Effect of Nitrogen Rates, Planting Dates, and Irrigation Regimes on Potato Production in the Eastern Shore of Virginia

Potatoes in the Eastern Shore of Virginia are traditionally planted between late February and early April and harvested between early June and late August. Potato prices are usually higher early into the harvest season and decrease slowly as the season progresses. Early planting dates are desirable for farmers, as it allows them to perceive higher prices for their product, but early planting is also associated with lower air temperature during the early season, which in turn can affect plant development, water and nutrient uptake, and overall yield. Additionally, variations in soil properties often affect nutrient and water availability for plants, as well as the distribution of soil-borne insect pests. Additionally, several techniques are available to map the variations of soil properties in commercial potato fields, but little effort has been made to relate this information to the potential presence of soil-borne pests. Hence, the objective of this project was to evaluate the effect of planting dates, nitrogen (N) rates, and irrigation regimes on potato production. Two comprehensive studies were conducted between February and July 2022 and 2023. The objective of the first study was to evaluate the effect of N rates, planting dates, and soil physicochemical properties in potato production and the presence of soil-borne pests. This study was established in a split-plot design with four replications, with planting dates on the main plot and N rates and time of application on the sub-plot. Late March planting resulted in the highest total tuber yield, while early planting produced significantly larger tubers. Early March planting reduced plant development and emergence, probably due to lower air and soil temperatures. There was no interaction between planting dates and N applications. Using N rates higher than 147 kg ha-1 resulted in no significant differences in total tuber yield. Regression analyses showed that the Normalized Differences Red Edge (NDRE) is an excellent predictor of N content in plant tissue and tuber yield. Moreover, Ca and H saturation percentages were linked to wireworm damage levels using classification algorithms. Similarly, K saturation percentage was identified as a potential predictor of nematode presence in this region. A second study was established with the objective of evaluating the effect of N rates and irrigation regimes on potato production. The study was established in a split-plot design with four replications, with the irrigation method on the main plot and total N rate on the subplot. Results from these experiments showed higher growth and tuber yield when combining overhead irrigation with crop evapotranspiration (ETc) estimation. Moreover, there were no significant differences when using N rates higher than 112 kg ha-1. Overall, results from these experiments suggest no changes in current N rate recommendations for this region. Additionally, these results suggest planting in late March and using irrigation regimes based on evapotranspiration with overhead irrigation systems. Future research should focus on adaptive fertilization based on growing degree days and refinement irrigation determination practices.