Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.A.)--University of Wisconsin--Madison, 2001. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 58-61).

Using the right planting spots when planting can provide a lot of advantages forthe plant more nutrients, less competition and redused risk of damage from pineweevil. In this study comparisons have been made between quality follow upsfor not approved and approved plantings made by SCA in the distrikt ofÅngermanland. Few significant differences were found but not approvedplantings had more opportunitis for improvement than approved plantings. Moreplantings vere not approved on moist sites.

An experiment was carried out at Redland Bay on the south-eastern coast of Queensland from (16/2/1991 to 27/6/1991) in an attempt to relate the performance of maize (Zea mays L.)/cowpea (Vigna unguiculata (L) Walp.) intercrops to radiation interception and to radiation availability to cowpea and to ascertain the effects of cowpea morphological characteristics. A quick maturing maize cultivar (DK529) and two cowpea cultivars (Red Caloona and 672330) were used. Changes in light availability to cowpea in intercrops were made by varying maize density. Three plant population densities were used: 22,000 plants ha^-1, 44,000 plants ha^-1, and 67,000 plants ha^-1. Both cowpea cultivars were very vegetative and vigorous in growth with little difference in their morphological characteristics. Cowpea cultivar 1 (Red Caloona) was however a better climber and retained green leaves for a longer duration. Increasing maize plant population density effectively reduced the amount of light reaching the cowpea canopy. Light availability was reduced to a minimum of 13% and 15% in the high maize plant population density and to a minimum of 47% and 42% in the low maize plant population density in cowpea cultivar 1 and 2 respectively. Intercropping reduced growth and yield of both cowpea cultivars through reductions in cowpea leaf area index (LAI), light interception and pod number. It also caused reductions in seed size in cowpea cultivar 2 (67233). Increasing maize plant population density further reduced all the above parameters. Maize growth and yield was affected by intercropping but to a lesser extent. Maize yields were reduced by 16% and 14% under cowpea cultivar 1 and cowpea cultivar 2 respectively, compared to an average reduction of 68% and 82% in cowpea cultivars 1 and 2 across the 3 maize plant population density. Radiation use efficiency (RUE) of the intercrops was lower than that of maize sole crop but higher than that of cowpea sole crop. Intercropping proved to be more advantageous in the vegetative stages of growth than in the reproductive stage except in the medium maize plant population density treatment. This was attributed to better light use efficiency in the early growth in intercrops than sole crops which was estimated to be between 1.1 and 2.9 time higher in intercrops than in sole maize in the first 20 days after sowing (DAMS) . Results indicated that LAI and leaf longevity had a large effect on radiation interception and use in cowpea. Cowpea cultivar 2 was better yielding in sole crop that cowpea cultivar 1 (954 Vs 621 Kgha^-1) but was more affected by intercrop (157 Vs Kgha^-1). An advantage of intercropping was only obtained in the medium maize plant population density intercrops. These were however small advantages (13% and 11%) in cowpea cultivar 2 and cultivar 1 respectively. Intercropping maize with these two cowpea cultivars would therefore be of advantage only, where the interest of the farmer is in the production of maize grain and cowpea leaf, wither for consumption, livestock feed or as green manure.

An experiment was carried out at Redland Bay on the south-eastern coast of Queensland from (16/2/1991 to 27/6/1991) in an attempt to relate the performance of maize (Zea mays L.)/cowpea (Vigna unguiculata (L) Walp.) intercrops to radiation interception and to radiation availability to cowpea and to ascertain the effects of cowpea morphological characteristics. A quick maturing maize cultivar (DK529) and two cowpea cultivars (Red Caloona and 672330) were used. Changes in light availability to cowpea in intercrops were made by varying maize density. Three plant population densities were used: 22,000 plants ha^-1, 44,000 plants ha^-1, and 67,000 plants ha^-1. Both cowpea cultivars were very vegetative and vigorous in growth with little difference in their morphological characteristics. Cowpea cultivar 1 (Red Caloona) was however a better climber and retained green leaves for a longer duration. Increasing maize plant population density effectively reduced the amount of light reaching the cowpea canopy. Light availability was reduced to a minimum of 13% and 15% in the high maize plant population density and to a minimum of 47% and 42% in the low maize plant population density in cowpea cultivar 1 and 2 respectively. Intercropping reduced growth and yield of both cowpea cultivars through reductions in cowpea leaf area index (LAI), light interception and pod number. It also caused reductions in seed size in cowpea cultivar 2 (67233). Increasing maize plant population density further reduced all the above parameters. Maize growth and yield was affected by intercropping but to a lesser extent. Maize yields were reduced by 16% and 14% under cowpea cultivar 1 and cowpea cultivar 2 respectively, compared to an average reduction of 68% and 82% in cowpea cultivars 1 and 2 across the 3 maize plant population density. Radiation use efficiency (RUE) of the intercrops was lower than that of maize sole crop but higher than that of cowpea sole crop. Intercropping proved to be more advantageous in the vegetative stages of growth than in the reproductive stage except in the medium maize plant population density treatment. This was attributed to better light use efficiency in the early growth in intercrops than sole crops which was estimated to be between 1.1 and 2.9 time higher in intercrops than in sole maize in the first 20 days after sowing (DAMS) . Results indicated that LAI and leaf longevity had a large effect on radiation interception and use in cowpea. Cowpea cultivar 2 was better yielding in sole crop that cowpea cultivar 1 (954 Vs 621 Kgha^-1) but was more affected by intercrop (157 Vs Kgha^-1). An advantage of intercropping was only obtained in the medium maize plant population density intercrops. These were however small advantages (13% and 11%) in cowpea cultivar 2 and cultivar 1 respectively. Intercropping maize with these two cowpea cultivars would therefore be of advantage only, where the interest of the farmer is in the production of maize grain and cowpea leaf, wither for consumption, livestock feed or as green manure.

Herbicide resistance, regulations on pesticide use, and cost of pesticides are all challenges for managing weeds in production agriculture. The use of cover crops (CC) has emerged as a promising integrated weed management tool to aid in weed suppression. There are many questions concerning the best management practices to reap the most benefits from CC. Research was conducted to determine if the application of a pre-plant herbicide as well as the type of CC planted would increase CC biomass and subsequent winter weed suppression. Early planting and selecting a cereal rye or a cereal rye-containing mixture are the most important factors to obtain the greatest CC biomass production. Additionally, the combination of a CC and a pre-plant herbicide increased weed suppression compared to a no CC (winter fallow) treatment or CC without a pre-plant herbicide. The difference in Palmer amaranth emergence between a rolled cereal rye CC or one that is left standing was also examined along with termination timing to achieve different CC biomass levels. Overall, greater CC biomass suppressed more Palmer amaranth, but treatments of rolled or standing or termination timing did not affect weed suppression consistently. Light penetration data also showed that greater CC biomass led to a decrease in light penetration through the CC canopy, which could be a factor in reducing Palmer amaranth emergence particularly at the greater CC biomass accumulation levels. Additionally, studies were conducted to investigate the effect of cereal rye CC termination timing (i.e., "planting green" being CC terminated at the time of soybean planting or "planting brown" being CC terminated 2 weeks prior to planting) on Palmer amaranth suppression, as well as to determine how termination timing influences herbicide program optimization. A delay in emergence and growth rate of Palmer amaranth was documented in the CC containing plots when compared to the no CC plots, but no differences were observed between the termination timings. Additionally, significantly lower Palmer amaranth densities were observed under CC containing plots when compared to the no CC treatments. Within CC treatment options, the most economical option was planting green with a single postemergence herbicide application, but overall, no CC treatments were more economical programs. Finally, research was conducted to understand weed and corn competition for nitrogen when hairy vetch + cereal rye CC was present. A range of side dress nitrogen fertilizer rates, weedy versus weed free herbicide programs, and CC versus no-CC treatments were compared. Overall, yield did not differ among treatments. Ear leaf and grain nitrogen was generally greater under weed free, CC, and when fertilized at or above yield goals respective of location. Despite these findings, early season weed control in corn is still necessary to achieve maximum potential yield. These studies indicate that CC biomass is consistently the most important factor for achieving weed suppression, and that CC results can vary in response to environmental and management effects. More research is therefore necessary to evaluate the effects of CC over greater periods of time. / Doctor of Philosophy / Herbicide resistant weeds are a major challenge for farmers across the globe. With the increased number of weed species resistant to multiple herbicides and the restrictions on pesticide use, farmers need more tools to control weeds. The use of cover crops (CC) to suppress weeds can be a viable integrated weed management tool for farmers. Although there are multiple benefits associated with CCs, there are also many drawbacks. CCs are an additional input cost for farmers, and require a greater level of management when compared to conventional systems. There are also many questions concerning best management practices in order to reap the benefits of CCs. Previous research indicates CC biomass is the most important factor in achieving weed suppression. Research trials were conducted at Virginia Tech to determine whether CC species as well as the application of preplant herbicide at the time of CC planting would affect CC biomass production as well as weed suppression. Cereal rye-containing plots produced more biomass overall compared to hairy vetch alone or crimson clover and earlier plantings accumulated greater CC biomass. Additionally, planting earlier was significant for CC biomass accumulation while applying a pre-plant herbicide was not. Weed suppression varied by species but was more successful when both a CC and pre-plant herbicide were applied as compared to no CC and no pre-plant herbicide application. Termination timing and mechanism of CC termination are both known to impact potential CC benefits. Many farmers roll their CC at termination, but it is unclear whether rolling is necessary for weed suppression benefits and soybean yield. Palmer amaranth counts were collected at four and six weeks after planting, as well as yield data across a range of cereal rye CC biomass levels, rolled or left standing at termination, and planted green (CC terminated at the time of planting) versus brown (CC terminated 2 weeks prior to planting). Light penetration measurements were also collected to observe changes in light availability through a CC canopy. Overall, CC treatments reduced Palmer amaranth emergence when compared to no CC, and suppression increased with greater CC biomass. Yield did not differ among treatments, therefore CC management can be tailored to weed suppression efforts. There were clear patterns of light penetration reduction as CC biomass increased. This reduction in light penetration could be part of the reason for the decreased Palmer amaranth emergence with greater CC biomass. Overall, the most important factor affecting weed suppression is accumulation of greater CC biomass. Research was conducted to determine differences in Palmer amaranth suppression due to CC termination timing, as growers have experimented with planting green while traditionally, planting brown or no CC at all was more common. Palmer amaranth groups were created and followed throughout a 10-week period to examine density and growth rates, which allowed various herbicide programs to be simulated and compared. A delay in emergence and growth rate of Palmer amaranth was documented in the CC containing plots when compared to the no CC plots, but no differences were observed between the termination timings. Additionally, significantly lower Palmer amaranth densities were observed under CC containing plots when compared to the no CC treatments. The most effective programs varied by year, but amongst CC options, planting green with a single POST herbicide was optimal, but overall, no CC treatments were more economical due to the expenses associated with CC seed and planting. If a grower is planning on using a CC, the recommendation is therefore to plant green, as lower costs were associated with this practice. In addition to weed suppression benefits, the potential for leguminous CC such as hairy vetch to provide nitrogen for the cash crop is another reason that farmers may plant CCs. However, the effect of a CC on weed competition for nitrogen is still unclear, as the nitrogen released by the CC can also stimulate weed emergence while the CC itself is physically suppressing weeds through its biomass. A study was established to evaluate the effects of CC or no CC, weedy or weed free herbicide programs, and six nitrogen side dress fertilizer rates on yield. Overall, greater concentrations of nitrogen in the ear leaf and in grain were found under CC, weed free, and when fertilized-to-yield goal for the respective locations. Yield was not responsive to treatment effects, and agronomic optimum analysis indicated that a side dress nitrogen to yield goal is still the best option even under CC to achieve optimal yields. Use of CCs is another tool for farmers to implement in their weed control programs. Proper management of CCs can result in increased weed suppression and provide other benefits not examined in this document. However, varying results by location calls for further research to explore the intricacies of CC management and its effect not only on other weed species, but also on other major cash crops.

No description available.

Three hundred and thirty lines of guar (Cyamopsis tetragonoloba (L.) taub.) were planted in five locations throughout central and southwestern United States to find diverse photoperiod response types for closer physiological and genetic study. Dates of planting studies were done in 1982 and 1983 in hopes that the photoperiod responses would be obvious in field conditions but they were not. The 1982 dates of planting studies in Arizona, Kansas, and Texas indicated that the date of planting was more important than the selection of cultivar in expectations of high yield even though cultivar selection was very important. The 1983 dates of planting experiment in Tucson, Arizona showed suggestions that photoperiod existed in guar but it took controlled, greenhouse conditions to characterize photoperiodism in guar and to be able to conduct genetic analysis. In greenhouse studies, guar was found to be a quantitative short-day plant, the initiation of buds and floral development were accelerated under short-day conditions. Six guar lines were characterized for the critical photoperiod in days from first true leaf to the first floral bud and from first floral bud to the first flower. No effect of photoperiod on the growth and development from emergence to the first true leaf was observed. The critical photoperiod for days from first true leaf to first bud for the lines are as follows: PI217925-1-1, Mesa, and Mills are between 14 and 15 hours, Kinman and SEAH-90 are between 13 and 14 hours, and PI217925-2 is between 12 and 13 hours. The critical photoperiod for days from first floral bud to first flower for the lines are: PI217925-1-1, Mesa, Kinman, and PI217925-2 are between 12 and 13 hours, SEAH-90 is between 13 and 14 hours, and Mills is day-neutral. Different photoperiodic responses occur for days from first true leaf to first floral bud and days from first floral bud to first flower. This follows a proposed genetic system of photoperiodic actions that has genes for photoperiod sensitivity, short-day versus long-day reaction, critical photoperiod, and genes for the amount of time delay for each developmental stage. The segregations of the guar crosses were explained by the model.

Research was conducted in the summers of 1985 and 1986 at the University of Arizona Marana Agricultural Center, with the objectives of (1) determining the best intercropping species combination under near optimum irrigation, using three cereals (sorghum (Sorghum bicolor), maize (Zea mays), and pearl millet (Pennisetum americanum) and three legumes (field bean (Phaseolus vulgaris), cowpea (Vigna unguiculata), and soybean (Glycine max) in all combinations, and (2) identifying species genotypes best adapted to intercropping. Results from 1985 determined sorghum x soybean as the most appropriate intercropping combination for the environment of the Marana Agricultural Center. In the 1986 cropping season, three sorghum genotypes (Pioneer 8493, Funks G-522DR, and California IO80H40) were combined with three soybean genotypes (Asgrow A6242, Asgrow A6520, and Rillito), to identify the best genotype combination for intercropping. Both 1985 and 1986 experiments were carried out in a randomized complete block design with four replications. Pearl millet was the cereal with the greatest decrease in yield when intercropped, indicating that this cereal was not a good competitor with legumes. Sorghum was the best cereal competitor with the legumes and soybean was the best legume competitor with the cereals. Among the three sorghum genotypes studied in 1986, only Pioneer 8493 showed higher yield in monocrop whereas the other two genotypes yielded higher in intercropping, indicating some benefit from this system. On the average, all three sorghum genotypes showed intercropping to be advantageous, with high Land Equivalent Ratio values. Soybean genotypes showed drastic decreases in yield when intercropped. Asgrow A6520 soybean had the highest yield in intercropping. Sorghum #3 (California IO80H40) and soybean #3 (Rillito) were chosen as the most appropriate genotypes for intercropping, for the environmental conditions of the study.

No description available.