No description available.

Animal pollination is responsible for the majority of the human food supply. Understanding pollination dynamics in agricultural systems is thus essential to help maintain this ecosystem service in the face of human disturbances. Surprisingly, our understanding of plant–pollinator interactions in widely distributed smallholder agricultural systems is still limited. Knowledge of pollination dynamics in these agricultural systems is necessary to fully assess how human disturbances may affect pollination services worldwide. In this study, we describe the structure of a plant–floral visitor network in a smallholder Cucurbitaceae agricultural system. We further identify the main floral visitors of these crops and tested their importance by simulating how their extinction affected network structure and robustness. The observed network was highly connected and generalized but it was neither nested nor compartmentalized. Our results suggest that the structure of agricultural plant–pollinator networks could be inherently different from those in natural communities. These differences in network structure may reflect differences in spatial distribution of floral resources between agricultural and natural systems. We identified Augochlora nigrocyanea and Peponapis limitaris as the two most frequent floral visitors. However, removal of these species did not affect network structure or its robustness, suggesting high levels of interaction rewiring. To our knowledge, this is one of the first studies to describe the structure of a plant–floral visitor network in diverse agricultural systems in the tropics. We emphasize the need for more studies that evaluate network structure in agricultural systems if we want to fully elucidate the impact of human disturbances on this key ecosystem service.

No description available.

Durum wheat (Triticum durum Desf.) is produced primarily in the Northern Great Plains and the Pacific Southwest of the United States. Current germplasm is predominantly of the spring growth habit. The objective of this study was to determine the feasibility of winter durum production in Virginia based upon both yield and quality parameters. Adaptation and yield potential of available winter durum lines were assessed from 1993-1998, in three physiographic regions in Virginia. The highest average durum yields were produced in the northern piedmont plateau at the Orange County location. Winter durum yields generally averaged 1600-2800 kg/ha less than soft red winter wheat, traditionally grown in the state. The price premium for high quality durum can compensate for this difference in yield. Based on average durum yields, and assuming the grain meets U.S. No. 2 Hard Amber Durum standards, durum production in Virginia would have been more profitable than soft red winter wheat production in 1994 and 1997. Physical and chemical quality analyses of the top 19 performing durum lines were performed to determine grain marketability, suitability for pasta, and potential consumer acceptance of the end product. Protein content and gluten strength of the Virginia grown durum were acceptable. Color, firmness, and cooking loss of pasta produced from Virginia grown durum were comparable to pasta produced from commercial semolina. Requirements for U.S. No. 2 Amber Durum were met by 21% of the lines in both 1996 and 1997. Overall, the wet, humid Virginia climate was the greatest hindrance to durum production and quality. The field trials and quality analyses showed that high quality durum production in Virginia is possible, but not consistent over all years. / Master of Science

Germination of mung bean, Phaseolus mungo L. , and wheat, Triticum aestivum L., seeds was used for bioassay to demonstrate the toxic effects of selected pesticides--menazon, disulfoton, and GS-14254-- and allergens-- alantolactone and usnic acid. The ability of gibberellic acid to counteract the toxic effects of these chemicals on germination and seedling growth was studied. Chemical composition of the treated and untreated seeds was made with special attention to starch and protein degradation. Effect of these toxicants on the synthesis of amylase, ATPase, and protease enzymes during germination was studied since these enzymes are synthesized de novo during germination. To ascertain their effect on protein synthesis in storage tissue of the germinating seeds, uptake and incorporation of 14C-L-leucine into protein was studied in potato tuber slices and germinating mung beans. Correlation of biochemical data and histochemical changes in the treated and untreated seeds of mung bean was obtained with menazon and usnic acid. Furthermore, ultrastructural changes were studied in order to relate functional and structural changes in the seeds .in conjunction with phytotoxic actions of these chemicals. Among the insecticides, menazon (250 ppm) was found to be more toxic to both species than was disulfoton. GS-14254 (100 ppm) also was equally inhibitory to seed germination and seedling growth of mung bean and wheat seeds. When a solution of the herbicide GS-14254 (100 ppm) was added to either of the insecticides at their maximum concentrations the inhibitory effect of the combined pesticides on seed germination and seedling growth was more pronounced, especially with wheat. Usnic acid (50 to 250 mg/1) and alantolactone (100 mg/1) significantly inhibited germination and root and shoot growth in both mung bean and wheat seeds. These two compounds appeared to be more phytotoxic than the pesticides. Gibberellic acid partially counteracted the inhibitory effects of the pesticides and allergens, thus these chemicals showed no antiauxin activity. Before any growth is observed there is a marked increase in respiration during germination that releases energy from food materials already present in usable form in the cells. At their maximum concentrations, menazon, disulfoton, GS-14254, alantolactone, and usnic acid significantly blocked the respiration of the germinating seeds at the end of 72 h after treatment. In all cases except alantolactone respiration of wheat seeds was considerably more affected than that of the mung beans. Compared to control seeds, pesticide chemicals as well as allergenic compounds caused significant reduction in the amounts of soluble reducing sugars and free amino acids after 72 h germination period. Similarly, starch degradation was less in the treated seeds. Among the species of seeds, considerably less amounts of reducing sugars and amino acids were formed in the pesticide-treated wheat seeds than in the mung beans as compared to their respective controls. Such differences in the inhibitory effects were not observed in seeds treated with allergenic compounds. The development of amylase and ATPase activity in the seeds treated with maximum concentrations of pesticides tended to be lower than that in the control seeds. In case of menazon, inhibition of amylase activity was more pronounced than that of disulfoton or GS-14254. Proteoiytic activity in control and disulfoton- and menazon-treated seeds was not significantly different during germination period, but in case of GS-14254, it was considerably lower. Usnic acid at highest concentration tested completely inhibited the development of amylase activity in mung beans whereas it was significantly lower in seeds treated with the maximum concentration of alantolactone. The inhibition of amylase activity in wheat seeds treated with these compounds was more or less similar. ATPase inhibition in seeds treated with usnic acid was more severe than that in alantolactone treated seeds. However, proteolytic activity in control and treated seeds showed almost the same trend during the germination period. The activity per se of amylase isolated from mung bean and wheat seeds germinated for 3 days was not significantly inhibited by the presence of the pesticides or allergens in the reaction mixture indicating that these chemicals do not inhibit already synthesized amylase enzyme. Observations with potato tissue and germinating mung beans indicated that both total uptake and incorporation of 14c-L-leucine into protein were significantly inhibited by menazon, disulfoton, GS-14254, and alantolactone. On the other hand, the uptake in germinating mung bean treated with usnic acid was not affected although both uptake and incorporation were inhibited in potato tissue. Menazon and usnic acid were then selected as the representative chemicals for pesticides and allergens, respectively, and their toxic effects were studied histochemically in 3-day germinating mung beans. It was observed that total nucleic acid content and RNA content in seeds treated with these chemicals were considerably less than that in the control seeds. Similarly, treated seeds showed more starch grains and protein bodies indicating less metabolic activity in these seeds. At the ultrastructural level, menazon- or usnic acid-treated mung bean cotyledons at day 3 of germination contained no vacuoles but many undigested protein bodies were observed. In contrast, fully developed mitochondria, endoplasmic reticulum with ribosomes, and vacuoles were seen in control cells indicating protein (enzyme) synthesis and digestion of the food reserves.

Irrigation water supplies in the arid West have become limited, yet the area of irrigable land is still extensive. To realize the more efficient use of the available supply, or for planning new irrigation projects, studies are needed to determine how much water is consumptively used by farm crops and native vegetation.

No description available.

A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science by Coursework and Research Report, University of the Witwatersrand, Johannesburg, March 2015. / Climate change is considered a dominant factor that controls species distribution at a large spatial scale. Changes in climate conditions are expected to have a significant impact on the distribution of maize in South Africa in the coming years. Determining the potential changes in maize distributions is important, as it is a staple crop for the majority of South Africans and contributes significantly to the country’s economy. The specific objectives of the study were to 1) determine potential distribution of maize under current and predicted climate scenarios using Maxent, 2) determine how the environmental factors change between current and predicted climatic habitat distributions and their influence on maize distributions in South Africa, and 3) statistically compare present and future distributions of maize to see how current and predicted climate habitats differed. Distribution models for high and low maize producing areas were built in Maxent using Bioclim variables from Worldclim. Predicted changes in distributions were then projected using predicted 2050 climate. Two emissions scenarios, RCP2.6 (low emission) and RCP8.5 (high emission), from HadGEM2ES model were used to predict the climate suitability of maize. Model evaluations showed that models had adequate predictability for maize under different climate scenarios (AUC values ≥ 0.7). Precipitation of warmest quarter (Bio18), precipitation of wettest quarter (Bio16), annual precipitation (Bio12), and maximum temperature of warmest month (Bio5) variables contributed the most to model predictions. The models showed a decrease in suitable areas for maize growth in the Highveld region. Present range area for maize as climate changes from low (RCP2.6) and high (RCP8.5) emission scenarios showed a contraction. Predictive models suggest that the most affected areas under future scenarios is the western part of the Highveld region, which is currently characterized by relatively low mean annual precipitation. However, there was an increase in suitability in the Eastern Cape province. Statistical comparisons of current and predicted climatic niches for maize showed that there was little difference, this indicates that climate suitability of maize will not change significantly due to climate change, but that the geographic ranges where these climatic habitats are found will change dramatically. The capacity to develop strategies that will enable maize to adapt to climate change will be vital for South Africa’s agro-ecosystem and food security. The results from this study highlight the possible imposition of climate change on maize distribution and could be useful for future work to minimize the potential negative impacts of climate change on food production. Keywords: Climate change, food security, maize, Maxent, niche quantification, South Africa.

Soil quality and health indicators are necessary to monitor and improve the agricultural sustainability. This experiment was conducted at Mississippi State, MS between 2015 and 2016. Soil samples were taken to determine bulk density, enzymatic activity, and total C and N. Results indicated greater bulk density, total C and N, and enzymatic activity for inter-row position than for within the corn row which was disturbed by strip-tillage. Soil bulk density tended to increase with soil depth; however, total C and N and total microbial activity decreased with depth both years. Total soil C and N increased from 2015 to 2016. Enzymatic activity was greatest at corn planting and decreased up thru four weeks apparently due to total C and N decomposition. Total C and N were related to bulk density and enzymatic activity because increase in soil C and N decreased the bulk density and increased the enzymatic activity values.

To date only a limited number of studies have been done at the field level to observe the effects of agricultural management practices on carbon sequestration, water quality, and bioenergy crop yield in Mississippi. Therefore, the goals of this study were to monitor soil organic carbon (SOC) levels at the field scale and perform a comprehensive analysis of the potential environmental impacts at the watershed scale using the Soil and Water Assessment Tool (SWAT) in two watersheds located in Mississippi. It was found that SOC levels generally are affected by depth, land use, and time. The SWAT models showed good performance overall and predicted that perennial grass production in the Town Creek watershed would render the most feedstock with the least environmental impact. The results of this study were consistent with the available literature, but a longer study period is recommended.