William O. Thom

Weathered Fly Ash Does Not Affect Soil And Biosolid Carbon Mineralization

Fly ash and biosolid wastes can be mixed and applied to soil as a means of disposal. A significant decline in soil respiration following waste application indicates restricted activities of functional microbial populations. Weathering decreases salinity and neutralizes alkalinity in fly ash, but there is little information on the effects of unweathered fly ash and biosolid mixtures on soil carbon (C) mineralization. The objective of this study was to determine the effects of a weathered fly ash–limestone scrubber residue (LSR) mixed with an aerobically digested biosolid on soil respiration in a laboratory incubation study. Biosolids significantly increased carbon dioxide (CO2) production (p < 0.05), but up to 6.75% (w/w) fly ash did not. Mean total C mineralization was 770 mg CO2‐C kg−1 soil in the control and 3,810 mg CO2‐C kg−1 soil in the 6.75% (w/w) biosolid treatment. Fly ash with neutral pH and low salinity appears unlikely to affect soil and biosolid C mineralization.

Denitrifying bacteria stratify above fragipans

Fragipans are impermeable layers in soil that affect more than 950,000 ha of land in Kentucky and create seasonally perched water tables that may promote denitrifier growth and activity. We used denitrification enzyme activity assays and Most Probable Number (MPN) estimates of soil and water samples

Effect of strip band and in‐row placement of phosphorus and potassium fertilizer on growth, yield, and efficiency of potassium use by burley tobacco

Abstract A replicated field experiment was conducted at Lexington, Kentucky on Maury silt loam soil (Typic Paleudalf) using burley tobacco (Nicotiana tabacum L. cv. KY 14). The purpose of the study was to determine the response of burley to placement (banding) of N‐P‐K fertilizer in or near the row. The experimental soil used tested low in potassium (K). Treatments consisted of various application rates of grade 6–24–32 (N‐P2O5‐K2O) fertilizer applied either broadcast, in 40 cm wide bands directly under and parallel to the row, in 10 cm wide bands applied 50 cm apart and perpendicular to rows, or in two drill bands each 10 cm to the side of the row. Additional nitrogen fertilizer (NH4NO3) was applied to all plots to provide a uniform rate of 265 kg N/ha. Results indicated that plant response increased as rate of 6–24–32 fertilizer increased and response was greater in all band treatments than the broadcast control. As contrasted to broadcast applications, in‐row placement of fertilizer in 40‐cm wide bands...

Soybean pod wall P and K as related to extractable P and K and grain yield

Abstract It was proposed that the pod wall surrounding the developing soybean seed (growth stage R6) could serve as a diagnostic indicator of crop nutritional status. This was evaluated by summarizing soybean responses (R1 trifoliate and R6 pod wall P and K concentrations, and yield) to various levels of soil P and K availability in ten field experiments. Pod wall P and K concentrations were closely related to available soil P (Bray P1) and K (MNH4C2H3O2‐pH 7.0), respectively. The relationship of pod wall P concentration to grain yield was superior to those found when either trifoliate leaf P or available soil P was related to grain yield. Pod wall K was similarly superior to leaf K or available soil K. Though further work is needed to describe changes in pod wall composition during grain‐fill, it appears that pod wall sampling offers an alternative or additional sampling interval in the evaluation of soybean nutrition