Dissertaç̂ão (Mestre em Ciências Sociais Rurais)--Escola Superior de Agricultura "Luiz de Queiroz" da Universidade de São Paulo. / English summary: leaves 120-125. Bibliography: leaves [126]-134.

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Master of Agribusiness / Department of Agricultural Economics / Michael R. Langemeier / This thesis was written for the purpose of looking at the feasibility of operating a prospective business; a farm and ranch in southern Idaho. For practical reasons, I looked at a specific farm consisting of 600 irrigated acres, which are irrigated via 5 center pivots. Attached to the farm is an additional 400 acres of pasture ground seeded to crested wheat. In conjunction with operating the farm, I examined the feasibility of leasing a 300 head commercial cow herd from a separate owner than the land owner. Summer pasture for the cows would be leased from a grazing association located in northern Nevada and winter feed would come from the farm pasture, crop aftermath located on the farm, and corn stalks from a neighboring farm. Crops looked at being produced were grain corn and alfalfa hay. Operating cost projections were made using current market values, while the price received for each commodity is based on ten-year historical prices. Historical prices were used to determine whether the business is viable in the long-run. Rent on the farm is based on a 60/40 percent crop share of which the land owner’s share is 40 percent. Lease payment for the cow herd is based on a 2/3, 1/3 calf crop split of which the cow owner’s share is 1/3 of the calf crop. After analyzing the operation’s financials the business is not feasible.

This thesis examines the economic and environmental impacts that precision agriculture technologies (PATs) can have on the carbon footprint of a grain farm. An analysis is offered using two manuscripts. The first examines the impacts of three PATs and compares the findings to a conventional farming method. It was found that all three PATs investigated showed a potential Pareto improvement over conventional farming. The second manuscript expanded the model used previously to in order to develop a process to construct a carbon efficient frontier (CEF). The model employed examined uniform and variable rate technologies. In addition to the CEF, a marginal abatement cost curve was constructed. Using these curves in a complementary fashion, more accurate information on the adaptive behavior of farmer technology adoption can be gleaned. the information gleaned for the two manuscripts can give both producers and policy makers the analytical tools needed to make more information decisions with regard to economic and environmental feasibility of PATs.

The communal (former homeland) areas of South Africa are characterised by high concentrations of black people many of whom live in extreme poverty. In recent years this has been exacerbated by the collapse of state-run farmer assistance schemes, which has resulted in very low levels of agricultural production in these areas. The new South African government has proposed the revitalisation of small-scale agriculture as an important mechanism for uplifting rural livelihoods here. This research was undertaken in the former homeland of Ciskei, in what is now central Eastern Cape Province. Here agricultural decline has resulted in large areas of land designated for crop production lying fallow in the long term. Livestock production offers greater livelihood potential in this region, and it was therefore posited that this essentially abandoned cropland might be better utilised as a permanent grazing resource for livestock, particularly cattle. The research sought to characterise current levels and patterns of utilisation of arable land by livestock and how this land might be more effectively managed as a grazing resource and thereby improve levels of livestock production. Enormous variation was found in the contribution made by arable land allocations to cattle production systems in communal areas of this region. From a social perspective grazing management systems were found to depend largely on the availability of grazing resources. Where these were plentiful, control was exercised at a communal level although this tended to devolve to the individual level as grazing areas became overutilised. Considerable variation was also evident at the ecological level. Pasture quantity and quality was largely dependent on local ecotopes and land management strategies. This in turn exerted a strong influence on cattle foraging behaviour and the extent to which they could satisfy their nutritional intake requirements and thereby maintain bogy condition. Recommendations are advanced for improving cattle production systems, which take adequate account of the social and ecological heterogeneity of the central Eastern Cape region.

Im Ergebnis der in den Jahren 2006 und 2007 an der TU Freiberg durchgeführten Gärversuche stand die Forderung nach weiteren Untersuchungen der in der Praxis vorherrschenden Mischsubstrate auf ihre grundsätzliche Vergärbarkeit, Gasproduktion und Gaszusammensetzung. So wurden Ganzpflanzensilage (GPS) Triticale, Kleegras-, Luzernegrassilage, Maissilage, Zuckerrübe, Gehaltsrübe, kaltgepresster Rapskuchen oder fusarienbelasteter Triticaleschrot als Cofermente zu Rindergülle oder Hühnerkot eingesetzt. GPS Triticale und Zuckerrüben lieferten als Monosubstrate keine stabile Vergärung und damit keine auswertbaren Ergebnisse. Spitzenwerte in der Methangasproduktion erzielten Rindergülle in Kombination mit GPS Triticale oder Zuckerrüben. Ebenfalls hohe Methangasausbeuten erzielte die Kombination von Maissilage und Hühnertrockenkot mit Rindergülle. Bei der Cofermentation von mykotoxinbelastetem Getreide ergab sich kein negativer Einfluss auf die Prozessstabilität. Die Zugabe von Enzymen als Betriebshilfsstoff bewirkte eine geringfügige Steigerung der Methangasproduktion. Für die Prozessoptimierung und damit optimale Auslastung der Biogasanlage sollten sprunghafte Veränderungen der Inputzusammensetzung vermieden werden.

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Today, 84% of young adults between the ages of 18-29 use at least one social media site (Pew Research Center, 2020) and are in the stages of emerging adulthood where they are making independent decisions for the first time (Arnett, 2000). As society becomes more technologically advanced, we become further removed from agriculture (Powell & Agnew, 2011; Dale et al., 2017). Thus, resulting in a separation between consumer and producer (Wilson & Lusk, 2020; Holt & Cartmell, 2013). This leaves the opportunity for society to turn to social media for agriculture information leading to negative perceptions of agriculture (Eyck, 2000; Holt & Cartmell, 2013; Howard et al., 2017; Verbeke, 2005). However, little research has been conducted on the impact social media may have on college students’ perceptions of agriculture or their purchasing decisions as a consumer (Howard et al., 2017). Therefore, this study further explores this area of research.

The savanna woodlands of Southern Africa, colloquially termed the miombo, are poorly described in terms of biodiversity compared to other biomes. They have therefore been underrepresented in the wider understanding of how land use intensification is shaping global biodiversity. Land use change is known to reduce biodiversity and disrupt intactness of ecological communities with consequences for ecosystem functioning, resilience, and services. Miombo woodlands are described as biodiversity hotspots due to a high endemism of species and the presence of megafauna. At the same time, they are also considered dynamic socio-ecological systems shaped by disturbances and the land use activities of people. The patterns of biodiversity change in these tropical ecosystems may, therefore, have their own unique contexts, understanding of which will be essential for biodiversity and land use management in these ecosystems. In this thesis, I identified the patterns of biodiversity change in response to the two major land use practices in the two dominant woodland types in southern African woodlands: the selective logging due to charcoal production in the mopane woodlands, and agricultural expansion in the miombo. I also examined the impact of two main disturbance agents, humans and elephants, on habitat structure and biodiversity in mopane woodlands. Across all chapters in this thesis, I investigated the effects of land use change and habitat modification on biodiversity empirically using chronosequences. To understand biodiversity change, I employed a hierarchical multilevel modelling approach making inferences at the three levels of ecological communities: species, community, and meta-community (set of ecological communities at different sites). I selected six villages in the charcoal production hotspot of southern Mozambique and carried out field surveys for three taxonomic groups: trees, mammals and ground beetles. I modelled the counts of trees and beetles and incidence of mammals using meta-community occurrence models in a Bayesian framework with the intensity class of the villages, above-ground biomass and land cover type as predictors. The results suggested that the species richness of trees and mammals declined by 12 and 8.5 % respectively while that of beetles increased by 3.5%, albeit non-significantly. In addition, the beta diversity of trees decreased while that of mammals increased. The results show that while both trees and mammals reduced in richness, they responded differently to charcoal production in terms of community organisation. The trees underwent subtractive homogenisation (decrease in alpha and beta diversities) primarily because of deterministic processes induced by selective harvesting of tree stems for charcoal. Mammal communities, on the other hand, showed subtractive heterogenization (decrease in alpha, but increase in beta diversity) mainly due to random extinctions. In the agriculture frontier of miombo-dominated northern Mozambique, I investigated the effects of fragmentation and habitat loss caused by agricultural expansion on diversity and composition of trees and mammals. I modelled the occurrences of trees and mammals using occupancy models with the fragmentation and quantity of woodland cover as predictors. The model showed that most tree species (n=10), mainly the timber and firewood species, linearly declined in population size as fragmentation increased. Mammals, on the other hand, showed a nonlinear response. Seven mammal species increased at the lower levels of fragmentation. However, at the higher levels, none of the mammal species increased while two declined. Similarly, the species richness of trees linearly declined, while that of mammals increased up to a fragmentation level of 55-65% and declined above this limit. The beta diversity of trees increased with fragmentation while that of mammals decreased. The results suggest that, although fragmentation reduces species richness of both trees and mammals, it affects their species compositions in different ways. Trees undergo subtractive heterogenization due to random species losses while mammals experience subtractive homogenisation mainly due to the combined effects of fragmentation-led habitat loss and intensified hunting. Finally, this study concludes that, above 75% fragmentation or below 26% habitat quantity, both taxonomic groups endure biodiversity loss. The threshold results here corroborate similar habitat quantity thresholds (20-30%) observed elsewhere in different ecosystems. However, they differ with the widespread notion that above 30% habitat quantity, the effect of fragmentation is non-existent. The results here emphasize that taxonomic groups respond differently, the diversity and population size of mammals reduced only after the habitat threshold, whereas, those of trees showed linear decrease with fragmentation most likely due to fragmentation-led habitat loss. Lastly, I examined the effects of disturbance by humans and elephants on habitat structure and bird diversity by conducting a space for time substitution comparison in the mopane woodlands of Zambia. To examine the woodland structure, I modelled the structural attributes of habitat (stem diameter, stand density, and basal area) using mixed models with the proportion of affected stems by humans and elephants as explanatory variables. I found that elephant disturbance was associated with higher stem diameters, low stand densities, but no change in basal area. Human disturbance, on the other hand, was related to reductions in stand density and basal area, but no change in the stem diameter. Further, I tested species and functional diversity of birds against the covariates of habitat structure and disturbance. I found that bird communities reduced in species richness in both, human as well as elephant disturbed areas. However, the functional diversity did not change with elephant disturbance. I concluded that human disturbance reduces woody biomass (basal area is correlated with woody biomass) of mopane woodlands and functional diversity of birds whilst elephants do not. In this thesis, I conclude that human driven land use change in the miombo woodlands erodes alpha diversity of all taxonomic groups. However, increases in beta diversity of mammals with charcoal land use and trees in agricultural land use may maintain their diversities at the meta-community level.