The Michigan State University Potato Outreach Program, MSU Extension and Styma Potato Farms of Posen, Michigan, continued russet and tablestock variety trails in Presque Isle County in 2019. This year’s trial, hosted by the Styma Potato Farm, included 48 different varieties consisting of russet, red, yellow, round white and novelty type tubers. Varieties were planted in single, unreplicated rows on June 5, 2019, on an Omena fine sandy loam soil. The previous crop was alfalfa and the field was not fumigated. Tubers were planted 10 inches apart on standard 34-inch rows. Starter and sidedress fertilizer were applied by the grower at recommended rates according to soil analysis and best practices for the adjacent commercial field.
The 2019 growing season overall was cold and wet. May and June featured below average temperatures with above average rainfall. Summer finally arrived in July, brining above normal temperatures with adequate rainfall. With August, however, temperatures fell back below normal and rainfall was scarce. By the end of August, the area was approaching drought conditions. September brought normal temperatures, as well as excessive rainfall, which persisted into October. The plot was irrigated, so dry weather in August was not a yield-limiting factor. Only 2,510 base 40 growing degree days (GDD) were accumulated at this plot from planting to vine kill, roughly 200 GDD lower than the five-year average of 2,700 GDD for Presque Isle County potato trials.
Vines were desiccated Sept. 20, and the plot was harvested Oct. 18. Overall, disease incidence was low across the plot. Raw tuber quality was also good across most varieties. Common scab ratings averaged 0.5, on a scale of 0.0 to 5.0, across the plot.
Of the russet types, Silverton was the top performing variety, producing 439 hundredweight per acre of U.S. No. 1 tubers out of a total 480 hundredweight per acre harvested. After grading was completed, 58 percent of tubers were As, 3 percent Bs, 35 percent oversize and 4 percent were pick-outs. Tuber quality was good overall, the only issue being vascular discoloration on 10 percent of tubers. No common scab was present.
Reveille russet was a close runner-up, producing 431 hundredweight per acre of U.S. No. 1 tubers out of a harvested total of 507 hundredweight per acre. Quality was excellent in this variety, and it would have been the highest-yielding had it not been for 10 percent of tubers grading as pick-outs due to knobs causing misshaped tubers. There was also some skinning experienced in this variety.
Of the red skin varieties, the experimental line NDAF113484B-1, a selection from the University of Maine potato breeding program, was the top yielding variety, producing 667 hundredweight per acre of U.S. No. 1 tubers out of a harvested total of 699 hundredweight per acre. This variety was very uniform, as the total breakdown of this variety after grading was 95 percent As, 3 percent Bs, 1 percent oversize and 1 percent pick-outs. There was no incidence of common scab, but there was a moderate presence of silver scurf. Ten percent of tubers did have some vascular discoloration, but that was the only tuber quality issue.
Of the yellow types, Arizona was the top yielding variety. Approximately 587 hundredweight per cre of US No. 1 tubers were harvested out of the total 708 hundredweight per acre. Total breakdown after grading was 78 percent As, 11 percent Bs, 5 percent oversize and 6 percent pick-outs. Tuber quality was not as good in this variety compared to other yellow types, as 20 percent of tubers had hollow heart and another 10 percent had brown center. Some pitted lesions were present, leading to a common scab rating of 2.0 on this variety. Fioretta, Picobello and NY149 all yielded over 500 hundredweight per acre of U.S. No. 1 tubers as well, however NY149 had the most uniformity and highest tuber quality of all the top-yielding yellow types.
White Beauty was best performing round white type variety this year, producing 613 hundredweight per acre of U.S. No. 1 tubers out of the total 673 hundredweight per acre harvested. The total breakdown after grading this variety was 91 percent As, 6 percent Bs and 3 percent were pick-outs. Tuber quality was excellent, as well as scab rating. MSV179-1 was the first runner up, producing 529 hundredweight per acre of U.S. No. 1 tubers out of 550 hundredweight per acre harvested. This variety was very uniform with excellent tuber quality and scab rating.
Complete variety trail results for russet lines can be viewed here: Potato Outreach Program 2019 On-Farm Russet Variety Trials.
Complete tablestock variety trial results can be viewed here: Potato Outreach Program 2019 On-Farm Tablestock Variety Trials.