Intermittent Flood Irrigation Research Articles

Phenology, gas exchange, biomass accumulation, and irrigated rice yield under alternative irrigation managements

AbstractIn Brazil, rice production is predominantly concentrated in the South region, employing a continuous flood irrigation system throughout the crop cycle. However, this irrigation management strategy in the tropical region contributes to low water‐use efficiency owing to adverse climatic conditions. Furthermore, with climate change projections indicating reduced water availability, the study aims to investigate the impact of alternative irrigation management strategies on the phenological development, gas exchange, biomass accumulation, and productivity of tropical irrigated rice. Three alternative irrigation management approaches—intermittent flood irrigation with aeration (IFA), intermittent flood irrigation throughout the growth cycle (IFC), and intermittent flooding up to the flowering stage (IFF)—were compared with the traditional continuous flood irrigation throughout the growth cycle. Phenological data, gas exchange, growth, and productivity dynamics were subject to analysis, providing overarching insights into management practices. Notably, irrigation management exhibited no influence on the vegetative phase of the crop. The implementation of intermittent flood irrigation facilitated a reduction in water supply without compromising the physiological performance of tropical irrigated rice. Strategies promoting judicious water utilization, such as IFA and IFC, can be readily integrated into the cultivation of tropical irrigated rice without detriment to grain yield or harvest index.

Seasonal variations in metallic mercury (Hg<sup>0</sup>) vapor exchange over biannual wheat–corn rotation cropland in the North China Plain

Abstract. Air–surface gas exchange of Hg0 was measured in five approximately bi-weekly campaigns (in total 87 days) over a wheat–corn rotation cropland located on the North China Plain (NCP) using the relaxed eddy accumulation (REA) technique. The campaigns were separated over the duration of a full-year period (2012–2013) aiming to capture the flux pattern over essential growing stages of the planting system with a low homogeneous topsoil Hg content ( ∼ 45 ng g−1). Contrasting pollution regimes influenced air masses at the site and corresponding Hg0 concentration means (3.3 in late summer to 6.2 ng m−3 in winter) were unanimously above the typical hemispheric background of 1.5–1.7 ng m−3 during the campaigns. Extreme values in bi-directional net Hg0 exchange were primarily observed during episodes of peaking Hg0 concentrations. In tandem with under-canopy chamber measurements, the above-canopy REA measurements provided evidence for a balance between Hg0 ground emissions and uptake of Hg0 by the developed canopies. During the wheat growing season covering ∼ 2 / 3 of the year at the site, net field-scale Hg0 emission prevailed for periods of active plant growth until canopy senescence (mean flux: 20.0 ng m−3), showing the dominance of Hg0 soil efflux during warmer seasons. In the final vegetative stage of corn and wheat, ground and above-canopy Hg0 flux displayed inversed daytime courses with a near mid-day maximum (emission) and minimum (deposition), respectively. In contrast to wheat, Hg0 uptake of the corn canopy at this stage offset ground Hg0 emissions with additional removal of Hg0 from the atmosphere. Differential uptake of Hg0 between wheat (C3 species) and corn (C4 species) foliage is discernible from estimated Hg0 flux (per leaf area) and Hg content in mature cereal leaves, being a factor of > 3 higher for wheat (at ∼ 120 ng g−1 dry weight). Furthermore, this study shows that intermittent flood irrigation of the air-dry field induced a short pulse of Hg0 emission due to displacement of Hg0 present in the surface soil horizon. A more lingering effect of flood irrigation is however suppressed Hg0 soil emissions, which for wet soil ( ∼ 30 % vol) beneath the corn canopy was on average a factor of ∼ 3 lower than that for drier soil (< 10 % vol) within wheat stands. Extrapolation of the campaign Hg0 flux data (mean: 7.1 ng m−2 h−1) to the whole year suggests the wheat–corn rotation cropland to be a net source of atmospheric Hg0. The observed magnitude of annual wet deposition flux ( ∼ 8.8 µg Hg m−2) accounted for a minor fraction of soil Hg0 evasion flux prevailing over the majority of the year. Therefore, we suggest that dry deposition of other forms of airborne Hg constitutes the dominant pathway of Hg input to this local ecosystem and that these deposited forms would be gradually transformed and re-emitted as Hg0 rather than being sequestered here. In addition, after crop harvesting, the practice of burning agricultural residue with considerable Hg content rather than straw return management yields seasonally substantial atmospheric Hg0 emissions from croplands in the NCP region.

Effects of deficit irrigation and groundwater depth on root growth of direct seeding rice in a column experiment

Rice is an essential crop in Iran that is grown mostly in areas where depth to groundwater is low. Root growth and water uptake of rice under shallow groundwater has not been thoroughly studied. This experiment was conducted to determine the lowland rice (cv. Ghasrodashti) root distribution above shallow groundwater in relation to deficit irrigation and groundwater depth in cylindrical greenhouse lysimeters. The irrigation treatments were continuous flood irrigation (CFI) and intermittent flood irrigation (4- and 8-day intervals IF-4 and IF-8). The groundwater depths (GWD) were 0.3, 0.45 and 0.6 m from the soil surface. In general, 40-60% of root dry weight was observed in the top 10 cm of soil in CFI treatments and IF-4 with 0.3 m GWD resulted in 20% increase in root dry weight in 10-20 cm layer compared with 0-10 cm. However, the root dry weight in 0-10 cm at 0.60 m GWD was 58% lower in intermittent irrigation compared to CFI. There was no significant difference in mean root length density in IF-4 with 0.3 m GWD compared with CFI. In general, lowland rice showed good ability to develop its root system in shallow groundwater level conditions in order to extract water due to lower soil water content in the intermittent flood irrigations. Simple equations were presented to predict the groundwater contribution to evapotranspiration based on the root length density and root weight density. Therefore, in areas with shallow groundwater depth (up to 0.45 m from the soil surface) and low potential evapotranspiration, application of IF-4 instead of CFI can be useful management especially where water scarcity is a serious problem.

Effects of water-saving irrigation and groundwater depth on direct seeding rice growth, yield, and water use in a semi-arid region

In Iran, rice is grown in areas where the groundwater depth (GD) is low. Therefore, water-saving irrigation (WSI) can be used instead of continuous flood irrigation (CFI) in order to use the groundwater. The objectives of this study were to investigate the interaction effects of irrigation regimes and GDs on growth and yield of rice and groundwater contribution (GC) to crop evapotranspiration (ET) in cylindrical greenhouse lysimeters. Irrigation regimes were CFI and intermittent flood irrigation (IFI) with 4- and 8-day intervals (IFI-4 and IFI-8, respectively), and GDs were 0.3, 0.45, and 0.60 m. Results indicated that in a climate condition similar to experimental environment in greenhouse, using IFI-4 at a GD of 0.3 m produced grain yield and straw and root dry matter (DM) similar to those obtained when using CFI, with 53% reduction in irrigation water use. However, straw and root DM increased in CFI with increasing soil column length. Maximum GC/ET (41%) was observed when using IFI-4 at a GD of 0.3 m. A multiple regression equation was presented to estimate GC/ET as a function of GD and soil moisture deficit (SMD). This equation indicates that at a given GD with extension of irrigation intervals and increased SMD GC/ET reached a maximum value followed by a decrease afterwards. Maximum values of GC/ET were obtained at SMD values of 0.47, 0.40, and 0.33 at GDs of 0.3, 0.45, and 0.6 m, respectively.

RESPONSE OF DIFFERENT RICE CULTIVARS (ORYZA SATIVA L.) TO WATER-SAVING IRRIGATION IN GREENHOUSE CONDITIONS

Due to increasing water and growing demand for food a more efficient water use system is needed for agriculture. This is more evidence for rice production with a higher water use for economical production. A large cultivar×water regime interaction exists for grain yield in rice. Therefore, information is required to adopt new rice cultivars with high yield potential under watersaving conditions. The objectives of this study were to analyze the straw yield, grain yield, yield components, water use and water productivity of six rice cultivars (Anbarboo-22, Ghasroddashti, Cross-Domsiah, Hasani, Rahmat-Abadi, and Doroodzan) under water-saving irrigation regimes (intermittent flood irrigation with 1-and 2-day intervals, I-1-D, and I-2-D, respectively) compared with continuous flood irrigation (CFI) to adopt the elite cultivars of semi-arid area for water-saving conditions. Results indicated that under water-saving irrigation regimes (I-1-D), Doroodzan, Anbarboo-22, and Cross-Domsiah cultivars produced higher grain yields and are elite cultivars, however, under I-2-D irrigation regime only Anbarboo-22 cultivar was an elite cultivar. Based on the harvest index criterion, Doroodzan and Anbarboo-22 cultivars are the elite cultivars under watersaving irrigation regimes. The grain yield of the cultivars was mostly controlled by 1000-grain weight and the order of the other yield components were number of grains per panicle > number of panicles per unit area > unfilled grain percentages. Under CFI, Doroodzan cultivar resulted in highest water productivity (WP) as 0.52 kg m -3 and Cross-Domsiah and Anbarboo-22 cultivars with WP of 0.40 and 0.31 kg m -3 were in second and third place, respectively. Furthermore, based on the drought tolerance indices, it is concluded that Doroodzan at first place and Anbarboo-22 and Cross-Domsiah cultivars at second place may be considered as drought tolerant cultivars that can be used in further field study with water-saving irrigation regimes i.e., intermittent irrigation with 1-and 2-day intervals in Fars province.

Effect of zeolite on saturated hydraulic conductivity and crack behavior of silty clay paddled soil

The addition of zeolites to soil modifies soil physical and chemical properties. The objectives of this research were to study the effect of zeolite on saturated hydraulic conductivity, K s, and crack behavior in a silty clay paddled soil. Soil samples were mixed with 0, 4, 8 and 12 g kg−1 of zeolite for K s determination, and 0, 2, 4, 8 and 12 g kg−1 for soil crack measurements. Saturated hydraulic conductivity was measured using the constant head method. The results indicated that K s was significantly increased at a zeolite application rate of 8 g kg−1. Furthermore, an increase in zeolite content up to 8 g kg−1 decreased soil crack area after paddling and first rewetting. Higher amounts of zeolite (e.g. 12 g kg−1) increased crack density after the second rewetting. However, a 50% reduction in crack depth occurred with zeolite application rates of 8 and 12 g kg−1 in comparison with controls. Thus, a zeolite application rate of 8 g kg−1 is recommended for soil crack reduction in intermittent-flood irrigation. Furthermore, a relationship was obtained between crack area density (Ln), gravimetric soil water content and zeolite application rate. After the second irrigation, a relationship was also obtained between crack depth, gravimetric soil water content and zeolite application rate. Crack depth showed a positive and highly significant linear correlation with crack width.

Effects of water-saving irrigations on different rice cultivars (Oryza sativa L.) in field conditions

A more efficient water use system is needed for agriculture. This is more evidence for rice production with a higher water use for economical production. A large cultivar×water regime interaction exists for grain yield in rice. Therefore, information is required to adopt new rice cultivars with high yield potential under water-saving conditions. The objectives of this study were to analyze the straw yield, grain yield, yield components, water use and water productivity (WP) of five rice cultivars (Anbarboo-22, Ghasroddashti, Cross-Domsiah, Hasani, and Rahmat-Abadi) under watersaving irrigation regimes (intermittent flood irrigation with 1-and 2-day intervals after disappearance of standing water, I-1-D, and I-2-D, respectively) compared with continuous flood irrigation (CFI) to adopt the elite cultivars for these conditions. In general, Anbarboo-22 cultivar totally failed in field trial due to susceptibility to disease in 2005 and 2006. Among the other cultivars, Cross-Domsiah showed the highest grain yield, harvest index, number of panicles per hill and the lowest unfilled grain percentage in two years field experiments. Furthermore, its grain yield was the highest at watersaving irrigation regimes in comparison with the other cultivars, therefore, Cross-Domsiah is the elite cultivar in water-saving irrigation conditions especially with 1-day irrigation interval, however, Ghasroddashti cultivar is recommended in next order for I-1-D treatment. Based on the selected drought indices, Cross-Domsiah was the most drought tolerant cultivar and Ghasroddashti was in the second order. Furthermore, it is concluded that unfilled grain percentage and harvest index are found to be the most suitable traits for selection of rice cultivars with high yield potential.

Methane and nitrous oxide emissions from a paddy field with Japanese conventional water management and fertilizer application

The seasonal courses of methane (CH4) and nitrous oxide (N2O) fluxes were simultaneously monitored in a paddy field using a closed chamber system with automated gas sampling and analyzing equipment. Water management and fertilizer application practices followed Japanese conventional ones. CH4 flux gradually increased after the first flood irrigation of the field and reached ∼150 mg CH4 m−2 d−1 at the beginning of July. After the first summer drainage, however, CH4 flux dropped rapidly to almost zero within a few days. CH4 flux then gradually increased again according to intermittent flood irrigations, but was much less than that before the first drainage. Immediately after the first flood irrigation, N2O flux rapidly increased, although its temporal peak lasted only within a few days. During the subsequent continuously and intermittently flooded periods, N2O flux remained at almost zero until the final drainage, except for slight and temporal peaks just after the top‐dress application of supplemental fertilizer. About 1 week after the final drainage in autumn, N2O flux gradually increased, and the most significant high peak of N2O flux was observed after the harvest of rice plants, which lasted for about 2 weeks. The amounts of cumulative CH4 and N2O emissions throughout the whole year of 2002 were 3128 mg CH4 m−2 and 60.2 mg N m−2, respectively. Both the amounts of cumulative CH4 and N2O emissions during the rice cultivation period were low compared with those reported in previous studies. These results suggest the advantage of Japanese conventional water management and fertilizer application for reducing the combined effect for global warming by CH4 and N2O emissions from paddy fields, since the practices of drainage and intermittent flood irrigation in summer markedly lessen CH4 emission in the latter half of the rice cultivation period with little enhancement of N2O emission.

Transport of Solutes as Affected by Irrigation Method

AbstractThe leaching behavior of agricultural chemicals depends on the application method of both the chemical and water. This study investigated the leaching behavior of conservative tracers under intermittent flood and drip irrigation on a clay loam soil. Slug applications of conservative tracers were applied sequentially to a single 37‐m2 plot and leached under the two irrigation regimes with the same daily application rate. Suction lysimeters, installed at seven depths (0.3, 0.6, 1.0, 1.4, 1.8, 2.4, and 3.0 m) and replicated four times, were used to withdraw daily soil solution samples during leaching. Pore water velocities, v, and dispersion coefficients, D, for a one‐dimensional advection‐dispersion model were fit to the resulting concentration vs. time curves by nonlinear least squares. Pore water velocities were slightly greater on average under drip irrigation and were more uniform across the plot (smaller variance) than under flood irrigation. Preferential flow was observed under both irrigation regimes. Breakthrough curves showed considerably more spreading under intermittent flood irrigation than under drip, indicating greater hydrodynamic dispersion under flood irrigation. Fitted D values were, on average, nearly three times greater under flood irrigation than under drip. Allowing free water at the soil surface during flood irrigation increased the dispersion of tracer compared with the drip irrigation system, where water was applied at a rate less than the saturated conductivity. The increase in D is most likely due to small‐scale spatial variability of the soil's hydraulic properties.

Effective Design for Small Flood‐Irrigated Field Plots

AbstractMany studies dealing with water flow in soil require water application through ponding. A method is described for the preparation of a large number of adjacent ponded field plots for experimental purposes. Individual plots are enclosed by corrosion‐resistant, metal strips extending 20 cm into the soil. A single border area around each group of plots functions as a buffer zone, similar to the outer zone of a double‐ring infiltrometer. Simultaneous uniform ponding of individual plots and the border area is achieved by a network of bubbler sprinkler units, with each plot having a separate water flow meter and valve unit to control the rate and amount of each irrigation episode. Such a system enabled study of the influence of macropore structure on the transport of various pesticides and dyes under continuous and intermittent flood irrigation.

Independent Calibration of a Mechanistic‐Stochastic Model for Field‐scale Solute Transport Under Flood Irrigation

AbstractSolute leaching at the field scale can show considerable variability because of variations in the hydraulic properties of the soil. A simple mechanistic‐stochastic model for predicting solute transport on this scale during intermittent flood irrigation is described and a method of calibrating the model independent of any leaching measurements is presented. The model assumes that the pore water velocity varies horizontally across the field but is uniform in the vertical direction. Explicit expressions for chemical diffusion and hydrodynamic dispersion are not included in the model. Instead, horizontal variations in the velocity serve to disperse the solute when measured on a field wide basis. The model requires knowledge of the probability density function for the velocity and estimates of the function parameters. These parameters were estimated from variations in infiltration rates measured within 63 ring infiltrometers and from water retention data. Model simulations of Br− leaching agreed well with most measured data for both position of the tracer peak and the degree of solute spreading, indicating that at least under flood irrigation, variations in infiltration as controlled by soil hydraulic properties explain most of the observed variations in Br− leaching over a field.

Transport of Conservative Tracers in the Field Under Intermittent Flood Irrigation

The velocity of downward percolating water measured using tracer concentration profiles was compared to the macroscopic velocity calculated from a water balance. Experiments were performed in a 37‐m2 field plot under intermittent flood irrigation. Five different soil water tracers were used to follow the movement of six applied water pulses over a period of 10 months under two irrigation regimes. Mean water velocities measured with the tracers averaged 60–70% greater than the calculated macroscopic velocity. The results indicated that a significant portion of the applied water moved downward through preferential flow paths even under unsaturated conditions. The measured velocities were not sensitive to irrigation frequency as long as total water applied remained constant. The data indicate that simple water balance models may overestimate arrival times of surface‐applied water and chemicals to ground water.

Nutrients and Associated Ion Concentrations in Irrigation Return Flow from Flooded Rice Fields

AbstractA 3‐year field study of nutrient and common ion concentrations in irrigation return flow (IRF) from flooded rice fields utilized replicated plots which received either recommended or excessive fertilizer rates with continuous flow or intermittent flood irrigation. All P and K and 40% of the (NH4)2SO4 nitrogen (N) were applied preplant and incorporated. The remaining N was applied just prior to permanently flooding (40%) and at 2‐mm panicle stage (20%). The irrigation and plot water were analyzed for NH4+‐N, NO3−‐N, NO2−‐N, PO43−‐P, K+, Ca2+, Mg2+, Na+, Cl−, and SO42−. Highest nitrate‐N concentrations occurred early in the season before the permanent flood period, but did not exceed drinking water standards. Nitrite‐N concentrations in the IRF were low at all times. Maximum NH4+‐N concentrations occurred following N fertilizer applications which were not incorporated into the soil and persisted in the floodwater for 5 to 7 days. These peak NH4+‐N concentrations exceeded acceptable drinking water standards concentration by a factor of 10 or greater. Concentrations of PO43−‐P and K+ in the floodwater were similar to those in the surface water used for irrigation. The concentration of the other common ions in the floodwater did not greatly exceed those in the irrigation water and all were within concentrations acceptable for drinking water. Method of fertilizer application had more influence on IRF nutrient concentrations than did fertilizer rates or irrigation management practices. Under the conditions of this study, it appears that only the ammonium concentrations may have a detrimental impact on the quality of IRF from flooded rice fields. This potential problem could be minimized by preventing IRF for a period of 1 week following surface applications of (NH4)2SO4 fertilizer.