Fescue toxicosis can produce negative effects on animal weight gain and physiology. Sixty-four steers were grazed on endophyte-infected (E+) KY-31 tall fescue for 77 days in 2007 and sixty steers grazed for 86 days in 2008 to evaluate interactions with implantation of steroidal implants and concentrate feeding on performance and physiology of yearling steers. Steers were stratified by body weight for assignment to six, 3.0-ha toxic tall fescue pastures. The main plot treatment of with or without pelleted soybean hulls (SBH) were randomly assigned to pastures. Pelleted SBH were group-fed to provide daily consumptions of 2.3 kg/steer/d (as fed). Sub-plot treatments of with or without ear implantation with steroid hormone (200 mg progesterone--20 mg estradiol were assigned to groups of five or six steers within each pasture. Average daily gain in the experiment showed an additive effect of feeding SBH and implanting (P

Corn nitrogen (N) applications are still done on a field basis in Kentucky, according to previous crop, soil tillage management and soil drainage. Soil tests, as well as plant analysis for N, are not very useful in making N fertilizer rate recommendations for corn. Recommended rates assume that only 1/3 to 2/3 of applied N is recovered, variability largely due to the strong affect of weather on the release of soil N and fertilizer N fate. Many attempts have been made to apply N in a more precise and efficient way. Two experiments were conducted at Spindeltop, the University of Kentucky’s experimental farm near Lexington, over two years (2010, 2011), using a commercially available active optical sensor (GreanSeekerTM) to compute the normalized difference vegetative index (NDVI), and with this tool/index assess the possibility of early (V4-V6) N deficiency detection, grain yield prediction by NDVI with and without side-dressed N, and determination of the confounding effect of soil background on NDVI measurements. Results indicated that the imposed treatments affected grain yield, leaf N, grain N and grain N removal. Early N deficiency detection was possible with NDVI. The NDVI value tended to saturate in grain yield prediction models. The NDVI was affected by tillage management (residue/soil color background differences), which should be taken into account when using NDVI to predict grain yield. Side-dress N affected NDVI readings taken one week after side-dressing, reducing soil N variability and plant N nutrition. There is room for improvement in the use of this tool in corn N management.

The use of exotic resistance quantitative trait loci (QTL) provides one strategy for breeding wheat cultivars resistant to Fusarium Head Blight (FHB), a devastating disease of wheat. The objective of this study was to evaluate the effectiveness of two QTL, Fhb1 and QFhs.nau-2DL, in diverse genetic backgrounds and to evaluate their effects on agronomic and quality traits. Five populations from crosses between FHB susceptible parents (26R58, KY97C-0574-01, 25R54, KY97C, KY97C-0554-02, 25R78 and KY93C-1238-17-1) and FHB-resistant VA01W-476, were evaluated in the FHB nursery at Lexington, KY in 2010 and 2011. The populations were also grown in yield trials at Lexington (2010 and 2011) and Princeton (2011), KY, to measure agronomic and quality traits. Fhb1 reduced Fusarium damaged kernels (FDK) by 32% and the toxin, deoxynivalenol (DON) by 20%. QFhs.nau-2DL significantly reduced mean FDK by 29% in two of five populations and DON by 24% in four of five populations. While the effects of these QTL on agronomic and quality traits were significant, the impact was small. One cycle of either direct or indirect simulated phenotypic selection was effective at reducing DON levels and the frequency of Fhb1-homozygous resistant lines among the selects was higher than the frequency of QFhs.nau-2DL-homozygous resistant lines.

Fusarium Head Blight (FHB) is a destructive disease caused by Fusarium graminearum that affects wheat (Triticum aestivum L.) worldwide. Breeding for resistance to FHB is arguably the best way to combat this disease. However, FHB resistance is highly complex and phenotypic screening is difficult. Molecular markers are a promising tool but breeding programs face the challenge of allocating resources in such a way that the optimum balance between phenotypic and genotypic selection is reached. An F2:3 population derived from a resistant x susceptible cross was subjected to phenotypic and genotypic selection. For phenotyping, a novel air separation method was used to measure percentage of damaged kernels (FDK). Heritability estimates were remarkably high, which was attributed to the type of cross and the quality of phenotyping. Genotypic selection was done by selecting resistance alleles at quantitative trait loci (QTL) on the 3BS (Fhb1) and the 2DL chromosomes. Fhb1 conferred a moderate but stable FHB resistance while the 2DL QTL conferred a surprisingly high level of resistance but with significant interaction with the environment. Phenotypic selection conferred higher or lower genetic gains than genotypic selection, depending on the selection intensity. Based on these results, different selection strategies are discussed.

Bermudagrass (Cynodon dactylon L.) is often used for athletic fields due to its wear tolerance and recuperative ability. Studies were conducted May 2007 through November 2008 in Lexington, Kentucky. The cultivars ‘Quickstand’, ‘Tifway’, ‘Riviera’, and ‘Yukon’ grown in a sand-based medium were used to investigate differences in wear tolerance and shear strength. Trinexapac-ethyl (TE) was applied at label rates and frequencies or untreated. Overseeding treatments were perennial ryegrass (Lolium perenne L.) at 0, 612, and 1225 kg PLS ha-1. Traffic treatments were applied with a Brinkman traffic simulator 3 d wk-1 August through October. Shear tests were conducted using the Clegg shear tester once wk-1 for the same period. The main effect of cultivar was significant (p Quickstand=Yukon) and overseeding at the medium and high rates. Significant differences (p Tifway =Yukon (2007) and with Riviera ≥ Quickstand > Tifway = Yukon (2008). Significant differences (p0.05) in either year for traffic tolerance or shear strength.

Creeping bentgrass (Agrostis stolonifera L.) is commonly used on golf course greens and fairways in cool-humid regions but is plagued by numerous fungal diseases, one of which is dollar spot disease (Sclerotinia homoeocarpa F. T. Bennett). Dollar spot occurs frequently throughout the growing season requiring biweekly fungicide applications for complete control. The objective of this study was to investigate methods of reducing the number of fungicide applications needed to maintain dollar spot at acceptable levels through dew removal and potential mechanisms of resistance in bentgrass. In the first study, a combination of mowing three times a week and dragging by hose the remaining four days to remove dew was used in an attempt to reduce disease severity. The main effect of this combination treatment was not significant (p>0.05) and did not reduce the number of fungicide applications compared to normal mowing three times a week. However, dollar spot was managed curatively with 20-80% fewer applications compared to a normal preventative fungicide program. In the second experiment, two experimental germplasms with varying disease resistance were tested for the possible production of antifungal compounds known as phytoanticipins. Preliminary results indicate the resistant line may contain compounds not present in the susceptible line.

Studies were conducted in 2011 and 2012 to determine if narrow row corn (Zea mays L.) and/or greater plant populations could affect yield, time to silking, and other physiological characteristics. Main plots of six hybrids were arranged as a randomized complete bock design with three replications. Split plots were row widths of 76-cm (wide rows) and 20-cm rows on 76-cm spacing (twin rows). Split-split plots were target plant populations of 75 000 and 111 000 plants ha-1. Corn was no-till seeded into soybean stubble near Lexington, KY in 2011 and 2012. Year interacted with most factors analyzed in the study. This was expected, given the extreme differences in weather. 2011 ASI (days) approached zero as plant population increased in wide rows in two out of four hybrids. ASI response to plant population in twin rows was not significant for any hybrid. In 2011, yield was greater in twin rows than wide rows. For significant equations, in 2011 grain yield increased as plant population increased, but in 2012 grain yield decreased as plant population increased, across both row widths. Kernel number per ear decreased as plant population increased in 2011 and 2012, but at different rates for wide and twin rows.

Corn or maize (Zea mays L.) has been grown in North America for many centuries, and an increase in corn production will continue to be needed. Agriculture producers must meet the demands of feeding and providing for an increasing population of people. In order to meet those needs, different production practices are being investigated as a way to increase grain yield. Field plots were conducted across the state of Kentucky in 2011 and 2012 to evaluate the interaction between hybrid, row width, and plant density on corn yield. The primary objectives were to test if 1) narrower rows increase grain yield, 2) higher plant densities increase yield in narrow and twin rows, and 3) the interactions among all factors. Three hybrids were evaluated in three row widths (76, 38 cm or twin) at target densities ranging from 74 000 to 124 000 plants ha-1. Interactions between hybrid, row width, and plant density occurred; however, effects on grain yield and plant physiological characteristics were small and variable across all environments. Plant density had the greatest impact on IPAR and grain yield. Field trials were conducted near Lexington and Princeton, Kentucky in 2011 and 2012 to evaluate the effects of row width on different weed management treatments in corn. The objectives were to 1) evaluate five weed management methods in three row widths (76, 38 cm or twin) and 2) estimate the effect of these practices on corn yield. Herbicides used within each weed management strategy included the residual herbicide S-metholachlor + atrazine (1.4 + 1.8 kg/ha) applied preemergence (PRE) and/or glyphosate (0.86 kg/ha) postemergence (POST). Weed management treatments consisted of a PRE only, PRE followed by POST, POST only, POST + PRE, and an untreated control. Row spacing had little effect on weed suppression and control except for two cases. In general, PRE followed by POST and POST + Residual treatments controlled weeds better compared to PRE only and POST only treatments. Corn yields were higher when a herbicide was used compared to applying no herbicide application. KEYWORDS: Row spacing, Plant Density, Corn Hybrids, Weed Management, Herbicide Application Timing

A field study evaluating the sustainability of four organic vegetable production systems was conducted in Lexington, Kentucky in 2006 and 2007. The four systems included no-till, raised beds covered with biodegradable black mulch, bare ground with shallow cultivation, and bare ground with shallow cultivation and wood chip mulch. The two-year study compared yield, weed control, labor, and costs associated with each system, as well as physical, chemical, and microbiological soil characteristics. In 2006, tomatoes (Lycopersicon esculentum Mill.) were grown in the four systems, with no significant difference in yield. Summer squash (Cucurbita pepo L.) was grown in the four systems in 2007. The no-till system had significantly lower yields than other systems. The bare ground with cultivation and mulch system had the best weed control in both years.

Corn (Zea mays L.) defoliation experiments have been conducted for more than 120 years. However, there is limited data on the effect of row width on defoliation in modern hybrids. A two-year experiment was conducted in Lexington, Kentucky with two hybrids (113 relative maturity (RM) and 120 RM), two row widths (38 and 76 cm) and a combination of defoliation timings and severities: 0% defoliation (control), V7-100%, V14-50%, V14-100%, R2-50% and R2-100%. No yield difference among hybrids was observed in 2012. Yields were 26% greater in 38-cm rows than 76-cm rows in 2012. For 2013, corn yield for 38-cm was 10% greater, but hybrid, row width and defoliation interacted. Lowest yields were caused by V14-100% followed by R2-100%. Defoliations of V14-50% and R2-50% reduced yields in some cases. Complete defoliations at V7 did not reduce yields in most comparisons. Light interception below 80% during the critical period was enough to attain maximum yields in defoliated plants. Kernel number and kernel weight were most reduced by V14-100% and R2-100% defoliations, respectively. There is a potential for narrow rows to reduce grain yield losses after a defoliation event, when compared with wide rows.