A major problem in irrigated agriculture in the Western U.S. is the gradual accumulation of salinity in the plant root zone. These nonuniformly saline soils contain increasing amounts of salinity with depth, and salt accumulation is accelerated in situations where leaching is minimized. Root growth and thus plant yield is limited in these soils due to decreased water uptake. We studied the root growth of two subpopulations of alfalfa differing in their ability to produce fibrous roots to determine if altering root morphology would increase plant yield and water extraction, in an irrigated saline soil. Soil profiles for a control and three treatments with increasing salinity were packed in to PVC cylinders fitted with a flat window down one side for root measurements. A single alfalfa plant was grown from seed in each cylinder, and irrigated with water enriched primarily in sulfate salts. Alfalfa plants were grown for five successive harvests in a greenhouse, and water extraction was measured in the control and high Salinity treatment by time-domain reflectometry. Final electrical conductivities of the soil ranged from 3.0 to 23 dS m-1. The yield of the high fibrous root subpopulation was not reduced by the soil salinity by the fifth harvest, while that of the low fibrous subpopulation was reduced 22%. Root growth of the high fibrous subpopulation was significantly increased by as much as 54% in the upper 30 cm of the root zone, compared to that of the low fibrous subpopulation. Water extraction was higher in the upper, least saline portion of the root zone for the high fibrous root subpopulation. The results of this study support the use of alfalfa with increased fibrous root production under saline irrigation with minimal leaching.

A soils infiltration rate (IR) is the measured rate that soil is able to absorb water, either from precipitation or irrigation. A low IR can cause damage to crops if the necessary amount of water cannot penetrate to the plant roots in the time needed. The damage can be common in permanent plantings such as almond and pistachio orchards where regular tillage is avoided. This indicates a physical aspect to the problem because tillage increases IR. However, there is also an electrochemical side to infiltration problems because certain calcium surfactant treatments can increase IR. Various other methods have been used to increase IR such as using cover crops and increasing organic matter. Despite these different approaches to the problem, the specific cause of low IR is often unknown. This study was conducted to determine what physical properties of soils from a site in California cause low IR. This research shows the relationship of these properties to low IR. It was assumed that high amounts of mica in the very fine sand and coarse silt fraction of soils in Northwestern Kern County, California may interact with other physical and chemical properties to reduce IR. Fourteen sites were sampled in the area near the towns of Wasco and Shafter. The soils sampled represented the typical agricultural soils of the area and exhibited three levels of infiltration, Good (no amendments), Moderate (requires gypsum), and Poor (gypsum application is insufficient). Mica percentages in the very fine sand and coarse silt were calculated using a petrographic microscope and compared to the overall IR of the fields. Mica was shown to be significant factor at all three levels of IR.

The purpose of this study was to determine the accuracy of mapping of pachic and cumulic soils in Cache County. The soil maps that were used for this study as the basemap were the Atlas sheets of the published soil survey of Cache County. Five map units from Mendou, Nebeker, Avon, Hendricks and Winn which include almost 52 percent of the pachic and cumulic soils in the survey area were selected for this study. These five soils cover large areas when compared to other soil series and they are distributed throughout the county. All these map units were recognized as pachic and cumulic in the published soil survey report. The thickness of the epipedon was therefore selected as the principal criterion for determining the accuracy of the map units. About 400 samples from the major delineations were studied in the field and the necessary data were collected and interpreted statistically in order to find: (1) the accuracy of each map unit, (2) the inclusions, misclassified and not classified pedons and their proportions, and (3) the estimated thickness of the epipedons. Attempts were made to select the pedons on transects with appropriate interval, depending on landforms and continuity of soils. Statistical interpretations were conducted by using the chi-square method. The results for each map units are as follows: for Mendon map unit (MeA) 42-56 percent and for Hendricks map unit (HdD) only 30-60 percent of the samples have characteristics required for the named soil in these map units. These values are less than 75 percent which is the critical value for the map units by definition. It is concluded therefore that with the available data the Mendon and Hendricks series have been mapped incorrectly. For Nebeker map unit (NbE) 77-93 percent and from Avon map unit (ArA) 85-99 percent of the samples have the characteristics required for the named soil in the map units. These values are more than the critical value (75) so it is concluded that with available data the Nebeker and Avon series have been mapped correctly. For Winn map unit (Wn) 54-82 percent of the samples have the required characteristics of this series. The statistical analysis did not reveal strictly whether the pedons are mapped correctly or not and additional samples are required to adequately test the accuracy of the Winn map unit. It is concluded that in Cache County the influence of different geologic depositions and variations in topography are two major factors responsible for poor accuracy in mapping the Mendon and Hendricks series.

Frequently, in evaluating plant deficiencies, one considers only those soil factors which are associated with the fertility of the soil-- mainly the levels of phosphorus, potash, nitrogen, and organic matter. A certain level of nutrition is essential for plant growth, but in order for the nutrients to exert their maximum influence on the productivity of the soil, it is equally important that a good soil environment be provided and maintained. A good environment requires that good physical conditions of soil, sir, and water be in balance.

Managing soil hydrophobicity caused by localized dry spots (LDS) on sand based golf greens has become one of the greatest challenges for golf course superintendents and managers, especially as water restrictions intensify. The purpose of this study was to evaluate the effectiveness of thirteen soil surfactants in eliminating LDS and in maximizing root zone soil moisture on a sand based USGA golf green located on the California Central Coast. Potential water repellency of air dried cores (measured utilizing the water droplet penetration time (WDPT) method), phytotoxicity, and climate were analyzed during two experimental trials. Phytotoxicity data was collected for Trial I using visual quality ratings and for Trial II using a chlorophyll meter. Phytotoxicity decreased during Trial I. Differences in phytotoxicity as measured using chlorophyll index were not at all significant during Trial II (p = 1). Ten of the thirteen wetting agent treatments significantly (p < 0.001) decreased soil hydrophobicity compared with the other wetting agent treated plots and the non-treated control. More frequent application of Cascade Plus resulted in a more significant reduction in soil hydrophobicity. Increasing the application rates also resulted in the reduction of soil hydrophobicity. Wetting agent treatment 6-CP(10day) maintained the highest volumetric water content (VWC) but treatment 13-2079337 maintained the highest levels for wetting agents treated monthly.

Rainier, Oregon, has experienced problems in the development of residential and commercial sites, utilities, and transportation facilities as a result of slope instability. This study of slope stability at Rainier was conducted at the request of city officials.

Modern urban stormwater infrastructure includes vegetated bioretention facilities (BRFs) that are designed to detain water and pollutants. Phosphorus (P) is a pollutant in stormwater which can be retained in BRF soils in mineral, plant, and microbial pools. We explored soil properties and phosphorus forms in the soils of 16 operational BRFs in Portland, OR. Since soil hydrology can significantly impact P retention, we selected BRFs along an infiltration rate (IR) gradient. We conducted sequential fractionation and tests of P pools and measured P release in a subset of soils after drying and flooding samples for ten days. We hypothesized that mineral or organic soil P forms would be correlated with IR, and that vulnerability to P release would depend on the interaction of drying and flooding treatments with P forms and pools. IR did not significantly explain differences in P forms. Soil TP was elevated across all sites, compared with TP in agriculturally-impacted wetlands and was substantially composed of soil organic matter (OM)-associated P. Phosphorus sorbed to mineral Fe and Al oxides- was variable but positively correlated with water-extractable P. The concentration gradient of water-extractable P was primarily controlled by overall P pools. Experimentally induced P releases were seen in 5 of 6 soils exposed to drying conditions, presumably released through microbial mineralization of OM. Only one site showed significant P release following the flooding treatment. Our measurements supported the idea that Fe and Al oxides provide P sorption capacity in these BRF soils. Variable inputs of P to BRFs through stormwater and litterfall may contribute to variability in P profiles and P release vulnerability across sites. Design specifications and management decisions relating to bioretention soils (e.g. establishment of acceptable soil test P levels, focusing on P forms known to influence vulnerability of P release) may benefit from detailed biogeochemical investigations.

Soil samples from 118 sites on 71 geologic units in southwest Oregon were collected and analyzed to determine the background concentrations of metals in soils of the region. Sites were chosen in areas that were relatively undisturbed by human activities. The U.S. Environmental Protection Agency approved total-recoverable method was used to recover metals from samples for analysis. The twenty six metals analyzed were: Ag, AI, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, La, Li, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Tl, V and Zn. The Klamath Mountains followed by the Coast Range contain the highest soil concentrations of AI, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, V and Zn. Soils of the Coastal Plain and High Lava Plains contain the lowest concentrations of these metals. Unusually high soil As concentrations are found at two sites in the Klamath Mountains. All Be and Cd values above laboratory's reporting limits are also from the Klamath Mountains and Coast Range. Concentrations of soil Ba and La are fairly uniform throughout the region. Soil Pb levels are generally low with a few exceptions in the Klamath Mountains, Coast and Cascade Ranges. The region west of the Cascade Range has higher soil Hg contents than in the east. Soil metal concentrations are generally much higher in the region west of the Cascade Range, excluding the Coastal Plain, than in the east with the exception ofNa, because of more ultramafic rocks and a wetter climate. Soil metal concentrations are directly related to soil development with the highest concentrations being found in well developed Alfisols and Ultisols and the lowest concentrations in poorly developed Entisols. Most metals have similar averages and ranges of concentration compared to the rest of the United States (U.S.). Metals with high values compared to the rest of the U.S. are Cr, Co, Cu, Mn and Ni. In general, AI, Co, Cr, Cu, Fe, La, Li, Mg, Na, Ni, and V are concentrated in the B horizon while Ba, Ca, Hg, K, Mn, Pb and Zn are concentrated in the A horizon.

Stormwater runoff from existing impervious surfaces needs to be managed to protect downstream waterbodies from hydrologic and water quality impacts associated with development. As urban expansion continues at a rapid pace, increasing impervious cover, and climate change yields more frequent extreme precipitation events, increasing the need for improved stormwater management. Although green infrastructure such as bioretention has been implemented in urban areas for stormwater quality improvements and volume reductions, these systems are seldom monitored to validate their performance. Herein, we evaluate flow attenuation, stormwater quality performance, and nutrient cycling from eight roadside bioretention cells in their third and fourth years of implementation in Burlington, Vermont. Bioretention cells received varying treatments: (1) vegetation with high-diversity (7 species) and low-diversity plant mixes (2 species); (2) proprietary SorbtiveMediaTM (SM) containing iron and aluminum oxide granules to enhance sorption capacity for phosphorus; and (3) enhanced rainfall and runoff (RR) to certain cells (including one with SM treatment) at three levels (15%, 20%, 60% more than their control counterparts), mimicking anticipated precipitation increases from climate change. Bioretention water quality parameters monitored include total suspended solids (TSS), nitrate/nitrite-nitrogen (NOx), ortho-phosphorus (Ortho-P), total nitrogen (TN) and total phosphorus (TP), which were compared among bioretention cells’ inflows and outflows across 121 storms. Simultaneous measurements of flow rates and volumes allowed for evaluation of the cells’ hydraulic performances and estimation of pollutant load and event mean concentration (EMC) removal. We also monitored soil CO2 and N2O fluxes, as they represent a potential nutrient loss pathway from the bioretention cells. We determined C and N stocks in the soil media and vegetation, which are critical design elements of any bioretention, to determine the overall C and N balances in these systems. Significant average reductions in effluent stormwater volumes and peak flows were reported, with 31% of the storms events completely captured. Influent TSS loads and EMCs were well retained by all cells irrespective of treatments, storm characteristics, or seasonality. Nutrient removal was treatment-dependent, where the SM treatments consistently removed P loads and EMCs, and sometimes N as well. The vegetation and RR treatments mostly exported nutrients to the effluent. We attribute observed nutrient exports to the presence of excess compost in the soil filter media. Rainfall depth and peak inflow rate undermined bioretention performance, likely by increasing pollutant mobilization through the filter media. While the bioretention cells were a source of CO2, they varied between being a sink and source of N2O. CO2 fluxes were orders of magnitude higher than N2O fluxes. However, soil C and N, and plant C and N in biomass was seen to largely offset respiratory CO2-C and biochemical N2O-N losses from bioretention soil. The use of compost in bioretention soil media should be reduced or eliminated. If necessary, compost with low P content and high C: N ratio should be considered to minimize nutrients losses via leaching or gas fluxes. In order to understand trade-offs stemming from compost amendments, we conducted a laboratory pot study utilizing switchgrass and various organic soil amendments (e.g., different compost types and coir fiber) to a sandy loam soil contaminated with heavy metals and studied potential nutrient leaching and pollutant uptake. Addition of organic amendments significantly reduced metal bioavailability, and improved switchgrass growth and metal uptake potential. While no differences in soil or plant metal uptake were observed among the amendments, significant differences in nutrient leaching were observed.

Phosphorus (P) is essential to life on Earth and often the limiting nutrient in agricultural systems. P fertilizer is thus an essential resource to maintain food security. In the last half century, agricultural intensification has led to an increase in P fertilizer consumption from 4.6 to 17.5 Tg of P/year to meet rising global food demand. Mineral P (i.e., phosphate rock) is a non-renewable resource in the context of the Anthropocene, and its price is vulnerable to global market fluctuations. Increased efficiency of P use on farms is considered the most effective strategy to conserve P. The soybean industry demands 9.7% of global P use, of which Brazil’s soy industry consumes the most, accounting for 5.8% of the world’s P2O5 use in 2014. This global source of soy production is challenged by the unique tendency of weathered tropical soils, such as Oxisols, to retain (i.e., fix) P in forms that are unavailable to crops. The accumulation of soil P due to years of P fertilization in excess of harvested P is referred to as “residual” or “legacy” P. Historical hotspots for crop production in the US and Europe have relied on residual soil P stocks to maintain yields despite reduced P inputs. Whether Brazil will be able to utilize the same strategy depends on the accessibility of residual soil P stocks when applied fertilizer P is reduced. Field research on this topic remains relatively scarce for cultivated Oxisols in tropical climates. I conducted a field trial at Tanguro Ranch in Mato Grosso, Brazil on a field that has been fertilized at standard high rates for 10 years to test whether residual soil P can be accessed by soy crops. Soy yield response differed significantly (p < 0.05) based on the interaction between fertilization treatment (0%, 50%, or 100% of standard P fertilization) and soil texture. My results highlight opportunities to enhance P fertilizer use efficiency in intensive tropical agriculture.