Every farmer has realized the dangers which follow from growing the same crop too frequently on the same land. Out of his experience and observations there has grown up the idea that one crop poisons another of the same kind, and that if he desires success he must do something to restore and maintain the fertility of the soil — and that crop rotation is one of the best means of accomplishing this result. To ascertain what really lies at the basis of this idea — whether a plant excretes poison? and if so what is their nature and what relation do these bear to soil fertility -- has attracted the attention of both practical farmers and scientific investigators from the very earliest times. But it is only during the last few years that any advance has been made in the study of these plant poisons, which promises to throw some light upon problems of soil conditions and ecological relations.

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A field experiment was conducted in the Rockpile appellation of Sonoma County during 2007 and 2008. The experimental design was a randomized complete block with five replicates. Zinfandel vines were subjected to three levels of cluster thinning during the lag phase of berry growth: vines were thinned to 2 clusters per shoot with shoulders retained if present (2CS), 1 cluster per shoot with shoulders retained if present (1CS), or 2 clusters per shoot with shoulders removed if present (2CNS). Cluster thinning Zinfandel grapevines during lag phase led to reductions in yield and crop load and increased °Brix of the fruit. In both years, wines that were made from vines with the lowest crop load had consistently higher amounts of small and large polymeric pigments, tannins and total iron-reactive phenolics. Cluster thinning vines to 2CNS at lag phase consistently decreased the number of berries per cluster and cluster weight. Thinning vines to 1CS resulted in fewer clusters per vine in 2008. Botrytis bunch rot tends to develop between the shoulder or wing and the main cluster in certain varieties. Shoulder removal in areas with a high risk of Botrytis should conclusively determine if this thinning method helps to decrease disease incidence. Additional research is also recommended with other varieties to assess possible differences between shoulder thinning and removing entire clusters on berry composition, yield, subsequent wine composition and crop load.

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Approved for public release; distribution unlimited / This thesis examines the role of alternative development in the Colombian and U.S. governments' counter drug strategies. Both governments include alternative development as a part of their policies, but provide limited funding to the programs when compared to the funding for forced eradication and security measures. Existing policies have produced reductions in drug cultivation in many areas and the Colombian government has made gains in security throughout the country, particularly the remote rural regions. These gains make conditions in Colombia suitable for large-scale alternative development supported by increased funding. Both governments are addressing components of successful alternative development programs, but funding disparities are hindering the effectiveness of the programs. While the international and European communities are staunch supporters of alternative development, the funding provided by them has been limited in scope because of disagreement with the U.S.-backed eradication policies. The U.S. and Colombian governments in conjunction with the international community must focus more on alternative development in order to consolidate the recent gains in democratic security. / Lieutenant, United States Navy

Thesis (M.Sc. (Agriculture Agronomy)) --University of Limpopo, 2017 / Among the fungal diseases infecting tomato crop, early blight caused by Alternaria solani (Ellis & G. Martin) is one of the most destructive fungal foliar diseases. The aim of this current study was to document the prevailing pathogenic diversity of A. solani populations in Limpopo based on morphological characteristics, fungicide sensitivity, and aggressiveness of A. solani isolates. The tested isolates were collected from four different areas across different tomato production sites in the Limpopo Province and pathogen isolations were carried-out under laboratory conditions. The the morphological variation of different A. solani isolates was evaluated. The results obtained in this study show that A. solani isolates exhibit high variations in mycelial pigmentation, number of septa, beak length and colony diameter. The current study also evaluated the sensitivity of A. solani isolates obtained from different areas in the Limpopo to commonly used fungicides. All the tested fungicides (chlorothalonil, copper oxychloride and mancozeb) reduced the mycelial growth of A. solani isolates, even at lower concentrations. However copper oxychloride fungicide provides better inhibition of mycelial growth as compared to other tested fungicides. Furthermore, the aggressiveness of the different isolates was investigated using Money-maker and Rodade tomato cultivars. The results obtained in our, study revealed that isolates from different areas differed in terms of their level of aggressiveness on both cultivars. However, all the tested isolates were aggressive in their ability to cause early blight in both cultivars. There was a difference on how both cultivars responded to isolates from different areas with the Money-maker being highly susceptible to all the tested isolates as than the Rodade Key words: Aggressiveness, Alternaria solani, Fungicide sensitivity, isolates, Limpopo Province, Morphological characterization, susceptible tomato cultivars. / NRF (National Research Foundation)

This study investigated the crop density in a New Holland BB960 (branch of CNH Global N.V.) large square baler as examined by crop trajectory from the precompression room to the bale chamber. This study also examined both the top and bottom plunger pressures and critical factors affecting the final top and bottom bale densities.<p>The crop trajectories (wad of crop) were measured using a high-speed camera from the side of the baler through viewing windows. The viewing windows were divided into four regions for determining the crop displacement, velocity and acceleration. Crop strain was used to evaluate the potential change in density of the crop before being compressed by the plunger. Generally, the vertical crop strain was found to be higher in the top half of the bale compared to the bottom. <p>Average strain values for side measurements were 12.8% for the top and 2.1% for the bottom. Plunger pressures were measured to compare peak pressures between the top and bottom halves of each compressed wad of crop, and to develop pressure profiles based on the plungers position. Results of comparing the mean peak plunger pressures between the top and bottom locations indicated the mean pressures were significantly higher at the top location with the exception of one particular setting. Resulting pressure profile graphs aided in qualitatively describing the compression process for both top and bottom locations.<p>A stepwise regression model was developed to examine the difference in material quantity in the top half of the bale compared to the bottom, based on bale weights. The model indicated that flake setting, stuffer ratio and number of flakes had the greatest effect on maintaining consistent bale density by comparing top to bottom halves of each bale. The R2 (coefficient of determination) value for the developed model was of 59.9%. The R2 was low although could be accounted for due to the limited number of data points in the developed model.

<p>Ethiopian mustard (<i>Brassica carinata</i> A. Braun) or gomenzer is an oilseed crop that is well adapted to the highlands of Ethiopia. Evaluation of the local germplasm has resulted in the registration of high yielding cultivars, such as Dodolla and S-67. The oil of gomenzer contains about 40% erucic acid and the meal is high in glucosinolates. The objective of this research was to study the inheritance of erucic acid content in gomenzer and to introgress genes for the non2-propenyl glucosinolate trait from <i>B. napus</i> and <i>B. juncea</i>. The erucic acid content of F₁ seed from reciprocal crosses between the high erucic acid cultivars Dodolla and S-67 and zero erucic acid line C90-14 was intermediate between the parents indicating that erucic acid content in B. carinata was controlled by two nondominant genes with two alleles acting in an additive manner. Backcross F₁ seed derived from the backcross to the low erucic acid parent fell into three erucic acid classes with $<$0.5%, 6 to 16% and $>$16% erucic acid at the ratio of 1:2:1 indicating that erucic acid was under the control of two alleles each of at two loci. F₂ seed segregation data supported this observation. Each allele contributed approximately 10% erucic acid. The high glucosinolate B. carinata line C90-14, low glucosinolate <i>B. napus</i> cultivar Westar and <i>B. juncea</i> line J90-4253 were chosen as parents for the development of non2-propenyl glucosinolate <i>B. carinata</i>. The objective was to transfer genes for non2-propenyl glucosinolate content from <i>B. napus</i> and <i>B. juncea</i> into <i>B. carinata.</i> Interspecific crosses were made between <i>B. carinata</i> and <i>B. napus</i>, <i>B. carinata</i> and <i>B. juncea</i> and the interspecific F₁ generations were backcrossed to <i>B. carinata</i>. Backcross F₁ plants from the two interspecific crosses were intercrossed in an attempt to combine the two sources for non2-propenyl glucosinolate content in one genotype. Seed of backcross F₁ plants of the cropss ((<i>B. carinata</i> x <i>B. napus</i>) x <i>B. carinata</i>) contained a high concentration of 2-propenyl glucosinolate similar to those of <i>B. carinata</i>. Introgression of C genome chromosomes of <i>B. napus</i> into <i>B. carinata</i> was not effective in redirecting glucosinolate synthesis away from 2-propenyl and into 3-butenyl glucosinolate. This indicated that C genome chromosomes do not contain genetic factors for C3 $\to$ C4 glucosinolate precursor chain elongation, and that 2-propenyl glucosinolate synthesis is primarily controlled by genes on B genome chromosomes. Seed of ackcross F₂ plants of the cross ((<i>B. carinata</i> x <i>B. juncea</i>) x <i>B. carinata</i>) contained much reduced levels of 2-propenyl glucosinolate indicating that genetic factors for C3 $\to$ C4 glucosinolate precursor chain elongation were introgressed from the B genome of <i>B. juncea</i> into the B genome of <i>B. carinata</i>. However, a complete diversion of glucosinolate synthesis from 2-propenyl to 3-butenyl was not achieved. Further selections in segregating F₄ and F₅ generations of <i>B. juncea</i> derived <i>B. carinata</i> populations could yield the desired zero 2-propenyl glucosinolate B. carinata. The double interspecific cross was unsuccessful.