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Recent experimental and simulation studies -conducted at the Department of Petroleum Engineering at Texas A&M University - confirm oil production is accelerated when propane is used as an additive during steam injection. To better understand this phenomenon, distillation experiments were performed using seven-component synthetic oil consisting of equal weights of the following alkanes: n-C5, n-C6, n-C7, n-C8, n-C9, nC10, and n-C15. For comparison purposes, three distillation processes were investigated: dry-, steam-, and steam-propane-distillation, the latter at a propane:steam mass ratio of 0.05. The injection rate of nitrogen during dry-and steam-distillation was the same as that of propane during steam-propane distillation, 0.025 g/min, with steam injection rate kept at 0.5 g/min. The distillation temperatures ranged from 115°C to 300°C and were increased in steps of 10°C. The cell was kept at each temperature plateau (cut) for 30 minutes. Distillation pressures ranged from 0 psig for dry distillation to 998 psig for steam-and steam-propane distillation. The temperature-pressure combination used represented 15°C superheated steam conditions. Distillate samples were collected at each cut, and the volume and weight of water and hydrocarbon measured. In addition, the composition of the hydrocarbon distillate was measured using a gas chromatograph. Main results of the study may be summarized as follows. First, the hydrocarbon yield at 125°C is highest with steam-propane distillation (74 wt%) compared to steam distillation (58 wt%), and lowest with dry distillation (36 wt%). This explains in part the oil production acceleration observed in steam-propane displacement experiments. Second, the final hydrocarbon yield at 300°C however is the same for the three distillation processes. This observation is in line with the fact that oil recoveries were very similar in steam- and steam-propane displacement experiments. Third, based on the yields of individual hydrocarbon components, steam-propane distillation lowers the apparent boiling points of the hydrocarbons significantly. This phenomenon may be the most fundamental effect of propane on hydrocarbon distillation, which results in a higher yield during steam-propane distillation and oil production acceleration during steam-propane displacement. Fourth, experimental K-values are higher in distillations with steam-propane for the components n-hexane, n-heptane, n-octane, and n-nonane. Fifth, vapor fugacity coefficients for each component are higher in distillations with steam-propane than with steam. Finally, Gibbs excess energy is overall lower in distillations with steam-propane than with steam. The experimental results clearly indicate the importance of distillation on oil recovery during steam-or steam-propane injection. The experimental procedure and method of analysis developed in this study (for synthetic oil) will be beneficial to future researchers in understanding the effect of propane as steam additive on actual crude oils.

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Plant growth regulator(s) (PGR) can be used as lodging inhibitors and/or yield promoters for spring barley (Hordeum vulgare L.). From 1987 to 1990 four field experiments were conducted to monitor barley main-stem apical development and to determine the effects of chlormequat (CCC) and ethephon on the development, physiology and yield of spring barley. Our data provide a description of barley apical development and the general pattern of leaf and spikelet primordium production under field conditions. In general, PGR treatment reduced the apical dominance of dominant sinks allowing the survival and greater development of more subordinate sinks. Early application of either CCC or ethephon retarded development of the main-stem apex from shortly after application to the awn elongation stage and reduced the number of aborted spikelet primordia, thus increasing the potential number of grains per spike and sometimes grain yield. Ethephon applied at ZGS 39 reduced plant height and lodging. Early application (ZGS 30) of ethephon, alone or in combination with CCC increased the number of spikes m$ sp{-2},$ but not grain yield. The number of spike-bearing shoots per unit area or per plant was increased by early PGR treatment, primarily by enhancement of tiller number rather than tiller survival. Early application of CCC or ethephon to spring barley is not justified, and caution must be taken when using ethephon at the currently recommended rate and stage for lodging control. Post-anthesis application of ethephon can efficiently enhance grain fill and yield of spring barley.

The primary hypothesis of this research was that improved cowpea genotypes (selected under sole crop) could yield well in several Nigerian cropping systems, and that there were cowpea characteristics that improved overall system productivity. Cowpea lines were identified which were high yielding and stable in several management systems. Practices such as not applying insecticide and intercropping both reduced cowpea grain yield significantly. Land equivalent ratios were greater than one for all tested intercrop systems: cassava-cowpea (1.21-2.35), maize-cowpea (1.31-4.23), maize-cassava-cowpea (1.63-3.40) and millet-cowpea (1.13-6.88). Nitrogen nutrition of component crops was investigated. Line influenced both maize grain (12.5-28.4 kg ha-1) and total biomass (48.7-69.0 kg ha-1) nitrogen yield. Evidence from pot and field experiments (including $ sp{15}$N-dilution studies) indicated same-season nitrogen transfer. Light interception studies also indicated the increased light harvesting ability of early sole cowpea lines compared to early intercropped lines systems.

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Dwarf apple tree growth and yield under several non-herbicidal ground management systems were compared. Six ground cover systems were established in two newly planted orchards. After two growing seasons, trees in the straw mulch and geotextile mulch treatments had larger trunk cross-sectional areas and more shoot growth than trees in the red fescue and insectary plant cover treatments. Growth of trees under the manure mulch and cultivation treatments was intermediate. When four of the systems were established along rows of five-year old trees in an existing orchard, the increase in trunk cross-sectional area over two growing seasons was greatest for trees in the manure mulch and straw mulch followed by tose in geotextile mulch, trees in the red fescue grew least. The use of a mulch, such as straw or geotextile, has a favourable effect on growth and has potential for use in organic orchards.

The genes encoding malate dehydrogenase (mdh), succinyl-CoA synthetase (sucCD), and subunits of 2-oxoglutarate dehydrogenase (sucAB) constitute an operon in the order mdh-sucCDAB in Sinorhizobium meliloti. Regulation of the operon was studied using beta-galactosidase gene fusions. Expression of the operon was assayed in response to the carbon source provided, and over the growth of the culture. A promoter upstream of the mdh gene was identified, and although the promoter was active in S. meliloti it was not expressed in Escherichia coli. It was demonstrated that the role of 2-oxoglutarate dehydrogenase (OGD) is minimal in symbiosis, as nodules with no OGD activity formed nodules able to fix nitrogen. Alfalfa plants inoculated with strains of S. meliloti carrying extra-chromosomal copies of the mdh gene did not show any increase in shoot dry weight compared to plants inoculated with the wild-type strain.

Phosphorous fertilizer has an efficiency of about 10 percent, and this efficiency must be improved, in order to avoid excessive loss of a non-renewable resource. Ammonium lignosulphonate (ALS), a by-product of the pulp and paper industry, is expected to improve efficiency of fertilizer phosphate (P) for corn (Zea mays L.) production. Field experiments were conducted to investigate effects of added ALS and P on soil organic matter and P fractions, as well as corn yields and nutrient uptake in a Ste. Rosalie clay soil and an Ormstown silty clay loam soil in 1990 and 1991. Incubation studies showed that added ALS increased organic matter but added P as diammonium phosphate (DAP) decreased organic matter in the fertilizer band location in both soils. Applied ALS with P increased Mehlich-III (M$ sb3$P) extractable P and bicarbonate extractable P in the fertilizer band location in both soils during early incubation periods. Soil Ca-P was decreased with increased ALS. However, soil Al-P and Fe-P compounds were increased with increased ALS. Applied P increased corn shoot P concentration at the six leaf stage, and increased grain yields, total dry matter (TDM) and N and P uptake in both soils. Applied ALS at up to 608 kg ha$ sp{-1}$ with P increased corn shoot P concentration at the six leaf stage in the Ste. Rosalie soil in 1991. Applied ALS at up to 304 kg ha$ sp{-1}$ with P increased grain yield, N and P uptake. However, applied ALS without P decreased stover N concentration. Thus, ALS may improve efficiency of fertilizer P for corn production depending on soil and application methods.