Academic literature on the topic 'Agriculture - Agronomy - Crop Science'

Companion crops are commomly seeded with alfalfa in the spring as an establishment method. The objectives of this research were to evaluate the performance of seedling Alfalfa (Medicago sativa L.) in terms of yield when grown with spring oats (Avena sativa) as a companion crop and to evaluate the amount of weed control in the alfalfa companion crop seeding, under various management practices. Six establishment treatments were imposed: (1) solo-seeded alfalfa raised according to standard procedures recommended for Kentucky, (2) solo-seeded alfalfa with a herbicide treatment, (3) alfalfa seeded with an oat companion crop and treated with a herbicide, (4) alfalfa seeded with an oat companion crop with harvest at 10cm to 21cm of height, (5) alfalfa seeded with an oat companion crop, oats removed for haylage, and (6) alfalfa seeded with an oat companion crop, allowing the oats to produce seed before harvest. In the first seeding year (1992) the alfalfa and oat companion crop that was treated with a grass herbicide had siginificantly higher yields than the check or alfalfa and oat companion crop that was allowed to produce seed. In the second seeding year (1993) there were no significant differences among the establishment methods. The second year of the 1992 seeding experiment had unexpected results. The alfalfa and oat companion crop treated with a grass herbicide had greater yields compared to all other treatments except the alfalfa and haylage oat companion crop treatment. These results indicate that proper management of the companion crop system for highest yields and best performance of alfalfa has not been determined or established.

The Triticeae tribe DUMORTER in the grass family (Poaceae) includes the most important cereal crops such as wheat, barley, and rye. They are also economically important forage grasses. Elymus is the largest and most complex genus with approximately 150 species occurring worldwide. Asia is an important centre for the origin and diversity of perennial species in the Triticeae tribe, and more than half of the Elymus are known to occur in the Asia. Cytologically, Elymus species have a genomic formula of StH, StP, StY, StStY, StHY, StPY, and StWY. About 40% of Elymus species are still unknown for the genomic constitution and some have questionable genomic combination. However, the origin of the Y genome is unknown. In order to identify the origin of the Y genome, 212 accessions of Elymus, Pseudoroegneria, and Hordeum species were tested using a Y genome specific Sequence Tagged Site (STS) marker. We obtained evidence supporting the hypothesis that the Y genome in some Elymus species shared a progenitor genome with the St genome. Our study suggested that Pseudoroegneria spicata (PI 232134), P. ferganensis (T 219), and P. libanotica (PI401326) are the donors of the Y genome in the Elymus species. The DNA sequences of the Y-genome marker in these three Pseudoroegneria species are more similar to those obtained from Elymus species having the Y genome than those from Hordeum marinum and H. murinum, making the Xa and Xu genomes less likely the donors of Y genome.

<p> Glyphosate-resistant weeds in North Dakota and Minnesota sugarbeet growing regions have necessitated research on S-metolachlor. S-metolachlor can be applied early-postemergence in sugarbeet but has not been labeled preemergence as reductions in sugarbeet safety have been observed. Field and growth chamber experiments were conducted to determine crop safety from S-metolachlor applied preemergence. S-metolachlor readily bonds to soil clay and organic matter. High clay and organic matter soils buffer S-metolachlor from soil solution and increase crop safety. Sugarbeet emergence was affected by soil series, temperature, and soil water, but was not affected by S-metolachlor or S-metolachlor rate. S-metolachlor affected sugarbeet growth, but a rate of 0.54 kg ai ha^-1 was safe across soils and growing conditions. No differences in varietal tolerance were observed. S-metolachlor applied immediately after planting or at the cotyledon and two-leaf stage injured sugarbeet less than application 3, 5, or 7 d after planting.</p>

The effect of black polyethylene mulching and drip irrigation on the yield and quality of three cultivars of bell pepper was studied during the 1987 growing season. This study was conducted on a Pembroke silt loam soil on the Western Kentucky University Farm in Bowling Green, Kentucky. The experimental design was a split-plot arranged in randomized complete blocks in four replications with treatment as the main plot and cultivars as the sub-plot. 'California Wonder,' 'Lady Bell F1 Hybrid: and' Keystone Resistant Giant' cultivars of bell pepper were established in the field during the last week of May. The cultivars were grown using black polyethylene, with application of irrigation (no mulch) and without irrigation or mulch (check) Irrigation was initiated in early August and continued throughout the remainder of the growing season; the amount per application was 158.8 m3/ha. At harvest, mature green fruit were removed from the plant, weighed, and classified as grade I or II. There were significant differences at the 5% level in the yield of the cultivars. There were significant differences at the 5% levels among the yields of the treatments. the higher yield was obtained with irrigation, followed by the use of mulch. The better yield under each of the three treatments was obtained with the cultivar Lady Bell. The production of grade II peppers Was higher than the production of grade I peppers, the average yield was 48.82 MT/ha, and 21.99 MT/ha, respectively. The yield of bell pepper grade II was higher in all three treatments.

The effects of within-row spacings and cultivars on the yield of bush snap beans (Phaseolus vulgaris L.) were studied in two experiments. In each experiment, two cultivars and four within-row spacings (8, 15, 23 and 30 cm) were arranged in a split-plot with four replications. Spacing treatments were the whole plots and cultivars were the split plots. In 1988, the two cultivars were 'Blue Lake 274' and 'White Half Runner'. In 1989, the cultivars were 'Blue Lake 274' and 'Kentucky Wonder 125'. All rows were spaced 91 cm apart. Pods were harvested and oven dried. The data were subjected to analysis of vlriance procedure for a split-plot design, assuming a fixed model. In 1988, White Half Runner was significantly higher yielding than Blue Lake 274. In 1989, yield of Kentucky Wonder 125 was significantly greater than that of Blue Lake 274. Bean yields were significantly influenced by spacing treatments in 1988 and 1989. Yields per plant were significantly higher for the 30-cm than for the 15- and 8-cm spacings. Yields for the 23-cm spacing treatment were significantly higher than those for the 8-cm treatment. Yields per meter of row showed no significant differences at any spacings. The linear effect for spacings was significant for both yield per meter of row and yield per plant in 1988 and 1989.

The removal of terminal buds (topping) and sucker control are two practices that have an impact on yield and quality of dark tobacco (Nicotiana tabacum L.). Topping breaks apical dominance and encourages the growth of axillary buds (suckers). Following topping, growth regulator chemicals known as suckercides are commonly used to prevent axillary bud growth. Research has demonstrated that topping time, height, and sucker control method influence the quality and yield of the final product. Delaying topping past a critical developmental stage has been shown to reduce leaf yield. Topping height varies among geographical regions with most dark tobacco producers topping to a height of 12 to 16 leaves. Previous studies indicate that plants topped to 16 leaves had higher leaf yields than those topped to 12 leaves if late-season soil moisture was adequate. The opposite effect was observed when late-season soil moisture was below average because the small upper leaves on plants topped to 16 leaves did not receive the moisture needed for proper development. The moisture they did receive could have been diverted to improve the yield and quality of the larger, more valuable leaves if the smaller ones had been removed. Several options exist for chemical control of tobacco axillary buds ranging from contact to systemic materials. Performance of these materials is influenced by several factors including environmental conditions prior to and following application. Research plots were established at Western Kentucky University's Agricultural Research and Education Complex in Bowling Green, Kentucky to evaluate the efficacy of various sucker control methods and evaluate the effect of topping height on axillary bud growth. Data collection was completed in the summer of 2000. Three sucker control methods and three topping heights were investigated. The first sucker control method was a single application of a local systemic suckercide at topping. The second method was a sequential application using a contact suckercide at topping followed by a local systemic applied seven days later. The third method, which served as the control, was topping the plants but not applying any suckercides. The experiment utilized a split-plot design with 9 treatments and 4 replications. The plots consisted of two 7 m rows per plot, with 102 cm row spacing and 89 cm in-row spacing. Data collected include number of suckers per plant and kilograms of sucker biomass per plant. Statistical analysis indicated no sucker control method by topping height interaction; thus sucker control and height data are discussed separately. Suckers per plant and sucker biomass per plant did not differ among those plots receiving a suckercide application. Topping height did not influence sucker number or biomass.

This research project that was conducted to provide evidence that composted organic waste materials do provide comparable nitrogen absorption efficiency in relation to an organic slow release fertilizer. Western's compost facility supplied the two different organic wastes, which had been composted for 1 year. The materials used were composted urban leaf litter, sawdust/manure mixture at a 50/50 ratio by volume and an organic fertilizer IBDU. These materials were applied to one cultivars of (Agrostis capillaries) and three cultivars of (A. palustris) at the rate of .S^/IOOO**2 in the months of April, June, and September. The plots were sampled one month after application to evaluate the nitrogen concentration of the leaf and thatch material. The nitrogen concentration was measured by using a Leco 2000 CHN provided in the Dept. of Chemistry. In comparison of N recovery in leaves, "Exeter" had lower N concentration than the other cultivars in October and no difference in May and July of the first year. The leaf concentration for the second year showed that Penncross and L-93 were lower in May and were the same for the other two sample dates. There was no difference found in the N concentration of thatch among the fertilizer sources for both years. IBDU showed better N recovery in all but the last sample date where all treatments were the same.

Isolates of Citrus Tristeza Virus (CTV) in Belize may be causing inverse stem pitting, stunting, and slow decline on sweet and sour orange rootstock combination on field trees. One isolate on Cleopatra mandarin rootstock expressed no field symptoms but may be a possible source of a detrimental isolate to more susceptible citrus rootstock combinations. Field plants and field source inoculated indicator plants were used in this study. The first objective was to determine whether field trees of sweet Valencia orange trees that expressed symptoms of CTV would test positive to a polyclonal (mild and severe symptoms) and a monoclonal (severe decline) antibody. Of the 81 trees tested, 56% tested positive to a polyclonal antibody G-604. None of the trees tested positive to the monoclonal antibody MCA-13. The second objective was to determine the biological and serological reactivity on host indicator plants of some of the most symptomatic trees having highest optical density value readings from the ELISA test. Mexican lime showed mild to moderate vein clearing on three of the isolates tested, while sweet orange showed mild to moderate translucent veins on two of the isolates tested. Four isolates from the indicator host plants tested positive to polyclonal antibody G-604 but none tested positive to MCA-13. The third objective was to determine if there were any differences among the nucleotide sequences of three CTV isolates. The CTV coat protein gene (CPG) of isolates which reacted to a polyclonal antibody G-604 but not to monoclonal antibody (MCA-13) was selectively amplified by polymerase chain reaction from infected tissue extracts and sequenced using negative sense CN 407 primer. All three isolates revealed between ninety-eight and ninety percent significant identities to known CTV isolates previously characterized from citrus growing regions around the world.

Field experiments were established in 2000 and 2001 at the Agricultural Research and Education Complex in Bowling Green, Kentucky to evaluate herbicide efficacy on annual morningglory (Ipomoea spp.) species and other weeds. A randomized complete block design was utilized in each study with each treatment being replicated three times. Plots consisted of four 76 cm rows, 9.1 m in length. The two center rows of each plot were treated, with the outside rows of each plot serving as a weedy check. Crop response, weed control, and grain yield data were collected. Four different experiments were conducted. Two experiments utilized treatments of glyphosate and sulfosate alone and with tankmixes on glyphosate-tolerant soybeans. Two experiments examined various herbicide tankmixes applied to non-glyphosatetolerant soybeans. Soybean injury influenced by postemergence treatments of glyphosate and sulfosate alone and with chlorimuron-ethyl ranged from 0 to 5% four days after treatment (DAT) with the addition of chlorimuron-ethyl resulting in greater injury. Morningglory control 14 DAT ranged from 48 to 63% with sulfosate at 700 g ai/ha providing less control than glyphosate at 1120 g ai/ha. No treatment differences occurred 29 and 42 DAT. No statistical differences among treatments occurred among other weed species evaluated. Soybean injury influenced by postemergence treatments of glyphosate and sulfosate alone and with fomesafen and chloransulam-methyl 4 DAT ranged from 0 to 17% with the addition of fomesafen resulting in greater injury than the addition of chloransulam-methyl. Momingglory control 14 DAT ranged from 60 to 88% with glyphosate + imazethapyr at 840 + 71 g ai/ha providing the least control and sulfosate + fomesafen at 700 + 201 g ai/ha providing greater control. Soybean injury influenced by pre and postemergence treatments 7 DAT ranged from 0 to 30% in conventional soybeans. Applications of carfentrazone resulted in the greatest injury. Momingglory control 20 days after planting (DAP) ranged from 0 to 99% with chloransulam + sulfentrazone providing the highest control. Momingglory control 28 DAT ranged from 30 to 99% with s-metolachlor + metribuzin + acifluorfen + fenoxaprop-ethyl + fluazifop-P providing the least control. Common cocklebur control ranged from 13% to 97% 20 DAP with pendimethalin + imazethapyr providing the least control. Treatments containing aciflourfen + bentazon controlled common cocklebur > 80% 28 DAT. Soybean injury influenced by preemergence and postemergence treatments 7 DAT in conventional soybeans ranged from 0 to 33% with sulfentrazone + clomazone + chlorimuron-ethyl + carfentrazone resulting in the greatest injury. Momingglory control 7 DAT ranged from 0 to 99% with sulfentrazone + clomazone plus chlorimuron-ethyl + carfentrazone having the greatest control. Momingglory control 28 DAT ranged from 82 to 94% with no differences among treatment.