Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Maize (Zea mays L.) is one of the most important crops in South Africa that is cultivated for food, feed and as a cash crop. Maize in the Eastern Cape is typically grown for consumption and the Province is one of the least producers owing to small landholdings, poor production conditions and pests. This study investigated: (i) the different maize cropping systems smallholder farmers practice in the Eastern Cape (EC), (ii) the major maize insect pests within the identified cropping systems, (iii) the perceptions of Eastern Cape smallholder maize farmers on the effects of insect pests, and (iv) the effects of crop residues on insect pests’ population dynamics. Four major cropping systems namely: maize sole cropping without rotations by government sponsored farmers (GCP) (94 percent), maize intercropping without rotations by independent farmers (IF) (79 percent), maize sole cropping without rotations by IF (67 percent) and maize intercropping without rotations by GCP (61 percent) were identified. The choice of a cropping system by the smallholder farmers was significantly influenced by source of sponsorship, the difference in their district localities, tenure system, availability of inputs and farming equipment, percentage of farmland farmers allocate to maize, maize varieties, farming experience, fallow operations and access to irrigation facilities. The major constraints faced by the farmers in maize production are the attack by insect pests, weeds competition, drought, the lack of fencing around the fields and destruction by mammals. The major insect pests identified were stalk borers (Busseola fusca, Chilo partellus), cutworms (Agrotis spp.), aphids (Rhopalosiphum maidis), bollworms (Helicoverpa armigera) and weevils (Sitophylus spp.). The most popular control measures employed were the use of GM maize and pesticides. Results from the field trial showed that field crickets were the major ground dwelling insect pests observed followed by bollworms and cutworms. However, there were no significant influence of residue retention on the insects’ diversity indices, richness, and evenness. Above ground insects sampling revealed the domination by four major insects namely, cutworms, maize stalk borer, bollworms, and spotted stalk borer. Residue management significantly influenced the infestation by spotted stalk borer only on maize plots. However, the general trend was that there was less infestation by the insects in plots where residues were retained than the ones with residue removed. Results from the study indicate that government sponsorship is significantly influencing the maize cropping systems of the smallholder farmers of the Eastern Cape.

The leaching of nitrogen (N) and phosphorus (P) from the rootzone of cropping systems is a major contributor of non-point source pollution resulting in deterioration of fresh water supplies. An escalating world population is forcing further intensification of agricultural production practices and the identification of suitable and effective management practices to reduce N and P leaching losses is becoming ever more important. Such leaching losses are, however, extremely challenging to measure and quantify due to uncertainties associated with the estimation of deep drainage and N and P concentrations in this drainage water. SWB-Sci is a locally developed, mechanistic crop model to which N and P subroutines have been added to enable analysis of leaching losses at the local scale. This involved novel approaches to estimate the effects of N deficiencies on yield; to simulate crop P demand, uptake and stress effects; to simulate banded P fertilizer applications; and to estimate incomplete solute mixing. New equations to estimate the size of the Labile P pool from soil P tests commonly used in South Africa, and guidelines on the classification of South African soils as calcareous, slightly weathered or highly weathered which is required to simulate P, were also developed. The upgraded more versatile model was tested using historical datasets from the Netherlands, Kenya and South Africa, and performed well in simulating N and P dynamics in maize and wheat cropping systems. Variables tested included aboveground dry matter production, yield, leaf area index, aboveground crop N and P mass, grain N and P mass, soil water content ABSTRACT xvii and soil inorganic N levels. A study was also conducted on a large drainage lysimeter into which suction cups and wetting front detectors were installed, and data from this experiment together with the SWB-Sci model was used to study vertical solute movement more closely. As hypothesized, wetting front detector nitrate (NO3-) and P concentrations were observed to align closely with simulated mobile phase concentrations, and suction cup NO3- concentrations were observed to align closely with simulated immobile phase concentrations. These results confirm that monitoring and modelling can be used together to improve understanding and obtain more accurate estimates of N and P leaching losses, and further work on this approach is recommended for a wide range of soils and cropping systems. Finally, long-term modelling with the SWB-Sci model was used to analyse and compare N and P leaching losses from a dryland versus an irrigated monoculture maize production system. Over a 30 year simulation period, irrigated maize was estimated to leach considerably higher loads of N and P (~ 4-fold higher). For dryland production, zero leaching was observed for consecutive years on several occasions, with major leaching losses associated with high rainfall events. A ‘room for rain’ irrigation scheduling management practice was estimated to reduce N leaching by 12% and P leaching by 14%, while a crop rotation system which incorporated wheat grown over the winter months was estimated to reduce N leaching by 23% and P leaching by 24%. From this study, long-term modelling was confirmed as an effective approach to investigate N and P leaching losses, to assist with the planning and design of field trials, and to assess the effectiveness of best management practices. It is envisaged that SWB-Sci will continue to evolve as a valuable tool for analysing and reducing N and P leaching losses from cropping systems to further reduce non-point source pollution. / Thesis (PhD)--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

A major challenge facing agriculture today is to sustain the productivity of agricultural systems with the reduction of weed invasion. The Swartland region in the Western Cape (South Africa) is intensively cropped, producing wheat (Triticum aestivum) as the major crop. As a result of the weedy ryegrass invasion the wheat yield is reduced. In addition, ryegrass has developed resistance to grass herbicides (graminicides). This situation has increased the need to use alternative practices for controlling the invasion of ryegrass in wheat fields. In this regard, crop rotation and tillage systems were proposed as techniques to suppress the ryegrass invasion. This could thus maintain a sustainable long-term wheat production system with less application of herbicides, decreased input costs and increased total grain yield. Against this background, the effects of crop rotation and tillage were determined on ryegrass seedling emergence in a field and shade netting experiment, while seed dormancy was determined in the laboratory. The objectives were to compare the wheat production of two crop rotations with mono-cropped wheat and assess the impact on the ryegrass population in no-till and minimum tillage systems. Analyses of variance on data sets of ryegrass seeds from 2009, 2010 and 2011 were used to determine germination and dormancy percentages in laboratory experiments. The performance of laboratory treatments was evaluated on the basis of germination percentage of seeds. In the field and shade netting experiments, analyses of variance for data from 2007, 2011 and 2012 were used to determine crop rotation x tillage system response. Field and shade netting performance were evaluated on the basis of ryegrass population inhibition and stimulation respectively. Ryegrass seeds from 2009 and 2010 showed higher germination percentages (80 per cent and 73 per cent) than 2011 (42 per cent). Primary dormancy prevented high germination of newly harvested seeds as dormancy release increase with age of the seed. Results of field and shade netting experiments showed stimulation of the ryegrass weed population in wheat monoculture under minimum tillage. However, when wheat was rotated with leguminous crops under both tillage systems (minimum-till and no-till) ryegrass was significantly inhibited. It was concluded that the critical period for weed competition is the first six weeks after planting. Results from this study provide a basis for producers of cereals to make good decisions with regards to timing weed control measures. It is essential to use competitive crop sequences which will inhibit weeds. The challenge is getting this practice adopted and implemented by producers as it will promote conservation agriculture within the region. This study promotes long-term sustainable wheat production systems with an efficient weed management programme that is environmentally friendly using less herbicides within the Swartland region.

Most of the western United States faces increasing water shortages in the coming years, which will prove a major challenge for maintaining sustainable farms. Incorporating an alternative crop that is well adapted to the projected climate could be a successful approach to increasing the sustainability of farms in the region. Quinoa, Chenopodium quinoa Willd., may be an ideal alternative crop to meet the demands of the Intermountain West. Before widespread adoption of this novel crop can occur, best management strategies need to be documented. This paper provides research on cropping systems, irrigation rates, and weed competition with quinoa. Additionally, the impacts of prior cropping history and compost addition on soil health parameters are presented. Quinoa responded to compost addition in an organic cropping system trial where low soil phosphorous was a limiting nutrient. Cover crops, 70% hairy vetch (Vicia villosa Roth.) and 30% winter wheat (Triticum aestivum L.), provided sufficient nitrogen inputs for the following quinoa crop. In response to a line source irrigation trial, varieties showed optimal irrigation rate from 23- 42 cm of water for biomass accumulation, although no seed was produced by any variety. In a greenhouse weed trial, quinoa was less impacted by the presence of any other species, lambsquarters (Chenopodium album L.), red root pigweed (Amaranthus retroflexus) and green foxtail (Setaria viridis), suggesting a high competitive advantage. Finally, organically managed soil increased soil health indicators, including microbial biomass and resistance to stress, regardless of compost addition. In addition, compost increased soil health indicators in conventionally managed soil. Seed set across all field trials was hindered by peak summer temperatures above 32°C, a known temperature sensitivity threshold during flowering for the varieties tested. Therefore, further work to select adapted varieties for the region must be accomplished before widespread adoption is feasible. An integrated approach involving a locallyadapted novel crop and soil health protection promises to increase future farm sustainability.

京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第18394号 / 地博第163号 / 新制||地||55(附属図書館) / 31252 / 京都大学大学院アジア・アフリカ地域研究研究科東南アジア地域研究専攻 / (主査)准教授 安藤 和雄, 教授 小林 繁男, 准教授 竹田 晋也 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM

No description available.

This study compares the energy costs of synthesizing, distributing, and applying manufactured nitrogen fertilizer to the overall energy costs associated with nitrogen-fixing legume production and use. The energetics of com silage and com grain production under standard and alternative practices are examined. Economic analyses of crop production practices are used to aid the selection of recommended alternative practices. In corn silage production, cover-cropped treatments had a significant advantage over standard practice treatments in terms of overall energy expenditures for field operations. Cover-cropped no-till treatments required an average energy expenditure of 9026 MJ/ha compared to 19,763 MJ/ha required by the standard-practice no-till treatment. Cover-cropped treatments that used disking to kill the cover crops required an average energy expenditure of 9781 MJ/ha compared to 18,488 MJ /ha required by the standard-practice winter-fallow treatment. Alternative-practice treatments that utilized vetches to provide nitrogen for com production performed significantly better than standard-practice treatments in terms of energy use per unit of crop output. In addition, the alternative hairy vetch - no-till treatment produced a $33/ha greater average net revenue than the standard-practice no-till treatment. Weed control energy requirements for cover-cropped ridge-tillage com grain production were compared. Broadcast application of pre-emergence herbicides required an energy expenditure of 1160 MJ fha. Cultivation of ridges to control weeds consumed 380 MJ/ha. Economic costs of ridge cultivation were $14/ha. Broadcast application of pre-emergence herbicides cost $49/ha. / Master of Science

M.S.

Successive cropping of two vegetable crops grown on the same site in one season utilizing trickle irrigation, plastic mulch, and soil fumigation was performed in two separate experiments. In 1980, cabbage (Brassicae olericea L. var capitata cv. Market Prize) was followed by tomato (Lycopersicon esculentum Mill cv. Pik Red). In 1981, cabbage was followed by broccoli (Brassicae oleracea L. var italica cv. Green Duke). Double cropping increased the annual productivity of the research plots both years and decreased production costs by 35% compared to conventional single cropping systems. Early spring planting of the first crop was essential for economic production of the second crop. Trickle irrigation increased yields of all crops grown and was the factor most responsible for yield response both years. Black plastic mulch increased yields of tomato and total yields in 1980 but cole crops showed no significant yield response to mulch either year. No difference in crop yield resulted from soil fumigation either year. Increased production costs have caused growers to seek improved methods to offset risks and costs involved. Trickle irrigation can reduce the risks involved in producing vegetables and is particularly suited to multiple cropping on plastic mulch. / Master of Science