Aggregate stability response to freeze-thaw cycles

Research has suggested that 1 to 3 freeze-thaw cycles (FTCs) may increase the stability of soil aggregates, when field-moist aggregates are wet sieved. The objectives of this laboratory experiment were to quantify aggregate stability of relatively wet aggregates from the Ap horizons of four soils when subjected to either 0, 1, 2, or 4 FTCs and, secondly, to identify a threshold number of FTCs for each soil below which aggregate stability increases. Moist soil was packed into 28-mm-diam., 50-mm-tall brass cylinders by tapping to a dry bulk density of 1.15 Mg m-3, sealed in polyethylene bags, then slowly frozen convectively at —5°C for 48 h, then thawed at +6°C for 48 h for each Fit. The first 1 to 2 FTCs in general increased aggregate stability, but additional Fits had little effect. For 3 of 4 soils, 2 to 3 FTCs appeared to increase aggregate stability to a plateau or threshold. Fits increased aggregate stability, when averaged across the four soils, more in the 0- to 15-mm depth increment than in the 15- to 30-mm increment

Surfactant effects on the water-stable aggregation of wettable soils from the continental USA

Surfactants may affect soil structure differently depending upon the soil or the quality of rainfall or irrigation water. This study examined whether the water-stable aggregation of 11 wettable soils was affected by surfactants and the water in which the soils were sieved. The study also examined whether the wettable soils’ water drop penetration time (WDPT) was affected by surfactants, water drop quality, and elapsed time since the surfactants were applied. Two nonionic surfactants and a surfactant-free water control were sprayed (by misting) upon air-dry soil, then WDPT was measured 1 and 72 h thereafter. Subsequently, this treated soil was slowly wetted with an aerosol to its water content at a matric potential of 3 kPa, then immediately sieved for 600 s in water that contained either appreciable or few electrolytes. Water-stable aggregation, quantified as mean weight diameter (MWD), varied widely among soils, ranging from 0.10 to 1.36 mm. The MWDs were affected (at p = 0.06) by surfactant treatments, depending upon the soil but not sieving water quality. Surfactants affected the MWD of an Adkins loamy sand and Feltham sand, two of the three coarsest textured soils. Although WDPTs never exceeded 5 s, depending upon the soil WDPTs were affected by surfactant treatments but not by water drop quality. After surfactant application, WDPTs generally decreased with time for three soils but increased with time for one soil. Findings suggested that surfactants interacted (1) with clay mineralogy to affect MWD and (2) with soluble calcium to affect WDPT for certain soils. Surfactant treatments but not water quality affected bothMWDand WDPT for some but not all of 11 wettable, US soils

Net Nitrogen Mineralization from Past Years' Manure and Fertilizer Applications.

Manure from the semiarid West’s dairy industries is a rich nutrient source, but its use for crops can be problematic because soil N availability from manure may vary substantially depending on the year of application. Experimental plots established in Idaho on a Portneuf silt loam (coarse silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) included six manure treatments and two non-manure treatments with four replicates. The six manure treatments included combinations of two manure rates, Man-1x (0.31 Mg total N/ha) and Man-3x (0.97 Mg total N/ha) applied in the fall either 1, 2, or 3 years previously. The two non-manure treatments were urea fertilizer applied per soil test (Fert) and a control with no amendment. We measured net N mineralization (0-30 cm) in the plots using buried bags in 2006, 2007, and 2009 for a sprinkler-irrigated barley, sugarbeet, and dry bean crop, respectively. This resulted in i) two years of net N mineralization data for each manure rate applied 1, 2, or 3 years prior to measurement; and ii) one year of data for each manure rate applied 4 or 5 years previous to the measurement year. A 5-year decay series for each of the two manure rates was derived from functions fitted to the net N mineralization data, expressed as a fraction of total manure-N applied. The decay series (y1-y5) for the manure-1x treatment was 0.23, 0.12, 0.10, 0.09, and 0.08 while that for the manure-3x rate was 0.20, 0.08, 0.05, 0.04, and 0.03. Soil at the 30-to-60-cm depth contributed up to 28% of the total N mineralized in the 0-to-60-cm soil layer of manure-amended soils in the 3rd year after application, with lesser amounts contributed in earlier years due to immobilization. The efficacy of N mineralization processes decreased as the manure application increased, thus using a single decay series to predict N availability across a range of manure application rates could lead to substantial estimation errors

Cheese whey effects on surface soil hydraulic properties

Whey, the liquid byproduct of cheese production, can improve the physical condition of sodic soils or those susceptible to erosion by increasing their aggregate stability. The effects of whey on soil hydraulic properties, however, are not known. In this experiment, we used tension infiltrometers to determine whey effects on infiltration rates of water (at suctions s 30 mm of water) and unsaturated hydraulic conductivities of Ap horizons of a Portneuf silt loam (coarse-silts mixed, mesic Durixerollic Calciorthid) after a winter wheat crop. In the summer of 1993 near Kimberly, ID, USA, liquid whey was flood-applied at either 0, 200, 400, or 800 t/ha to plots planted to wheat the previous September. At suctions of 60 and 150 mm, infiltration rates decreased linearly by about 0.7 µtm/s with each additional 100 t/ha of whey applied. As whey applications increased, hydraulic conductivities at 60 mm suction increased slightly but as applications exceeded 400 t/ha decreased significantly. We concluded that summer whey applications up to 400 t/ha would not adversely affect surface hydraulic properties

Sprinkler Irrigation Effects on Infiltration and Near-Surface Unsaturated Hydraulic Conductivity

Sprinkler 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

Nutrients in Runoff from a Furrow-Irrigated Field After Incorporating Inorganic Fertilizer or Manure.

Use of dairy manure to supply crop nutrients is gaining broader acceptance as the cost of fertilizer rises; however, there are concerns regarding manure’s effect on water quality. In 2003 and 2004, we measured sediment, NO3-N, NH4-N, K, dissolved reactive P (DRP), and total P (TP) concentrations in runoff from furrow irrigated field plots (6-7 irrigations/y). Annual treatments included: (M) 13 to 34 Mg/ha stockpiled dairy manure; (F) 78 to 195 kg N/ha inorganic N fertilizer; or (C) control--no amendment. Available N in manure applied each year was similar to amounts applied in fertilizer. Constituent concentrations (mg/L) in runoff ranged widely: sediment, 10 to 50,000; NO3-N, 0 to 4.07; NH4-N, 0 to 2.28; K, 3.6 to 46.4; DRP, 0.02 to 14.3; and TP, 0.03 to 41.5. Fertilizer and manure treatments increased irrigation mean values for NO3-N runoff concentrations (C=0.21, F=0.26, M=0.30 mg/L) and mass losses (C=0.33, F=0.42, M=0.50 kg/ha) relative to controls. Manure treatment also increased mean irrigation runoff DRP (C=0.08, F=0.09, M=0.19 mg/L) and K concentrations (C=0.62, F=0.79, M=1.13 mg/L) compared to controls. Average DRP and K runoff mass losses were 2.0x to 2.4x greater in manure treatments than in controls. Nutrient amendments did not affect season-long cumulative infiltration or seasonal runoff mass losses for sediment or TP. Runoff DRP and inorganic N losses appeared to be influenced more by the timing of the amendment application and environmental conditions, than by the quantity of nutrients applied. Incorporation of nutrients, whether from fertilizer or manure, into furrow irrigated soils can potentially increase nutrient losses in irrigation runoff, depending on the nutrient, amount and timing of application, and whether inorganic fertilizer or manure was applied

The WEPP model for runoff and erosion prediction under center pivot irrigation

The USDA Water Erosion Prediction Project (WEPP) Hillslope model was tested with data taken under traveling lateral irrigation in Southern Idaho. The main parameter affecting infiltration and runoff was the effective hydraulic conductivity. The model was found to predict average runoff and soil loss reasonably well for small slope areas (<40m) and can be used to analyze for potential runoff problems on steep critical areas within a larger field

Nitrogen Availability and Uptake by Sugarbeet in Years Following Manure Application

The use of solid dairy manure for sugarbeet production is problematic because beet yield and quality are sensitive to deficiencies or excesses in soil N, and soil N availability from manure varies substantially depending on the year of application. Experimental treatments included combinations of two manure rates (0.33 and 0.97 Mg total N ha-1) and three application times, and no manure treatments (control and urea fertilizer). We measured soil net N mineralization and biomass, N uptake, and yields for sprinkler-irrigated sugarbeet. On average, the 1-year-old, low-rate manure, and 1- and 2-year-old, high-rate manure treatments produced 1.2-fold greater yields, 1.1-fold greater estimated recoverable sugar, and 1.5-fold greater gross margins than that of fertilizer alone. As a group the 1-year-old, low-rate manure, and 2- and 3-year-old, high-rate-manure treatments produced similar cumulative net N mineralization as urea fertilizer; whereas the 1-year-old, high-rate manure treatment provided nearly 1.5-fold more N than either group. With appropriate manure application rates and attention to residual N and timing of sugarbeet planting, growers can best exploit the N mineralized from manure, while simultaneously maximizing sugar yields and profits

Sprinkler droplet energy effects on infiltration and near-surface, unsaturated hydraulic conductivity

Reducing the impact energy of sprinkler droplets through irrigation management should minimize surface soil aggregate breakdown and seal formation while maintaining infiltration rates. From 1997 through 1999 in southern Idaho, we quantified sprinkler droplet energy effects on infiltration and near-surface hydraulic conductivity measured under tension after crop stand establishment. The treatments were droplet energies: 0 or 7 J kg - (0 or 7 J m - min-1), produced with a low-pressure, lateral-move irrigation system. After planting sugarbeet (Beta vulgaris L.) into a Portneuf silt loam (Durinodic Xeric Haplocalcid) and irrigating 2-3 times, we used tension infiltrometers to measure unconfined (three-dimensional) infiltration rates through undisturbed soil surfaces at three supply potentials. Reducing droplet energy significantly increased steady-state infiltration, averaged across years, at supply potentials of -20 and -40 nun and kept soil surfaces rougher with less aggregate breakdown. Pores with diameters between 0.75 and 1.5 mm were most affected by droplet energy

Sprinkler droplet energy effects on soil penetration resistance and aggregate stability and size distribution

Sprinkler droplet energy degrades surface soil structure. Modifying sprinkler irrigation systems to reduce droplet energy may reduce surface sealing and crusting, thereby increasing emergence. From 1997 to 2001, we evaluated the effects of sprinkler droplet kinetic energies of 0, 8, and 16J kg-1 on in situ surface penetration resistance (PR, a measure of crust strength), aggregate stability (a measure of a soil's resistance to breakdown), and water-stable aggregate size distribution, expressed as a mean weight diameter (MWD). Each year near Kimberly, ID, we planted sugarbeet (Beta vulgaris L.) into an initially tilled field of structurally weak Portneuf silt loam (Durinodic Xeric Haplocalcid), then irrigated two to four times using a lateral-move sprinkler system with spray heads having either smooth or spinning, four-groove deflector plates. After the first and last irrigation each year, we measured PR in situ and collected soil samples at the surface, 0 to 6 mm. When measured after one irrigation, PR increased, and aggregate stability generally decreased as droplet energy increased, although the magnitude of the response differed from year to year. After multiple irrigations, PR decreased linearly with increasing droplet energy, likely due to erosion of the crusted surface. Five-year average MWD after multiple irrigations decreased by 10%, to 0.42 mm, with droplet energies of 8 J kg-1 or more. Trend analysis of soils data from 1998 to 2001 revealed that droplet energies ~10.6 J kg -1 decreased MWD most. Producers should reduce sprinkler droplet kinetic energy to <10.6 J kg-1 to minimize surface structural breakdown of recently tilled soil