Field and lab experiments were conducted to determine the efficacy of sudangrass (Sorghum X drumondii (Nees ex Steud.) Millsp. & Chase) cover crop management techniques and soil solarization on important agricultural weeds and pathogens in organic strawberry production in Central California. Lab experiments assessed the time needed to kill weed seeds at temperatures typically achieved during soil solarization (40°C, 45°C, 50°C, 55°C, and 60°C) in California. Seeds tested included little mallow, redstem filaree, bristly oxtongue, annual sowthistle, common purslane, nettleleaf goosefoot, and redroot pigweed. Efficacy of simulated solarization temperatures differed between different species. Cool-season annuals annual sowthistle and bristly oxtongue were more susceptible to heat treatments than warm-season annuals common purslane, redroot pigweed and nettleleaf goosefoot. Hard seeded weed species little mallow and redstem filaree were the least susceptible to heat treatments. Annual sowthistle, bristly oxtongue and nettleleaf goosefoot were affected at all temperatures. Redroot pigweed and little mallow were not affected by temperatures below 40°C. Common purslane was not affected by temperature below 45°C and redstem filaree was not affect by any temperatures tested. Hours of exposure and percent mortality of weed seeds were used to create thermal death models for weed seeds. Field experiments were conducted at the Cal Poly Organic Farm in San Luis Obispo, CA testing the effects of soil solarization and sudangrass residues on weeds, Verticillium dahliae populations, plant health, and yields in organic strawberry production. Using a split plot design, sudangrass was grown, mowed and then developed into two treatments: surface mulch or incorporated into the soil. The sudangrass treatments and a control were tested with and without soil solarization (n=4). Maximum soil temperatures in solarized treatments were 53°C at a soil depth of 5 cm and 42°C at a soil depth of 15 cm. Solarization reduced weed biomass between 49.8 and 95.2% during the first 3.5 months after tarp removal (p=0.03), reduced Verticillium dahliae populations by 80.7% (p=0.01), reduced plant mortality by 54.9% (pV. dahliae populations (p=0.33) or yields (p=0.25). However, mulched treatments reduced weed biomass between 45.0 and 61.3% (p=0.03) compared to other sudangrass treatments. Results indicate solarization can be used in central coast organic strawberry production to reduce hand-weeding, disease incidence, and increase yields.

Mississippi ranks among the leading states in sweetpotato production in the US. However, managing weeds in sweetpotato fields presents a significant challenge, and the limited availability of herbicides labeled for use in sweetpotato makes it even more challenging. The widespread and repeated use of herbicides has led to the development of weed resistance. In addition, herbicides are incompatible with the organic production system. Finding sustainable weed management strategies to provide weed control options for organic cultivation and detain the development of herbicide-resistant weeds under conventional crop production is imperative. The natural chemicals released by the plants, also called allelochemicals, can potentially suppress weeds and be used for weed management under conventional and organic cultivation systems. The current study aimed to 1) screen the sweetpotato varieties for their weed-suppressing effect on the growth of weeds in controlled conditions using a stair-step structure, 2) evaluate the allelopathic suppression of selected sweetpotato varieties under field conditions, and 3) identify and quantify allelochemicals released by the roots of seventeen sweetpotato varieties. Results of the current study on the availability of allelopathic sweetpotato varieties will benefit organic producers by enhancing crop productivity. They will decrease reliance on synthetic herbicides in conventional farming systems. Identifying and quantifying allelochemicals will also improve our knowledge of allelopathy and provide valuable information for developing allelopathic sweetpotato varieties.

Knowledge of sex allocation trade-offs with tree growth in insect-pollinated woody plants is limited, particularly in invasive plants. This study examined patterns of growth and reproductive investment in a North American invasive plant species, Triadica sebifera, I hypothesized that the energy limitations of smaller trees may result in the production of more male reproductive structures that are energetically less costly. Diameter at breast height was a significant predictor of seed and catkin mass and regression can describe these relationships across sites. Seed and catkin mass were positively correlated across sites. The relationship between the seed mass:catkin mass ratio and DBH was not significant, nor was seed mass:catkin mass and total investment. Results showed a significant positive relationship between total reproductive investment and tree size across sites. Seed mass:catkin mass ratio and reproduction investment showed substantial variation among individual trees of similar size within sites.

Elevated atmospheric CO2 has been implicated as a driver of increased liana abundance worldwide. Known as disturbance creators and beneficiaries, lianas possess the potential to significantly influence forest ecosystems. I investigated the early-invasion dynamics of Euonymus fortunei (wintercreeper), an evergreen liana that is invading forests in eastern North America, disrupting native plant communities and ecosystem functions. Wintercreeper is widely cultivated as an ornamental groundcover, frequently invading natural areas via asexual stem growth. Invasion of remote natural areas is dependent upon seed transport and may occur less frequently. I examined the mechanisms of seed dormancy by conducting a ‘move-along’ experiment using fresh and after-ripened seeds. Additionally, I sought to characterize the nature of seed dispersal by birds by deploying seed traps within an invaded forest in central Kentucky. Wintercreeper seeds displayed conditional nondeep physiological dormancy. Although germination occurs at high velocity following cold stratification, a cold period was only facultative to break dormancy. While fresh seeds had greater germination rates (98.6%) compared to after-ripened seeds (85.7%), after-ripened seeds experienced earlier germination (41 days across all treatments). My findings also indicate that bird-mediated seed dispersal occurs throughout the winter from seeds that after-ripen on maternal liana phanerophytes. Overall, these data suggest wintercreeper seeds are capable of dispersing and recruiting in areas with mild to non-existent winters. The invasion of natural areas by exotic invaders is regulated by biotic and abiotic processes, which influence the invader’s success or failure. I studied the vegetation and soil effects of paired invaded (INV), uninvaded (NAT), and ‘restored’ (RES) sites on the germination and survival of wintercreeper seeds and seedlings. The effect of aril (with vs. without) was also tested, both in the field and in vitro. In the field, total germination and first year survival were 55.6% and 24.2%, respectively, across treatments. Total germination was unaffected by treatments, yet vegetation (P = 0.0016) and aril (P = 0.001) treatments significantly influenced germination rates over time, including delayed germination of seeds with arils. The proportion of germinated seedlings that survived was significantly different based on vegetation (P = 0.054) and aril (P = 0.071) treatments after the first winter of growth, but not prior to the first winter. The proportion of seedling survival was significantly lower among seeds dispersed with an aril and seeds sown within INV treatments; there were no interactive effects. Finally, I examined how seedling density and growth habit (horizontal vs. vertical) influenced plant survival, growth, and allometry. I also tested extractable soil C, N, P, K, Ca, and Mg prior to planting and after 17 months of soil conditioning. I found evidence that increased planting density negatively influenced growth among individual plants (lower survival, basal diameter, shoot mass, root mass). At the plot level, high-density plantings yielded greater stem length, and shoot, root, and combined biomass, indicating positive frequency dependence for this species. Soil analyses indicated C, N, P, Ca, and Mg significantly increased (P < 0.05) over the course of the experiment. I conclude that in wintercreeper, prominent asexual propagation leads to aggregate populations whose total contributions to above- and belowground biomass are positively correlated with density, even though individual plant fitness is not. Altogether, this work provides insight into how wintercreeper invasions occur at broad and fine scales. This information will provide a foundation for future wintercreeper studies and aid land managers in their prevention and control strategies.

A pesquisa teve como objetivo verificar o fluxo de emergência das plantas daninhas e determinar o banco de sementes em condições de semeadura direta e convencional e verificar a eficácia do glyphosate em plantas daninhas de difícil controle. Para tanto, foi realizado no período de 2001 e 2002, um experimento de campo, onde de 15 em 15 dias, foi feito o levantamento de plantas daninhas para determinação do fluxo de emergência. O delineamento experimental foi o de blocos casualizados, com parcelas subdivididas. As doses de glyphosate foram de 0, 540, 720, 900, 1080, 1260 e 1440 g.i.a / ha. O banco de sementes foi avaliado através da retirada de 20 sub-amostras de solo, em cada parcela, nas profundidades de 0,0-2,5; 2,5-5,0; 5,0-10,0; 10,0-15,0 e 15,0-20,0 cm. Também foram realizados dois experimentos em câmara de crescimento com o objetivo de avaliar o controle e curvas dose - resposta das espécies de plantas daninhas Bidens pilosa L., Commelina benghalensis L., Digitaria insularis L. (Feed), Tridax procumbens L. e Ipomoea grandifolia Dammer e Spermacoce latifolia Abul. ao herbicida glyphosate. Para avaliar o controle, foram aplicadas as seguintes doses de glyphosate: 0, 720, 960; 1200, 1440, 1680, 1920 g.i.a/ha, após 25 dias da emergência das plantas daninhas. Na determinação das curvas-dose resposta as aplicações das doses de glyphosate foram de 0,0; 11,3; 22,5; 45; 90; 180; 360; 720 e 1440 g.i.a. / ha. A elaboração da curva dose - resposta foi feita através do ajuste da biomassa verde utilizando modelo matemático log-logístico: Y = C+D-C / 1 + Exp(b(log(x)-log(GR50))), calculado por modelo não linear dos dados. Nas análises estatísticas foram utilizados os programas estatísticos SAS e SANEST para analisar a variância dos dados. Nas condições locais de campo em que foi realizado o experimento podemos concluir que o herbicida glyphosate mostrou-se ser eficaz no controle de plantas daninhas existentes na área a partir da dose de 540 g.i.a/ha. No ano de 2001 ocorreram fluxos das espécies Leucas martinicensis Jacq. e Richardia brasilensis Gomes de uma forma mais diferenciada no direto do que no convencional. Também as espécies Cenchrus echinatus L. e Digitaria insularis (Feed) L. apresentaram maior emergência no sistema direto do que no convencional. No ano de 2002 essas diferenças dos fluxos das espécies não foram tão expressivas como em 2001. As sementes concentraram-se nos 2,5-5,0 cm superficiais do solo, no sistema direto, enquanto que o preparo convencional distribuiu as sementes em maiores profundidades. Os resultados obtidos em câmara de crescimento indicaram que o herbicida glyphosate controlou Bidens pilosa e Digitaria insularis. Commelina benghalensis foi considerada de difícil controle. A dose de glyphosate necessária para atingir índices de controle acima de 91% foi de 1680 g.i.a/ha para Commelina benghalensis, 960 g.i.a/ha na espécie Tridax procumbens e 1440 g.i.a/ha aos 21 DAA para Ipomoea grandifolia. Após a determinação da curva dose - resposta concluiu-se que a espécie Bidens pilosa foi considerada a planta daninha mais suscetível ao herbicida glyphosate, pois foi a espécie que obteve menor GR50 (31,86 g.i.a/ha). As espécies Tridax procumbens, Digitaria insularis, Spermacoce latifolia, Ipomoea grandifolia, Commelina benghalensis obtiveram GR50 de 58,40; 128,50; 250,44; 615,49 e >1440,00 g.i.a/ha, respectivamente. / The research had the objective of determining the emergence periodicity, seeds bank for the no tillage and convencional tillage systems, and verify the efficacy of glyphosate on weeds of difficult control. During 2001 and 2002, a field experiment was conducted where after applications of glyphosate in the no tillage and convencional tillage systems was made every 15 days the emergence periodicity and seeds bank determination. The experimental design was the randomized blocks with subdivide plots. The applied glyphosate rates were 0, 540, 720, 900, 1080, 1260 and 1440 g.i.a.ha -1 . The bank of seeds was evaluated through the retreatment of 20 soil sub-samples, in each plot, in the depths of 0.0-2.5; 2.5-5.0; 5.0- 10.0; 10.0-15.0 and 15.0-20.0 cm. Experiments were also led in a completely randomized black growth chamber with the objective of evaluating the susceptibility and dose-response curves of the species of weeds Bidens pilosa L., Commelina benghalensis L., Digitaria insularis L. (Feed), Ipomoea grandiofolia L., Tridax procumbens L. and Spermacoce latifolia Abul. to the herbicide glyphosate. To evaluate the control the following glyphosate doses: 0, 720, 960; 1200, 1440, 1680, 1920 g.i.a.ha -1 . The applications of glyphosate were doses of 0, 11.3, 22.5, 45, 90,180, 360, 720, and 1440 and g.i.a.ha -1 . The elaboration of the curves dose - response was made through the adjustment of the green biomass it dries using the following mathematical model log - logistic: Y = C+D-C / 1 + Exp(b(log(x)-log( GR50))), using the statistical procedure of non linear analyses. The SANEST program was used to the statistical analyses and SAS program to analyze the variance of the data. In field conditions of field were experiment was carried out, glyphosate was effective to control of weeds starting from dose of 540 g.i.a.ha -1 . In the year of 2001, emergence periodicity of the species dicotiledons Leucas martinensis Jacq. and Richardia brasilensis Gomes in a more different way in the no tillage than in the convencional tillage; also, the species monocotiledons Cenchrus echinatus L. and Digitaria insularis L. (Feed) presented a larger emergence in the no tillage than in the convencional tillage systems. In the year of 2002, that differences of the flows of the species were not as expressive as in 2001. The seeds concentrated on the 2.5-5.0 cm superficial of the soil, in the no tillage system, while the convencional tillage distributed the seeds in the soil. The results in the chamber showed that glyphosate controlled Bidens pilosa and Digitaria insularis. Commelina benghalensis was considered a specie of difficult control. The glyphosate rate to reach control indexes above 91% was of 1680 g.i.a.ha -1 of glyphosate for Commelina benghalensis, 960 g.i.a.ha -1 in the Tridax procumbens and 1440 g.i.a.ha -1 of glyphosate for Ipomoea grandifolia in 21 DAA. After the curves dose - response determination it was ended that Bidens pilosa was considered the more susceptible weed to glyphosate, because it was the species of smaller GR50 (31.86 g.i.a.ha -1 ). On the other hard species Tridax procumbens, Digitaria insularis, Spermacoce latifolia, Ipomoea grandifolia, Commelina benghalensis obtained GR50 equal to 58.40, 128.50, 250.44, 615.49 and >1440,00 g.i.a.ha -1 , respectively.

A pesquisa teve como objetivo verificar o fluxo de emergência das plantas daninhas e determinar o banco de sementes em condições de semeadura direta e convencional e verificar a eficácia do glyphosate em plantas daninhas de difícil controle. Para tanto, foi realizado no período de 2001 e 2002, um experimento de campo, onde de 15 em 15 dias, foi feito o levantamento de plantas daninhas para determinação do fluxo de emergência. O delineamento experimental foi o de blocos casualizados, com parcelas subdivididas. As doses de glyphosate foram de 0, 540, 720, 900, 1080, 1260 e 1440 g.i.a / ha. O banco de sementes foi avaliado através da retirada de 20 sub-amostras de solo, em cada parcela, nas profundidades de 0,0-2,5; 2,5–5,0; 5,0–10,0; 10,0-15,0 e 15,0-20,0 cm. Também foram realizados dois experimentos em câmara de crescimento com o objetivo de avaliar o controle e curvas dose - resposta das espécies de plantas daninhas Bidens pilosa L., Commelina benghalensis L., Digitaria insularis L. (Feed), Tridax procumbens L. e Ipomoea grandifolia Dammer e Spermacoce latifolia Abul. ao herbicida glyphosate. Para avaliar o controle, foram aplicadas as seguintes doses de glyphosate: 0, 720, 960; 1200, 1440, 1680, 1920 g.i.a/ha, após 25 dias da emergência das plantas daninhas. Na determinação das curvas-dose resposta as aplicações das doses de glyphosate foram de 0,0; 11,3; 22,5; 45; 90; 180; 360; 720 e 1440 g.i.a. / ha. A elaboração da curva dose - resposta foi feita através do ajuste da biomassa verde utilizando modelo matemático log-logístico: Y = C+D-C / 1 + Exp(b(log(x)-log(GR50))), calculado por modelo não linear dos dados. Nas análises estatísticas foram utilizados os programas estatísticos SAS e SANEST para analisar a variância dos dados. Nas condições locais de campo em que foi realizado o experimento podemos concluir que o herbicida glyphosate mostrou-se ser eficaz no controle de plantas daninhas existentes na área a partir da dose de 540 g.i.a/ha. No ano de 2001 ocorreram fluxos das espécies Leucas martinicensis Jacq. e Richardia brasilensis Gomes de uma forma mais diferenciada no direto do que no convencional. Também as espécies Cenchrus echinatus L. e Digitaria insularis (Feed) L. apresentaram maior emergência no sistema direto do que no convencional. No ano de 2002 essas diferenças dos fluxos das espécies não foram tão expressivas como em 2001. As sementes concentraram-se nos 2,5-5,0 cm superficiais do solo, no sistema direto, enquanto que o preparo convencional distribuiu as sementes em maiores profundidades. Os resultados obtidos em câmara de crescimento indicaram que o herbicida glyphosate controlou Bidens pilosa e Digitaria insularis. Commelina benghalensis foi considerada de difícil controle. A dose de glyphosate necessária para atingir índices de controle acima de 91% foi de 1680 g.i.a/ha para Commelina benghalensis, 960 g.i.a/ha na espécie Tridax procumbens e 1440 g.i.a/ha aos 21 DAA para Ipomoea grandifolia. Após a determinação da curva dose - resposta concluiu-se que a espécie Bidens pilosa foi considerada a planta daninha mais suscetível ao herbicida glyphosate, pois foi a espécie que obteve menor GR50 (31,86 g.i.a/ha). As espécies Tridax procumbens, Digitaria insularis, Spermacoce latifolia, Ipomoea grandifolia, Commelina benghalensis obtiveram GR50 de 58,40; 128,50; 250,44; 615,49 e >1440,00 g.i.a/ha, respectivamente. / The research had the objective of determining the emergence periodicity, seeds bank for the no tillage and convencional tillage systems, and verify the efficacy of glyphosate on weeds of difficult control. During 2001 and 2002, a field experiment was conducted where after applications of glyphosate in the no tillage and convencional tillage systems was made every 15 days the emergence periodicity and seeds bank determination. The experimental design was the randomized blocks with subdivide plots. The applied glyphosate rates were 0, 540, 720, 900, 1080, 1260 and 1440 g.i.a.ha -1 . The bank of seeds was evaluated through the retreatment of 20 soil sub-samples, in each plot, in the depths of 0.0-2.5; 2.5-5.0; 5.0- 10.0; 10.0-15.0 and 15.0-20.0 cm. Experiments were also led in a completely randomized black growth chamber with the objective of evaluating the susceptibility and dose-response curves of the species of weeds Bidens pilosa L., Commelina benghalensis L., Digitaria insularis L. (Feed), Ipomoea grandiofolia L., Tridax procumbens L. and Spermacoce latifolia Abul. to the herbicide glyphosate. To evaluate the control the following glyphosate doses: 0, 720, 960; 1200, 1440, 1680, 1920 g.i.a.ha -1 . The applications of glyphosate were doses of 0, 11.3, 22.5, 45, 90,180, 360, 720, and 1440 and g.i.a.ha -1 . The elaboration of the curves dose – response was made through the adjustment of the green biomass it dries using the following mathematical model log - logistic: Y = C+D-C / 1 + Exp(b(log(x)-log( GR50))), using the statistical procedure of non linear analyses. The SANEST program was used to the statistical analyses and SAS program to analyze the variance of the data. In field conditions of field were experiment was carried out, glyphosate was effective to control of weeds starting from dose of 540 g.i.a.ha -1 . In the year of 2001, emergence periodicity of the species dicotiledons Leucas martinensis Jacq. and Richardia brasilensis Gomes in a more different way in the no tillage than in the convencional tillage; also, the species monocotiledons Cenchrus echinatus L. and Digitaria insularis L. (Feed) presented a larger emergence in the no tillage than in the convencional tillage systems. In the year of 2002, that differences of the flows of the species were not as expressive as in 2001. The seeds concentrated on the 2.5-5.0 cm superficial of the soil, in the no tillage system, while the convencional tillage distributed the seeds in the soil. The results in the chamber showed that glyphosate controlled Bidens pilosa and Digitaria insularis. Commelina benghalensis was considered a specie of difficult control. The glyphosate rate to reach control indexes above 91% was of 1680 g.i.a.ha -1 of glyphosate for Commelina benghalensis, 960 g.i.a.ha -1 in the Tridax procumbens and 1440 g.i.a.ha -1 of glyphosate for Ipomoea grandifolia in 21 DAA. After the curves dose – response determination it was ended that Bidens pilosa was considered the more susceptible weed to glyphosate, because it was the species of smaller GR50 (31.86 g.i.a.ha -1 ). On the other hard species Tridax procumbens, Digitaria insularis, Spermacoce latifolia, Ipomoea grandifolia, Commelina benghalensis obtained GR50 equal to 58.40, 128.50, 250.44, 615.49 and >1440,00 g.i.a.ha -1 , respectively.

Onion thrips (Thrips tabaci) and Iris Yellow Spot Virus (IYSV) constitute a pest complex of global concern for allium growers. Yield losses due to onion thrips alone can be heavy, and in tandem with IYSV, these losses can be complete. This study was one phase of a multi-phase research project intent on exploring the potential drivers of thrips and virus infestation in onion. Preliminary observations in participating growers’ fields in northern Utah pointed towards a potential link between weedy field borders and thrips/IYSV infestation in onion. Field work was carried out at the Kaysville experiment station examining the possible relationships between thrips and IYSV incidence in onion and the presence of adjacent weed populations. This research was conducted with the intent of guiding growers’ decisions regarding field border management, and to provide additional insights into onion thrips behavior. While implications for growers remain unclear, thrips preferences regarding host plant utilization were identified, as well as preliminary evidence of additional plant species capable of hosting IYSV.

Lygodium microphyllum, native to the Old World tropics, has invaded central and southern Florida, destroying native habitats, reducing biodiversity and altering fire regimes. Prescribed fire, one of several methods used to manage L. microphyllum infestations, reduces fern biomass over large areas, but its effects on spore viability are unknown. To provide tools to evaluate whether fire-dispersed spores are viable, this research determined how heat affects spore viability. Spores were exposed to temperatures of 50°C to 300°C for durations of 5 seconds to 1 hour, then allowed to germinate on agar in petri plates. Percent germination was assayed after two weeks. Temperatures of 50°C had little effect; 300°C killed spores for all durations. Results indicate that while viability of unburnt spores decreases with increasing temperature and duration of heat exposure, spores are killed when exposed to relatively low temperatures compared to those in fires.

Fall-planted forage radish (Raphanus sativus L. longipinnatus) cover crops have shown successful weed suppression and recycling of fall-captured nutrients. This research evaluated the nutrient cycling and weed suppressive benefits of forage radish cover crop mixtures to develop an integrated system for no-till sweet corn (Zea mays L. var rugosa) production that improves crop yield and soil health. Treatments included forage radish (FR), oats (Avena sativa L.) and forage radish (OFR), a mixture of peas (Pisum sativum subsp arvense L.), oats and forage radish (POFR), and no cover crop control (NCC). Subplots were assigned to nitrogen fertilizer treatments to evaluate N sufficiency and timing: 0 kg N ha-1 as the control, 28 kg N ha-1 at side-dress, and 56 kg N ha-1 with application split between planting and side-dress. Results indicated that POFR and OFR provided improved N cycling and sweet corn yield compared with FR and NCC. Early season N from decomposing cover crop residue was sufficient to eliminate the need for N fertilizer at sweet corn planting, thereby reducing input costs and risks of environmental pollution.

Winter cover crops grown in rotation with grain crops can be an efficient integrated pest management tool (IPM). However, cover crop biomass production and thus successful provisioning of ecosystem services depend on a timely planting and cover crop establishment after harvest of a cash crop in the fall. One potential management adaptation is the use of short-season soybeans to advance cover crop planting date in the fall. Cover crops planted earlier in the fall may provide a greater percentage of ground cover early in the season because of higher biomass accumulation that may improve weed suppression. However, adapting to short-season soybeans could have a yield penalty compared to full-season soybeans. In addition, it is unclear if further increasing cover crop growing season and biomass production under environmental conditions in Kentucky could limit nitrogen and water availability for the next cash crop. This thesis combines the use of field trials and a crop simulation model to address the research questions posed. In Chapter 1, field trials evaluating yield and harvest date of soybean maturity group (MG) cultivars from 0 to 4 in 13 site-years across KY, NE, and OH, were used to calibrate and evaluate the DSSAT crop modeling software (v 4.7). The subsequent modeling analysis showed that planting shorter soybean maturity groups (MG) would advance date of harvest maturity (R8) by 6.6 to 11 days per unit decrease in MG for May planting or by 1 to 7.3 days for July planting. The earliest MG cultivar that maximized yield ranged from MG 0 to 3 depending on the location, allowing a winter-killed cover crop to accumulate between 257 to 270 growing degree days (GDD) before the first freeze occurrence when soybean was planted in May, and between 280 to 296 GDD when soybean was planted in July. Winter-hardy cover crops could accumulate 701 to 802 GDD following soybean planted in May and 329 to 416 GDD after soybean planted in July. In Chapter 2, a two-year field trial was conducted at Lexington, KY to evaluate the effect of a soybean – cover crop rotation with soybean cultivars MG 1, 2, 3 or 4 on cover crop biomass and canopy cover, and on weed biomass in the fall and the following spring. Results showed that having cover crops was an efficient management strategy to reduce weed biomass in the fall and spring compared to no cover treatment. Planting cover crops earlier in the fall after a short-season soybean increased cover crop biomass production and percentage of ground cover in the fall, but not the following spring. Planting cover crop earlier after a short-season soybean did not improve weed suppression in the fall or spring compared to a fallow control with full-season soybean. Having a fall herbicide application improved weed control when there was a high pressure of winter annual weeds. By the spring, delaying cover crop termination increased cover crop biomass but also did weed biomass. In Chapter 3, a soybean – cover crop – corn rotation was simulated to evaluate the effect of different soybean MG and cover crop termination, as well as year to year variability on water and nitrogen availability for the next corn crop in Lexington, KY. Simulations showed that when cover crops were terminated early, they did not reduced soil available water at corn planting. However, introducing a non-legume cover crop reduced total inorganic nitrogen content in the soil profile by 21 to 34 kg ha-1 implying 15 to 30 kg ha-1 less in corn nitrogen uptake. Cover crop management that was able to maintain similar available water values than fallow treatment while minimizing nitrogen uptake differences was cover crops planted after soybean MG 4 with an early termination. However, the best management strategies that will maximize ecosystem services from cover crops as well as cash crop productivity may need to be tailored to each environment, soil type, irrigation management, and must consider year-to-year variability.