The application rate of gypsum was calculated based on exchangeable calcium (Ca) contents and soil cation exchange capacity (CEC) to maintain 60 % exchangeable calcium percentage (ECP) of CEC in soil and the average amount treated was 1570 kg ha−1 year−1. The changes in ESP and EC were monitored from 2006 to 2010, and 2013. The ESP dropped from 80 % in 2006 to 34 % in 2013. The EC of the soil was decreased by 73 %, from 11.5 dS m−1 in 2006 to 3.1 dS m−1 in 2013. Eventually, it was estimated that the ESP will be lowered below 15 % in 2023 with continuous treatment of gypsum according to ECP calculation, and EC will be declined to reach at 0.5 dS m−1 in 2035, the average EC level of Korean rice paddy. This field scale study evidenced that gypsum application effectively improves the soil properties of reclaimed tidal soil by decreasing ESP and EC.

Control of sulfonylurea-resistant Diplachne fusca (DF) and reduction of rice yield by occurrence densities of DF in reclaimed paddy fields

Control of sulfonylurea-resistant <i>Diplachne fusca</i> (DF) and reduction of rice yield by occurrence densities of DF in reclaimed paddy fields

일반답과 간척답에서 사료용벼 재배시 생육특성 및 사료가치

본 연구는 간척지에서 사료용벼를 재배하여 조사료를 생산함으로써 간척지 이용률 증진과 조사료생산의 두가지 가능성을 검토해보고자 일반답과 간척답에서 사료용벼를 재배하여 생육특성, 총체수량 및 사료가치 등을 조사하였다. 1. 출수기는 일반답에서 8월15일에서 8월30일, 간척답에서 8월14일에서 8월 29일이었으며, 간척답이 일반답보다 1~2일 빨랐으며, 목우는 일반답에서 8월 26일, 간척답에서 8월 27일로 수원 544호를 제외하고는 가장 늦었다. 2. 초장은 일반답에서 105~135 cm범위이었고, 간척답에서 97~126 cm범위였으며 일반답에서는 목양이 간척답에서는 수원544호가 가장 컸다. 주당경수는 일반답과 간척답 모두 녹양이 16개로 가장 많았고 총체수량은 일반답은 <TEX>$15.26{\sim}23.24MT\;ha^{-1}$</TEX>, 간척답은 <TEX>$11.94{\sim}18.89MT\;ha^{-1}$</TEX>범위이었으며 목우벼가 두지역에서 가장 많이 생산되었다. 각품종별 수량은 일반답에 비하여 78~84% 수준이었다. 3. 단백질 함량은 일반답에서는 녹양벼가 높았으나 간척답에서는 6.7~8.7%로서 상대적으로 낮은 수치를 보였고 목양벼가 8.7%로 가장 높았다. 각 품종별 NDF는 31.2~55.5% 수준을 나타냈으며 ADF는 일반답에 비하여 큰 차이를 보이지 않았으며 가소화 양분총량을 계산해본 결과 일반답에서 목우벼가 71.2%로 가장 높았고 전체적으로 60%이상의 함량을 보여 간척지에서 재배하여도 사료로서의 가치는 충분할 것으로 생각되었다. 4. TDN수량을 비교해본 결과 일반답에서 TDN수량은 목우벼가 <TEX>$16.54MT\;ha^{-1}$</TEX>로 가장 높았으며 간척답에서도 <TEX>$12.69MT\;ha^{-1}$</TEX>로 가장 높은 수량을 보였다. 5. 이상의 결과로 간척지에서 사료용벼를 재배할 경우 일반답에 비하여 80%정도의 수량을 보여 간척지에서 재배가능성을 확인하였으며 목우를 재배할 경우 수량 및 사료가치면에서 가장 좋을 것으로 생각된다. This study was carried out to compare the growth characteristics and feed values of the whole crop silage rice from paddy field and reclaimed paddy field. The heading dates of tested varieties was August 8 to August 30 in the paddy field, 1~2 days later than the reclaimed paddy field's August 6 to August 29. Plant height was in the range of 105~135 cm in paddy field, and 97~126 cm in reclaimed paddy field, respectively. The plant height of Mokyang was tallest in the paddy field, but Suwon 544 was tallest in the reclaimed paddy field. The number of tiller per plant of Nokyang was largest in the paddy field. Dry matter (DM) yield of whole crop rice ranged from 15.26 to <TEX>$23.24MT\;ha^{-1}$</TEX> in the paddy field and 11.94 to <TEX>$18.89MT\;ha^{-1}$</TEX> in the reclaimed paddy field. The highest DM yield in both fields was attained by Mokwoo. Comparing with the paddy field, the reclaimed paddy field achieved 78~84% in the DM yield. The crude protein content of varieties was 8.5 to 11.6% in the reclaimed tidal land and 6.7~8.7% in the paddy field. Neutral detergent fiber (NDF) of varieties in both fields ranged from 31.2 to 55.5%. Suwon 544 recorded the highest NDF contents in both fields. All varieties did not show any significant difference in acidic detergent fiber (ADF) which had values ranging from 22.3 to 33.2%. Total digestion nutrient (TDN) was more than 60% overall in both fields. Regarding TDN yield, Mokwoo recorded <TEX>$16.54MT\;ha^{-1}$</TEX> in reclaimed tidal land and <TEX>$12.69MT\;ha^{-1}$</TEX> in the paddy field, which showed the highest figure among the varieties. These results suggest the feasibility for cultivation of the whole crop silage rice in reclaimed paddy field, which showed 80% of the yield compared to paddy field, and implied that Mokwoo would show the most excellent yield and feed value.

Characteristics of TN and TP in Runoff from Reclaimed Paddy Field of Fine Sandy Loam

This study investigated the runoff from rice paddy located on reclaimed fine sandy loam soil to provide data for the development of policies to protect water quality of estuaries. Total N (TN), Total P (TP) concentrations and runoff loads at outlet were monitored from 2006 to 2008. Soil phosphate adsorptivity was measured and compared with typical paddy soil in watersheds. TP concentration of the paddy water and TP runoff loads were much greater than those of typical paddy field in watershed because phosphate adsoptivity in reclaimed paddy field of fine sandy loam appeared to be a third of those of typical paddy soils by relatively low soil OM and high sand content of the reclaimed soil. Thus, nutrient runoff, particularly phosphate from the reclaimed paddy field needs to be managed more thoroughly to protect estuarine water quality.

Clay Mineralogy and Vertical Distribution of Cadmium in a Soil Profile in a Reclaimed Paddy Field in Kyushu, Japan

Clay Mineralogy and Vertical Distribution of Cadmium in a Soil Profile in a Reclaimed Paddy Field in Kyushu, Japan

Soil and water indicators for optimal practices when reclaiming acid sulphate soils in the Plain of Reeds, Viet Nam

In the Plain of Reeds (Mekong delta, Viet Nam), water and soil characteristics show a high temporal variability which can be explained by changes in relative soil/water levels. Acid, aluminium and iron concentrations in canal water increase (pH drops from 6 to less than 3.5) when the annual river flood water recedes and the drainage/flushing of the acid sulphate soils begins. The high intra-annual variability of soil chemical characteristics is explained by sensitivity to changes in redox potential. Due to the high concentrations of toxic ions, cropping conditions are favourable for an extremely short period (2–3 months), which starts at the end of the annual flood. Optimal time window for cultivation, and optimal cropping techniques are related to the microelevation of the fields and to their permeability, which is very high in the first years following reclamation. In newly reclaimed paddy fields, water control is very limited and, even with frequent irrigation, maintaining favourable conditions is not possible before a less permeable plough-pan has been created by cultivation. To reclaim these soils, the only solution is then to start cultivation as early as possible. Farmers in the Plain of Reeds developed a technique consisting of sowing pregerminated rice seeds in deep water (20–40 cm) when flood water recedes. Determination of the sowing date is a key issue. Flood characteristics, in particular the speed of recession and water turbidity, the elevation and the age of the field as they determine permeability and water control should be taken into account.

Kilimanjaro Agricultural Development Centre and water management on reclaimed paddy fields.

Kilimanjaro Agricultural Development Centre and water management on reclaimed paddy fields.

Studies on the Behavior of Wintering Geese

(1) White-fronted (numbered 6, 000 in 1978) and Bean geese (numbered 1, 500 in 1978) winter in Lake Izunuma in Miyagi Prefecture. Lake Izunuma is now the only roosting place of geese on the Pacific coast of Japan. The authors studied the distribution of feeding area of the geese wintering at Lake Izumuna for eight years from 1971 to 1978. These geese feed chiefly in harvested paddy fields. This feeding habit is in contrast to that in England or other European countries where geese feed in arable lands and grasslands. (2) In ordinary years the feeding areas of the geese at Lake Izunuma is limited to the alluvial plains in northern half of Miyagi Prefecture. In years of heavy snow, however, they move to the areas with light snow for feeding, south to the southern part of Miyagi Pref. and the northern part of Fukushima Pref., sometimes reaching to the Kanto Plain which is three hundred kilometers south of Lake Izunuma. (3) The past history of decrease of the geese populations in Japan accounts for the present situation of the geese whose feeding areas are restricted to the Senpoku Plain in northern Miyagi Prefecture. Due to heavy hunting and gradual worsening of environments since the Imperial Restoration of Meiji, geese in Japan have lost their wintering grounds one by one from Kyushu to Kanto, namely from the south to the north, and today the Senpoku Plain has left as the last remained wintering place of geese on the Pacific coast of Japan. (4) The Feeding areas of White-fronted Geese and those of Bean Geese in the Senpoku Plain are separated topographically with each other. The feeding areas of White-fronted Geese are situated in the northern and the western parts of the Senpoku Plain and they are distributed along the middle to the upper reaches of the Hazama and the Naruse rivers. Bean Geese feed in the eastern and the southern parts of the Senpoku Plain, in which the feeding areas are located along the middle and the lower reaches of the Hazama, Naruse and Yoshida rivers. The two species were occasionally seen feeding together in the same field in a few districts, but such is rather rare.However, in the years of heavy snow and when the geese migrated to the south, they were more frequently observed to feed in mixed flocks. (5) The spatial separation of feeding areas of the two species may be due to their former habitats in their history, that is a habitual attachment for the former feeding sites ('traditional attachment'). The feeding areas of Bean Geese before the reclaim for fields are presumed to have been a vast marsh area, where the Been Geese could obtain water-chestnuts (Tarapa Linn.) and other aquatic plants. Water-chestnuts are growing over in marshes and must be a 'traditional diet' of Bean Geese in Japan.The reclaimed paddy fields supply a fairly good amount of paddy gleans for geese so that they still hold the habitual attachment to the places of the former feeding areas. In the case of White-fronted Geese, the 'traditional attachment' is also the main factor for separation of feeding areas from Bean Geese and the aquatic plant Makomo (Zizania Linn.) is supposed to be one of their 'traditional diet' in Japan.

The Role of Cracks in Subsoil on Underdrainage in Clayey Reclaimed Paddy Fields

The Role of Cracks in Subsoil on Underdrainage in Clayey Reclaimed Paddy Fields

豊橋市の海岸干拓田におけるツヅミモとケイソウについて

1958年8月13, 15日に豊橋市西方の神野新田 (干拓田) のツヅミモ, ケイソウを分類, 生態学的に研究した.1. 水質はpH6.3～7.1, Cl-0.02～0.4g/lであった.然し, 海岸から100～150mのCl-が比較的高く (175～396mg/l), 500～1500mの地点では低かった (19～42mg/l).2. ケイソウ類は9科28属92種, 然し, N3'のケイソウ泥を除くと, 鹹水域に普通みられるものが31種で38%を占め, 鹹水種が優占種又は亜優占種として出現したものは海岸から500～800mまでの地点であった.更に離れた地点でも少数個体の海産種が数種見出された.ツヅミモ科は4属30種でN1 (産せず) を除いて普通近畿地方の内陸水田に見られる分布とよく似ていた.

台地の開発と新田集落の成立過程

Innamino in Banshu District is so to speak the western entrance of the district, situating on the main road to the west. But, as is the case with the upl-and districts, mixed with gravels. And, though lands around the upland had been cultivated before the Nara Period, it was left for a long time as a barren field, and even in the middle age, it was only used as a retreat by the fugitve Samurais who had lost their lords owing to the successive civil wars. The period when the cultivation of this land was taken up on a full scale was after the dawn of the modern age when it became possible to pump the water in the low land up into the ponds of upland with the improvement of engineering wo ks according to that of technique of fortification in our country. At the same time, in the modern age, the lord paid more attention to stabilize the feelings of the people, and in due course, the cultivation of the low swampy land or uncultivated fields in his dominion was was exceedingly promoted. First, Okubo low land, the eastern entrance of Innamino, and Iwaoka and kande high uplands, which situates north to Okubo low land, were cultivated by the Akashi Clan at the beginning of the Edo Period. And Kako, Mori, and Temma uplands in the central part were cultivated with the unstinted support of the lord of Himeji Castle; and the neighbouring Choice Reclaimed Paddy Fields belonged to the village headman were one by one cultivated by the method of Cut-Off-Reclaimed Paddy Fields, with the help of the local people. After the temporary stagnation in the middle of the Edo Period, the shallow sea around the sea-shore was reclamated, while the cultivation of the upland was proceeded to the highest part in the north-east corner, and the cultivation in Innamion was almost completed at the end of the Edo period, in which the capital of rich merchants was great in its assistance. To begin with, this upland was so slow to be cultivated due to the shortage of water; bnt now this upland had been of paddy fielde, the problem of water supply remained causing incessant irrigation disputes, though there had been made numerous ponds getting water either from the rain or from the river running in the low land be low. At the same time, the newly cultivated area was a confused land and, as those lands were increased, the disputes on their possession took place and this resulted the complicated boundaries of villages in this part in the later period.

RELATION BETWEEN IRRIGATION WORK AND RECLAMATION OF INNAMINO UPLAD, HARIMA DISTRICT, HYOGO PREFECTURE

Innamino upland has the highest density of irrigation reservoirs for paddyfields in Japan. As the upland is made up of sand and gravel beds, water for drinking and irrigation was difficult to be obtained. So it was almost impossible to cultivate the land in ancient time. In the prehistoric age, paddy fields were opened only in a small area near the springs at the foot of the marginal cliffs of the upland. In the Nara period, reservoir irrigation was begun by damming up some of the shallow ravines in the upland. But as the relative height of the upland is large, it was difficult to lead the water from rivers. up to the surface of the upland. At the end of the middle age, when engin eering techinique developed in connection with fortification, the technique was possibly applied to the irrigation work, and there came a new epoch in the reclamation of the upland. At first, the river course of the Kako River was improved and its delta plain was reclaimed. Then it was successfully carried out to lead the water from. the Kako River and its tributaries and the Akashi River up into the reservoirs. constructed on the upland. Thus the upland surface was rather rapidly reclaimed. But as the time-period for supplying river water into reservoirs was ordinarily limited, irrigation water for the newly reclaimed paddy fields on the upland could not be sufficient, so the quarrel for water constantly occurred. At present, a new method of welldrilling irrigation has been applied, while the improvement of irrigation canals and reservoirs has been also promoted. The development of new paddyfields which had been so eagerly promoted in the years of the feudal-clan government, was irresistively ceased in the Meiji era. And, thereafter, conversion of upland fields into paddy-fields was made. Nowadays, the rice-and-ccorn agriculture has become intensive intending to meet the demands of a big city to which the surrouding agricultural villages are being centralized.