Thesis (M.Sc. (Agronomy))--University of Limpopo, 2010 / Refer to document.

Thesis (M.Sc (Plant Production)) --University of Limpopo, 2015 / Information on the performance of the maize and pigeonpea intercropping system under dryland conditions of South Africa is scanty. The aim of this study was to determine the optimum P level and productivity of pigeonpea and maize under the dryland intercropping system. Five P rates (0, 15, 30, 45, and 60 kg P ha-1) were applied to both sole and pigeonpea intercropped with maize in a randomized complete block design with 4 replicates. Growth parameters and yield and yield attributes of pigeonpea and maize were measured to determine performance of both crops. There were significant differences in grain yield of pigeonpea as influenced by P rates in both seasons. Highest grain yields of 781 kg ha-1 during 2009/10 and 894 kg ha-1 during 2010/11 were obtained at P rate of 45 kg ha-1. Cropping system significantly influenced grain yield of pigeonpea in 2010/11 season with 37.1% higher pigeonpea grain yield from intercropped plots than in sole pigeonpea plots. There was 21.8% increase in grain yield of pigeonpea across two seasons as influenced by P rate. Maize grain yield showed little response to P rate only during the first season. However, highest maize grain yield of 1699 kg ha-1 was obtained at 60 kg P ha-1 during the 2009/10 season. Maize grain yield was only significantly influenced by cropping system during the 2010/11 season where sole plots achieved higher grain yield of 4148 kg ha-1 compared to 3297 kg ha-1 from intercrop plots. The results revealed that P application increased grain yield of pigeonpea significantly, especially in intercropped plots. The calculated total land equivalent ratio (LER) for the two crops gave positive and higher than one values, which suggests a favourable grain yield advantage for maize/pigeon pea intercrop.

Thesis (M.Sc. Agriculture (Agronomy)) -- University of Limpopo, 2015 / Low yields in dry bean are often reported to be associated with lack of inoculation of seeds prior to planting. This also results in little fixed nitrogen contributed by the crop. Soil phosphorus (P) is another important yield limiting factor in most of the dry bean producing regions. Two field experiments were conducted to investigate the response of dry bean cultivars to inoculation and phosphorus application under dryland farming conditions during 2011/2012 and 2012/2013 growing seasons at the Syferkuil farm of University of Limpopo. The experiments were carried out as a split split-plot arrangement in randomized complete block design with four replications. Main plot factor comprised two dry bean cultivars viz, red speckled bean and small white haricot. Rhizobium phaseoli inoculation levels (inoculated and uninoculated) were assigned in the sub-plot whilst the sub-sub plot was applied with three phosphorus rates at 0, 45 and 90 kg P kg/ha. Growth parameters, phenological characteristics and yield data were collected during the course of the experiments. The results of the two experiments showed that there was no interactive effect of treatments on growth and yield parameters. However, there was a significant interactive effect of cultivar and inoculation on phenological characteristics in both growing seasons. Main effects of cultivar and inoculation significantly affected most of the parameters measured. Inoculated red speckled bean produced tallest plants which reached 50% flowering and maturity earlier than the small white haricot variety. In both growing seasons grain yield was significantly different between the two cultivars (P ≤ 0.01). The red speckled bean produced higher grain yield of 1657 kg ha-1 and 2547 kg ha-1 in 2011/2012 and 2012/2013, respectively. In contrast, the small white haricot bean achieved grain yield of 1396 kg/ha and 1797 kg/ha in the respective seasons. Grain yield was significantly increased by approximately 16.15% and 27.50% with Rhizobium inoculation in the respective seasons. Phosphorus application at varying rates did not have a significant influence on all parameters measured the experiment in both 2011/2012 and 2012/2013 seasons.

No description available.

There has been significant interest in developing dry adhesives mimicking the gecko adhesive system, which offers several advantages compared to conventional pressure sensitive adhesives. Specifically, gecko adhesive pads have anisotropic adhesion properties: the adhesive pads (spatulae) stick strongly when sheared in one direction but are non-adherent when sheared in the opposite direction. This anisotropy property is attributed to the complex topography of the array of fine tilted and curved columnar structures (setae) that bear the spatulae. In this thesis, easy, scalable methods, relying on conventional and unconventional techniques are presented to incorporate tilt in the fabrication of synthetic polymer-based dry adhesives mimicking the gecko adhesive system, which provide anisotropic adhesion properties. In the first part of the study, the anisotropic adhesion and friction properties of samples with various tilt angles to test the validity of a nanoscale tape-peeling model of spatular function are measured. Consistent with the Peel Zone model, samples with lower tilt angles yielded larger adhesion forces. Contact mechanics of the synthetic array were highly anisotropic, consistent with the frictional adhesion model and gecko-like. Based on the original design, a new design of gecko-like dry adhesives was developed which showed superior tribological properties and furthermore showed anisotropic adhesive properties without the need for tilt in the structures. These adhesives can be used to reversibly suspend weights from vertical surfaces (e.g., walls) and, for the first time to our knowledge, horizontal surfaces (e.g., ceilings) by simultaneously and judiciously activating anisotropic friction and adhesion forces. Furthermore, adhesion properties between artificial gecko-inspired dry adhesives and rough substrates with varying roughness are studied. The results suggest that both adhesion and friction forces on a rough substrate depends significantly on the geometrical parameters of the substrate. The results in this study may be helpful for understanding how geckos overcome the influence of natural surface roughness. The novel designs of our dry adhesives open the way for new gecko-like adhesive surfaces and articulation mechanisms that do not rely on intensive nanofabrication. / acase@tulane.edu

Urea and ammonium nitrate were applied to leaves of maize plants growing in growth chambers on nutrient solutions containing three different concentrations of ammonium nitrate. Dry weights, and the soluble protein contents of leaves, sterns and roots we remeasured. Both urea and ammonium nitrate did increase the dry weights of leaves and stems when ammonium nitrate was used in the nutrient solutions (0.5 and 2.5 mM/ liter). When nitrogen was not used in the nutrient solutions, no increments of dry weight occurred. The protein contents of leaves were increased for plants in the same nutrient solutions that produced increases in the dry weights, except that urea did not increase protein contents of stems. The dry weights of roots were increased by foliar applied urea when ammonium nitrate was used in the nutrient solutions but not when the nutrient solutions were without nitrogen. Ammonium nitrate applied to the foliage did not increase the dry weights of roots. The protein contents of roots were not increased by urea or ammonium nitrate applied to the leaves. The increments in the dry weights and protein contents given by foliar applied urea were superior to those of foliar applied ammonium nitrate, with the exception of the protein content of stems.

In a dry-land winter wheat field, patterns of mineral nitrogen distributions were investigated before and after fertilizer additions. Large differences in the added mineral nitrogen recoverable three weeks after treatment were found to be specific to nitrogen source and treatment within source. Initial losses averaged 50 percent for urea treatments, 40 percent for calcium nitrate treatments, and varied from a loss of 18 percent to a gain of 22 percent for ammonium nitrate treatments. Ammonium sulfate proved the most variable with a 36 percent average loss for the before-planting treatment and a 61 percent gain for the after-planting treatment. This initial gain and loss behavior correlated at the 2 percent level of significance with the subsequent grain yield (r=0.774, 8 df), and was still discernable in soil test results of late April, where total mineral nitrogen depletion since before treatment correlated positively at the 10 percent level of significance with the nitrogen loss found 3 weeks after treatment. For a small sample of nine plots, a late July sampling revealed that depletions of mineral nitrogen since April were much more predictive of grain yields than were the actual April-N levels (r2=0.787 versus r2=0.460). This result confirms the large role played by differential moisture stress regimes in the field, since depletions during the drying season of late spring and early summer depend on the availability of moisture. Initial fertilizer behavior, determining fertilizer losses before the onset of crop usage, and a favorable later moisture regime were seen as the two largest determinants of yield under the conditions of this experiment. Since the latter factor is largely beyond further control, the former is the only factor open to manipulation. Generally, after planting treatments were lower in initial losses of mineral nitrogen, and also generally provided somewhat higher surface mineral nitrogen levels in early spring, which was found to be weakly correlated with yield. Surface accumulations in early spring can only be beneficial if sufficient spring moisture is available for downward transport into the root zone, however, and a drier spring than prevailed during this experiment could forseeably reverse this relationship by keeping such surface nitrogen accumulations from becoming available to the plant in spring.

Two studies were conducted to evaluate the effects of milk solids on restructured and emulsified turkey rolls. the milk solids used were nonfat dry milk (NFDM), whey protein concentrate (WPC), and calcium caseinate (CC). Turkey rolls consisted of 100% breast meat or 90:10 or 70:30 breast-to-thigh, salt (1%), water (10%), internal or cluster fat (10%), and 3% of various milk solids (WPC, NFDM, CC). The objectives of these studies were to 1) determine which ratio between light and dark meat is preferred; 2) determine which of milk solids evaluated will permit the highest level of dark meat incorporation into evaluated products; 3) determine if there is a mechanism by which milk proteins lighten poultry meat; and 4) determine which milk protein produces the best bind between meat pieces. Panelists were used in the first study to evaluate cooked meat attributes of color intensity, color uniformity, cohesiveness, tenderness, roasted turkey flavor, juiciness, and overall acceptability. The attributes were rated on a seven-point scale. Rolls made with WPC or NFDM scored significantly higher for color uniformity, cohesiveness, roasted turkey flavor, and overall acceptability than rolls made with CC. No differences were noted among treatments for juiciness or toughness with rolls of the same light-to-dark meat ratio. However, the 90:10 rolls were rated significantly more tender than the rolls made with the 70:30 ratio. Rolls containing milk solids had significantly higher yields than the controls. In the second study, rolls were made using the preferred meat ratio (90:10 breast:thigh meat). NFDM and WPC were used as binders, but not CC, since in the first study it was an ineffective binding agent. The second study showed that no whitening or lightening occurred in turkey rolls. This researcher also found that both NFDM and WPC increased bind strength between meat pieces. Controls made without added milk solids had less bind strength between the meat particles. Meat particle size also affected bind strength in finished products, with finely chopped rolls having higher bind strength than coarsely ground rolls. Moreover, the second study had unexpected results indicating that NFDM will prevent development of pink discoloration during refrigerated storage. The penetrometer used for bind measurements is described.

The goals of this project are study Cu free back contact alternatives for CdS/CdTe thin film solar cells, and to research dry etching for CdTe surface preparation before contact application. In addition, an attempt has been made to evaluate the stability of some of the contacts researched. The contacts studied in this work include ZnTe/Cu2Te, Sb2Te3, and Ni-P alloys. The ZnTe/Cu2Te contact system is studied as basically an extension of the earlier work done on Cu2Te at USF. RF sputtering from a compound target of ZnTe and Cu2Te respectively deposits these layers on etched CdTe surface. The effect of Cu2Te thickness and deposition temperature on contact and cell performance will be studied with the ZnTe depositions conditions kept constant. C-V measurements to study the effect of contact deposition conditions on CdTe doping will also be performed. These contacts will then be stressed to high temperatures (70-100 degrees C) and their stability with stress time is analyzed. Sb2Te3 will be deposited on glass using RF sputtering, to study film properties with deposition temperature. The Sb2Te3 contact performance will also be studied as a function of the Sb2Te3 deposition temperature and thickness. The suitability of Ni-P alloys for back contacts to CdTe solar cells was studied by forming a colloidal mixture of Ni2P in graphite paste. The Ni-P contacts, painted on Br-methanol etched CdTe surface, will be studied as a function of Ni-P concentration (in the graphite paste), annealing temperature and time. Some of these cells will undergo temperature stress testing to determine contact behavior with time. Dry etching of CdTe will be studied as an alternative for wet etching processes currently used for CdTe solar cells. The CdTe surface is isotropically etched in a barrel reactor in N2, Ar or Ar:O2 ambient. The effect of etching ambient, pressure, plasma power and etch time on contact performance will be studied.

It is essential to properly monitor in-situ soil compaction properties during most earthwork construction projects. Traditional in-situ soil compaction monitoring methods are often limited in their application. As a result, new methods are being developed to more accurately measure in-situ compaction parameters. Time domain reflectometry (TDR) is one such method. Relying on the propagation of an electromagnetic wave through the soil sample, TDR can be used to measure both in-situ moisture content as well as soil dry density. Although TDR is relatively new to the field of geotechnical engineering, it has previously been implemented in other fields with success. Researchers at Purdue University have made several advances to further incorporate the use of TDR technology into the field of geotechnical engineering and as a result an innovative TDR measurement system has been developed for compaction control monitoring. The method was standardized in the form of ASTM D 6780 in 2002. Further advancements led to an improved method referred to as the Purdue one-step TDR method. Research has indicated that the ASTM TDR method is sufficiently accurate for application in compaction monitoring applications. A comparison between the ASTM TDR method and traditional methods was carried out to evaluate the accuracy of the TDR method to traditional methods. To further expand the application of the TDR method, a correlation was developed between the TDR spike driving process with the in-situ CBR test. A comprehensive review of previous research was conducted to examine recent advancements leading to the improved Purdue one-step method. A study was also performed to evaluate the effect of variable pore fluid conductivity on the calibration of the Purdue one-step method.