Concentration In Floodwater Research Articles

Phosphorus interception in floodwater of paddy field during the rice-growing season in TaiHu Lake Basin

A field experiment located in TaiHu Lake Basin in China was conducted, by application of superphosphate or a mixture of superphosphate with manure, to elucidate the interception of P export during a typical rice growing season through ‘zero-drainage water management’ combined with sound irrigation, rainfall forecasting and field drying. P concentrations in floodwater rapidly declined before the first event of field drying, and subsequently tended to return to the background levels. Before the first field drying TPP was the predominant P form in floodwater on fields with no P input, DRP on plots that received superphosphate only, and DOP on plots treated with the mixture of superphosphate and manure. Thereafter TPP became the major form. No P export was found from the paddy fields, but a retention of 0.65 kg ha −1, mainly due to soil P sorption. The results recommend the zero-drainage water management for full-scale areas for minimizing P export.

Ammonia volatilization from the surface of a Japanese paddy field during rice cultivation

Ammonia (NH3) volatilization from the surface of a Japanese paddy field during rice cultivation was measured using the dynamic chamber method with a dry NH3 collector. A preliminary investigation showed that a dry NH3 collector with phosphoric-acid-impregnated filters could collect volatilized NH3 with sufficient efficiency. The experimental field included six lysimeter plots of Gray Lowland soil with a soil pH (H2O) of 5.7. Urea was applied as nitrogen fertilizer at a rate of 50 kg N ha−1 by incorporation with puddling into the plowed layer as the basal fertilization (BF) and at rates of 30 and 10 kg N ha−1 by top-dressing as the first (AF1) and second (AF2) additional fertilizations, respectively. Relatively strong NH3 volatilization occurred immediately after AF1 with a maximum flux of 45 g N ha−1 h−1. In contrast, the NH3 volatilization fluxes following BF or AF2 were weaker. The ammonium (NH+ 4) concentration and the flooded water table were found to be major factors influencing NH3 volatilization; higher NH3 volatilization fluxes were often observed with a higher NH+ 4 concentration in floodwater and a lower water table. Incorporation of urea with puddling resulted in lower NH+ 4 concentrations in floodwater than in the case of top-dressing application, which likely resulted in fewer NH3 volatilization fluxes after BF than after AF1 and AF2. In contrast, relatively strong NH3 volatilization occurred in the plots immediately drained after AF1, which suggested that a top-dressing application under nearly drained conditions enhanced NH3 volatilization. The ratio of NH3 volatilization loss to applied nitrogen for each application of fertilization was 0.2 ± 0.1, 3.8 ± 2.2 and 0.7 ± 0.5% for BF, AF1 and AF2, respectively. In addition, the total ratio of NH3 volatilization loss to total applied nitrogen throughout rice cultivation was estimated to be 1.4 ± 0.8%. These values were smaller than those reported from other Asian paddy fields, with the exception of the maximum NH3 loss after AF1, 9.0%, which was comparable to the minimum NH3 loss reported in Asian paddy fields. The application rates of nitrogen fertilizer in the present study were smaller than those in Asian paddy fields, although they are conventional for Japan. In conclusion, the very small values of NH3 volatilization recorded in the present were ascribed to the small rates of urea application per fertilization, which restrained increases in NH+ 4 concentrations in floodwater, and to the relatively low soil pH, which resulted in prevention of NH+ 4 dissociation in floodwater.

Simulating the fate of molinate in rice paddies using the RICEWQ model

The contamination of drainage channels and creeks with pesticides used in the production of rice is of concern in south eastern Australia. Of major concern is the molinate that at times has been detected in over 25% of water samples from surface drains and creeks. The objective of this study was to evaluate the rice pesticide model RICEWQ version 1.7.2 for its applicability in simulating the fate of the pesticide molinate in paddy rice floodwater in south eastern Australia. The model was successfully calibrated using water depths and molinate concentrations obtained from a rice bay. By using the calibrated model, the effects of the different application methods and the rates of molinate on water quality were investigated. The molinate, which was applied directly onto ponded water, led to higher maximum concentrations in the ponded water than for application onto a dry bay, which was subsequently filled. However, the concentrations in water declined more rapidly for the application onto a ponded bay than those for the application onto a dry bay. The simulation results suggest that water and chemical management has great effects on chemical concentration in the runoff water. Overall, the RICEWQ model accurately predicted the molinate concentrations in floodwater and this model can be used to develop best management practices in rice farming.

Assessment of insecticide contamination in runoff and stream water of small agricultural streams in the main soybean area of Argentina

The first- and second-order streams, Brown and Horqueta, respectively, which are located in the main area of soybean production in Argentina were examined for insecticide contamination caused by runoff from nearby soybean fields. The insecticides most widely used in Argentina (chlorpyrifos, cypermethrin and endosulfan) were detected in sediments, suspended particles and water. Highest concentrations in suspended particles were 318 μg/kg for endosulfan in the stream Horqueta, while 226 μg/kg chlorpyrifos and 13.2 μg/kg cypermethrin were measured in the stream Brown. In the Horqueta stream 150 and 53 μg/kg chlorpyrifos and cypermethrin were detected in runoff sediments, respectively. Whereas cypermethrin concentrations in the suspended particles were relatively low, levels in the floodwater of Brown reached 0.7 μg/l. The highest chlorpyrifos concentration in floodwater was 0.45 μg/l in Brown. However, endosulfan was not detected in the water phase. In runoff water the highest concentrations measured were 0.3 μg/l for chlorpyrifos in Horqueta and 0.49 μg/l for cypermethrin in the Brown stream. On five sampling dates during the pesticide application period in Brown stream (2002/2003) the concentration of chlorpyrifos and cypermethrin in runoff and/or floodwater exceeded the water quality criteria for freshwater mentioned in this study. In three cases this insecticide concentration was measured in stream water, indicating an acute risk to aquatic life. The acute toxicity–exposure-ratio (TER) for chlorpyrifos and cypermethrin also shows an acute risk for aquatic invertebrates in the Brown stream. In the Horqueta chlorpyrifos concentrations in the runoff exceeded the safety levels three times during the application period (2001/2002), potentially endangering the aquatic fauna. Effects on aquatic macroinvertebrates after insecticide contamination were reported in earlier studies in Horqueta stream.

High Dissolved Oxygen Concentration of Floodwater Reduces Carbohydrate Concentration of Cranberry Uprights during Flooding

Cranberry production involves the use of flooding for several purposes during the growing season, including pest control, winter protection, and harvest. The effect of the dissolved oxygen concentration in floodwater on carbohydrate concentration of uprights and roots during flooding was investigated using potted `Stevens' cranberry (Vaccinium macrocarpon Ait.) vines. Pots were placed in large bins filled with water to simulate a spring pest control flood (called late water) over a 21-day period. Two treatments were applied: oxygenated and nonoxygenated (control). Uprights and roots were collected every 3 days and prepared for HPLC analysis to quantify nonstructural carbohydrate concentration. Soluble sugar (sucrose, glucose, and fructose) and starch concentration, as well as total nonstructural carbohydrate (TNSC) concentration, decreased over the 3-week period in uprights but not roots regardless of treatment. Interestingly, the sucrose, glucose, fructose, and starch concentrations of uprights in the oxygenated treatment were lower than those of uprights in the control treatment throughout the experiment. This research indicates that vines in flooded bogs demonstrate a net carbon loss, resulting in reduced carbohydrate concentration available for growth and fruit production.

The release of nitrous oxide from the intertidal zones of two European estuaries in response to increased ammonium and nitrate loading

Nitrous oxide (N2O) release and denitrification rates were investigated from the intertidal saltmarsh and mudflats of two European river estuaries, the Couesnon in Normandy, France and the Torridge in Devon, UK. Sediment cores and water were collected from each study site and incubated for 72 h in tidal simulation chambers. Gas samples were collected at 6 and 12 h intervals from the chambers during incubation. From these N2O emission rates were calculated. The greatest rates for both N2O production and denitrification were measured from saltmarsh cores. These were 1032 µmol N2O m−2 day−1 and 2518 µmol N2 m−2 day−1, respectively, from the Couesnon and 109 µmol N2O m−2 day−1 and 303 µmol N2 m−2 day−1 from the Torridge. A strong positive correlation was apparent with N2O emission rates and ammonium concentration in the sediment, nitrate concentration in floodwater and sediment aerobicity.

Presubmergence and green manure affect the transformations of nitrogen‐15‐labeled urea under lowland soil conditions

AbstractThe effect of presubmergence and green manuring on various processes involved in [15N]‐urea transformations were studied in a growth chamber after [15N]‐urea application to floodwater. Presubmergence for 14 days increased urea hydrolysis rates and floodwater pH, resulting in higher NH3 volatilization as compared to without presubmergence. Presubmergence also increased nitrification and subsequent denitrification but lower N assimilation by floodwater algae caused higher gaseous losses. Addition of green manure maintained higher NH4+‐N concentration in floodwater mainly because of lower nitrification rates but resulted in highest NH3 volatilization losses. Although green manure did not affect the KCl extractable NH4+‐N from applied fertilizer, it maintained higher NH4+‐N content due to its decomposition and increased mineralization of organic N. After 32 days about 36.9 % (T1), 23.9 % (T2), and 36.4 % (T3) of the applied urea N was incorporated in the pool of soil organic N in treatments. It was evident that the presubmergence has effected the recovery of applied urea N.

Denitrification in drained and rewetted minerotrophic peat soils in Northern Germany (Pohnsdorfer Stauung)

This study was conducted to assess the nitrogen removal potential of a minerotrophic peatland in Northern Germany, where hydrological conditions were partly restored in the beginning of the 1990s. Actual denitrification and the effect of nitrate (NO3-) and glucose additions on denitrification rates were determined in two flooded and one drained histosols in spring and summer 1998. In the flooded soils, denitrification was insignificant, but the drained field emitted significant rates. Additions of NO3- stimulated denitrification at all sites in spring and summer, whereas glucose additions had no effect. Low NO3- concentration in floodwater was obviously limiting denitrification in the flooded soils. In the drained soil, a coupled nitrification/denitrification might explain the low, but significant denitrification rates. No spontaneous production of nitrous oxide occurred in the flooded soils, whereas at the drained site an increase in spontaneous nitrous oxide concentration was measured during incubation in the summer samples. The suggested introduction of NO3- rich water from a stream flowing through the area would apparently induce denitrification in the flooded fields. (Less)

Influence of redox potential on phosphorus solubility in chemically amended wetland organic soils

Conversion of agricultural lands to wetlands results in solubilization of residual fertilizer P, thus increasing soluble P concentration of floodwater. Previous studies have shown that application of chemical amendments such as alum, FeCl 3 and CaCO 3 were found to be effective in decreasing soluble P of the soil porewater. Water-table fluctuations and variable hydraulic loading rates in wetlands can alter soil redox conditions, and the solubility of P compounds. The objective of this study was to determine the influence of oxidized and reduced soil conditions on P solubility of a wetland organic soil amended with chemicals. Soil treatments evaluated include: (i) control, (ii) CaCO 3 at 15.3 g kg −1, (iii) alum at 14.5 g kg −1, and (iv) FeCl 3 at 1.8 g kg −1. Dissolved reactive P of soils in the control and FeCl 3 amended soils responded to changes in Eh, while a less pronounced effect was noted in alum and CaCO 3 amended soils. Overall, dissolved P concentrations were higher under reduced conditions and decreased with increase in Eh. The KCl-P (labile inorganic P) decreased with increase in Eh, while NaOH-RP (Fe- and Al-bound P) increased with Eh, especially in control, FeCl 3 and alum amended soils. Soil amended with CaCO 3 showed minimal changes in either KCl-RP or NaOH-RP. In CaCO 3 amended soil, the solubility of P was regulated by the solid phases of Ca-P compounds, while in other treatments solubility was controlled by variscite, strengite, and vivianite. Amendments (such as CaCO 3 and alum) that are less sensitive to changes in redox conditions may be suitable for binding P under wetland environments.

DEEP PLACEMENT OF FERTILIZER SOLUTION IN PUDDLED SOILS PART 1: NITROGEN LOSSES

Deep placement of fertilizer solution in puddled rice fields has been found to be effective in reducing floodwater and volatilization losses of applied nitrogen (N). However, the effects of the depth and manner of placement of N solution to losses has not been determined. Determination of N losses would help improve mechanical fertilizer application. Placement depths of 3, 7, 11, and 15 cm, and point versus band placement of N solution were evaluated using a prototype pressurized injector by measuring the ammonium-nitrogen concentration in floodwater and determining the partial pressure of ammonia as the relative indicators of runoff and volatilization losses, respectively. Results showed high losses of N at shallower point placement (3 and 7 cm particularly) as the high pressure of injection aided in the diffusion of N towards the soil surface and high losses with placement holes further exposed to water. Deeper point injection at 11 and 15 cm depth resulted in less loss of N, with placement above the hard pan having the least loss with depth. Band injection at 7 cm seems to be better in keeping the injected N from the water (with the skid and covered furrows) than point placement at the same depth. However, improvements in the design and performance of the injection device are necessary to make deep placement more effective and practical.

Nitrogen transformations in a flooded soil in the presence and absence of rice plants: 1. Nitrification

Nitrification rates (n) in the floodwater of an alkaline clay were measured in the absence or presence of rice plants by inhibition of ammonium oxidation and 15N-dilution techniques. Floodwater nitrate concentrations in control treatments showed a marked diurnal variation, and were higher than in the inhibitor treatments after the first day. Ammonium concentrations in floodwater declined exponentially in all treatments, being markedly affected by diffusion and NH3 volatilization but little affected by nitrification and plant uptake. Nitrification rates in floodwater estimated by 15N-dilution were generally higher than the rates estimated by the inhibitor method. Estimates of n were generally higher during daylight hours than at night, and did not differ significantly between planted and unplanted pots. Microbial immobilisation of labelled ammonium and gross N immobilisation were not affected by addition of the nitrification inhibitor 2-ethynylpyridine.

Concentrations of N and P in floodwater and uptake of 15N by Spartina alterniflora in oilcontaminatd mesocosms

Fertilization of salt marshes to enhance oil biodegradation may not be effective if nutrients in floodwater are rapidly removed by plants or adsorbed to sediments. Three 15N labeled fertilizers and two commercial nitrogen (N) and phosphorus (P) slow-release fertilizers were applied at rates of 75–210 kg N ha −1 with and without 40 kg ha −1 of supplemental P to oil-contaminated, flooded mesocosms growing Spartina alterniflora. Phosphorus concentrations in floodwater ranged between 0.05 and 2.82 μg P ml −1 39 days after P application. Urea and NO 3 −1 concentrations in floodwater were below detection limits by 2 weeks after N application, but NH 4 + remained detectable for approximately 3 weeks. Approximately 20% of N from urea and ammonium fertilizers was recovered in shoots of Spartina, but only 7% from nitrate fertilizer was recovered. Frequent applications of fertilizers may be needed to maintain desirable nutrient concentrations in floodwater for enhancing oil biodegradation.

Evaluation of factors contributing to diurnal changes in O2 concentrations in floodwater of deepwater rice fields

SUMMARYGlass chambers were used to isolate 0–75 m deep water columns in situ in deepwater rice fields in Thailand to evaluate the contribution by various factors to the pronounced diurnal changes in O2 concentrations in the floodwater Chambers filled with distilled water provided estimates of O2 flow from the air into the water, indicating the importance of eddy currents associated with wind action and evaporative cooling. Darkening the natural water gave estimates for O2 evolution due to photosynthesis, while comparisons between columns with and without rice distinguished between O2 evolution and consumption by the rice and the biomass other than rice respectively. Removal of the above water portions of the rice shoots showed the importance of the emergent portion of the canopy to O2 movement from the air into the aquatic part of the ecosystem. This flow may be associated with O2 flow through the lacunae and via air envelopes around the leaf, and with turbulence caused by swaying of the rice leaves in the wind.The changes in O2 concentration were analysed quantitatively using several simplifying assumptions. One major input was a net O2 flow from the air into the water, about half being due to a net flow across the air–water interface and the other half to flow associated with the rice plants. During the night, these flows were less than the O2 uptake by the biomass, hence O2 concentrations decreased. In the underwater portion of the rice stand, about 60 % of the O2 uptake was due to the rice and about 40% due to the biomass other than rice. During the day, the O2 requirements by respiration were more than compensated for by O2 evolution due to photosynthesis, resulting in increases in O2 concentration of the water.

Concentrations of CO2 and O2 in floodwater and in internodal lacunae of floating rice growing at 1–2 metre water depths

Abstract. Environment and plant measurements were made to determine what factors may limit growth of deepwater and floating rice plants during partial or complete submergence. Field surveys included measurements of temperature, pH, light, O2 and CO2 in floodwater in Thailand. In addition, measurements were made of O2 and CO2 concentrations inside internodal lacunae of deepwater and floating rice growing at 0.5–2.0 m water depths.The bulk of measurements were taken during periods when the changes in water level were less than 50 mm d−1. In the 0–0.02 m surface layer of floodwater at any location there were large changes in oxygen concentrations over diurnal cycles: there were decreases during the night down to 0.02–0.18 mol m−3 O2 at 0600 h and increases during the day to 0.13–0.28 mol m−3 O2 at 1500 h (0.28 mol m−3 being 120% of the O2 concentration of air saturated water at 30°C). During the day oxygen concentrations decreased with increasing water depth; concentrations just above the soil surface were occasionally zero. Most of this gradient disappeared during the night, and at dawn the 0.6 m surface layer of water had uniform low O2 concentrations.O2 concentrations were also measured during flash floods in Thailand. In contrast to the conditions with only small increases in water level, the O2 concentrations in the water during flash floods were more uniform with depth and changed little over a diurnal cycle, the O2 ranging between 0.14–0.19 mol m−3.In most locations floodwater contained 0.2–1.9 mol m−3 CO2 and 0.7–1.6 mol m−3 bicarbonate; however, in a location with acid sulphate soil CO2 was only 0.05–0.2 mol m−3, and bicarbonate concentrations were several fold lower. Concentrations of CO2 in floodwater increased with increasing water depth.O2 and CO2 concentrations inside internodal lacunae of rice were determined in the field when water depth were 1–2 m. Concentrations of O2 in internodes at the water surface were 16–20%, and decreased to 10% and 5% at 0.8 and 1.8 m water depth respectively. There was no diurnal cycle in O2 concentrations inside internodes. In contrast, CO2 concentrations in the lacunae increased with water depth and ranged from 1–3% in internodes at the water surface to 5–10% in internodes at 1.8 m water depth. There was evidence for a diurnal cycle in CO2 concentrations in the basal internode near the soil surface, CO2 increased during the day and decreased during the night.The above data are used to show that there is little or no relationship between gas concentrations in floodwater and internodal lacunae of rice plants. Results are discussed in relation to O2 supply to submerged portions of rice and metabolism of these tissues at low O2 concentrations.

Response ofAzollato P, K, and Zn in Different Wetland Rice Soils in Relation to Chemistry of Floodwater

A pot culture test in the greenhouse investigated the supply of P, K, and Zn to Azolla from flooded soils and the kinetics of P, K, and Zn in floodwater. Eleven Philippine rice soils, ranging from loamy sand to clay and with a pH range of 4.7 to 7.7, were used. In each soil, no addition, minus P, minus K, minus Zn, and PKZn treatments were designed. Three elements were added just before Azolla inoculation, and Azolla was harvested 3 weeks after inoculation. The concentration of phosphate in floodwater decreased sharply to a level of minus P treatment within a week after its application. Phosphorus content in Azolla at harvest did not change by phosphate application. The decrease of K and Zn concentrations in floodwater was slower than that of P. Hence, K and Zn content of Azolla at harvest increased with K and Zn application. Phosphate concentration in floodwater at 1 week after Azolla inoculation and a high correlation coefficient (R=0.83) with Olsen P content in soils except for one soil. Azolla biomass ranged from 9 (dry weight) to 53 mg/10cm2 and its N content ranged from 2.1 to 5.2%. The N percent in Azolla had a high correlation coefficient with dry weight (R=0.953). All dry weight, N%, and total N of Azolla had a high correlation (R=0.63–0.55) with P content of Azolla, but not with either K or Zn, indicating that P supply limited the growth of Azolla. Critical level of P content in Azolla was about 0.15%. An alkaline soil gave lower biomass than expected from its P content. Among the P concentrations in floodwater measured at 1, 2, 3 weeks after Azolla inoculation, the measurement at 1 week gave the highest correlation with P content in Azolla (R=0.739). When floodwater P at 1 week was less than 0.1 ppm, Azolla was certainly deficient in P. When floodwater P was higher than 0.4 ppm P, the supply of P to Azolla was sufficient. In only two soils, minus K or minus Zn treatment gave a lower biomass than the PKZn treatment. But it was difficult to confirm the presence of K or Zn deficiency based on the K and Zn contents in Azolla.

Effect of Placement Methods on Floodwater Properties and Recovery of Applied Nitrogen (15N‐Labeled Urea) in Wetland Rice

AbstractStudies at the International Rice Research Institute (IRRI) during the 1981 dry and wet seasons evaluated the effects of placement methods on recovery of fertilizer N by rice (Oryza sativa L.) using 15N‐labeled urea in field microplots. Uniform placement and point placement of urea supergranules (USG) gave the highest yield (6.4 Mg/ha) with efficiency of 51 kg rough rice/kg N in the dry season. In the wet season, point placement by USG produced the highest yield (4.4 Mg/ha) with efficiency of 40 kg rough rice/kg N. Higher floodwater pH and total N (urea + NH4‐N) concentration in floodwater were recorded after fertilization with split application and band placement of urea indicating the greater potential for NH3 volatilization and denitrification losses from these methods. Lower floodwater pH and low total N concentration in floodwater (5 mg/kg) were detected with uniform placement of prilled urea and point placement of USG, demonstrating that these methods can reduce N losses in lowland rice. Most fertilizer N (15N‐labeled urea) uptake occurred during the early crop growth stages. However, fertilizer N uptake was sustained with point placement of USG and uniform placement of prilled urea. Native soil N was taken up by the rice crop during the entire growing season, and was the major N source at the later part of crop growth in the wet season. Fertilizer 15N as high as 75% in the dry season and 65% in the wet season were recovered by the rice plant at harvest (grain and straw) with point placement of USG.