10:15am-10:45am
Evaluation the effects of variable vine-kill, and harvest date on tuber dormancy of three russet potatoes
Thomas r. Stefaniak, University of Minnesota

               Pre-harvest vine-kill, which is the desiccation of potato vine to halt the tuber growth, ensures reduction of secondary growth, better separation of tuber from stolon during harvest, desirable tuber skin set and wound-healing. The common potato agronomic practice includes application of contact broad spectrum herbicide to accomplish vine-kill before harvest. We postulate that the total growing days or timing of vine-kill and duration between vine-kill and harvest impact, postharvest storage qualities such as duration of tuber dormancy. Therefore, the primary objective of this study was to determine the effects of growing days and the period from vine-kill to harvest on dormancy progression of three russet potato cultivars (Elk River Russet, Mercury Russet, and Russet Norkotah). Potato tubers were grown in Sand Plains Research Farm in Becker, MN. Vine-kill was done by hand by severing them at soil level with a sickle at two dates after planting (95 and 115). The plots were then harvested at two and three weeks after each vine-kill treatment. Additionally, one set of tubers from each vine-kill treatment were harvested at 14 days post vine-kill, while a second set of tubers were harvested 21 days post vine-kill. Field experiment was repeated in three consecutive years (2021-2023). After harvest, tubers were cured for two weeks (20°C and 95% RH), cooled down (1.5°C/day) and placed in cold storage (8°C and 95% RH). Commencing of dormancy and sprout growth were monitored at weekly intervals. Initiation of eye movement was recorded, and length of sprout was measured separately for primary and secondary meristems. Results from the first year (2021) suggested that vine-kill after 115 growing days delayed sprouting in all three cultivars when compared to vine-kill treatment of 95 growing days. Among potato cultivars, tubers of Elk River Russet and Russet Norkotah exhibited longer dormancy than Mercury Russet.

10:45am-11:00am
Effects of Cover Crops on Soil Health of the Fumigated Potato Field in the Columbia Basin
Haoyang Lyu, Oregon State University

               Soil fumigation and cover crops as the main field practices may affect soil health and potato production, but the relevant information is limited. To fill the knowledge gap, two-year field experiments were carried out using a split-plot design with four replicates at the Adkins sandy loam soil in Hermiston, OR. The main plots were fumigation treatments including metam sodium, Telone, Telone plus metam sodium (Mix), and non-fumigation control, while the subplots were cover crop treatments including wheat, mustard, winter pea, radish, and non-cover crop control. Soil fumigation occurred in early October. Cover crops were planted two weeks later and terminated in early April, followed by potato season from late April to early September. Soil health parameters including physical, chemical, and microbial properties were determined after fumigation, at cover crop termination, and potato harvest. Potato yield and quality were measured upon harvest. The results showed that the soil pH, NH4-N, K, Ca, Mg, S, Zn, Fe, Mn, and Cu are significantly affected by fumigation treatment across the whole experimental period, although no differences were shown right after fumigation. Soil organic matter and soil organic nitrogen decreased in the fumigated treatments in comparison with non-fumigation control. Cover crops significantly improved soil CEC compared with no cover crop treatment. Among the cover crops, the total nitrogen in the soil of wheat decreased by about 7%, and phosphorus decreased by about 37% compared with other cover crop treatments. Soil health parameters changed greatly among different sampling events. Soil fumigation did not impact potato yields but specific gravity was improved by metam sodium compared with Telone and non-fumigation control. Our study suggests that fumigation affects soil health significantly, while cover crops have limited effect. Further studies are needed to search for solutions to improve the effect of cover crops on soil health in fumigated soils.

11:00am-11:15am
Modeled Evapotranspiration Efficacy Dependent on Potato Spatial Arrangement and Plant Population
Jacob P. Meeuwsen, Washington State University

               Potato growers facing water shortages will likely lose yield and money; however, adjustments in plant populations and spatial arrangement may minimize losses by optimizing crop water productivity. Alternately, do changes in plant populations and spatial arrangement affect the efficacy of modeled evapotranspiration (ET)? To provide growers solutions, field trials were conducted during 2023 using two potato cultivars (Clearwater Russet and Ranger Russet) planted into 6 spatial arrangements (two row widths (32 and 34 in.) x four in-row spacings (6, 9, 12, and 15 in.)) and irrigated with four season-long, ET replacement rates: 60%, 80%, 100%, and 120%. Plant populations ranged from 12,299 to 32,670 plants/A. Irrigation treatments were implemented following full plant emergence. ET was measured and predicted using soil moisture and environmental data. When data were averaged across cultivar and in-row spacing, the lower plant populations of the 34-in. rows (19,730 plants/A) produced higher yields and economic returns than the more populated 32-in. rows (20,963 plants/A) when irrigation was reduced to 60% of modeled ET; however, production with 80% and above ET replacement resulted in the highest overall yields and economic values when plants were grown in 32-in. rows. The highest yield was produced by the highest plant population (32,670 plants/A) irrigated with the most water (32-in. rows x 6-in. in-row and 120% ET replacement); this plant population also produced the lowest economic return when ET replacement was reduced to 60%. The highest economic return was produced with 32-in. rows x 15-in. in-row and 80% ET replacement. Data from the first of a three-year trial indicate that indeed, growers should reduce plant population if faced with significant water shortages and that the efficacy of modeled ET is dependent on spatial arrangement and plant population.

11:15am-11:30am
Optimizing Nitrogen Rate and Timing for Alturas Potatoes in the Columbia Basin of Oregon
Ruijun Qin, OSU             

               The Columbia Basin region of Oregon is a major potato producer, where growers often apply 300 to 450 kg ha-1 of nitrogen (N) to guarantee economical yield. Nitrogen fertilizer is applied as pre-plant fertilization and in-season fertilization, and the efficiency of split application is unknown for growers. Therefore, there is a need to assess the optimum rate and timing for nitrogen application. A field trial was conducted on an Adkins fine sandy loam soil in Hermiston, OR, to determine the effect of eight treatments consisting of various N fertilizer rates and timing (0, 168 pre-plant, 280 pre-plant, 392 pre-plant, 56 pre-plant + 336 in-season, 112 pre-plant + 168 in-season, 112 pre-plant + 280 in-season,  224 pre-plant + 168 in-season N kg ha-1) on the yield of Alturas potatoes. Urea and UAN32 (foliar application) were applied for pre-planting, and in-season, respectively. Results showed that N treatments have significant effects on tuber size (i.e., <113 g and 171-283 g), US No. 1, total yield, and specific gravity. The treatment of 112 pre-plant + 168 in-season had the highest US No. 1, total yield, and tuber size of 171-283 g. However, the control had the lowest tuber yield and size. Nitrogen application decreases specific gravity. The best N rate should be 280 kg/ha with the split application (40% pre-plant, and 60% in-season). Increasing the application rate to more than 280 N kg/ha not only cannot increase the yield but also may decrease the tuber quality.

11:30am-11:45am       
Analysis of weight loss in Russet potatoes based on transpiration and respiration rates
Gustavo Teixeira, University of Idaho

               Potatoes are usually stored at low temperatures and high relative humidity (RH) to control water loss, which is the most important component of tuber’s weight loss. In general, potato water loss is related to the tubers’ evaporation through its skin 97.6% and only 2.4% via the lenticels along with the carbon dioxide (CO2) produced by respiration. However, underestimating the contribution of respiration as a water-loss mechanism can result in inaccurate weight-loss determination. Thus, the objective of this study was to analyze and evaluate the contribution of respiration to water loss, associated with transpiration in Russet potatoes. Tubers of ‘Russet Burbank’, ‘Ivory Russet’, ‘Dakota Russet’, and ‘Rainier Russet’ were cured at 12.8°C and 95% RH for 14 days. After curing, the temperature was reduced to 5.5°C, 7.2°C, and 8.9°C with 95% RH, and maintained for up to 9 months. ‘Dakota Russet’ had the highest mass loss during nine months in storage, regardless of the storage temperature. Different Russet potato cultivars had varying rates of mass loss, with ‘Dakota Russet’ having the highest mass loss and effective diffusivity (Deff) and ‘Rainier Russet’ having the second-highest mass loss. The transpiration rate per unit of initial mass (TRm) varied based on storage temperatures from 0.014 ± 0.005 g kg-1 h-1 at 5.5°C, 0.016 ± 0.006 g kg-1 h-1 at 7.2°C, and 0.017 ± 0.007 g kg-1 h-1 at 8.9°C, respectively. The transpiration rate per unit area (TRs) decreased faster until the 4th - 5th month in storage. The main factor contributing to the total mass loss was the water vapor pressure deficit, though respiration rates also played a role. Respiration rates contributed to 3.9% (‘Dakota Russet’), 6.0% (‘Rainier Russet’), 7.8% (‘Russet Burbank’), and 11.8% (‘Ivory Russet’). Further studies are needed to understand why ‘Dakota Russet’ experiences greater mass loss than other Russet cultivars.

11:45am-12:00pm
Potato Tuber Nutrition as Affected by Potassium Fertilization
Ruijun Qin, OSU

               Potato (Solanum tuberosum L.) crops require a high amount of potassium (K) to achieve the ideal yield and quality. However, the effect of K fertilization on potato tuber nutritional value is largely unknown. Based on the tubers from two-year field trials on a Quincy loamy fine sand soil in the Columbia Basin region of Oregon, we evaluated yield, specific gravity, nutritional contents (i.e., ascorbic acid, tyrosine, chlorogenic acid, tryptophan, phenylalanine), and nutrient contents (nitrogen [N], phosphorus [P], K, and sulfur [S]) of three potato varieties (Clearwater Russet, Russet Burbank, and Umatilla Russet) under three K rates (0, 448, and 897 kg ha-1). Our results showed that the K application increased the yield of >170 g tubers but had no considerable effect on the total tuber yield. The application of K tended to decrease specific gravity regardless of varieties and years. Russet Burbank had the lowest specific gravity while Clearwater Russet had the highest one. Most of the nutritional contents were higher in 2020 than in 2021. Russet Burbank generally had the highest nutritional contents except for ascorbic acid compared to two other varieties. The application of K generally did not affect tuber nutritional contents but reduced the amounts of tyrosine in Clearwater Russet and Umatilla Russet in 2020. Fertilization of K resulted in an enhanced K content in the tuber, with the highest K application rate exhibiting a 35% increase in K compared to the control. However, it did not have any discernible effects on N, P, and S contents in the tubers. The tuber P and S were lower in Russet Burbank than other varieties. In general, there is no strong relationship between K fertilization and tuber nutritional contents.