David L. Bjorneberg

EVALUATING WEPP-PREDICTED INFILTRATION, RUNOFF, AND SOIL EROSION FOR FURROW IRRIGATION

The Water Erosion Prediction Project (WEPP) model contains a furrow irrigation component to simulate hydrology and erosion in irrigation furrows. It currently is the only multiple-event furrow erosion simulation model available for public use. However, the furrow irrigation component has not been evaluated yet. Therefore, we evaluated the WEPP model for furrow irrigation by comparing predicted infiltration, runoff, and soil loss with field measurements from three southern Idaho studies on Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids). Baseline effective hydraulic conductivity, rill erodibility, and critical shear were calibrated using data measured from the upper quarter of two fields. Calibrated effective hydraulic conductivity was within the range of WEPPdefined values for Portneuf soil. Calibrated rill erodibility of 0.0003 s m–1 was almost two orders of magnitude less than the WEPP-defined value of 0.02 s m–1, while calibrated critical shear of 1.2 Pa was about one-third of the WEPP-defined value of 3.5 Pa. Predicted infiltration correlated poorly with measured infiltration for most fields. Regression coefficients for predicted versus measured infiltration ranged from –0.07 to 0.35, indicating that predicted infiltration did not vary with measured infiltration. Predicted soil loss correlated well (R2 = 0.57) with measured soil loss from the upper end of the two fields used to calibrate erodibility parameters. At the field ends however, runoff was underpredicted and soil loss was overpredicted. When runoff was predicted reasonably well for an irrigation, cumulated predicted soil erosion across a field did not match cumulated measured erosion at field quarter segments because transport capacity was overpredicted. Deposition was not predicted unless runoff was greatly under-predicted. The WEPP model cannot be recommended for use with furrow irrigation until erodibility parameters and sediment transport are better defined for irrigation furrows.

Greenhouse Gas and Ammonia Emissions from an Open-Freestall Dairy in Southern Idaho

Concentrated dairy operations emit trace gases such as ammonia (NH), methane (CH), and nitrous oxide (NO) to the atmosphere. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. Our objective was to determine the emission rates of NH, CH, and NO from the open-freestall and wastewater pond source areas on a commercial dairy in southern Idaho using a flush system with anaerobic digestion. Gas concentrations and wind statistics were measured and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open-freestall source area were 0.08 kg NH, 0.41 kg CH, and 0.02 kg NO. Average emissions from the wastewater ponds (g m d) were 6.8 NH, 22 CH, and 0.2 NO. The combined emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.20 kg NH and 0.75 kg CH. Combined NO emissions were not calculated due to limited available data. The wastewater ponds were the greatest source of total farm NH emissions (67%) in spring and summer. The emissions of CH were approximately equal from the two source areas in spring and summer. During the late fall and winter months, the open-freestall area constituted the greatest source area of NH and CH emissions. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and other open-freestall production systems in similar climatic regions.

Conservation practice effectiveness in the irrigated Upper Snake River/Rock Creek watershed

The Upper Snake River/Rock Creek Conservation Effects Assessment Project was initiated in 2005 to determine the effectiveness of conservation practices in an irrigated watershed. Our objectives were to determine water and salt balances and water quality effects of using sprinkler rather than furrow irrigation in the Twin Falls irrigation tract in southern Idaho. Data from the current study were compared with earlier studies conducted from 1968 to 1971. Irrigation water diverted from the Snake River supplied 73% and 83% of the hydrologic input to this 82,000 ha (202,000 ac) watershed in 2005 and 2006, respectively, with approximately 40% flowing back to the Snake River through furrow irrigation runoff, unused irrigation water, and subsurface drainage. Net suspended sediment loss decreased from 460 kg ha-1 (400 lb ac-1) during the 1971 irrigation season to 220 kg ha-1 (190 lb ac-1) in 2005 and 10 kg ha-1 (9 lb ac-1) in 2006 by switching from furrow to sprinkler irrigation, applying polyacylamide, and installing sediment ponds. The relative amount of sprinkler irrigation in a subwatershed did not correlate with the total loss of suspended sediment for July 2005 and 2006 (r = 0.12). The lack of correlation was primarily due to extremely high sediment concentrations in two of the five subwatersheds, possibly due to furrow irrigation management. Two potential concerns identified during this initial analysis were an accumulation of total salts in the watershed and increased nitrate concentrations in four return flow streams compared to earlier studies. Future analyses will determine the effects of specific practices with this watershed.

Zone-subsoiling relationships to bulk density and cone index on a furrow-irrigated soil

Zone subsoiling on irrigated land has been successfully used to improve potato (Solanum tuberosum L.) yield and quality. Zone subsoiling under furrow irrigation may disrupt water flow and influence infiltration and soil erosion. We hypothesized that zone subsoiling, done appropriately, will maintain integrity of irrigation furrows, improve small grain and dry bean (Phaseolus vulgaris L.) growth and yield, and not adversely affect water flow, infiltration, or erosion on furrow–irrigated soils. The experiment was conducted at the USDA–ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho. The soil is a Portneuf silt loam (coarse–silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids). Tillage treatments were disk, disk + paratill, paratill, and no–till.There were no differences in water infiltration, runoff, or soil erosion among treatments. Bulk density differences among treatments were largest at the 0.15 to 0.20–m depth, and bulk density was about 16% to 18% greater on disk and no–till treatments than on paratill treatments. The highest frequency of low cone index (CI) values belonged to paratill treatments (65% to 80% frequency of CI values less than 2 MPa); the lowest frequency of low CI values belonged to no–till treatment (20% frequency less than 2 MPa). Cone index versus bulk density relationships depended on soil water content with a slope of 5.81 (r 2 = 0.70) in the wetter year of 1997, and 2.90 in the drier year of 1995 (r 2 = 0.60). Subsoiling can be accomplished on furrow–irrigated lands with no adverse effects on runoff, infiltration, and erosion, but under our conditions did not improve crop growth and yield.

Changes in soil test phosphorus and phosphorus in runoff from calcareous soils receiving manure, compost, and fertilizer application with and without alum

Intensification of the dairy industry in southern Idaho has led to the overapplication of manures and a buildup of soil phosphorus (P), which is a potential threat to water quality in the region. As the use of alum has been shown to reduce both soluble manure P and runoff P from alum-treated manures, the objective of this study was to determine if surface applications of alum to dairy manure and compost before soil incorporation would reduce P losses under furrow irrigation on a calcareous soil. The effects of manure, compost, and fertilizer application with and without alum treatment on soil P, runoff P, and aluminum under furrow irrigation, crop yield, tissue P concentrations, and P removal during a 4-year period were investigated in Kimberly, Idaho, on a Portneuf silt loam (coarse-silty, mixed superactive, mesic Durinodic Xeric Haplocalcids). Fertilizer and manure addition had the greatest potential to increase soluble P in soils compared with compost, which translated to greater soluble P losses with irrigation in some instances. The addition of alum to manure did not have any effect on soil-extractable P or soluble P losses from furrow irrigation and therefore, when surface applied to manure before incorporation, is not a good best management practice for stabilizing P in manure-treated calcareous soils.

PRE–WETTING EFFECT ON FURROW IRRIGATION EROSION: A FIELD STUDY</

Flowing water quickly saturates dry surface soil as water advances in irrigation furrows. Conversely, rain wets surface soil before runoff occurs. Rapid wetting destroys soil aggregates as water quickly displaces trapped air. Slowly increasing soil water content prior to saturation increases aggregate stability. We hypothesized that instantaneous wetting of dry surface soil during furrow irrigation results in greater soil erosion than if furrow soil was pre–wet immediately before irrigation. We conducted ten irrigation trials on 27–m long furrows in three different fields. Soil was pre–wet by surface drip irrigation (12 to 14 mm) or by lightly spraying with water (1.3 mm). Pre–wetting with drip irrigation significantly (P < 0.05) reduced soil loss for 5 of the first 7 irrigations compared to dry soil. The pre–wetting effect on soil loss was not always dramatic, but cumulative soil loss for the first seven irrigations was significantly different among the three treatments: 16, 30, and 56 Mg ha –1 for drip, spray, and dry treatments, respectively. The dry treatment never had less soil loss than either pre–wetting treatment. Pre–wetting furrow soil by spraying apparently did not add enough water to stabilize soil aggregates and decrease soil erosion for most irrigations. This study demonstrated that erosion was greater when water flowed over initially dry soil, which is typical with furrow irrigation, compared to water flowing over initially wet soil, which occurs during rain.

Estimation of Furrow Irrigation Sediment Loss Using an Artificial Neural Network

AbstractThe area irrigated by furrow irrigation in the United States has been steadily decreasing but still represents about 20% of the total irrigated area in the United States. Furrow irrigation sediment loss is a major water quality issue, and a method for estimating sediment loss is needed to quantify the environmental effects and estimate effectiveness and economic value of conservation practices. Artificial neural network (NN) modeling was applied to furrow irrigation to predict sediment loss as a function of hydraulic and soil conditions. A data set consisting of 1,926 furrow evaluations, spanning three continents and a wide range of hydraulic and soil conditions, was used to train and test a multilayer perceptron feed forward NN model. The final NN model consisted of 16 inputs, 19 hidden nodes in a single hidden layer, and 1 output node. Model efficiency (ME) of the NN model was ME=0.66 for the training data set and ME=0.80 for the test data set. The prediction performance for the complete data se...

Comparison of atmospheric stability methods for calculating ammonia and methane emission rates with WindTrax

Inverse dispersion models are useful tools for estimating emissions from animal feeding operations, waste storage ponds, and manure application fields. Atmospheric stability is an important input parameter to such models. The objective of this study was to compare emission rates calculated with a backward Lagrangian stochastic (bLS) inversedispersion model (WindTrax) using three different methods for calculating atmospheric stability: sonic anemometer, gradient Richardson number, and Pasquill-Gifford (P-G) stability class. Ammonia and methane emission data from a compost yard at a 10,000-cow dairy were used for the comparisons. Overall, average emission rates were not significantly different among the stability methods. Emission rates correlated well between the sonic and other methods (r2 > 0.79, p < 0.001). The slopes of the regression lines between the sonic and Richardson methods were 0.95 and 1.0 for CH4 and NH3, respectively. The regression line slopes for the P-G method were about 1.9 for CH4 and 1.6 for NH3, which means emission rates predicted with the P-G method tended to be 50% to 100% greater than rates predicted with sonic anemometer data. Based on this limited data set, using the gradient Richardson method to represent atmospheric stability resulted in emission rates that more closely matched emission rates from the sonic method. Considering the amount of variability inherent in emissions calculations, a three-dimensional sonic anemometer should be used, if possible, to directly provide the necessary data to calculate parameters representing wind properties, rather than inferring values from other stability classification methods.

Influence of tillage and daily manure application on the survival of bacterial pathogens indicators in soil and on radish.

We measured Escherichia coli, and Enterococcus sp. numbers in soil and on fresh radish (Raphanus sativus L.) at 1, 7, 14, 28, 54, and 84 days after the addition of high and low amounts of solid dairy manure in combination with chisel tillage to a 20 cm depth (deep) or roller tillage to a 10 cm depth (shallow). When the high or low amount of solid dairy manure was added to the soil, E. coli populations in soil were higher in the 54 days following manure addition compared to the control treatment. Dairy manure addition increased Enterococcus sp. in soils compared to the control treatment for the entire 84 days sampling period. At harvest, which was 84 days after application, we did not detect E. coli in radish in rhizosphere soil or on radish roots. Addition of solid dairy manure increased Enterococcus sp. numbers in radish rhizosphere soil and on radish roots. We suggest that fresh animal manure be applied to soil at least 120 days prior to planting to allow die-off of human pathogenic bacteria and reduce the incidence of bacterial adhesion on or bacterial colonization of ready to eat vegetables.

Technologies to Minimize Water Quality Impacts of Irrigated Agriculture.

Irrigation transformed arid land in the Pacific Northwest into productive agricultural land. However, much of this land is prone to erosion during irrigation, which can cause problems on and off of the field. Management practices have been developed to control soil erosion on irrigated land and improve the quality of water returning to streams and rivers. Applying polyacrylamide (PAM) with irrigation water can reduce erosion from furrow irrigated fields more than 90%. Using PAM in combination with other practices, such as applying straw mulch in furrows and installing small sediment ponds on fields, can virtually eliminate sediment loss fromfields. Once soil runs off a field, it can be removed by settling in sediment ponds, although soluble nutrients remain in the water. Applying 20 mg/L alum to irrigation return flow water can remove about 50% of the soluble phosphorus that will not be removed as suspended sediment settlesin ponds. Using these management practices allows irrigation to continue with minimal impact on water quality.