Micronutrients, particularly boron (B), iron (Fe), manganese (Mn), and zinc (Zn), are pivotal for cotton (Gossypium spp.) growth, reproductive success, and fiber quality. However, their critical roles are often overlooked in fertility programs focused primarily on macronutrients. This review synthesizes recent advances in the physiological, molecular, and agronomic understanding of B, Fe, Mn, and Zn in cotton production. The overarching goal is to elucidate their impact on cotton nutrient use efficiency (NUE). Drawing from the peer-reviewed literature, we highlight how these micronutrients regulate essential processes, including photosynthesis, cell wall integrity, hormone signaling, and stress remediation. These processes directly influence root development, boll retention, and fiber quality. As a result, deficiencies in these micronutrients contribute to significant yield gaps even when macronutrients are sufficiently supplied. Key genes, including Boron Transporter 1 (BOR1), Iron-Regulated Transporter 1 (IRT1), Natural Resistance-Associated Macrophage Protein 1 (NRAMP1), Zinc-Regulated Transporter/Iron-Regulated Transporter-like Protein (ZIP), and Gossypium hirsutum Zinc/Iron-regulated transporter-like Protein 3 (GhZIP3), are crucial for mediating micronutrient uptake and homeostasis. These genes can be leveraged in breeding for high-yielding, nutrient-efficient cotton varieties. In addition to molecular hacks, advanced phenotyping technologies, such as unmanned aerial vehicles (UAVs) and single-cell RNA sequencing (scRNA-seq; a technology that measures gene expression at single-cell level, enabling the high-resolution analysis of cellular diversity and the identification of rare cell types), provide novel avenues for identifying nutrient-efficient genotypes and elucidating regulatory networks. Future research directions should include leveraging microRNAs, CRISPR-based gene editing, and precision nutrient management to enhance the use efficiency of B, Fe, Mn, and Zn. These approaches are essential for addressing environmental challenges and closing persistent yield gaps within sustainable cotton production systems.

Consumption of nutrient-rich vegetables in sufficient amounts is recommended to meet vitamin and mineral needs in the diets of rural communities of sub-Saharan Africa. Access to more locally available nutritious foods in Uganda is critical in ensuring thriving local communities that are food and financially secure through improved food production and market access. Smallholder farmers in the rural communities of Kamuli, Uganda rely on subsistence agriculture for production of crops for home consumption and opportunity to sell surplus. Supporting farmers by providing them with information on vegetable production and marketing practices is important so they may produce quality and quantities of vegetables demanded by the markets and minimize the risks of losses in the value chain. An increased demand and market opportunity for horticultural produce in rural regions and urban centers of Uganda and East Africa is due to awareness about the potential benefits of consuming fruits and vegetables. Like other vegetables, tropical squash has great potential for contributing to the nutrition, income, and food security for rural livelihoods. Studies regarding its sustainable production and marketing practices are needed for the rural communities to increase availability and consumption of tropical squash. The studies in this thesis were aimed at improving the production and marketing of tropical squash among smallholder youth farmers in Kamuli, Uganda. The first study, presented in Chapter 2, assessed the production and marketing practices of tropical squash by smallholder youth farmers in Kamuli, Uganda. The study included face-to-face surveys with adult (18-35 years) and young (15-17.9 years) smallholder farmers, all considered to be “youth” in Africa. Farmers included those who had grown tropical squash in Kamuli district and market vendors who sell tropical squash in Jinja and Kamuli districts, Uganda. The study indicated that tropical squash production and marketing among all study respondents is female-dominated with local growers as the primary producers of the tropical squash sold in Kamuli and Jinja markets. Results also indicated that tropical squash was produced on small and marginal areas of agricultural land. Most farmers relied on saved seed or seed given from other farmers and stated challenges of prolonged dry spells, pests, and minimal market access during its production. Most study respondents grew tropical squash for home consumption, and few (45%) sold the surplus produce. Market vendors faced challenges of poor-quality produce, seasonal supply and demand of tropical squash, and high transportation costs to the markets. Smallholder farmers and market vendors were able to differentiate four cultivars presented to them based on the color of the fruit skin and pulp, rind texture, and appearance of seeds. The most grown local cultivars of tropical squash were named in the Lusoga language spoken in the Kamuli district. Most participants were not involved in record keeping but indicated that they would be interested in learning how to maintain records. Most youth farmers would be willing to join farmer group associations to be able to learn about vegetable production and marketing, develop together as a community, and get access to quality agricultural inputs (agro-inputs) and potential markets. The second study, which is presented in Chapter 3, evaluated the effect of straw mulching and improved cultivars on the production of tropical squash in Kamuli, Uganda and Iowa. The study treatments included straw mulching (±) using dried plant mulch as main plots and cultivars of tropical squash as subplots in two different soil types in a randomized complete block design with a split arrangement of treatments in one temperate (May-Sept. 2021) in Ames, Iowa and two tropical growing seasons (Oct. 2020 to Feb. 2021 and Oct. 2021 to Feb. 2022) in Kamuli, Uganda. In Uganda, two hybrid cultivars, Arjuna F1 and Pujinta F1 (C. moschata Duch.) and two open-pollinated cultivars, Orange Flesh, and Flat White Boer Ford (C. maxima Duch.), were used in the study, while in Iowa, one open-pollinated, Squash Sweet Meat, (C. maxima), and one hybrid, Winter Sweet (C. maxima) were evaluated. Yield (total and marketable numbers and weights), gross margins, above ground weed biomass (kg), and soil temperature (oC) were measured in Kamuli, Uganda. Additionally in Iowa, gravimetric soil water content and percent total soluble solids of harvested and stored fruit were measured. In Kamuli Uganda, the interacting effects of seasons and straw mulching affected the total fruit number and marketable fruit number and weight of tropical squash. Interactions between season and cultivars and location affected the total and marketable fruit number and weight of tropical squash in Kamuli and gross margin of tropical squash produced in Uganda. Gross margins from tropical squash were affected by the interacting effects of subcounty location and cultivars and straw mulching in different seasons. Gross margins were higher in mulched plots than in the non-mulched plots during season two. Hybrid cultivars; Arjuna F1 and Pujinta F1 had higher gross margins in season one and two at Namasagali subcounty location and season two at Butansi subcounty location. Results in Ames, Iowa indicated cultivars affected the total and marketable fruit number and weights of kabocha squash. The interacting effects of straw mulching and location affected the total and marketable weight of kabocha squash. Straw mulching lowered soil temperature and increased soil moisture at soil depth of 0.15 m but did not differ at a deeper depth of 0.3 m. The study revealed that straw mulching and use of hybrid cultivars could improve yield and gross margins obtained from tropical squash production by smallholder youth farmers in Kamuli, Uganda.

Limited access to quality seed constrains vegetable productivity and food security in Uganda, where informal seed systems remain central to farmers’ access to seed but are inadequately documented and largely unregulated. This study documented vegetable seed production and management practices, identified opportunities and constraints within informal seed systems, and examined the role of community seed banks in strengthening seed security. Using a mixed-method approach, quantitative surveys and key informant interviews were conducted with seed producers, seed traders, and community seed bank leaders across Uganda. Study respondents were predominantly men, with most respondents aged ≥35 years, despite women’s and youth’s primary role in vegetable production. Respondents reported key seed management constraints of seed storage pests, low-quality seeds, inconsistent market supply and price fluctuations, limited capital, and weak regulatory oversight. Seed treatment practices primarily consisted of sun-drying and plant-based pesticides, while seed quality assessment relied largely on experience and visual inspection, using cues such as seed color, size, and cleanliness, with limited use of standardized testing. Given that most vegetable growers obtain seeds through community-based seed channels, strengthening actors’ capacity to produce and supply high-quality seed is essential for sustaining vegetable production, improving farmer incomes, and enhancing food and nutrition security.

Plinthite is a major pedogenic feature in the Kamuli catena, posing significant challenges for agricultural land use. This study investigates the morphological expression and mineralogical insights into plinthite within the soil-landscape of Kamuli District. Soil characterization involved detailed field morphological descriptions along the Kamuli catena followed by laboratory characterization of major soil properties. Plinthite mineralogy was determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Morphology of plinthic soils varied along the catena with summit pedons exhibiting shallow plinthic horizons and backslope pedons showing comparatively deeper occurrences. The lowlands underlain by alluvium of the Holocene lacked plinthite. Mineralogical analysis of ten plinthite samples identified two distinct assemblages. Group 1 (quartz, kaolinite, hematite, goethite, manganite) represents a highly weathered endmember associated with stable summits. Group 2 (muscovite, kaolinite, hematite, goethite, manganite), with elevated K, Mg, Na, and Ca in SEM-EDS, indicating they are recent compared to Group 1. This elemental composition directly reflects the signature of the parent material preserved within Group 2 samples. Plinthite in the Kamuli catena is a relict feature, whose formation is tied to past drainage regimes. Its multi-stage history is recorded in the two mineralogical groups separated by hundreds of thousands of years of landscape evolution. Group 1 represents plinthite from the deeply weathered African Surface. Group 2 is later formed on the substrate exposed by stripping along the Victoria Nile.

Tropical pumpkin (Cucurbita spp.) is an underutilized, nutrient-dense vegetable crop with potential to enhance food and nutrition security and generate household income among farming communities. In Uganda, farmers primarily obtain pumpkin seed through informal seed systems, including farmer-produced and -managed sources where seed quality is largely undocumented. This study evaluated the quality of pumpkin seeds collected from 16 selected districts in Uganda and provides the first baseline assessment of tropical pumpkin seed quality within farmer-produced and farmer-managed systems. Seed quality in this study was defined as the ability of seeds to germinate, exhibit high vigor, and remain free of fungal growth. Pumpkin seeds were assessed at 0, 3, and 6 months of storage under conditions representative of local seed traders (25 ± 5 °C; 60 ± 5% RH). Seed-associated fungi recovered on PDA containing streptomycin sulfate after 14 days of incubation were identified morphologically. Seed purity ranged widely (43.8–99.5%), indicating substantial variability among seed sources. Seed germination varied among districts, with most seeds showing improved germination after storage, whereas seed vigor declined with storage duration. Five putatively seedborne fungal genera, Fusarium, Aspergillus, Colletotrichum, Alternaria, and Rhizopus spp., were identified. The findings demonstrate substantial heterogeneity in farmer-produced and -managed seed, which is a predominant seed source in Uganda.