Application of phosphorus fertilizer can lead to changes in soil test P and increase both labile and non-labile phosphorus pools. Sequential fractionation showed that the labile (H2O-P and NaHCO3-P) fractions significantly (P < 0.05) increased with the addition of phosphorus fertilizer across all sites. Significant increase was observed in the non-labile (NaOH-P, HCl-P and Residual-P) fractions during the accumulation phase. During the depletion phase, when no further P was added, the accumulated P in the labile P fractions declined but not to the original level. The rates of P application, soil properties, soil test P methods used and time effect all had significant effects on soil test P changes in the extraction experiment. Mehlich-3 extracted the greatest amount of P from the two depths and Olsen-P was intermediate while the smallest amount was extracted with water. The pattern of the rate of change in extractable P with P addition for the 0 – 7.5 cm depth was not site dependent as the results obtained at the different sites were similar. / October 2016

Land application of biosolids as a soil fertility amendment is an alternative to traditional disposal methods. The influence of annual Alkaline Treated Biosolids (ATB) land application on phosphorus (P) dynamics in acidic soils needs to be better understood for more efficient P management. This study examines plant uptake, plant available, soil total phosphorus (P) content and potential P accumulation as a function of rate and frequency of application of an ATB amended to an agricultural soil over four years. The results suggest that applying high rates of ATB annually can increase the soil pH, Mehlich 3 and water extractable P, and crop P uptake in an acidic agricultural soil. No significant soil P accumulation was observed and P related environmental concerns were limited in this study. Potential soil P accumulation and higher P loss needs to be considered with annual high ATB rates application over a longer period study. / N/A

Master of Science / Department of Agronomy / David B. Mengel / Over the last decade low (< 130 mg kg -1) soil test potassium (K) levels and increased crop K deficiency have become a major concern in the clay-pan soils of southeast Kansas. The use of more intense crop rotations and the increased production of high K extracting crops (e.g. soybeans (Glycine max L.)) has significantly increased K removal from these soils. In addition, the traditional use of the nutrient sufficiency-based fertilizer recommendations has resulted in K application rates being substantially lower than removal rates. Because of these practices, many soils that had naturally elevated K availability 25 years ago have declined in K content. More troubling is the extreme yearly variation of soil test exchangeable K levels reported in the region, which has many producers and consultants concerned about proper K management. This study was initiated to examine the extent of K soil test variation and to determine if the variability is impacting plant K availability by analyzing soybean leaf K content and crop yield. A major objective of our research is to identify the mechanism(s) driving these changes in soil test K levels and K availability to crops during the growing season. The long-term goal is to be able to design a soil sampling system and develop alternative K fertilizer recommendation strategies that could alleviate K deficiency impacts on crop yield. Evaluation of different K fertilizer application practices including rate of application and broadcast or surface band methods of application were studied as tools to correct soybean K deficiency. The direct and residual impacts of K fertilization and placement were also evaluated on corn (Zea mays L.) grown in the rotation with the soybeans. Results observed from this research showed that monthly soil samples taken during three crop years at multiple locations have ammonium acetate exchangeable K levels that indeed change dramatically. The data we collected together with data accumulated by farmers and crop consultants showed significant fluctuation in exchangeable K levels of up to 50% on a yearly and even on a monthly basis. Levels seem to demonstrate seasonal changes: higher in the spring months and then decline in the summer and fall. Potassium soil test levels also appear to follow a similar trend as monthly precipitation and soil moisture status. During wet months soil levels tend to increase and then decline during drier months, however, this is not a perfect relationship and other factors are likely to be involved in regulating soil test K levels. No clear effect of K fertilization or method of placement on soybean or corn yields was observed during the study. However, soybean leaf samples revealed that on very low (< 90 mg kg -1) soil test sites surface band applied fertilizer increased leaf K concentrations compared to broadcasted applications. Furthermore, the corn study revealed no distinct difference between using a split annual or biannual fertilizer application system. Maintaining soil test K levels above 130 mg kg -1 using a spring soil test appears to be a successful strategy for avoiding K deficiency. Traditionally most soil sampling occurs in late summer or fall when soil conditions are dry. Our data has demonstrated that during this period one should expect to encounter low soil test results that may not be true indicators of soil K levels during the spring planting months. With that said, spring soil sampling can be difficult to do in a timely fashion due to weather, as well as potential labor restrictions. Another critical point is to not switch back and forth between spring and fall sampling dates. Staying consistent with your sample timing will minimize the seasonal variability that is frequently experienced. Additionally, adopting a build and maintain fertilizer recommendation philosophy rather than a nutrient sufficiency-based recommendation approach is a better nutrient budgeting method to avoid having removal rates exceeding nutrient additions. The best K management proposal would be to consider using a build and maintain approach in combination with basing fertilizer rates on spring soil test K levels.

A field experiment was conducted at two locations in Utah, one at Erda in Tooele County and the other at Minersville in Beaver County. Each experiment was designed as a randomized block design with five treatments and four replication s for each treatment. The test crop was alfalfa. Three cuttings were taken from each location to estimate the yield. Soil samples from the first 12 inches and subsoil samples from 12-24 inches were taken to determine the available NaHCO3-P in the soils. Plant samples were taken to determine the P content of the crop. The results showed that with 5 ppm soil-test P, P content in crop was above the critical level. There was no increase in yield resulting from adding different levels of P to the soil. This conclusion suggests that the criteria used at the soil -testing laboratory at Utah Stat e University should be modified. The criteria used had heen based on samples from the first 6 inches of the soil and from previous investigations. The limit used for low P status for the soil s was 8 ppm.

Increased adoption of compost bedded pack dairy barns (CBP), a relatively new housing and manure handling strategy, warrants study to facilitate proper use of CBP waste as a soil amendment. This study: 1) characterized in situ nutrient content and availability of CBP waste in terms of nitrogen (N) and phosphorus (P); 2) examined the decomposition of surface-applied CBP waste compared to an alternative processed solid waste amendment; 3) examined nutrient dynamics of incorporated CBP waste in high and low soil test phosphorus (STP) environments. Quick anaerobic mineralization assays revealed that bed management affects nutrient content and availability of CBP waste. A Fall surface-applied litter bag study showed that different particle sizes of CBP waste and a biosolid decomposed at similar rates. The biosolid had greater nutrient density and availability, but the decomposition was similar to CBP waste in terms of mineralization dynamics. Aerobic mineralization of CBP waste in high and low STP soils amended on a uniform P basis was compared with fresh manure. In general, CBP increased STP more and yielded more plant available P than fresh manure. These studies provide recommendations for CBP management and further study to ensure the proper land application of CBP waste.

Soil quality problems such as erosion, depleted soil organic matter, salinity, depleted or excessive nutrient reserves and reduced water holding capacity are of increasing concern to farmers in the Intermountain West. Marginal soils require higher rates of fertilizers and other amendments to meet crop needs. As input costs rise and water resources are increasingly limited, simple and effective methods for evaluating and improving soil quality and fertility are of growing importance. Practices known to improve soil quality include reduced to no tillage, cover crop use- especially legumes, and addition of mulch and other carbon rich amendments. Comprehensive soil quality testing is often not routine, cost prohibitive, unavailable or confusing to interpret. The purpose of this study was to develop tools to help growers improve and monitor soil quality. Chapter 1 provides a general overview of the project. Chapters 2 and 3 discuss the effectiveness of simple soil tests that can be performed by growers on-site. The most effective simple soil testing methods were found to be modified slake tests, the Solvita® respiration test kit, and soil organism biodiversity counts (R = 0.88, R = 0.88, R = 0.68 respectively). Simple nutrient test kits, correlated somewhat with laboratory results (the highest correlation was R = 0.80), however no simple test kit was accurate across all tests provided. Chapters 4 and 5 investigate organic nutrient management practices for peach orchards in the Utah, illustrating examples from: Captiol Reef National Park, Torrey, in southcentral Utah; and Utah State University Horticultural Research Farm, Kaysville, in northern Utah.

Newer multi-trait soybean varieties have resulted in greater yields, bringing into question whether current soil test K (STK) correlation, calibration, and recommendations need updating to maximize yield. The objective of this study was to refine soil test correlation and calibration using a range in residual STK levels and response in temporal leaf and seed K concentrations and yield across soybean maturity groups IV and V. For the 0- to 15-cm soil depth STK levels greater than 125 mg K kg-1, K did not limit yield. Critical tissue K varied between years and maturity group. Critical K at R1, R3, and R5 for group IV soybean were 13.5, 13.2, and 12.9 g K kg-1, respectively and 12.9, 12.6, and 10.9 g K kg-1 for group V, respectively. Maintaining optimal STK levels can help ensure profitable and sustainable soybean production in Mississippi.

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The increase in soybean production in Manitoba has raised many questions about phosphorus management for achieving high yields of modern varieties. Soybean’s tolerance to seed-placed fertilizer and response to added fertilizer P were evaluated in a 28 site-year study, and the yield response to soil test P concentrations was evaluated in seven site-years, in a second study. Plant stand reduction caused by fertilizer toxicity when applied with the seed was rare, but was most likely in soils with medium to coarse texture or when seeding equipment lightly disturbed the soil, or provided little seed bed utilization. Severe plant stand reduction decreased seed yield in two site-years. Seed yield increase to P fertilization was rarely observed, regardless of fertilizer P rate, P placement or soil test P. In only one site-year there was a significant effect of fertilizer rate, where 45 and 90 kg P2O5 ha-1 increased yield by approximately 15%, compared to the control. Regardless of soil test P, seed yield response to soil P fertility was never observed. / October 2016

<p>Wood plastic composite (WPC) materials have seen a continuous market growth worldwide in the last decade. So-called extruded WPC profiles are today mainly used in outdoor applications, e.g. decking, railing and fencing. In outdoor conditions, moisture sorption in the wood component combined with temperature induced movements of the polymer matrix causes deformations of such composites. On the macroscopic scale this may lead to unacceptable warp, cup and bow of the WPC products, but on a microscopic scale, the movements will cause interfacial cracks between the particles and the matrix, resulting in little or no ability to transfer and re-distribute loads throughout the material. Moisture within the composite will also allow fungi and micro organisms to attack the wood particles.</p><p>The conceptual idea of this work is to use a chemically modified wood component in WPCs to enhance their long term performance. These chemically modified wood particles exhibit reduced susceptibility to moisture, resulting in better dimensional stability and a higher resistance to biological degradation as compared to that of unmodified wood. The objective of this thesis is to study the effects of using modified wood in WPCs on their moisture sorption behaviour, micromorphology and microbiological durability. The modification methods used were acetylation, heat treatment and furfurylation.</p><p>Equilibrium moisture content (EMC) and sorption behaviour of WPCs were determined by water vapour sorption experiments. The use of thin sections of the composites enabled EMC to be reached within a comparably short time span. The micromorphology was studied by LV-SEM (low vacuum-scanning electron microscope) using a specially designed sample preparation technique based on UV laser. The biological durability was evaluated by laboratory fungal test methods.</p><p>The moisture sorption experiments showed lower moisture levels for all the composites when modified wood particles were used. This was also reflected in the micromorphological studies where pronounced wood-plastic interfacial cracks were formed due to moisture movement in the composites with unmodified wood particles. The sample preparation technique by UV laser proved to be a powerful tool for preparing surfaces for micromorphological studies without adding mechanical defects caused by the sample preparation technique itself. Results from the durability test showed that WPCs with modified wood particles are highly resistant to decay by fungi.</p>