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Phosphorus Biogeochemistry Across a Precipitation Gradient in Grasslands of Central North America
Get PDFSoil P transformations and distribution studies under water limited conditions that characterize many grasslands may provide further insight into the importance of abiotic and biotic P controls within grassdominated ecosystems. We assessed transformations between P pools across four sites spanning the shortgrass steppe, mixed grass prairie, and tallgrass prairie along a 400-mm precipitation gradient across the central Great Plains. Pedon total elemental and constituent mass balance analyses reflected a pattern of increased chemical weathering from the more arid shortgrass steppe to the more mesic tallgrass prairie. Soil surface A horizon P accumulation was likely related to increased biocycling and biological mining. Soluble P, a small fraction of total P in surface A horizons, was greatest at the mixed grass sites. The distribution of secondary soil P fractions across the gradient suggested decreasing Ca-bound P and increasing amounts of occluded P with increasing precipitation. Surface A horizons contained evidence of Ca-bound P in the absence of CaCO3, while in subsurface horizons the Ca-bound P was associated with increasing CaCO3 content. Calcium-bound P, which dominates in water-limited systems, forms under different sets of soil chemical conditions in different climatic regimes, demonstrating the importance of carbonate regulation of P in semi-arid ecosystems
Managing Runoff Water Quality From Recently Manured, Furrow Irrigated Fields
Get PDFNutrient losses in furrow irrigation runoff potentially increase when soils are amended with manure. We evaluated the effect of tillage, water soluble polyacrylamide (WSPAM) and irrigation management on runoff water quality during the first furrow irrigation on a calcareous silt loam soil, which had received 45 Mg/ha (dry wt.) dairy manure applied in the fall. In Exp. 1 the amended soil was rototilled and irrigated that fall; furrow inflows were either treated with 10 mg/L WSPAM injected into furrow inflows only during furrow advance (Fall-WSPAM), or were untreated (Fall-Control). In Exp. 2 the first irrigation on the amended soil was delayed until the following spring and treatments included rototilled WSPAM (Spring-WSPAM) and untreated rototilled (Spring-Control), or moldboard-plowed soils (Spring-Moldboard). Exp. 3 also delayed irrigation until spring and compared conventional vs. buried lateral furrow irrigation systems. We measured sediment, dissolved organic carbon (DOC), NO3-N, NH4-N, dissolved reactive P (DRP), and total P (TP) concentrations in irrigation furrow runoff. Runoff mass losses from Fall-Control furrows were relatively large: sediment, 4505 kg/ha; DOC, 10.7 kg/ha; NO3-N, 28.1 g/ha; NH4-N, 68.1 g/ha; DRP, 132 g/ha; and TP, 3381 g/ha. Delaying the first irrigation until spring or treating the fall irrigation with WSPAM reduced runoff component losses 80 to 100% relative to Fall-Controls. The Spring moldboard plow reduced runoff DRP mass losses 58% compared to spring rototill (Spring-Control). The buried lateral furrow system decreased runoff losses for sediment 89%, DOC 90%, and TP 82% relative to conventional irrigation. Results from this research demonstrate that several types of management approaches may be successfully employed to substantially reduce offsite nutrient transport during the first irrigation on manured, furrow-irrigated fields
Effects of Insecticide Seed Treatments Impove Sugarbeet Storability
Get PDFSucrose loss in sugarbeet storage is a concern for all roots, but particularly those stored under ambient conditions. In order to control or suppress insect issues in sugarbeet production and consequently improve root storability, two neonicotinoid seed treatments, Poncho Beta (60 g a.i. [active ingredient] clothianidin + 8 g a.i. beta-cyfluthrin/100,000 seeds) and Cruiser Tef (60 g a.i. thiamethoxam + 8 g a.i. tefluthrin/100,000 seeds), were used to produce roots from four commercial sugarbeet cultivars grown in Declo, ID. At harvest, eight-beet samples from each cultivar-treatment combination were collected and placed inside an outdoor pile. Samples were removed on approximately 30-day intervals beginning on December 6 and 8 in 2008 and 2009, respectively. Discolored and frozen root area, weight and sucrose reduction, and sucrose yield were evaluated. Across six-sampling dates, Poncho Beta was always ranked first for recoverable sucrose and performed well for the other variables assessed. Over the three sampling-dates when Poncho Beta was significantly better (P < 0.10) than the non-treated check, recoverable sucrose was increased by an average of 17%. Cruiser Tef tended to rank intermediate between Poncho Beta and the non-treated check for recoverable sucrose and other variables. The insecticide seed treatments not only have the potential limit yield losses and increase profits in the field, but also improve sucrose recovery in storage
Droplet Kinetic Energy from Center-Pivot Sprinklers
Get PDFThe kinetic energy of discrete water drops impacting a bare soil surface is generally observed to lead to a drastic reduction in water infiltration rate due to soil surface seal formation. Under center-pivot sprinkler irrigation, kinetic energy transferred to the soil prior to crop
canopy development can have a substantial effect on seasonal runoff and soil erosion. In the design of center-pivot irrigation systems, selection of sprinklers with minimum applied kinetic energy could potentially minimize the seasonal runoff and erosion hazard. The size and velocity of drops from common rotating spray-plate sprinklers center-pivot sprinklers with flow rates of
approximately 40 and 20 L/ min were measured using a laser in the laboratory. The data were used to evaluate two approaches to characterize the kinetic energy transferred to the soil by rotating spray-plate sprinklers on a center-pivot irrigation system lateral with 3 m spacing between sprinklers. Specific power represents the rate at which kinetic energy per unit area is transferred to the soil as a function of distance from a sprinkler and is analogous to a sprinkler radial water application rate distribution. Specific power was used to estimate actual kinetic energy transferred to the soil by overlapping specific power profiles of sprinklers equally spaced along a center-pivot lateral. Kinetic energy of irrigation sprinklers has traditionally been characterized using area-weighted kinetic energy per unit drop volume. This method heavily favors the largest drops, which travel the farthest from the sprinkler and have the largest kinetic energy and does not account for the volume of water applied by each drop size. Sprinkler kinetic energy per unit volume of sprinkler discharge was not well correlated to actual kinetic energy transferred to the soil by the sprinklers
Infrequent Composted Biosolids Applications Affect Semi-arid Grassland Soils and Vegetation
Get PDFMonitoring of repeated composted biosolids applications is necessary for improving beneficial reuse
program management strategies, because materials will likely be reapplied to the same site at a future
point in time. A field trial evaluated a single and a repeated composted biosolids application in terms of
long-term (13–14 years) and short-term (2–3 years) effects, respectively, on soil chemistry and plant
community in a Colorado semi-arid grassland. Six composted biosolids rates (0, 2.5, 5, 10, 21, 30 Mg ha�1)
were surface applied in a split-plot design study with treatment (increasing compost rates) as the main
factor and co-application time (1991, or 1991 and 2002) as the split factor applications. Short- and longterm
treatment effects were evident in 2004 and 2005 for soil 0–8 cm depth pH, EC, NO3-N, NH4-N, total
N, and AB-DTPA soil Cd, Cu, Mo, Zn, P, and Ba. Soil organic matter increases were still evident 13 and 14
years following composted biosolids application. The repeated composted biosolids application
increased soil NO3-N and NH4-N and decreased AB-DTPA extractable Ba as compared to the single
composted biosolids application in 2004; differences between short- and long-term applications were
less evident in 2005. Increasing biosolids rates resulted in increased native perennial grass cover in 2005.
Plant tissue Cu, Mo, Zn, and P concentrations increased, while Ba content decreased depending on
specific plant species and year. Overall, the lack of many significant negative effects suggests that shortor
long-term composted biosolids application at the rates studied did not adversely affect this semi-arid
grassland ecosystem
Sprinkler Irrigation Effects on Infiltration and Near-Surface Unsaturated Hydraulic Conductivity
Get PDFSprinkler irrigation alters soil hydraulic properties both at and below the soil surface, yet its effects are not well characterized. We evaluated the effects of sprinkler irrigation on infiltration and near‐surface hydraulic conductivity (K) measured under tension in a poorly structured, recently roller‐harrowed Portneuf silt loam (Durinodic Xeric Haplocalcid). The experimental design was a randomized complete block with two treatments (pre‐ and post‐irrigation) and four replications. We used two half‐circle spray heads to apply 127 mm of water at 70 mm h-1 in one irrigation to duplicate 1 × 2 m plots. Unconfined (three‐dimensional) infiltration rates at steady‐state were measured at potentials of -55, -35, and -15mm of water before and about 10 days after irrigation. Irrigation increased surface bulk density (0 to 34 mm) by 18% and increased the saturation ratio by 35%. At -15 mm, the unconfined infiltration rate was 53 mm h-1 before, but 16 mm h-1 after irrigation. At -35 and -55 mm, irrigation decreased infiltration by 68%. Irrigation also decreased infiltration nearly 5‐fold through pores with diameters ranging from 0.55 to 0.86 mm. At each measured potential, irrigation tended to decrease hydraulic conductivity by 48%, on average. Sprinkler droplet impact consolidated unprotected soil and greatly reduced tension infiltration. Our findings provide useful input data regarding this and similar soils for models requiring hydraulic properties. In addition, our results provide valuable insight for managing infiltration and avoiding runoff during a growing season when surface properties change as recently tilled soils are sprinkler irrigated
Commercial Sugar Beet Cultivars Evaluated for Resistance to Bacterial Root Rot in Idaho, 2008
Get PDFEighteen commercial sugar beet cultivars were grown in a commercial sprinkler-irrigated sugar beet field near
American Falls, ID where potatoes were grown in 2007. The plots were planted on 21 Apr 08 and managed according to
standard cultural practices. Plants were free of foliar and root disease symptoms. Four roots representative of each cultivar
were hand topped and harvested on 1 Oct. The roots were then placed in a cold room at 3°C and 90% relative humidity until
they were assayed on 7 Jan 09. The roots were washed, dipped in 0.6% sodium hypochlorite solution for 1 min, rinsed in
sterile reverse osmosis water, and then air dried in a laminar hood. A cross section of the root 8-10 mm thick and 45-70 mm
in diameter was cut just below the widest portion of root and placed in a Petri dish on sterile filter paper moistened with sterile
tap water. A 2-mm diameter and 3-mm deep hole was created with a sterile tooth pick in the center of the root slice. A sterile
tooth pick was then dipped in a 48-hr old culture of Leuconostoc mesenteroides subsp. dextranicum B322 grown on MRS
media at 30°C, and placed in the hole along with a drop of sterile tap water. Four additional root slices served as the non-inoculated check (no bacteria inoculated). The root slice/Petri dish combination was placed in a plastic bag and incubated at
30°C. The experiment was a randomized complete block design with four replications (1 root slice = 1 replication for each
cultivar). The diameter of rotted root area was recorded after 72, 96, and 120 hr. Bacteria from the lesions in each replication
were re-isolated by streaking onto MRS to prove only L. mesenteroides was present. Data were analyzed using the general
linear models procedure (Proc GLM-SAS), and Fisher’s protected least significant difference was used for mean comparisons.
The plants from which the roots were collected were healthy in appearance (no signs or symptoms for any disease
problem). The root slices in the non-inoculated check developed no rot. In the inoculated slices, only L. mesenteroides was
isolated from the bacterial rot lesions. After 120 hr, bacterial rot ranged from a high of 14.8 mm on cultivar HM080012 to a
low of 1.5 mm on cultivar B-13. These data should provide a starting point in the search to identify resistance to L.
mesenteroides in sugar beet. Given the range of responses, improving sugar beet cultivars for resistance to bacterial rot should
be possible
Fifteen Years of Wheat Yield, N Uptake, and Soil Nitrate-N Dynamics in a Biosolids-Amended Agroecosystem. Agriculture, Ecosystems and Environment
Get PDFUnderstanding N dynamics in biosolids-amended agroecosystems can help avoid over-application and the potential for environmental degradation. We investigated 15-years of biosolids application to dryland-wheat, questioning what is the relationship between cumulative grain yield and N uptake (N removal) and biosolids or N fertilizer rates and how many times biosolids or N fertilizer are applied? How are wheat-grain production and N uptake intertwined with residual soil nitrate-N? We found that biosolids or N fertilizer rates plus the number of applications of each material produced planar-regression (3-dimensional) models with 15-years of grain yield and N uptake data (all R2 > 0.93). To evaluate how yield or N uptake impacted residual soil nitrate-N, we completed linear regressions on yield, N uptake, and soil nitrate-N. We then correlated the slopes where P<0.10 for the yield and soil nitrate-N and the N uptake and soil nitrate-N. A significant negative relationship was found for biosolids application for each of these comparisons while the N fertilizer results were inconsistent. For the biosolids treatments, as yield or N uptake increased, residual soil nitrate-N decreased. Our findings show that planar regression models could aid biosolids beneficial-use management programs when considering agroecosystem N dynamics
Nitrogen Response and Economics for Irrigated Corn in Nebraska
Get PDFNitrogen management recommendations may change as yield levels and efficiency of crop production increase. The mean yield with adequate nutrient availability in 32 irrigated corn (Zea mays L.) trials conducted across Nebraska to evaluate crop response to split-applied N was 14.8 Mg per ha. The mean economically optimal N rates (EONR) for irrigated corn varied with the fertilizer N to grain price ratio. At a fertilizer N:corn price ratio of 7, the EONR was 171, 122, and 93 kg per hectare, respectively, for cropping systems with corn following corn (CC), soybean (Glycine max L.) (CS), and drybean (Phaseolus vulgaris L.) (CD). At this price ratio the present University of Nebraska (UNL) recommendation procedure gave mean N recommendations that were 17.2, 0.3, and 68.1 kg per hectare higher than the mean EONR determined in this study for CC, CS, and CD, respectively. The UNL algorithm, adjusted for mean cropping system EONR gave more accurate prediction of site-year EONR than alternative N rate predictions for CC and CD with returns to applied N (RTN) of -13 per hectare compared with measured site-year EONR. Prediction of site-year EONR using mean EONR adjusted for soil organic matter was more accurate for CS than other methods with an RTN of -$6 per hectare compared with measured site-year EONR. Further research is needed to extend the results to: lower yield situations, alternatives to split application of N, and adjustment of EONR to protect against inadequate N in atypical seasons or for environmental protection
Collector design for measuring high intensity time variant sprinkler application rates
Get PDFPeak water application rate in relation to soil water infiltration rate and soil surface storage capacity is important in the design of center pivot sprinkler irrigation systems for efficient irrigation and soil erosion control. Measurement of application rates of center pivot irrigation systems has traditionally used tipping bucket rain gauges. Calculation of application rate from tipping bucket rain gauge measurements restricts computed application rate to a discrete multiple of the rain gauge resolution and time interval. This limits the resolution of application rate measurement, especially for time intervals less than 15 minutes. A collector was designed to measure time variant high intensity sprinkler application rates under field conditions with greater resolution than a tipping bucket rain gauge. The collector funnels water into a 50 mm (2 in.) diameter tube providing a depth multiplication factor of 18.26:1. The depth of water in the tube is measured with a low pressure piezo-resistive pressure sensor connected to a differential amplifier circuit. Combination of the depth multiplication factor of the collector and differential amplifier circuit provides a collector resolution of 1.4 mm/mV. A data logger is used to record water depth in the collector tube during an irrigation event. A digital differentiating filter was designed and used to reduce the effect of random electrical noise in the sensor output on calculated application rate. The collector was tested in the laboratory and under field conditions emulating center pivot sprinkler irrigation. For a range in application rates from 15 to 200 mm/h in the laboratory, the maximum collector error was 2.1 mm/h. Collector measured application rate patterns under field conditions were well correlated to simulated application rate patterns using radial application rate profiles for the sprinklers tested. Collector measured peak application rates were not significantly different from those predicted by the Kincaid (2005) model. The collector functioned as designed in field tests and provided an effective and efficient means of measuring high intensity application rates from center pivot irrigation systems under field conditions