Improving sweet corn fertilizer-N efficiency promotes a more vigorous and healthy crop, rewards the grower with greater profits, and protects our water resources from nitrate-N pollution. Two areas of research that have the potential to improve the efficiency of fertilizer-N applications are the Minolta SPAD 502 chlorophyll meter and the presidedress soil N test. The SP meter is a rapid and nondestructive technique for assessing sweet corn leaf levels, and SP readings have been correlated to leaf N concentration. A presidedress soil N test measures the amount of soil N that will be available to the plant during the remainder of the growing season. SP meter readings combined with presidedress soil N analyses may be used to determine crop N needs and fertilizer-N sidedress application rates. Basing fertilizer-N sidedress application rates on actual crop N needs will reduce excess fertilizer-N applications and the resulting leaching of nitrates.
Carol A. Miles
Carol A. Miles
Sales of organic foods are one of the fastest growing segments of Washington state's food industry. In response to grower demand for information on organic and sustainable production practices, Washington State University (WSU) created an Extension Agricultural Systems position. This position has been instrumental in helping WSU gain the trust and recognition of organic growers. The position enabled WSU to demonstrate that it has a commitment to organic and sustainable research and extension activities. This paper describes the key activities of this position: 1) finding out research needs, 2) on-farm research approaches, 3) formation of regional research programs, and 4) creation of the WSU Food and Farm Connections Team. Grant funded on-farm research, interdisciplinary teams, and extension publications have been major emphases of the position.
Carol A. Miles
New foods have been introduced to the North American populations from many world cultures in both planned and unplanned situations. Success of such crops will depend on the acceptance of the consumers. Growers and retailers must educate customers about these new crops in order to ensure that the customer comes back for more. The different strategies that can be used successfully in the process of education, marketing, and promotion, including developing recipe cards, brochures, newspaper and magazine press releases, and talks and presentations to local and regional groups, will be discussed.
Carol A. Miles
Commercial edamame (Glycine max) varieties and advanced edamame breeding lines from the Asian Vegetable Research Development Center (AVRDC) were tested for adaptability to southwest Washington. Edamame, or green vegetable soybeans, are specialty varieties of soybeans that are eaten at the green stage as a vegetable. For the vegetable market, 25 beans must weigh at least 20 g. Experimental procedure was a randomized complete block design with four replications. Recommendations from AVRDC for plant spacing and fertilizer application and timing were followed. In 1995, 13 commercial varieties and 10 AVRDC breeding lines were tested in an on-farm location in Chehalis. At the same location in 1996, 10 of these commercial varieties were again tested along with an additional six commercial varieties. Also in 1996, 12 new AVRDC breeding lines were tested along with the single line that was selected in 1995. Both years, all commercial varieties were harvested more than 40 days later than their advertised days to maturity. Three commercial varieties, White Lion, Shironomai, and Butterbeans, were high-yielding in both years. In 1995, one AVRDC breeding line was selected in Chehalis, and in 1996 five additional AVRDC breeding lines were selected. Earliness is a key factor affecting suitability of commercial varieties and breeding lines to the Chehalis area. In this region, irrigation also appears essential for production of large beans for the vegtable market. Pod weight was not a good indicator of bean weight. Seed was collected in Chehalis from AVRDC breeding lines for use in future trials.
Sahar Dabirian and Carol A. Miles
Rootstock regrowth can prevent effective healing of grafted vegetable seedlings and outcompete the scion for light, space, and nutrients later in production. Rootstock regrowth is especially problematic for watermelon (Citrullus lanatus) because the crop is most commonly grafted using methods where meristematic tissue remains on the rootstock. The objective of this study was to test whether sucrose solutions [0% (water control), 1%, 2%, and 3%] applied as a drench to rootstock seedlings before grafting would increase the survival of watermelon grafted using the splice method where both rootstock cotyledons were removed to eliminate meristem tissue and rootstock regrowth. Starch accumulation in rootstock seedlings was the highest for plants that received 3% sucrose solution (71%), followed by plants that received 2% sucrose solution (52%), 1% sucrose solution (29%), and water (6%) (P < 0.0001). Survival (%) of splice-grafted watermelon seedlings 21 days after grafting was the greatest for plants that received 2% and 3% sucrose solution (89% and 82%, respectively), followed by plants that received 1% sucrose solution (78%), and was the lowest for plants that received water (58%) (P < 0.0001). There was a significant interaction due to repeat for both starch accumulation and grafted transplant survival; however, environmental conditions were similar for both repeats: the daily average temperature was 23 °C, the relative humidity (RH) was 64% to 67%, and the daily average light intensity was 224–243 µmol·m−2·s−1. Furthermore, while the vapor pressure deficit from 1:00 to 6:00 pm was 2.49 kPa for repeat 1 and 1.42 kPa for repeat 2, plant survival was greater in repeat 1 than repeat 2. These results indicate that drench applications of sucrose solution to rootstock seedlings before grafting can increase grafting success when both cotyledons are removed from the rootstock before grafting, but further research is needed to optimize the environmental conditions for the survival of grafted plants.
Sahar Dabirian and Carol A. Miles
The one-cotyledon splice grafting method is commonly used for watermelon (Citrullus lanatus) because it is relatively rapid and there is less rootstock regrowth than with other grafting methods. However, plants must rely on moisture in the air for survival during at least the first 4 days after grafting. In 2015 and 2016, greenhouse experiments were conducted to investigate if application of commercial stomata-coating and stomata-closing antitranspirant products, applied 1 day before grafting to both scion and rootstock seedlings, could increase the survival of watermelon transplants grafted using the one-cotyledon method. ‘TriX Palomar’ watermelon was grafted onto rootstock ‘Tetsukabuto’ (Cucurbita maxima × C. moschata) in Expt. 1, and onto rootstock ‘Emphasis’ (Lagenaria siceraria) in Expt. 2. The survival of grafted watermelon differed because of experiment (P = 0.0003), antitranspirant treatment (P < 0.0001), and experimental repeat (P < 0.0001). The survival of ‘TriX Palomar’ grafted onto ‘Tetsukabuto’ was greatest for plants treated with the stomata-coating + stomata-closing antitranspirants (92% to 100%), followed by the stomata-closing antitranspirant (79% to 97%), water (72%), and the stomata-coating antitranspirant (50% to 60%). For ‘TriX Palomar’ grafted onto ‘Emphasis’, plants treated with the stomata-closing antitranspirant had the greatest survival (87% to 97%), followed by stomata-coating + stomata-closing antitranspirants (84% to 94%), the stomata-coating antitranspirant (50% to 67%), and water (53% to 68%). In Expt. 3, stomatal conductance (g S) was similar for both ‘TriX Palomar’ and ‘Emphasis’ seedlings before treatment application, but differed because of the treatments 1 and 2 days after application. Stomatal conductance did not change for ‘TriX Palomar’ seedlings after application of the stomata-coating antitranspirant or water, or for ‘Emphasis’ seedlings after application of the stomata-coating antitranspirant. Stomatal conductance of ‘TriX Palomar’ seedlings decreased 57% to 62% after application of the stomata-closing antitranspirant and decreased 48% to 60% after application of the stomata-coating + stomata-closing antitranspirants. Stomatal conductance for ‘Emphasis’ seedlings increased 37% after water application, and decreased 58% to 68% after application of the stomata-closing antitranspirant, and decreased 42% to 45% after application of the stomata-coating + stomata-closing antitranspirants. The survival rate of grafted ‘TriX Palomar’ transplants was increased nearly 30% by application 1 day before grafting of the commercial stomata-closing antitranspirant or stomata-coating + stomata-closing antitranspirants in this study. Increase in grafting success is likely due to a reduction in transpiration that occurs when the stomata-closing antitranspirant is applied to the seedlings before grafting.
Carol A. Miles and Jaqueline King
In this 2-year study of ‘Brown Snout’ specialty cider apple (Malus ×domestica) grafted onto Malling 27 (M.27) and East Malling/Long Ashton 9, we compared weight of total harvested fruit, labor hours for harvest, tree and fruit damage, and fruit and juice quality characteristics for machine and hand harvest. Machine harvest was with an over-the-row small fruit harvester. There were no significant differences due to rootstock; however, there were differences between years for most measurements. Weight of harvested fruit did not differ because of harvest method; however, harvest efficiency was 68% to 72% for machine pick and 85% to 89% for machine pick + clean-up weight (fruit left on trees and fruit knocked to the ground during harvest) as compared with hand harvest. On average for the 2 years, hand harvest required 23 labor-hours per acre at a total cost of $417, while machine harvest required 5 labor-hours per acre at a cost of $93. There were no differences due to harvest method on damage to spurs (four to eight spurs damaged per tree) or limbs (0.5–0.8 limbs damaged per tree). Although there were also no differences due to harvest method on fruit bruising (100% for both harvest methods in this study), 10% of fruit were sliced and 4% of fruit were cut in half inadvertently with machine harvest, and none were sliced or cut with hand harvest. Harvest method had no effect on fruit quality characteristics, specifically, soluble solids concentration (SSC), pH, specific gravity, titratable acidity (malic acid equivalents), or percent total tannin, when fruit was pressed immediately after harvest or stored for 2, 3, or 4 weeks before pressing. Juice quality characteristics were affected by storage, and SSC increased 11% in 2011 (3 weeks storage), and 12% and 18% in 2012 (2 and 4 weeks storage, respectively). Similarly, specific gravity increased both years after storage, 1% in 2011, and 1% and 2% in 2012 (a 1% increase in juice specific gravity corresponds to a potential 1.3% increase in alcohol by volume after fermentation for cider). Both years, juice pH tended to decline when fruit was stored (0.01 pH units in 2011, 0.06–0.12 pH units in 2012). Overall, cider apple harvest with an over-the-row small fruit machine harvester used four times less labor than hand harvest, yield reached 87% that of hand harvest (when clean-up yield was included), and juice quality characteristics were not negatively affected. These results suggest that machine harvest may be suitable for cider apples if equipment is available and affordable.
Pinki Devi, Scott Lukas, and Carol A. Miles
Splice grafting with both cotyledons removed from the rootstock may significantly increase watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] grafting efficiency, eliminate rootstock regrowth, and reduce costs of watermelon transplant production. We evaluated the efficacy of antitranspirant and sucrose treatments on the survival of splice-grafted transplants and assessed the effects of grafting method and rootstocks on fruit yield and quality. First, in a greenhouse experiment, four commercial antitranspirants, applied to rootstock seedlings before splice grafting, increased transplant survival 21 days after grafting (DAG) from 7% to 35% to 68% (P < 0.0001). In a second greenhouse experiment, survival of splice-grafted seedlings was 91% for plants that received 2% sucrose solution + antitranspirant, compared with 67% for plants receiving 2% sucrose alone and 25% for plants that received only water (P < 0.0001). Finally, in a field experiment we compared splice- vs. one-cotyledon grafting with two rootstocks (‘Shintosa Camelforce’ and ‘Tetsukabuto’) vs. nongrafted plants. At 54 days after transplanting (DAT), survival of all grafted transplants averaged 96% with a plant vigor rating of 7.7/10 (10 = most vigorous), compared with 84% survival (5.8/10 vigor rating) for nongrafted transplants. Flowering was delayed by an average of 2 days for splice-grafted watermelon (37 DAT) vs. one-cotyledon grafted and nongrafted plants (P < 0.0001), but harvest date was the same for all treatments (70 DAT). Fruit were harvested 0, 7, and 14 days after fruit reached physiological maturity, and there was no difference in total yield or fruit quality between grafted and nongrafted treatments, with two exceptions. Fruit with splice-grafted ‘Shintosa Camelforce’ rootstock had the firmest flesh (8.2 N) compared with nongrafted transplants (5.3 N), and lycopene increased from 16.7 µg·g−1 at physiological maturity to as high as 31.4 µg·g−1 when harvested 7 days after physiological maturity (P = 0.0002). These results indicate that application of sucrose with antitranspirant to rootstock seedlings before grafting can increase the survival of splice-grafted watermelon, and splice-grafted watermelon perform similarly to one-cotyledon grafted and nongrafted watermelon plants in field production.
Sahar Dabirian, Debra Inglis, and Carol A. Miles
Verticillium wilt, caused by the soilborne fungus Verticillium dahliae, is a significant disease affecting watermelon (Citrullus lanatus) production in Washington State. This field study at three locations in Washington in 2015 compared verticillium wilt susceptibility, fruit yield and quality of nongrafted watermelon, and grafted plants grown with black plastic and clear plastic mulch. Overall for grafting treatments, area under disease progress curve (AUDPC) values were higher for nongrafted ‘TriX Palomar’ (765) than for ‘TriX Palomar’ grafted onto ‘Super Shintosa’ (132), ‘Tetsukabuto’ (178), or ‘Just’ (187). Overall for mulch, the AUDPC value was higher for plants grown with black plastic mulch (385) than for plants grown with clear plastic mulch (237). Overall for location, the AUDPC value was lowest at Eltopia (84), intermediate at Othello (182), and highest at Mount Vernon (680). At season end, more Verticillium microsclerotia were present in stems of nongrafted ‘TriX Palomar’ than in grafted treatment stems at Eltopia and Mount Vernon, but not at Othello. Differences in microsclerotia presence occurred only in the top or scion portion of the stem, but not in the graft union, rootstock, or crown portions of the stem. There was no difference due to mulch in regard to Verticillium microsclerotia detected in stem assays. After harvest, V. dahliae soil density under black plastic mulch increased 6-fold at Eltopia, 4.7-fold at Othello, and 1.9-fold at Mount Vernon. In contrast, V. dahiae soil density under clear plastic mulch was nearly identical to the level at planting at each location (<1, 2.6, and 27 cfu/g at Eltopia, Othello, and Mount Vernon, respectively). There was a significant interaction between grafting and location for fruit yield such that there was no difference at Eltopia and Othello, but at Mount Vernon, yield of nongrafted ‘TriX Palomar’ was lower (7.4 kg/plant) than for grafted plants (average 13.0 kg/plant). The number and weight of marketable fruit per plant were higher at Othello (4.0 and 27.65 kg/plant, respectively) than at Eltopia (2.0 and 12.23 kg/plant, respectively) and Mount Vernon (2.2 and 11.63 kg/plant, respectively). Fruit firmness was greater overall for all three grafted treatments (average 2.67 N) than for nongrafted ‘TriX Palomar’ (2.20 N), but there was no difference in total soluble solids (TSS) or lycopene content of fruit due to grafting. Yield, fruit firmness, and TSS did not differ due to mulch type; however, lycopene content was greater for plants grown with black plastic mulch than with clear plastic mulch at Eltopia. There was no difference in TSS due to location, but fruit firmness was lower at Eltopia and Othello (2.20 and 2.44 N, respectively) than at Mount Vernon (3.00 N), whereas lycopene content was less at Mount Vernon (27.85 μg·g−1) than at Eltopia or Othello (38.58 and 36.54 μg·g−1). The results of this study indicate that although verticillium wilt symptoms were visible in watermelon plants when V. dahliae level was <3 cfu/g of soil, watermelon yield was not reduced. However, when V. dahliae soil density was >50 cfu/g of soil, yield was greater for grafted plants and for plants grown with clear plastic mulch.
Sacha J. Johnson and Carol A. Miles
Successful grafting of vegetables requires high relative humidity (RH) and optimal temperatures for ≈1 week following grafting to reduce transpiration of the scion until rootstock and scion vascular tissue are healed together and water transport is restored. This study evaluated the effect of three healing chamber designs on the survival of grafted eggplant (Solanum melongena), tomato (Solanum lycopersicum), and watermelon (Citrullus lanatus). The three healing chamber designs were 1) an industry design, which was hand-misted, 2) a research design, which contained a humidifier, and 3) a simplified design, which was shadecloth only and hand-misted. All plants were self-grafted using the splice grafting technique, placed in the healing chamber for 7 days after grafting and evaluated for signs of wilting and graft failure from day 6 to day 14 after grafting. During the 7-day healing period, the industry design had the greatest fluctuation in temperature, the research design had the greatest fluctuation in RH, and the shadecloth only design had the least fluctuation in both temperature and RH. When the healing chambers were closed on day 2 after grafting, the industry healing chamber had higher mean temperature and RH (24.9 °C, 98%) than both the research (23.4 °C, 81%) and shadecloth only (23.3 °C, 52%) healing chambers. These results suggest that a humidifier may not be necessary to maintain high RH. Mean graft survival rates in the industry (69%) and research (66%) healing chambers were similar, and both were higher than that in the shadecloth only healing chamber (52%). Tomato had the highest rate (98%), eggplant was intermediate (82%), and watermelon had the lowest mean survival rate (7%); there was no interaction between healing chamber and crop. The very low survival rate of watermelon was most likely due to the grafting technique used in this study, which is not optimal for watermelon. Tomato graft survival was high in all three healing chambers (96% to 98%), suggesting that high RH is not essential for tomato graft survival. Eggplant graft survival decreased from 90% to 60% when RH was decreased, suggesting that high RH is essential for eggplant graft survival.