Reduction of runoff and soil loss over steep slopes by using vetiver hedgerow systems

Vetiver hedgerow system has potential for reducing runoff and soil loss especially on steep slope areas, but the dynamics of these reductions are not fully understood. This research was conducted to determine reduction in runoff and soil loss by vetiver hedgerow system. Vetiver hedgerow systems with three vertical intervals of hedgerow were tested on three land slopes and compared with the case without hedgerow for six simulated rainfall amounts. The vetiver hedgerows reduce runoff volume and soil loss by 31–69 and 62–86 %, respectively compared to the case without vetiver hedgerow. Runoff volume increases with rainfall amount, and hence increases soil loss. Therefore soil loss increases with land slope, runoff volume, rainfall amount, and vertical hedge interval. Two final equations for estimating soil loss are presented in this study. The first equation contains parameters of runoff volume, land slope, and vertical hedge interval, while the second equation contains rainfall amount instead of runoff volume. The correlation coefficients between estimated soil losses and the experimental data in this study and in the literatures were found to be 0.94 and 0.90 for the first and second equations, respectively.     

High-yield SRI in West Java by decomposing straw in waterlogged paddy field

System of Rice Intensification (SRI) often achieved higher yield than conventional practice. We identified the high-yielding farmers from the yield records of 1909 paddy fields belonging to an organic farmers’ association. Farmers whose yields were from 8.4 to 10.4 t ha^?1 were interviewed and their fields surveyed. Their yields had increased by an estimated average of 40% following the adoption of SRI practices. They applied 2–12 t ha^?1 of compost. Compared to the conventional practice, they shortened seedling age at transplanting from 27.4 to 17.6 days and reduced the number of seedlings per hill from 4–6 to 2–3, while hill spacing remained unchanged. Instead of intermittent irrigation which is recommended in standard SRI, they kept shallow flooding of 1–2 cm. Although they applied a lot of compost, no correlation was found between the amount of compost application and the yields. Instead, high-yielding farmers returned rice straw into waterlogged paddy after harvest, which presumably is an ideal condition for biological nitrogen fixation. This may occur around rice straw during decomposition under waterlogged condition and might supplement the negative nitrogen balance, thereby enabling the high yield as compared with conventional practices where the fresh rice straw is removed and/or burned.     

Modelling of groundwater recharge potential from irrigated paddy field under changing climate

Groundwater recharge from irrigated paddy field under various projected climate change scenarios was assessed using HYDRUS-1D model. Recharge flux, root water uptake, evaporation and surface runoff were simulated on daily time step for the growing period of paddy. Crop evapotranspiration and effective rainfall during the simulation period were estimated to be 301.9 and 269.4 mm, respectively. Cumulative bottom flux, root water uptake, evaporation and surface runoff were 69.2, 23.2, 30.8 and 0.0 cm for sandy loam and 37.2, 23.0, 30.8 and 0.7 cm for clay loam soils, respectively. Simulation results showed that the groundwater recharge potentials in sandy loam and clay loam soils with paddy crop are 69.2 and 37.2 cm, respectively. Cumulative recharge under various climate change scenarios from paddy field varied from 63.9 to 74.4 cm, 33.7 to 39.8 cm, 29.3 to 35.4 cm and 27.1 to 34.3 cm from land units A1 (sandy loam), B1 (clay loam with slight salinity), C1 (clay loam with moderate saline and slight sodic) and D1 (clay loam with strong saline and sodic), respectively. Cumulative recharge flux under the scenarios in which increase in relative humidity along with decrease in duration of sunshine hours was associated with rise in average temperature and wind speed, groundwater recharge would increase by 7.4 %. Cumulative recharge flux under the scenarios which were based on rise in temperature along with the increase in rainfall, groundwater recharge would increase by 0.2–3.9 %. Simulation results also showed that cumulative recharge would decrease under all those scenarios, which were based on rise in temperature only.     

Seed priming and in situ moisture conservation measures in increasing adaptive capacity of rain-fed upland rice to moisture stress at Eastern Himalayan Region of India

In the uplands of Eastern Himalayan Region (EHR) of India, dry-seeded rain-fed rice occupies considerable area. However, productivity of rice in this region is very low and is mainly due to frequent occurrence of intermittent soil moisture stress, weed infestation, and poor crop establishment. Keeping this in view, a field experiment on rain-fed direct-seeded rice was conducted during two consecutive years 2011 and 2012 at the EHR of India (27° 95′N latitude and 94° 76′E longitude, 662 m above MSL) to evaluate the effect of seed priming (SP) with different durations (0, 12, 18, and 24 h) and in situ furrows at various row intervals as moisture conservation measures (MCM) on seed germination, plant stand, profile moisture recharge, rice productivity, water and energy use efficiency, and harvest monetary benefits. Results revealed that SP for 24 h duration significantly (p < 0.05) improved the seed germination and crop stand, rice grain yield by 30–36 %, water use efficiency by 29–36 %, and energy productivity by 15–22 %. In situ furrows at regular and alternate row intervals also registered 1.89–3.2-fold increase in profile moisture recharge, 20–34 % higher rice productivity, 23–33 % improvement in water use efficiency, and 6–16 % increase in energy productivity over without MCM. Seed priming helped in improving seed germination, seedling establishment, and plant stand, while MCM was useful in mid-season rainfall capture and profile moisture recharge during intermittent moisture stress for better plant growth. However, adoption of in situ furrows (regular and alternate row intervals) as MCM increased the cost of cultivation by 13–27 % over normal practices but was compensated by the significant increase in grain yield, water use efficiency, benefit:cost ratios, and farmers’ profit.     

Cover Crops as Affecting Soil Chemical and Physical Properties and Development of Upland Rice and Soybean Cultivated in Rotation

Cover crops can provide changes in soil chemical and physical properties, which could allow a sustainable development of soybean and upland rice rotation in Brazilian Cerrado. The objective of this study was to determine the effects of cover crops(cultivated in the offseason) in the soybean-upland rice rotation(cultivated in the summer season) on the soil chemical and physical properties, yield components and grain yield of the cash crops. The experimental design was a randomized block design in factorial scheme 4 × 2 with six replications. Treatments were composed by four cover crops: fallow, millet(Pennisetum glaucum) + Crotalaria ochroleuca, millet + pigeon pea(Cajanus cajans), and millet + pigeon pea + Urochola ruziziensis in the offseason with one or two cycles of cover crops, with rice(Oryza sativa)or soybean(Glycine max) in the summer season. Cover crops alone provided no changes in soil chemical properties. However, the rotation cover crops/cash crops/cover crops/cash crops reduced p H, Al and H + Al and increased Ca, Mg, K and Fe contents in the soil. The cover crops millet + pigeon pea and millet + pigeon pea + U. ruziziensis improved soil physical properties in relation to fallow,especially in the 0–0.10 m soil layer. In spite of the improvement of the soil physical properties after two years of rotation with cover crops and cash crops, the soil physical quality was still below the recommended level, showing values of macroporosity, S index and soil aeration capacity lower than 0.10 m3/m3, 0.035 and 0.34, respectively. Upland rice production was higher under mixtures of cover crops than under fallow, mainly because of soil physical changes done by these mixtures of cover crops.Soybean grain yield was similar under all cover crops tested, but was higher after the rotation cover crops/upland rice/cover crops than after only one cycle of cover crops.     

Influence of paddy rice terraces on soil erosion of a small watershed in a hilly area of Northern Vietnam

Soil erosion is the main cause of soil degradation in northern Vietnam. In this study, soil erosion was measured in 2 m² field plots, a 19.1-ha sub-watershed, and a 248.9-ha main watershed in Tam Quan commune, Tam Duong district, northern Vietnam during 2 years, i.e., 2004–2005. The main watershed includes lowland paddy fields, and is representative for watersheds in the northern Vietnamese landscape. Soil erosion was measured for eight events, at all the three scales to increase our understanding of erosional processes and to assess the effects of paddy fields within the main watershed. The results show that total discharge and sediment yield in both sub-watershed and main watershed were much lower than those in the field plots. Total discharge per unit area in the main watershed was higher than in the sub-watershed, because during the growing season, the paddies are filled with water and any rainfall on them therefore becomes runoff. Sediment yield in the main watershed fluctuated, depending on the soil erosion contribution from many sub-watersheds. Annual rainfalls in 2004 and 2005 were 1,172 and 1,560 mm, respectively, resulting in corresponding total discharges of 54 and 332 mm and total soil losses of 163 and 1,722 kg ha^?1 year^?1. High runoff volumes occurred in July, August, and September, but April, June, the last 10 days of September and October, were the susceptible periods for soil erosion in the study area because of low plant cover and many agricultural activities during these periods.     

Influence of rice varieties,nitrogen management and planting methods on methane emission and water productivity

A field experiment was conducted during rainy seasons of 2009 and 2010 at New Delhi, India to study the influence of varieties and integrated nitrogen management (INM) on methane (CH₄) emission and water productivity under flooded transplanted (FT) and aerobic rice (AR) cultivation. The treatments included two rice (‘PB 1’ and ‘PB 1121’) varieties and eight INM practices including N control, recommended dose of N through urea, different combinations of urea with farmyard manure (FYM), green manure (GM), biofertilizer (BF) and vermicompost (VC). The results showed 91.6–92.5 % lower cumulative CH₄ emission in AR compared to FT rice. In aerobic conditions, highest cumulative CH₄ emission (6.9–7.0 kg ha^?1) was recorded with the application of 100 % N by organic sources (FYM+GM+BF+VC). Global warming potential (GWP) was significantly lower in aerobic rice (105.0–107.5 kg CO₂ ha^?1) compared to FT rice (1242.5–1447.5 kg CO₂ ha^?1). Significantly higher amount of water was used in FT rice than aerobic rice by both the rice varieties, and a water saving between 59.5 and 63 % were recorded. Under aerobic conditions, both rice varieties had a water productivity of 8.50–14.69 kg ha^?1, whereas in FT rice, it was 3.81–6.00 kg ha^?1. In FT rice, a quantity of 1529.2–1725.2 mm water and in aerobic rice 929.2–1225.2 mm water was used to produce one kg rice. Thus, there was a saving of 28.4–39.6 % total water in both the rice varieties under AR cultivation.     

Water productivity,nutrients uptake and quality of aerobic rice as influenced by varieties and iron nutrition

Field experiments were carried out at the research farm of ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi, India, during Kharif (June–October) seasons of 2011 and 2012 to study the effect of rice varieties and iron fertilization on water productivity, nutrient uptake and quality of aerobic rice. Treatments comprised of two rice varieties (PRH-10 and PS-5) and eight sources and modes of iron fertilization—control (no iron), iron sulphate @ 50 kg/ha + one foliar spray of 2.0% iron sulphate, iron sulphate @ 50 kg/ha + one foliar spray of 0.5% iron chelate, iron sulphate @ 100 kg/ha, two foliar sprays of 2.0% iron sulphate, three foliar sprays of 2.0% iron sulphate, two foliar sprays of 0.5% iron chelate and three foliar sprays of 0.5% iron chelate. Study results indicated that variety PRH-10 had higher concentration and uptake of nitrogen, phosphorus, potassium and iron than PS-5 variety in grain, straw and grain + straw. Three foliar sprays of 2.0% iron sulphate or 0.5% iron chelate favoured higher NPK and iron concentration and uptake in grain and straw of aerobic rice. Grain quality in respect of hulling, milling and head rice recovery was, however, superior in PS-5 than PRH-10. But the protein content was significantly higher in PRH-10 than in PS-5. Application of three foliar sprays of 2% iron sulphate and three foliar sprays of 0.5% iron chelate recorded significantly higher hulling, milling and head rice recovery as compared to control and remained statistically similar with each other. Irrigation and total water productivity was substantially higher in PRH-10 over PS-5. Growing of rice with PRH-10 recorded ~7.7% higher total water productivity as compared to PS-5, across iron fertilizations. Three or two foliar sprays of 2.0% iron sulphate or 0.5% iron chelate favoured higher irrigation and total water productivity of aerobic rice over control (no iron).     

海南岛典型农业土壤产流与面源污染特征分析

采用径流场结合人工模拟降雨方式,研究各种降雨条件下海南岛不同土地类型产流产沙的规律与面源污染特征。结果表明：土壤（泥沙）产流系数与平均流失速率表现为暴雨＞大雨＞中雨,且暴雨时的泥沙平均流失速率为中雨时的416％、大雨时的261％,在中雨、大雨和暴雨强度下,平均径流系数分别为24.49％、33.97％和53.40％;雨强对土壤营养物质流失速率的影响达到显著水平,COD、有机质和氮素以径流流失为主,磷素以泥沙流失为主;土壤径流和泥沙中的COD、有机质、氮素和磷素流失速率随雨强的增大而增大,坡度也可明显影响面源污染物的流失;海南岛农业土壤平均流失量为3.79 t/（hm2·a）,中雨强度条件时为1.92 t/（hm2·a）,大雨强度条件时为2.57 t/（hm2·a）,暴雨强度条件时为6.87 t/（hm2·a）。海南岛农业土壤的水土流失强度较高,海南农业土壤的水土流失与农田污染物输出状况不容乐观。     

Feasibility of SRI methods for reduction of irrigation and NPS pollution in Korea

An experimental study on the System of Rice Intensification (SRI) methods was conducted to investigate the feasibility of using them to conserve irrigation water and reduce non-point source (NPS) pollution in Korea. Eight experimental runoff plots were prepared at an existing paddy field. Runoff and water quality were measured during the 2010 growing season in which a Japonica rice variety was cultivated. The irrigation water requirements of SRI methods and conventional (CT) plots were 243.2 and 547.3 mm, respectively, meaning that SRI methods could save 55.6% of irrigation water. Runoff from SRI methods plots decreased 5–15% compared with that from CT plots. Average NPS pollutant concentrations in runoff from SRI methods plots during rainfall-runoff events were SS 89.4 mg/L, COD_Cr 26.1 mg/L, COD_Mn 7.5 mg/L, BOD 2.0 mg/L, TN 4.2 mg/L, and TP 0.4 mg/L. Except for COD_Cr and TN, these concentrations were significantly lower than those from CT plots. Measured pollution loads from SRI methods plots were SS 874 kg/ha, COD_Cr 199.5 kg/ha, COD_Mn 47 kg/ha, BOD 13 kg/ha, TN 36.9 kg/ha, and TP 2.92 kg/ha. These were 15.8–44.1% lower than those from CT plots. Rice plants grew better and healthier in SRI methods plots than in CT plots. However, rice production from SRI methods plots ranged between 76 and 92% of that of CT plots because the planting density in SRI methods plots was too low. It was concluded that SRI methods could be successfully adopted in Korea and could help save a significant amount of irrigation requirement in paddies and reduce NPS pollution discharge.     

Reducing rice field algae and cyanobacteria abundance by altering phosphorus fertilizer applications

In California’s water-seeded rice systems, algal/cyanobacterial biomass can be a problem during rice establishment and can lead to yield reductions. Laboratory, enclosure, and field-scale experiments were established to evaluate the effects of fertilizer P management on algal/cyanobacterial growth. Two field-scale experiments evaluated the response of algal/cyanobacterial growth to three P management strategies: conventional surface applied, incorporated into the soil, and delaying P applications by 30 days. Results from these experiments indicated rice fields that received conventional surface-applied P fertilizer had 4–8 times more algal/cyanobacterial biomass and 3–11 times higher concentrations of soluble reactive phosphate (SRP) than those in which P fertilizer was incorporated or delayed. Laboratory experiments evaluated the ability of field water to support growth of Nostoc spongiaeforme. Results indicate that water from the incorporated or delayed P application fields was P limited for N. spongiaeforme growth. Water from the surface-applied fields was not P limited. Enclosure experiments evaluated the effects of delayed P applications on algal/cyanobacterial biomass and rice yields. Algal/cyanobacterial cover and biomass increased in enclosures which received added P. Soluble reactive phosphate concentrations were also significantly greater in these enclosures. Delaying the application by up to 28 days did not reduce rice yields in the enclosures. One management implication is that reducing SRP concentrations early in the season in rice field water will result in reduced algal/cyanobacterial biomass. Strategies to reduce water SRP include incorporating fertilizer P or delaying the P application by up to 30 days.     

Effects of rice and rye straw extracts on the growth of a cyanobacterium, <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

This study investigated the effect of extracts with time (a range of extraction periods: 0.2 days to maximum 150 days) of rice and rye straw on the growth of Microcystis aeruginosa (a cyanobacterium). The effect was assessed by an effective concentration 50 (EC₅₀) of extracts measured by a carbon (C) content, when 50% normalized maximum growth yield (50% inhibition effect) of M. aeruginosa occurred. We found that extracts of rice and rye straw inhibited the growth of M. aeruginosa. Extracts from the earliest incubation phase (0.2 days) for rice straw and the 40-day extract for rye straw showed the most inhibitive EC₅₀ value of 28.0 mg C L^?1 and 18.9 mg C L^?1, respectively. The inhibition effect was positively related to the extraction period of the rye straw, but inversely of the rice straw. Our results suggested that the long-term decomposition of extracts during straw extraction be linked with the formation of allelochemicals. These results provided information on how allelochemicals derived from agricultural by-products affect algal growth in aquatic ecosystems.     

Water regimes: an approach of mitigation arsenic in summer rice (Oryza sativa L.) under different topo sequences on arsenic-contaminated soils of Bengal delta

Arsenic (As)-contaminated groundwater has been widely used in agricultural purposes especially for summer rice cultivation in South East Asia. Therefore, the present experiments were carried out at low (diara) and medium land topo sequences with the eight water regimes to reduce the As accumulation in summer rice (Oryza sativa L.). Experimental results revealed that the intermittent ponding of 2–4 days after disappearance (DAD) were significantly reduced the As accumulation in root, stem, leaves, flag leaf, husk, and grain (21.86–31.78, 23.55–37.20, 14.83–30.93, 23.53–31.19, 21.33–28.19, and 22.98–25.37 %, respectively), which was followed by aerobic rice (21.34–22.08, 22.49–30.72, 12.21–23.02, 22.06–27.52, 20.14–23.94, and 22.12–22.30 %, respectively), and saturation of top soil (17.43–17.85, 21.91–28.01, 10.76–20.27, 20.59–24.77, 18.96–23.14, and 20.75–21.15 %, respectively) as compared to continuous ponding or farmer practice, where the As accumulation in root: 13.43–17.20 mg/kg; stem: 8.64–10.36 mg/kg; leaves: 2.91–3.44 mg/kg; flag leaf: 0.68–1.09 mg/kg; husk: 1.88–2.11 mg/kg; and grain: 0.52–0.67 mg/kg. However, aerobic rice and saturation of top soil recorded significantly higher grain yield at diara land (7,104–7,141 kg/ha) and only in saturation of top soil at medium land topo sequence (6,654–6,717 kg/ha). The correlation study showed the positive correlation in between grain As and root, straw, husk As, grain Zn, and grain Fe (R ² = 0.893–0.976, p > 0.01), but the negative correlation with the grain P, soil P, soil Fe, and soil Zn (R ² = 0.633–0.841, p > 0.01). About 3.904–6.063 kg/ha of As was added on the surface soil by the contaminated groundwater and most of the added As was accumulated and remained on the top soil (0–30 cm).     

Effects of plastic-hole mulching on effective rainfall and readily available soil moisture under soybean (<Emphasis Type="Italic">Glycine max</Emphasis>) cultivation

Plasticulture is becoming popular to control soil temperature and increase water-use efficiency in rain-fed agriculture. Non-perforated plastic mulching reduces effective rainfall by preventing infiltration, while perforated plastic mulching (plastic-hole mulching) increases effective rainfall by enhancing infiltration; both mulching control soil temperature. The comparative performance of these mulching is not, however, well investigated yet. So, a field experiment was conducted by cultivating soybean (Glycine max) under non-perforated plastic mulching (hereafter denoted by P), plastic-hole mulching (hereafter denoted by PH) and bare soil to investigate soil temperature, effective rainfall, total readily available soil moisture (TRAM), soil-moisture extraction pattern (SMEP) and yield of soybean. The mulching treatments reduced soil temperature by 2 °C at 5 cm depth compared to the bare treatment and created a favorable environment for soybean growth under high air temperature during summer in Japan. The PH treatment increased effective rainfall by as much as 9% of total rainfall compared to the P treatment. The SMEP in the 0- to 30-cm soil profile revealed that soil moisture was consumed, mostly, from the upper soil layer in the bare treatment, while in the P and PH treatments, soil-moisture consumption occurred both from the upper and from the lower soil layers. Consequently, the P and PH treatments provided greater TRAM (57.3 and 54.0 mm) than the bare treatment (48.0 mm), indicating that mulching contributed increasing soil-moisture availability in the root zone. The mulching treatments augmented plant height, number of nodulations per plant, and seed and biomass yields; the PH treatment produced the maximum seed yield.     

Comparative effectiveness of different infiltration models in estimation of watershed flood hydrograph

The present study aims to evaluate performance of different infiltration models, namely initial and constant rate, soil conservation service (SCS) curve number and Green–Ampt in simulation of flood hydrographs for the small-sized Amameh Watershed, Iran. To achieve the study purpose, the infiltration rates were measured using rainfall simulator in work units acquired through overlaying topography, land use, drainage network and soil hydrologic group maps. All parameters of the study infiltration models were determined with the help of the Infilt. software package. The performances of the models in simulation of the observed output hydrographs from the entire watershed were ultimately evaluated for 28 rainfall–runoff events in the HEC-HMS environment. The different components of the observed and estimated hydrographs including time to peak, runoff volume, peak discharge, discharge values and peak time deviation were compared using relative error (RE), coefficient of determination (R²), peak-weighted root mean square error (PWRMSE) and Nash–Sutcliffe (NS) criteria. The general performance of estimations was also qualitatively assessed using scatter plot and distribution of study variables around standard lines of 1:1 slope. The results revealed that the SCS infiltration model with PWRMSE = 0.61 m³ s^?1 and NS = 0.53 performed better than initial and constant rate model with PWRMSE = 1.1 m³ s^?1 and NS = 0.54, and Green Ampt model with PWRMSE = 1.35 m³ s^?1 and NS = 0.29 in estimation of flood hydrograph for the Amameh Watershed.     

Elevated carbon dioxide and temperature effects on rice yield,leaf greenness,and phenological stages duration

The present field experiment was conducted during two consecutive cropping seasons in central Portugal to study the effects of simultaneous elevation of carbon dioxide concentration ([CO₂]) (550 μmol mol^?1) and air temperature (+2–3 °C) on japonica rice (Oryza sativa L. “Ariete”) yield, crop duration, and SPAD-values across the seasons compared with the open-field condition. Open-top chambers were used in the field to assess the effect of elevated air temperature alone or the combined effect of elevated air temperature and atmospheric [CO₂]. Open-field condition was assessed with randomized plots under ambient air temperature and actual atmospheric [CO₂] (average 382 μmol mol^?1). Results obtained showed that the rice “Ariete” had a moderate high yielding under open-field condition, but was susceptible to air temperature rise of +2–3 °C under controlled conditions resulting in reduction of grain yield. The combined increase of atmospheric [CO₂] with elevated air temperature compensated for the negative effect of temperature rise alone and crop yield was higher than in the open-field. SPAD-readings at reproductive stage explained by more than 60 % variation the straw dry matter, but this finding requires further studies for consolidation. It can be concluded that potential increase in air temperature may limit rice yield in the near future under Mediterranean areas where climate change scenario poses a serious threat, but long term field experiments are required.     

Growth behavior,productivity, leaf rolling,and soil cracks on transplanted rice in response to enforce surface drainage

Intermittent and prolonged dry spell during growth of transplanted rice is an important abiotic problem in north eastern region (NER). However, the productivity of rice in the region is very low, and this is mainly associated with reduced plant population, growth, and yield attributes with lower relative water content and leaf rolling with formation of soil cracks by erratic and aberrant rainfall. Keeping this in view, a field experiment on transplanted rice was conducted during two consecutive years 2011 and 2012 at NER of India, to evaluate the imposition of forced surface drainage (SD) at various growth stages (continuous drainage, SD at tillering, SD at panicle initiation, SD at booting, SD at flowering, SD at milking, and 15 days intermittent SD) and was compared with continuous flooding on growth and yield attributes, yield, relative water content, leaf rolling, and formation of soil cracks. Results revealed that continuous flooding has significant (p < 0.05) improved the plant population, growth and yield parameters, rice grain yield (3,406.7 kg ha^?1) and straw yield (4,683.3 kg ha^?1), relative water content maintained >90 %, no leaf roll, and soil crack. However, imposition of SD at tillering has lower tillers hill^?1, but yield was compensated by improvement in yield attributes. As per the availability of water, growers of the region can utilize the water for scheduling of water and most critical stages can be avoided by moisture stress to obtain higher productivity.     

麦田降雨产流时间计算模型研究

为探讨多种因素对麦田降雨产流时间的影响及其相应的定量关系,通过模拟降雨试验,研究了麦田降雨强度、冠层覆盖及初始土壤剖面含水量对降雨产流时间的影响。结果表明,在相同初始土壤剖面含水状态条件下,降雨强度与产流时间呈显著幂函数关系(P<0.01);产流时间与叶面积指数呈极显著线性正相关(P<0.01),与株高相关性较差;0～20、0～40cm土层初始土壤剖面含水量与产流时间具有较明显的线性正相关关系(P<0.01),40cm以下土层土壤含水量对产流时间影响相对较小。通过多元回归分析建立的产流时间幂函数计算模型具有较好的模拟效果。     

Analysis of water balance in the Tedori river alluvial fan areas of Japan: focused on quantitative analysis of groundwater recharge from river and ground surface, especially paddy fields

Water balance in the Tedori River alluvial fan areas was analyzed for all components of the hydrological cycle based on exchange of the channel/soil surface and aquifer horizon fractions with river water. The results were summarized on an annual basis, as well as for the irrigation and non-irrigation periods. The study area received 6.28 mm/day of precipitation and had an outflow of 2.32 mm/day as direct runoff, resulting in 3.96 mm/day of water being supplied to the soil surface. The channel/soil horizon fraction received this 3.96 mm/day, as well as 9.12 mm/day intake water from the head works. Conversely, 2.74 and 2.85 mm/day were lost by evapotranspiration and percolation, respectively. Thus, surface runoff of 7.49 mm/day flowed from the study area to the Sea of Japan or drainage canals near the river mouth. In the aquifer horizon fraction, 2.85 mm/day of water was supplied from the channel/soil horizon fraction and 2.15 mm/day was supplied from the Tedori River, while 1.73 mm/day was extracted by groundwater. Thus, 3.27 mm/day of groundwater flowed out to the Sea of Japan or into downstream drainage canals. An outline of the water balance of the irrigation and non-irrigation period is also shown. Because various hydrological components are closely related to each other, planning and management of water resources for individual goals are not adequate, but require the integrated aspect of water balance for sustainable water use.