1995 CROP SEASON EXTENSION DEMONSTRATION AND RESEARCH REPORT ALASKA COOPERATIVE EXTENSION UNIVERSITY OF ALASKA FAIRBANKS FAIRBANKS, AK

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1 1995 CRP SEASN EXTENSIN DEMNSTRATIN AND RESEARCH REPRT ALASKA CPERATIVE EXTENSIN UNIVERSITY F ALASKA FAIRBANKS FAIRBANKS, AK Ken Krieg Editor February 1996

2 1995 RAINFED PTAT VARIETY DEMNSTRATIN KENAI PENINSULA DISTRICT, ALASKA by Thomas R, Jahns, Land Resources.District Agent Alaska Cooperative Extension CPERATRS: Agriculture and Forestry Experiment Station (AFES), Palmer; Plant Materials Center, Division of Agriculture, Palmer; Alaska Cooperative Extension, Kenai Peninsula District; Kathy Wahl, AK Work Program, Kenai; and Cheryl Wickstrom, IPM Pest Scout, Alaska Cooperative Extension, LCATIN: FUNDING SURCE: BJECTIVE: METHDS: Warren Larson Memorial Test Site, Kenai, Alaska Alaska Cooperative Extension; Plant Materials Center, Alaska Division of Agriculture. Assess rainfed yield performance of ten potato varieties for making varietal recommendations to central Kenai Peninsula commercial and home horticulture clientele. Certified potato seed was furnished by Mr. Bill Campbell of the Plant Materials Center, Division of Agriculture, Palmer, AK. Total experiment size was 24 ft x 70 ft ( a). The potato plots have been in yearly potato production since 1989 (Larson, 1993). A1995, 0-6 in, pre-fertilizer analysis (Michaelson, et al, 1992) of the Soldotna silt loam soil showed a ph of 5.8 and a ppm reading of: 37 nitrogen (N), 7 phosphorus (P) and 110 potassium (K). The experimental plots were broadcast fertilized on May 22,1995, using a hand-push, lawn-type, fertilizer spreader. All plots received a total application rate of Ib/a of N, P205 and K20, respectively. Following the fertilizer application, the fertilizer was rototilled into the top 4 in of the soil. No agricultural lime or pesticides were used. Varietal treatment plots measured 3 ft x 10 ft. Ten varietal treatments were randomly assigned to the experimental area, utilizing a completely randomized design, with 3 replications per treatment (30 total plots). Ten individual potato seed pieces, with a minimum of 2 eyes and weighing 1.5 to 2.0 oz, were hand planted approximately 2 in deep and 12 in apart down the middle of each varietal plot, on May 22,1995. Three bumper plants of a purple potato variety were planted (at 12 in spacings) between each varietal treatment plot (down the row) and two were planted on both ends of each row. Finally, an additional outside buffer row of a purple potato variety was planted on each side of the experiment. Potatoes were hilled July 26, Potatoes were harvested September 22,1995, Treatments were weighed and counted within 7 days of harvest. Green-growth, cracked and knobby tubers were excluded. Precipitation'and temperature data were monitored at the Kenai FAA Airport, adjacent to the north end of the Warren Larson Memorial Test Site. Growing degree day and precipitation data were supplied by USDA Agricultural Statistics Service, Palmer, AK (Brown, 1995). RESULTS: Environmental Data The following figure summarizes the heat units - growing degree days (GDD) accumulated and precipitation received during the 1995 potato growing season and the past 34 year average at the Warren Larson Memorial Test Site, Kenai, AK, 13

3 KJ 00 LL b s C Q LLJ Q z o heat unit accumulation data was not available after 9/14/ YEAR AVERAGE 9/22/95' C 8 o. o WEEKS F PTENTIAL PTAT GRWTH Cumulative growing degree days and precipitation between 1995 and the 34 year average, during potential potato growth (May through September). Warren Larson Memorial Test Site, Kenai, AK. In general, the 1995 potato growing season was warmer and wetter than average. In 1995 approximately 200 more GDD's were accumulated during the potato growing season than in 1994 (Brown, 1994); and approximately 400 more GDD's than normal (Brown, 1995). Total precipitation received during the 1995 potato growing season (11.34 in) was approximately double the precipitation received during the 1994 potato growing season. 14

4 (5.77 in; Brown, 1994); and 1.4 in more of accumulated precipitation than the 34 year average (Brown, 1995). The 1995 potato growing season (123 days) was 18% longer than in 1994 (104 days). Varietal Yield Performance The following table summarizes production data for each of the 10 potato varieties grown in 1995, f the four potato skin types tested, the white potato skin type had the highest average yield (12.7 T/a) and the highest average U.S. no. 1 production (9.0 T/a), while the yellow potato skin type had the lowest average yield (7.7 T/a) and the lowest U.S. no. 1 production average (4.2 T/a), Yield of 10 potato varieties grown at the Warren Larson Memorial Test Site, Kenai, AK, 1995, Production of Production of Skin Total Production1 U.S. No. 1 U.S. No. 1 Variety Type (Tons /Acre) (Tons /Acre) (%) Iditared % Rote Erstling % Sang re % Allagash Russet Russet % Lemhi Russet Russet % Bake-King % Butte % Green Mountain % Superior % Yukon Gold Yellow % AVERAGE % 1Total Production includes U.S. No. 1, U.S. No, 2 and oversize potatoes. Green growth, cracked and knobby tubers were excluded. 15

5 DISCUSSIN: Total production ranged from a high of 13,9 T/a (Green Mountain) to a low of 6.2 T/a (Allagash Russet), with an average yield, across all varieties of 11,1 T/a. While Green Mountain had both the highest total and U.S. no. 1 production of the varieties tested, Bake-King produced the highest U.S. no. 1 to total yield percentage (80%). f all varieties tested, Allagash Russet and Rote Erstling had the greatest disparity in total versus U.S. no. 1 production, 35% and 39%, respectively. A similar yield and % U.S. no. 1 production response from Rote Erstling has been observed in the Mat-Su area, as well (Jerry Purser, 1995 personal communication). The Allagash Russet variety has been one of the poorest overall performers in the rainfed potato variety demonstration conducted on the Kenai Peninsula since 1993 (Jahns, B). Healed-over growth cracks present on many of the potatoes harvested indicate symptoms of moisture stress. To what extent rainfed conditions are affecting total yield and U.S. no. 1 production remains to be investigated. Despite a relatively cool start and a generally wet summer, the 1995 potato growing season sustained higher average yields than in 1993 or 1994 (Jahns, 1994-B). This may, in part, have been the result of enhanced K20 fertility levels: (1993: ; 1994: ; 1995: ), as discussed in last year's potato variety trial report (Jahns, 1994-A). A reduction in moisture stress via 1995's higher precipitation levels, an 18% longer growing season than 1994, and a slight increase in heat units (GGD) may also have resulted in greater yields. No serious potato scab or other disease/insect infestations were encountered in any of the potato varieties evaluated in In conclusion, it is no surprise that the local favorites Green Mountain, Iditared, Superior and Bake-King continue to produce well. Less common varieties such as Butte and Lemhi Russet also deserve consideration. REFERENCES: Brown, D. 1995, Alaska Crop-Weather, Agricultural Statistics Service, U.S.D.A., Palmer. Brown, D Alaska Crop-Weather, Agricultural Statistics Service, U.S.D.A., Palmer.. Jahns, T.R A, "Rainfed fertilizer and potato variety demonstration Kenai Peninsula District, Alaska," Demonstration and Research Report, Alaska Cooperative Extension, University of Alaska Fairbanks, pp Jahns, T.R B. "Summary of potato variety trials Kenai Peninsula District, Alaska," Demonstration and Research Report, Alaska Cooperative Extension, University of Alaska Fairbanks, pp Larson, W, 1993 (1992 Crop Year).) "Potato Variety Trial," Demonstration and Research Report, Cooperative Extension Service, University of Alaska Fairbanks, pp Michaelson, G.J., C.L. Ping, G.A. Mitchell and RJ. Candler Methods of soil and plant analysis, University of Alaska Fairbanks soil and plant analysis laboratory. University of Alaska Fairbanks, Agricultural and Forestry Experiment Station,, Misc. Pub pp. 6, 7,14,17,18. Purser, Jerry Mat-Su District Agricultural Development Agent, Alaska Cooperative Extension, Palmer, AK. * Walworth, J.L Field crop fertilizer recommendations for Alaska potatoes. University of Alaska Fairbanks, Alaska Cooperative Extension Pub. 10G-00246A. 16