Influence of irrigation water properties on furrow infiltration: Temperature effects

For surface irrigation, the rate and spatial characteristics of infiltration processes influence crop productivity, water use efficiency, and erosion potential of stream flows. A change in infiltration rate alters furrow stream flow velocity and shear, and hence irrigation-induced erosion. Furrow irrigation models may be improved if they can account for the influence of water properties on these processes. Water temperature may influence furrow infiltration by altering fluid viscosity. We conducted laboratory soil column intake (constant head), and field recirculating furrow infiltrometer experiments, to determine whether irrigation water temperature significantly altered infiltration. The soil was Portneuf silt loam (coarse-silty, mixed superactive, mesic, Durinodic Xeric Haplocalcids). Soil column intake increased by 0.8 to 3.0 percent per degree C. This increase was not significantly different from that observed for furrows, 2.0 to 2.9% deg.-1. While more field studies are needed, these data show that diurnal and seasonal changes in irrigation water temperature can significantly alter furrow infiltration and stream flow. These effects may help explain observed field-infiltration variability. Inclusion of temperature algorithms in furrow irrigations models may increase their predictive accuracy

PAM and straw residue effects on irrigation furrow erosion and infiltration

Water soluble anionic polyacrylamide (PAM) is a highly effective erosion deterrent in furrow irrigation, but little is known about the effect of plant residue on PAM efficacy. We hypothesized that increasing plant residue in irrigation furrows may decrease PAM's ability to control erosion. Treatments included furrows with 3.2 g and 10 g m-1 straw applications irrigated with PAM or untreated water, and conventionally irrigated furrows (no PAM and no straw). Five irrigations were monitored on a field with 1.5% slope and silt loam soil (Durinodic Xeric Haplocalcids). PAM was applied as a granular patch at the furrow inflow end (33 g or 1 kg active ingredient ha-'). Irrigation inflows of 23 L min' were cutback to 15 after runoff began. Adding more straw, or adding PAM to straw-treated furrows decreased furrow sediment loss and increased net infiltration, but only for the first two irrigations after treatment. For fresh furrows, straw treatments reduced sediment loss an average of 86% and straw + PAM reduced sediment loss nearly 100%, compared to conventionally irrigated furrows. High-straw+PAM and lowstraw+PAM treatments produced the same furrow sediment losses and net infiltration amounts, i.e. increasing plant residues in furrows did not decrease PAM's efficacy on these soils

Sediment pond effectiveness for removing phosphorus from PAM-treated irrigation furrows

Polyacrylamide (PAM) greatly reduces erosion on furrow-irrigated fields and sediment ponds can be constructed to remove suspended sediment from irrigation runoff. Both practices are approved for reducing phosphorus (P) loading in the Lower Boise River Pollution Trading Project in southwest Idaho, but information is not available about using both practices on the same field. The objective of this study was to measure the combined effects of PAM application and sediment ponds on sediment and P losses from a furrow-irrigated field. Small sediment ponds (5.8 m 2) with a 60-min design retention time were installed on two fields to receive runoff from PAM-treated or control furrows. Pond inflow and outflow were monitored during a total of 11 irrigations on the two fields. Three crop years of data showed that applying PAM to furrows reduced sediment and total P mass transport to the ponds 50% to 80%, which reduced the mass of sediment and total P retained in the ponds. However, PAM application did not change the percentage of sediment (86%) and total P (66%) retained. The PAM-sediment pond combination reduced average total P loss by 86% to 98%, based on the difference between untreated inflow and PAM-treated outflow. PAM and sediment ponds had little or no effect on dissolved reactive P (DRP) concentrations. The mass of DRP retained in sediment ponds was directly related to the amount of water that infiltrated within the ponds. Applying PAM to irrigation furrows and installing sediment ponds at the end of the field can be an effective combination for reducing sediment and total phosphorus losses from furrow-irrigated fields, but these practices only reduced soluble P losses by decreasing the volume of water that ran off the fields

Polyacrylamide and straw residue effects on irrigation furrow erosion and infiltration

Water-soluble anionic polyacrylamide (PAM) is a highly effective erosion deterrent in furrow irrigation, but little is known about the effect of plant residues on PAM efficacy. We hypothesized that increasing plant residue in irrigation furrows may alter PAM's ability to control erosion. Furrows with 10 g (485 kg ha-1) on treated area and 3o g m-1 (1490 kg ha-1) wheat straw applications, irrigated with PAM or untreated water, and conventionally irrigated furrows (no PAM and no straw) were used. Five irrigations were monitored on a field with 1.5% slope and silt loam soil (Durinodic Xeric Haplocalcids). PAM was applied as a granular patch at the furrow inflow end (33 g or 1 kg active ingredient ha 1). Compared to controls, individual straw and PAM+straw treatments reduced sediment loss in all irrigations by 64% to 100%, but increased infiltration (1.3x to 2.54 only for irrigation one, when furrows were fresh. Adding more straw to low straw (with or without PAM) treatments increased average sediment loss reduction from 86% to 94% in the first two irrigations, but provided no extra benefit in subsequent irrigations (relative to controls). Adding PAM to low and high straw treatments increased average sediment loss reduction from 80% to 100% in the first two irrigations, and from 94% to 99.8% in subsequent irrigations. Combining plant residue and PAM in furrows produced greater erosion control and larger infiltration enhancements than with straw alone. An important additional benefit of PAM is that it greatly reduced detachment, transport, and redistribution of residue in furrows, which helped prevent furrow blockage and attendant overflow problems, allowing farmers to use conservation tillage in furrow irrigated fields

Influence of polymer charge type and density on polyacrylamide ameliorated irrigated furrow erosion

Previous experiments have shown that an initial application of 5-10 g m-3 (5-10 ppm) polyacrylamide to furrow irrigation water during flow advance can substantially reduce sediment loss. This study determined polyacrylamide charge type or charge density influences on furrow erosion. The study area was located near Kimberly, Idaho; soil was Portneuf silt loam (coarse-silty, mixed, mesic, Durixerollic Calciorthid); and slope was 1.5%. Polyacrylamides with contrasting charge type (neutral, anionic, cationic) and charge density (0, 8-10, 19-20, 30-35%) were employed in the treatments. Polymers were applied at a concentration of 10 g m-3 (10 ppm) during the initial 30 min of each treated irrigation, and a 10 min additional application was introduced every 4 hrs (twice) during the remainder of the irrigation. Inflow rate was 23 L min-1 (6 gpm) during furrow advance, and 15 L min-1 (4 gpm) for the balance of the irrigation. The nature of charge on the polyacrylamide did influence efficacy of erosion control. On Portneuf soils, the order of effectiveness with respect to PAM charge type was: anionic > neutral > cationic. Within anionic and cationic charge types, polyacrylamide efficacy increased with increasing charge density

Furrow irrigation water-quality effects on soil loss and infiltration

Irrigation-induced erosion is a serious problem in the western USA where irrigation water quality can vary seasonally and geographically. We hypothesized that source-water electrical conductivity (EC) and sodium adsorption ratio (SAR = Na/[(Ca + Mg)/2]^0.5, where concentrations are in millimoles of charge per liter) affect infiltration and sediment losses from irrigated furrows, and warrant specific consideration in irrigation-induced erosion models. On a fallow Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid), tail-water sediment loss was measured from trafficked and nontrafficked furrows irrigated with waters of differing quality. Treatments were the four combinations of low or high EC (0.6 and 2 dS m-1) and low or high SAR (0.7 and 12 [mmolc L-1]^0.5). Slope is 1%. Twelve irrigations were monitored. Each furrow received two irrigations. Main effects for water quality, traffic, and first vs. second irrigations were significant for total soil loss, mean sediment concentration, total outflow, net infiltration, and advance time. Average tail-water soil losses were 2.5 Mg ha-1 from low EC/low SAR furrows, 4.5 Mg ha-1 from low EC/ high SAR furrows, 3.0 Mg ha-1 from high EC/high SAR furrows; and 1.8 Mg ha-1 from high EC/low SAR furrows. Elevating water EC decreased sediment concentration from 6.2 to 4.6 g L-1, but increasing SAR increased sediment concentration from 6.2 to 8.7 g L-1. Net infiltration decreased 14% in high SAR compared with low SAR treatments. Soil loss increased 68% for second irrigations, and net infiltration fell 23% in trafficked furrows, but water-quality effects were the same. Water quality significantly influenced infiltration and erosion processes in irrigated furrows on Portneuf soils

Influence of irrigation water quality on sediment loss from furrows

Agricultural erosion research has focused on rainfall-induced soil loss, with comparatively little attention to furrow irrigation-induced erosion. One rationale for this is that rill erosion is mechanistically similar to erosion in irrigated furrows. However, significant differences exist between the two processes. These are related to soil conditions during initial stream advance, downstream flow rates, and chemical characteristics of the water stream. The salinity and sodicity of water in rills are low, owing to its atmospheric origin, whereas, irrigation water quality varies geographically and seasonall

Changes in groundwater quality and agriculture in forty years on the Twin Falls irrigation tract in southern Idaho

Better understanding agriculture’s effect on shallow groundwater quality is needed on the southern Idaho, Twin Falls irrigation tract. In 1999 and 2002-2007 we resampled 10 of the 15 tunnel drains monitored in a late-1960s study to determine the influence of time on NO3-N, dissolved reactive P (DRP), and Cl concentrations, and flow rates of shallow groundwater outflows.Since the late-1960s, an 8-fold increase in the dairy herd has driven shifts toward increased feed cropping, which, along with improved hybrids and production, increased inorganic and manure fertilizer use. The late-1960s to early-2000s period saw a consistent 1.4-fold increase in mean tunnel-drain outflow NO3-N concentrations (from 3.06 to 5.06 mg/L), a 10% decrease in mean Cl (from 49.2 to 44.2 mg/L), and an overall 14% decrease in DRP (14 to 12 µg/L). However, 3 of the 10 tunnels exhibited increased DRP concentrations during the period, and the rate of DRP increase was positively related to increasing encroachment of confined animal feeding operations or residential development. Decreases in tunnel flow between sampling periods were linearly related to corresponding increases in the fraction of sprinkler irrigation employed on lands drained by the tunnels (P = 0.01). Further conversion to sprinkler irrigation is unlikely to reduce tunnel drain NO3-N concentrations since the latter were unrelated to changes in sprinkler coverage. The amount and timing of applied N, and availability for crop uptake or leaching should be more carefully managed in these soils to prevent continued increases in groundwater NO3-N concentrations

Preventing irrigation furrow erosion with small applications of polymers

Soil erosion is a serious problem threatening sustainability of agriculture globally and contaminating surface waters. The objective of this study was to determine whether low concentrations of anionic polymers in irrigation water would appreciably reduce irrigation furrow erosion on Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid), a highly erodible soil. Furrow slope was 1.6%, furrow length was 175 m, and irrigation rates ranged from 15 to 23 L min-1. Inflow during the first 1 to 2 h of the first 8-h irrigation was treated. Subsequent irrigations were untreated. Polyacrylamide (PAM) or starch copolymer solutions were injected into irrigation water entering furrows at concentrations of 0, 5, 10, and 20 g m-3 . Sediment loss from polymer-treated furrows was significantly less than that of control furrows in the first (treated) and second (untreated) irrigations, but not in the fourth (untreated). The PAM provided better erosion control than the starch copolymer. Efficacy of PAM treatments varied depending on its concentration, duration of furrow exposure, and water flow rate. In the initial (treated) irrigation and at low flow rates, 10 g m-3 PAM reduced mean sediment load by 97% compared with untreated furrows. Residual erosion abatement in a subsequent irrigation, without further addition of PAM, was approximately 50%. The PAM increased net infiltration and promoted greater lateral infiltration. Effective erosion control was achievable for a material cost below $3 ha-1 irrigation-1

Unique aspects of modeling irrigation-induced soil erosion

The mechanics of soil erosion from irrigated and rainfed lands are similar. Soil particles are detached, transported and deposited. However, there are some systematic differences between irrigation and rainfall erosion. Electrolyte concentrations in irrigation water, for example, are almost always greater than in rain water. Differences between rainfall and irrigation are more prominent for surface irrigation than for sprinkler irrigation. For instance, rainfall wets the soil before runoff begins, but water initially flows onto dry soil in irrigation furrows. Furthermore, furrow flow rate decreases with distance and increases with time, while the opposite tends to occur with rainfall. For sprinkler systems, travel direction and slope aspect interact, so runoff can flow within the irrigated area or from the irrigated area onto dry or wet soil. Thus, a sprinkler-irrigation erosion model must consider both the rainfall-runoff situation and the furrow flow situation. These differences in soil and water interactions must be considered before computer models can accurately simulate irrigation-induced soil erosion