3 pp. / The influence of crop species, seed size, seed viability, seed depth,irrigation practices,stand establishment and uniformity, seeding equipment, planting date, crop variety, and planting configuration on optimum seeding rate for small grains is discussed.

xiii, 270 leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Computing Science, 1976

Thesis (Ph.D.) -- University of Adelaide, Dept. of Computing Science, 1976.

Thesis (Ph.D.)--Ohio University, March, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.A.)--Simon Fraser University, 2006. / Also issued in digital format and available on the World Wide Web.

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 78-81).

Doctor of Philosophy / Department of Agronomy / Nathan O. Nelson / Augustine K. Obour / Emerging sustainability issues with summer-fallow period has prompted producers to identify fallow replacement crops in wheat (Triticum aestivum) production systems. Camelina [Camelina sativa (L.) Crantz] has been identified as a potential fallow replacement crop in the semiarid Great Plains. Camelina has uses in animal and human nutrition, biofuel production, and bio-based products. Three field experiments were conducted to develop production recommendations for camelina in wheat production systems in the semiarid Great Plains. In the first study, three camelina cultivars were evaluated in mid-March (March 17, 2014; March 18, 2015), early-April (April 3, 2013; April 1, 2014 and 2015), and mid-April (April 16, 2013; April 15, 2014 and 2015) at Hays, KS. Findings from this study showed delaying camelina planting until early- or mid-April resulted in 34% increase in seed yield. Planting date affected oil concentration, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and linolenic acid concentration. The concentrations of SFA, MUFA, PUFA, linoleic acid, and linolenic acid were also different among cultivars. A second study was conducted to evaluate the response of camelina to nitrogen (N), and sulfur (S) fertilizer application. Nitrogen rates (0, 22, 45 and 90 kg ha⁻¹), and S rates (0 and 20 kg ha⁻¹) were applied in a randomized complete block design with a split-plot arrangement. The main plots were S application rates and the subplot factor was N rates. Sulfur application did not affect seed yield, oil, protein, or seed nutrient concentration. The agronomic optimum N rate was 49 kg N ha⁻¹, however, the economic optimum N rate ranged from 25 to 31 kg N ha⁻¹ based on current N fertilizer cost, and camelina seed price. Nitrogen application had no effect on SFA, MUFA, and PUFA. Moderate N application increased seed calcium (Ca) concentration, whereas higher N rate increased zinc (Zn), and manganese (Mn) concentration in the seed. There was a general negative relation between N application with copper (Cu), and molybdenum (Mo) in camelina seed. Our study shows that camelina needed to be applied with a minimum of 25 kg N ha⁻¹ for optimum production. A third study investigated effects of crop rotation on crop yield, soil water, soil CO₂ flux, and soil health in wheat-camelina rotation systems. Rotation systems in this study were wheat-fallow (W-F), wheat-sorghum (Sorghum bicolor) -fallow (W-S-F), wheat-spring camelina (W-SC), and wheat-sorghum-spring camelina (W-S-SC). Crop rotation had no effect on sorghum grain yield. However, winter wheat yield decreased by 15% when fallow was replaced by camelina in the rotation system. Camelina yield in W-SC was 2-fold greater than that in W-S-SC. Soil water content in the more intensified rotations were less than rotations with fallow, irrespective of sampling period. Soil pH, phosphorus (P), and total nitrogen (TN) were not different among rotation systems. Nonetheless, soil profile N, soil organic carbon (SOC), microbial biomass carbon and N (MBC and MBN), and potentially mineralizable nitrogen (PMN) were different among rotation systems. Soil particle aggregation increased with increasing cropping intensity. This suggests improved soil structure with cropping intensification.

3 pp. / Originally published: 2009 / Production practices for grain sorghum are discussed including hybrid selection, planting date, seeding rate, row configuration, irrigation, fertilization, pest control, and harvesting. Grain sorghum (milo) is a warm season, annual grain crop. It is more resistant to salt, drought, and heat stress than most other crops. Nevertheless, highest yields are obtained when stresses are minimized. Revised 10/2016. Originally published 06/2009.

This study attempted to examine representative soils of Denton County in an effort to determine seasonal and soil type variations in the fungous flora both quantitatively and qualitatively.

Increased demand for barley has changed the proportion of crops grown in Virginia and the Mid-Atlantic USA. Winter wheat is the predominant small grain crop, but barley can be a direct substitute, although much less of it is grown. Soybean is grown full-season and double-cropped after both small grains. Historically, wheat was the primary small grain in the soybean double-crop rotation because of its greater profitability. The barley-soybean cropping system is not a new concept in the region, but the literature is outdated. New agronomic and economic data that directly compares full-season soybean, barley-soybean, and wheat-soybean systems using modern cultivars and management practices is needed. The objectives of this research were to: i) determine soybean yield and compare cropping system profitability of the three cropping systems; ii) perform a breakeven sensitivity analysis of the three cropping systems; and iii) determine the effect of planting date and previous winter crop on soybean yield and yield components. Soybean grown after barley yielded more than full-season soybean in two of six locations and more than soybean double-cropped after wheat in three of six locations. Net returns for the barley-soybean system were the greatest. These data indicate that soybean double-cropped after barley has the potential to yield equal to or greater than full-season soybean or double-cropped soybean following wheat, but its relative yield is very dependent on growing conditions. The profitability comparison indicated that the barley-soybean cropping system was generally more profitable than the full-season soybean and double-cropped wheat-soybean systems. This conclusion was supported by the breakeven sensitivity analysis, but remains dependent on prices that have been extremely volatile in recent years. In another study, soybean yields declined with planting date at two of four locations in 2009, a year that late-season rainfall enabled later-planted soybean to yield more than expected. In 2010, soybean yield decline was affected by the delay in planting date at both locations. Winter grain did not affect soybean yield in either year. Yield component data reinforced these results and indicated that the lower seed yield in the later planting dates was due primarily to a decrease in the number of pods. / Master of Science