The legacy phosphorus (P) in the Eastern Shore of Virginia poses significant challenges for crop nutrition and water quality. Nutrient losses from row crop agriculture and poultry litter applications have potential to cause water quality impairments affecting the environment, aquaculture, and tourism industries. To address these concerns, this study investigated P management strategies across various scales. The first component of the study focused on optimizing edamame production in the context of high legacy soil P levels and harvest efficiency. Over three years, field experiments on Bojac sandy loam soil assessed the effects of different P fertilizer rates and legacy P levels on edamame yield, biomass, and P uptake. Results showed that short-season edamame in high legacy P soils had significantly more yield than long-season varieties. However, additional P fertilization was deemed unnecessary for soils with P concentrations above 21 kg P ha-1, as current edamame P recommendations exceed the crop's P removal needs. Moreover, mechanical harvesting efficiency was notably higher for short-statured edamame varieties (89.3%) compared to tall varieties, indicating their preference for improved harvesting. The second component examined the influence of agricultural lime on legacy P phases in the soil. Lime was applied at rates ranging from 0 to 2690 kg ha-1 to an acid sandy loam Ultisol (pH < 5.1). Using partial Hedley P fractionation, changes in water-soluble P, soil test P (Mehlich-1 extraction), and total soil P (nitric acid digest) were monitored. Although lime application significantly affected soil pH, calcium (Ca), and magnesium (Mg), it did not significantly alter the relative proportions of water-soluble and soil test P. This indicates that while lime can improve soil pH and nutrient availability, it does not substantially impact P phase distribution. The final study utilized historical water quality data from the Virginia Institute of Marine Sciences and GIS technology to analyze the impact of land use and land cover (LULC) on nitrogen (N) and P concentrations in 52 watersheds. Row crop LULC was significantly correlated with higher total nitrogen (TN) concentrations (p = 0.03), while forested LULC was linked to lower TN (p = 0.02) and nitrate-nitrite (NOx) concentrations (p = 0.05). Thirty-two out of 52 watersheds had mean total P concentrations exceeding 0.10 mg L-1, with stormflow conditions showing significantly higher total P concentrations and loadings compared to baseflow. Landscape-scale turbidity strongly correlated with elevated total P levels, emphasizing the role of particulate P transport. Baseflow samples also had higher ammonia (NH3) and NOx concentrations, but stormflow resulted in higher loadings. In conclusion, effective P management on the Eastern Shore requires a coordinated approach that addresses soil, crop, watershed, and landscape-scale factors in cooperation with multiple stakeholder groups. This study highlights the importance of optimizing agronomic practices and implementing targeted conservation strategies to mitigate nutrient and sediment losses, thereby improving both crop production and environmental quality. / Doctor of Philosophy / The Eastern Shore of Virginia has high levels of phosphorus (P) due to past farming and poultry litter use, which can have a major impact on both farming and water quality. To address high soil P, our study looked at different ways to manage P effectively. First, we studied how to grow edamame (a type of soybean) more efficiently in soils with different P levels. Over three years, we tested various P fertilizer amounts and found that fast-growing edamame plants grew better in soils with high P than long-season varieties. We also discovered that adding more P fertilizer was not necessary. Additionally, short-statured edamame varieties were easier to harvest mechanically and had better harvesting efficiency compared to taller varieties, making them ideal for mass production. Next, we explored how adding agricultural lime might change the way P is stored in soil. We applied lime at different amounts to very acidic sandy soil and measured its effects. Although lime improved soil pH and availability of certain nutrients, it did not significantly change how P was distributed in the soil. Finally, we used maps and water quality data to see how different land uses, like row crops and forests, affect P and nitrogen (N) levels in local streams. We found the areas with more row crops had higher N levels, while forested areas had lower levels. We noticed that rainy conditions led to higher P levels in streams compared to normal flow conditions because the P was attached to soil particles, suggesting that reducing soil erosion and nutrient runoff is crucial. In summary, managing P is essential for both better crop yields and cleaner water. This study provides important insights to land managers to improve agricultural practices and protect local waterways.