This study explores two interlinked aspects of human-environment relationship—cash crop development and biodiversity conservation—by examining the situations of the Hmong people, the largest traditional pioneer swidden group in the Thai highlands. Cash crop adoption among the Hmong have occurred in two main ways. The first involves the adoption of low-input upland crops and a shift to high-input vegetable crops. This pattern is found in the Lower North and spread to the Upper North, particularly in Tak, Phrae, Nan, Payao and Chiang Rai. The adoption is closely linked to the development of roads into the uplands and the diffusion of maize cultivation in the lowlands. The second pattern is a direct shift from opium to high-input crops, particularly cabbage. Large scale cabbage growing began in the early 1980s as a response to the demand for off-season vegetables. The most important driving factors behind cash crop adoption were the government poppy eradication activities, the contacts between market agents and the Hmong and the increased accessibility of Hmong villages. Adoption was facilitated by favourable market prices at the initial period and by the Hmong clan network. Each type of cash crops has had its particular effects on the Hmong socio-economy. Cut-flowers bring small but regular income into a household while cabbages bring a lump sum, a few times a year. Cabbage production induces high level of truck ownership leading to increased mobility, rapid diffusion of innovations, changing cultural values and increased uses of lowland services (such as health care, schools, market, etc.). Flower production, on the other hand, allows women to take active parts in marketing. The study also found a type of movement not discussed in earlier literature, the temporary migration of households or parts of households to take advantage of successful cash crop cultivation in other villages for a period of 1–2 years. The examination of four cash crops: opium, maize, cabbage and carnations shows that the Hmong have gradually shifted from land extensive to land intensive cash crops. This move to economize on land is, however, recompensed by the need for high inputs in agriculture. The more land intensive the crop is, the more fertilizers and pesticides are used. Comparisons between crops on three variables: population-land ratio, income and pesticide used per unit area, suggest that cut-flowers may be a superior crop, if measures to reduce pesticide uses can be found. Cash crop adoption affect the relationships between the people and wildlife in three ways. First, the labour-intensive nature of cash crop production prevents farmers from spending as much time in the forest as in the past. Second, cash crops provide incomes which allow the people to obtain meat from the market and thus reducing the needs for wild meat. Third, cash crop economy orients people toward the lowland, resulting in weakening traditional knowledge about wildlife behaviours, hunting or trapping. Most Hmong view hunting as a leisure activity, and some, particular women, see it as a waste of time. Reduced hunting, however, has not lessen the pressure on wildlife as the population of all species are reportedly declining. Many Hmong villages have rules against hunting some species, particularly gibbons. This rule is respected by most people but not all. Since the people do not feel that their livelihood is greatly affected by the disappearance of wildlife, the direct relationships between economic improvement and conservation is not clearly apparent. / Graduate

This study explores two interlinked aspects of human-environment relationship—cash crop development and biodiversity conservation—by examining the situations of the Hmong people, the largest traditional pioneer swidden group in the Thai highlands. Cash crop adoption among the Hmong have occurred in two main ways. The first involves the adoption of low-input upland crops and a shift to high-input vegetable crops. This pattern is found in the Lower North and spread to the Upper North, particularly in Tak, Phrae, Nan, Payao and Chiang Rai. The adoption is closely linked to the development of roads into the uplands and the diffusion of maize cultivation in the lowlands. The second pattern is a direct shift from opium to high-input crops, particularly cabbage. Large scale cabbage growing began in the early 1980s as a response to the demand for off-season vegetables. The most important driving factors behind cash crop adoption were the government poppy eradication activities, the contacts between market agents and the Hmong and the increased accessibility of Hmong villages. Adoption was facilitated by favourable market prices at the initial period and by the Hmong clan network. Each type of cash crops has had its particular effects on the Hmong socio-economy. Cut-flowers bring small but regular income into a household while cabbages bring a lump sum, a few times a year. Cabbage production induces high level of truck ownership leading to increased mobility, rapid diffusion of innovations, changing cultural values and increased uses of lowland services (such as health care, schools, market, etc.). Flower production, on the other hand, allows women to take active parts in marketing. The study also found a type of movement not discussed in earlier literature, the temporary migration of households or parts of households to take advantage of successful cash crop cultivation in other villages for a period of 1–2 years. The examination of four cash crops: opium, maize, cabbage and carnations shows that the Hmong have gradually shifted from land extensive to land intensive cash crops. This move to economize on land is, however, recompensed by the need for high inputs in agriculture. The more land intensive the crop is, the more fertilizers and pesticides are used. Comparisons between crops on three variables: population-land ratio, income and pesticide used per unit area, suggest that cut-flowers may be a superior crop, if measures to reduce pesticide uses can be found. Cash crop adoption affect the relationships between the people and wildlife in three ways. First, the labour-intensive nature of cash crop production prevents farmers from spending as much time in the forest as in the past. Second, cash crops provide incomes which allow the people to obtain meat from the market and thus reducing the needs for wild meat. Third, cash crop economy orients people toward the lowland, resulting in weakening traditional knowledge about wildlife behaviours, hunting or trapping. Most Hmong view hunting as a leisure activity, and some, particular women, see it as a waste of time. Reduced hunting, however, has not lessen the pressure on wildlife as the population of all species are reportedly declining. Many Hmong villages have rules against hunting some species, particularly gibbons. This rule is respected by most people but not all. Since the people do not feel that their livelihood is greatly affected by the disappearance of wildlife, the direct relationships between economic improvement and conservation is not clearly apparent. / Graduate

Master of Agribusiness / Department of Agricultural Economics / Jason S. Bergtold / Cover crops can be used as forage for cattle and other grazing animals. This research investigated the net returns of using cover crops for forage or grazing under four scenarios. These scenarios were: 1) a mixed crop and livestock producer who owns a herd of cattle and has both dry or pregnant cows and weaned calves available to graze corn stover and cover crops; 2) a crop farmer who purchases stocker cattle for the purpose of grazing the cover crop and corn stover; 3) a crop farmer who leases out a corn stover and cover crop field to a livestock producer (and who provides value-added services to the livestock producer for a fee); and 4) an integrated operation with crops and cattle where cover crops are not grown and hay is fed to cattle during the winter months. Each of these scenarios had different budgets, risks, and profit potentials. The research aimed to address the risks and profit potentials for each scenario. The stocking density was initially set at three cows and 31 steers for a period of 90 days, and alternatively, three cows and 25 steers for a period of 120 days. Two sets of cattle pricing data were used: the average historical prices from 1992 to 2011 and reported prices from a regional stockyard for the period of November 2016 to March 2017. The results showed that the initial stocking densities used for scenarios one and two were too low to provide profitable net returns regardless of pricing data used. Net returns for scenario three were also not profitable based on the services rendered and the management fee charged. Scenario four was profitable on one occasion. November steers with a 500 lb. average starting weight fed hay and concentrate for 120 days resulted in a positive net return of $375. A second analysis was done using stocking rates of 50, 75, or 100 steers to determine if increasing stocking density would result in a positive net return using only the 2016/2017 pricing data and only evaluating net returns on 2.0 and 2.5 lbs. of average daily gain. Positive net returns were achieved at various start weights and average daily gain rates at stocking rates of 75 and 100 animals. No positive net returns were realized at the stocking rate of 50 animals/100 acre field. The management fee charged for providing management services under scenario three was adjusted based on stocking densities to determine if a positive net return could be achieved at the set fee rate of $0.875/head/day. At that rate, no stocking rate resulted in a positive net return. Using the cost data, less the $900 field lease income, a breakeven pricing point for the management fee was determined for each stocking density and grazing duration within the scenario. Management of cost factors to achieve greater chances of profitability and additional research needs are discussed.

Ph.D. (Geography) / Skillful management and planning of the earth's natural resources and of agricultural production necessitates a great deal of Information regarding the resources and relevant soclo-economlc factors, as well as better Information on crop yield expectations throughout the year. These Intricate processes can often be simplified Into models. Most of Nature's systems (for example climatic systems) are, however, too complex to allow realistic models to be evaluated numerically and are therefore examined by means of simulation models through which the Interaction with time between physical processes Is established. The purpose Is to understand these processes In order to forecast the results of these changes and Interactions. The aim of this study Is to construct a composite climate model that (1) computes missing climate values, and (2) extrapolates climate values until the expected date of harvesting, by simulation using the random sampling of values from reference ("look-up") tables, In order that (3) the climate files, with simulated climate values, could be used with the parameter files as Input files for the CERES-Maize model. The CERES-Maize model uses dally values to simulate the growth, development and yield of the maize plant. The respective crop forecasting results obtained for actual and simulated climate values are then to be evaluated. Climate files, with four variables, were obtained on magnetic computer tape from the South African Weather Bureau for the study area In the Eastern Transvaal. The preliminary processing was done by the use of SA5-programmes and these files were then exported from the mainframe computer to a personal computer and stored on floppy disks. Climate reference flies were compiled from the original climate flies by sorting the climate data according to the Julian date. The missing values In the climate reference flies and the original climate files were restored from the files of neighbouring weather stations, as calculated orestimated values by.means of a suitable method of computation. Some of the methods used, were derived after comparing the graphs of the time-series of a number of climate files. Aclimate simulation model was compiled In which climatic elements were simulated by sampling values a set number of times randomly from the climate reference files. The mean of these sampled values were adjusted by multiplying It with a factor representing the climatic change over time. A climate file, also containing simulated values, and a theoretical parameter Input file were then used as the Input flies for a revised edition of the CERES-Maize model. A comparison of the results obtained for the 1986/87 growing season when the climate files, with actual and simulated values respectively, were used as Inputs for the CERES-Maize model, Indicated very promising results. The values predicted for two climate flies (1962-1987) differed by about 18%, whereas a difference of only about 8% between those predicted for two smaller climate files (actual and simulated values respectively), representing only the 1986/87 season, was recorded. The difference between values predicted for the climate file, mentioned last, and consisting only of simulated climate values, and those forecasted for the original and complete climate data file, was only 5%. As Indicated by the arithmetic mean, there is again a tendency towards the mean values.

6 pp. / The plant nursery business is complex and requires knowledge about the technical aspects of growing plants and managing a business. This publication is an introduction for those interested in starting their own wholesale nursery business. Different types of production systems - container and field production- are discussed as well as the types of plants typically grown in Southwest nurseries. Starting a business involves many decisions that will culminate in the development of a business plan. Resources for new producers include national, regional, and local trade organizations. A worksheet with questions is included to help future operators consider whether they want to start a new wholesale production nursery. Publication AZ1393 Revised 07/2017. Originally published 2006

One of the most important photosynthetic enzymes in a plant is ribulose-1,5¬bisphosphate carboxylase/oxygenase (Rubisco), which plays a key role in carbon fixation. Degradation of this enzyme leads to decreased carbon fixation and poor photosynthetic performance by the plant. It is therefore of interest to investigate possible ways of protecting this enzyme during stress conditions in order to generate plants that would perform better under extreme climates. In this study the effect of an expressed, exogenous rice cysteine proteinase inhibitor (OCI) in transformed tobacco plants on Rubisco stability/content under chilling and senescence was investigated. Results showed that there is no significant protective role for exogenous OCI on the degradation/content of Rubisco when tobacco plants were exposed to chilling. This result was found using native gel-based quantification procedures, as well as immuno-blotting, spot densitometric analysis, and a radioactive quantification assay as analysis techniques. The study, however, provided evidence for protection of Rubisco against degradation by expression of OCI under a more severe stress condition, such as senescence using native gel-based quantification procedures as detection techniques. Tobacco plants were also transformed with a newly designed vector allowing expressed OCI to be transported to the chloroplast. Failure to detect so far any OCI-¬expressing transformed plants and the idea that delay of senescence could prove beneficial to farmers by providing a more nutrient-dense crop with higher tolerance against stress-induced cell death are discussed. / Dissertation (MSc(Botany))--University of Pretoria, 2006. / Plant Science / unrestricted

The purpose of this study was to determine the uptake and distribution of nutrients during the growth of the Cayenne cultivar of Ananas comosus (L) Merr under field conditions in the Eastern Cape. The study was also done to help explain the apparent drop in the nutrient levels in the basal section of the "D"- leaf of the pineapple plant during the winter months and to determine the best part or parts of the plant to sample in order to measure the nutrient status of the pineapple plant at any stage of its growth. The investigation was conducted by selecting a plot within a production land on two farms in the pineapple growing region of the Eastern Cape. Plants were sampled from each plot at regular intervals from planting of the pineapple tops until the harvesting of the fruit of the first plant crop. Plant growth was measured and the nutrient concentrations in each section of the plant were determined. The total amounts of nutrients for each plant part were calculated and the nutrient uptake was compared and plotted on distribution diagrams.

With the high rate of human population growth in Africa, it is imperative that food production be increased through improving yields and bringing more land under cultivation. Nitrogen is a key element required for plant growth and with the low input of fertilizers into African farming-systems, it is necessary to harness biological nitrogen fixation (BNF) to its fullest extent. To maximize nitrogen fixation in crop and pasture legumes under various conditions and cropping systems requires intensified research. In this study the diversity of root nodule bacteria associated with Lotononis species in South Africa was investigated. To our knowledge, no past attempts have been made to investigate the diversity of rootnodule-bacteria associated with the genus Lotonollis. Eighty nodulated plants representing thirty-two Lotononis spp. were collected from all the main geographical and climatological regions in South Africa. Isolates obtained from rootnodules were purified and characterized with sodium dodecyl-sulphate gel polyacrylamide gel electrophoresis (SDS-PAGE), supplemented at the genomic level with 16S rDNA sequence data of selected strains. Initial screening (SDS-PAGE) showed that most isolates obtained from the same plant species, grouped into various clusters within the dendrogram. A few of the isolates from similar host plants seemed to cluster with high similarity. It is thus reasonable to conclude that host specificity in the symbiotic interaction is less applicable for most species of Lotononis. When considering the geographical origins of the isolates, their diverse nature was clearly illustrated. It was showed that isolates from similar geographical regions were evenly distributed throughout the dendrogram. Some of the isolates obtained from arid environments formed closely related electrophoretic groups. It was subsequently shown that root-nodule bacteria associated with Lotononis species are not restricted to a particular rhizobial genus, but that heterogeneity is evident. Some of the isolates were also related to genera outside the Rhizobiaceae, namely Methylobacterium and Burkholderia. / Dissertation (MSc (Microbiology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Plant productivity is greatly affected by environmental stresses such as drought, salinity and insect herbivory. Plants respond and adapt to these stresses by exhibiting physiological as well as biochemical changes at the cellular and molecular levels in order to survive. Expression of a variety of genes which encode numerous membrane transporters have been demonstrated to be induced by these stresses in a variety of plants. The nutritional status of plants is controlled by these transporters, which are regulated by the transcription of the corresponding genes. In spite of these adverse stress effects on agricultural yield, only a few studies have focused on gene transcriptional and translational regulation of membrane transporters during environmental stress situations. Rice, like other plants, contains a number of sucrose transporters encoded by a family of genes. However, detailed knowledge of their roles, localization and regulation during environmental stress conditions is lacking. Bioinformatic tools were used to identify putative cis-acting regulatory elements that may be involved in the regulation of rice and Arabidopsis thaliana sucrose transporters. The possible cis-acting regulatory elements were predicted by scanning genomic sequences 1.5 kbp upstream of the sucrose transporter genes translational start sites, using Plant CARE, PLACE and Genomatix Matinspector professional data bases. Several cis-acting regulatory elements that are associated with plant development, plant hormonal regulation and stress response were identified, and were present in varying frequencies within the 1.5 kbp of 5′ regulatory region. The putative cis-acting regulatory elements that possibly are involved in the expression and regulation of sucrose transporter gene families in rice and Arabidopsis thaliana during cellular development or environmental stress conditions were identified as: A-box, RY, CAT, Pyrimidine-box, Sucrose-box, ABRE, ARF, ERE, GARE, Me-JA, ARE, DRE, GA-motif, GATA, GT-1, MYC, MYB, W-box, and I-box. Expression analysis was used to elucidate the role of rice (Oryza sativa L. cv Nipponbare) sucrose transporter (OsSUT) genes during drought and salinity treatments of three week old rice plants ( at four leaf stage) over a 10 days. Among the five rice OsSUT genes identified, only OsSUT2 was observed to be progressively up-regulated during drought and salinity treatments, while OsSUT1, OsSUT4 and OsSUT5 were expressed at low levels, and OsSUT3 showed no detectable transcript expression. Sucrose transport will be essential to meet the cellular energy demands and also for osmoprotectant activities during drought and salinity stresses. It therefore indicates that OsSUT2 which facilitates transport of sucrose from photosynthetic cells will be III essential for rice plants to cope with drought and salinity stresses, and cultivars with a higher OsSUT2 expression should be able to tolerate these environmental stresses better. The role of OsSUT in assimilate transport during rusty plum aphids (Hysteroneura setariae; Thomas) infestation on the leaves of three week old rice (Orzya sativa L. cv Nipponbare) cultivar plants, over a time-course of 1 to 10 days of treatments, was also examined by combination of gene expression and β-glucuronidase (GUS) reporter gene analysis. Real Time PCR analysis of the five OsSUT genes revealed that the expression of OsSUT1 was progressively up-regulated during the course of aphid infestation. OsSUT2 and OsSUT4 expression were comparatively low in both the control and treated plants. OsSUT5 showed no clear difference in transcript expression in both control and treated plants, while no detectable transcript expression of OsSUT3 could be found. The up-regulation of OsSUT1 gene was verified at protein level by western blot analysis in both the control and treated plants. OsSUT1 protein expression was found to increase with time during aphid infestation. A similar trend was noticeable in the control plants, however at a lower expression level. These demonstrate that the cellular expression of OsSUT1is regulated by both developmental and environmental factors. OsSUT1-promoter:::GUS reporter gene expression was observed within the vascular parenchyma and/or companion cells associated with phloem sieve elements of the large and small bundles in the phloem tissues of the flag leaf blade regions where feeding aphids were confined, which progressively increased with time of infestation. It is suggested that OsSUT1 may primarily play an essential role in phloem transport of assimilate to wounded tissues from adjacent health tissues or may be involved in the retrieval of assimilate back into the phloem to minimize loss caused by the infestation. Some OsSUT1-promoter:::GUS expression was also found in the metaxylem at 10 days after infestation, which could signify a recovery system in which sucrose lost into the xylem as a result of aphids feeding are retrieved back into the phloem through the vascular parenchyma. This was supported by the exposure of cut ends of matured OsSUT1-promoter:::GUS rice plant leaf to 2% sucrose solution. OsSUT1-promoter:::GUS expression was observed within the protoxylem, xylem and phloem parenchyma tissues. This indicates that sucrose translocating within the xylem tissues are retrieved into the phloem via the OsSUT1 localized within the parenchyma tissues. In conclusion, the differential expression and regulation of rice (Orzya sativa L. cv Nipponbare) sucrose transporters as reported here suggest that OsSUT2 and OsSUT1 were constitutively expressed compared to other rice sucrose transporters during drought and salinity, and rusty plum aphids (Hysteroneura setariae; Thomas) infestation stresses respectively. Thus, the expression and regulation of the sucrose transporters could be related to the physiological and nutritional requirements of the cells during plant developmental or environmental stress state that allows their differential expression.

Intensive tillage and monoculture cropping practices reduce soil C accumulation hence increasing soil vulnerability to chemical, physical and biological degradation. This study focussed on enhancing biomass production of wheat and oat winter cover crops as a means of increasing C sequestration in the low organic C soils of the central part of Eastern Cape Province. The specific objectives were (i) to evaluate the short-term effects of no till and cereal-fallow based crop rotations on; soil organic matter related parameters, pH and electrical conductivity, (ii) soil bulk density, water retention and aggregate stability, (iii) soil microbial biomass C and N, mineralizable N, soil respiration, and dehydrogenase enzyme activity, (iv) grain yield, soil nutrient concentration (N, P and K) and their uptake by maize, and (v) to identify soil parameters with high sensitivity to tillage under maize-fallow-maize, maize-wheat-maize and maize-oat-maize rotational cover cropping practices. The experiment was laid out as a split-plot arrangement in a randomized complete block design with 4 replicates. Tillage treatments (CT and NT) were applied on the main plots which measured 8 × 18 m while crop rotation treatments were applied in the subplots which measured 8 × 6 m. The rotation treatments were maize-fallow-maize (MFM), maize-wheat-maize (MWM) and maize-oat-maize (MOM). Weed control in NT plots involved preplant application of glyphosate to control mainly the grass weeds while post emergence weed management was done using Atrazine (485 atrazine and 15 g l-1 triazines). Initial weed control in CT plots was achieved through ploughing to a depth of 20 cm followed by disking while post emergence weed iii management was done by hand hoeing. Soil parameters measured were; (i) particulate organic matter (POM), soil organic carbon (SOC), total nitrogen (TN), pH and electrical conductivity (EC), (ii) soil bulk density (b), moisture at field capacity (FC), aggregate mean weight diameter (MWD) determined by fast wetting (FW), slow wetting (SW), mechanical breakdown by shaking (MB) and the stability index (SI), (iii) soil microbial biomass C (MBC) and N (MBN), mineralizable N (MN), soil respiration (SR), and dehydrogenase enzyme activity (DHEA). No-till increased POM and TN compared to CT in Lenye and Burnshill, respectively. The MWM and the MOM rotations increased TN relative to the MFM rotation in Lenye. The MWM and MOM rotations enhanced SOC relative to MFM in all sampled soil depths at Burnshill and similar observations were made under MOM rotation in the 5-20 cm depth in Lenye. The MWM and MOM rotations tended to depress soil pH relative to the MFM rotation in both sampled soil depths in Lenye while NT reduced soil pH relative to CT on the surface soil layer in Burnshill. Soil EC and pH varied with depth across tillage practices but both parameters remained within the ideal range for successful crop production over the study period. Soil stability index (SI) and aggregate MWD determined by FW, SW and MB were higher in Lenye compared to Burnshill. The MOM rotation enhanced the SI relative to MFM and MWM rotations at both sites. Scanning electron microscope (SEM) showed that more organic C was incorporated into the soil under NT and MOM rotation compared to CT and MFM rotation which had few organic coatings on the soil particles. Microbial properties varied with plant biomass input as influenced by tillage and type of rotational cover crop at both sites. Like in other past studies, NT showed higher levels of MBC, MBN, NM and SR at the soil surface layer compared to CT in Burnshill. No till increased MN iv relative to CT in both sampled soil depths in Lenye and resulted in higher DHEA compared to CT in Burnshill. The MOM rotation increased MBC, MBN, MN relative to MFM rotation especially within surface soil layer. Similar observations were made with respect to MN and SR in both sampled soil layers at Lenye. By contrast, the DHEA was higher under the MFM relative to the MWM and MOM rotations in Lenye but similar under the MFM and MOM rotations in Burnshill. Maize grain yield was not affected by both tillage and crop rotations but varied with cropping season. Comparable grain yields observed under the two tillage practices with similar fertilizer application rates indicated the advantage of NT over CT in saving on labour costs in maize production without compromising yields. High plant biomass retention under NT relative to CT contributed to high soil N and P levels under the former compared to the latter tillage practice especially on soil surface layer at both study sites. Principal component analysis (PCA) revealed that soil chemical and biological parameters closely linked to organic matter, namely SOC, MN, MBC and MBN showed the highest sensitivity to tillage and crop rotation treatments. Soil aggregate MWD determined by SW and b were the physical parameters which were highly altered by agronomic management practice. The MWM and MOM rotations were clustered together and clearly separated from the MFM rotation and this observed trend only applied to the 0-5 and 5-20 cm depths in Lenye site only. No till, MWM and MOM rotations enhanced POM, SOC and TN relative to CT and MFM rotation suggesting these practices have greater potential to improve soil chemical properties compared to intensive tillage and maize monoculture based production practices. Reduced soil b under MOM rotation and improved SI under NT compared to MFM and CT, respectively v indicate that these practices have the potential to improve degraded soils. Although not significantly different, NT values for MBC, MBN, MN, SR and DHEA were higher compared to CT indicating the potential of the practice to improve soil biotic activity relative to conventional tillage practices. No till enhanced surface soil nitrate N and extractable P compared to CT at both sites revealing the long-term potential of NT in improving the supply of these essential plant nutrients compared to CT. Principal component analysis showed that SOC, MN, K, P, MBC, MBN, soil aggregate MWD determined by SW and b were the most sensitive parameters to tillage and crop rotations. Therefore, these parameters could constitute the minimum data set for assessments of the impact of selected CA practices on soil quality attributes.