While much research has been conducted in organic farming, little has focused on tropical systems. Tropical, versus temperate, systems present additional challenges for organic producers, including differences in soils, temperature, daylength, rainfall, and humidity. Pest management in tropical organic systems can be particularly demanding due to the year-round pest pressure and optimal environment for pest proliferation. Weed management is essential for the production of high-quality watermelons, but can be difficult when herbicides are not permitted. Weeds also serve as a source of inoculum for disease organisms and a habitat for insects, both beneficial and detrimental. Many products have been advertised for pest control in organic farming systems, most of which have not been adequately evaluated in independent, replicated trials. Here we investigated alternatives to pesticides for the control of weeds, insects, and diseases in `Crimson Sweet' watermelons. A split plot on a RCBD with four replications per treatment was used, with weed treatment (± paper-grass mulch) as the main plot and 12 insect and disease control alternatives as subplots. The alternatives for insect and disease control included traditional copper-based fungicides, biological control agents, potassium bicarbonate, hydrogen dioxide, milk, and commercial formulations of essential oils. Weed abundance (percentage cover), disease severity (percentage disease), and insect damage (percentage foliar damage) were evaluated weekly using a modified Horsfall-Barratt scale. Yield and quality were measured at harvest on five plants from each replication. While none of the products should be relied upon as the sole means of managing pests, those with efficacy could be integrated into organic management programs.
Annette L. Wszelaki and Bryan Brunner
Matthew D. Kleinhenz and Annette Wszelaki
Yield and relationships among head traits were recorded in order to better understand the effects of planting date and cultivar selection on crop quality characteristics and to help increase the efficiency of cultivar development, evaluation, and selection. A total of seven cultivars of fresh market-type cabbage (Brassica oleracea L., Capitata Group) were planted in May and June of 1999 and 2000 at the OARDC Vegetable Crops Research Branch in Fremont, Ohio. Total and marketable yield, head traits (e.g., size, weight, density), and core dimensions were recorded at harvest. Main effects of year (Y), planting date (PD), and cultivar (C) and the Y × C interaction significantly affected seven to 10 of 10 head and core traits. However, the PD × C interaction was significant for head density, the ratio of head polar and equatorial diameter, and core base width. The Y × PD interaction was significant for six of 10 head and core traits. May planting tended to result in greater yield and larger, heavier heads with greater polar/equatorial diameter values relative to June planting. However, head density was unaffected by planting date. The number of head and core traits affected by planting date differed among cultivars. For example, six of 10 head and core traits were significantly affected by planting date in `Cheers' and `DPSX315' while one trait was affected by planting date in `SuperElite Hybrid'. The weight of numerous, individual, market-ready, trimmed heads showed a strong (avg. R 2 value = 0.92) quadratic relationship to average head diameter. These data suggest that large-scale germplasm evaluations may benefit by including multiple plantings, as head weight, volume, diameter, and shape were affected by planting date, possibly due to variation in temperature and rainfall patterns. The data also suggest that routine measurement of numerous head traits in the same evaluations may be unnecessary, as selected traits (e.g., diameter and weight, head volume, and core volume) were strongly related.
Annette Wszelaki and Matthew D. Kleinhenz
This is the second of two related reports dealing with the effects of cultivar × environment interactions on cabbage (Brassica oleracea L., Capitata Group) crop traits. This study examined planting date and cultivar effects on physical head traits of processing cabbage and compared these findings to those from a similar study of fresh market cabbage. Six cultivars of processing cabbage were planted in May and June-July of 1999 and 2000 at the OARDC Vegetable Crops Research Branch in Fremont, Ohio. Marketable yield for each crop was determined, and measurements were taken of head weight, diameter, density, and volume, and core length, base width, and volume on more than 450 individual heads. Head and core volume and head density were calculated from these direct measures. Year, planting date, and cultivar significantly affected the majority of head traits. May planting led to higher marketable yield and heavier heads with larger diameters than June-July planting. The most variable trait across cultivars was head volume, which was affected by planting date in all cultivars. Differences between processing and fresh market cabbage were found. Average head polar/equatorial diameter values were affected by planting date in the fresh market but not the processing study. In contrast, head density and core volume as a percent of head volume were affected by planting date in the processing but not the fresh market study.
Annette L. Wszelaki and Elizabeth J. Mitcham
Controlled atmospheres have been proven an effective postharvest disease deterrent for strawberries both in transport and storage. However, these treatments do not provide residual protection once the commodity is removed from the atmosphere, and the atmospheres can cause off-flavors in the fruit. Elevated oxygen atmospheres are a novel addition to this technology and could potentially provide better decay control without the harmful effects on fruit flavor aspects. Elevated oxygen will potentially discourage microbial growth, as anaerobes grow best under very low oxygen levels and aerobes grow best under atmospheric oxygen. Threshold elevated oxygen levels to prevent Botrytis cinerea growth in vitro and in vivo on strawberry were assessed. Botrytis cultures (mycelial plugs and spores) and fresh strawberry fruit were exposed to 21%, 40%, 60%, and 80% oxygen atmospheres at 5 °C for 5, 7, and 14 d. Growth of cultures from mycelial plugs was evaluated after treatment and during post-treatment incubation by measuring the diameter of the fungus. Spore germination and germ tube elongation were evaluated every 24 h for 3 days after treatment by counting the number of germinated spores and measuring elongation, respectively. Strawberry quality including firmness, color, soluble solids, titratable acidity, ethylene production and respiration rates, and presence of defects were evaluated upon removal from the elevated oxygen atmospheres as well as after 1, 3, and 5 d storage in air at 20 °C simulating market conditions.
Mary A. Rogers and Annette L. Wszelaki
High tunnels are rapidly gaining favor from growers in many regions of the United States because these structures extend the growing season and increase quality of high-value horticultural crops. Small to midsized organic growers who sell tomatoes (Solanum lycopersicum) for the fresh market can benefit from lower disease pressure and higher marketable yields that can be achieved in high tunnels. High tunnels also protect crops from environmental damage and benefit production of heirloom tomatoes as these varieties often have softer fruit and are more susceptible to diseases and cracking and splitting than hybrid varieties. The objective of this study was to determine the impacts of high tunnel production and planting date on heirloom and hybrid tomato varieties by observing differences in plant growth, yield, marketability, and early blight (Alternaria solani) development within an organic production system. This study showed no increase in total yields in high tunnels as compared with the open field, but increased marketability and size of tomatoes, and lowered incidence of defoliation resulting from early blight. Tomato planted earlier in both high tunnels and the open field yielded more marketable fruit during the production season than plants established on later planting dates. Hybrid varieties yielded more marketable fruit than heirloom varieties; however, heirloom tomatoes can have equivalent market value because of greater consumer demand and premium prices attained in the local market.
Annette Wszelaki, Karla Deza-Duran, and Carol Harper
Pigeon pea is an important food crop for the Puerto Rican diet, as well as the economy. Pigeon pea ranks fourth in production among edible legumes in production worldwide. It can be consumed dried or as a vegetable (fresh, frozen, or canned). Canned, frozen, and dried peas are commonly used when fresh peas are no longer available. Due to the preferred flavor of fresh pigeon pea, it commands a higher market premium, selling for more than twice the price of the dried product. Although there is a great demand for this vegetable in Puerto Rico, virtually no research has been done on fresh pigeon pea postharvest physiology and its overall keeping quality. Baseline data on pigeon pea physiology, including respiration and ethylene production rates, soluble solids, titratable acidity, color reflectance, chlorophyll content, and responses to ethylene are presented here in order to establish the optimum storage temperature. Using this information, fresh pigeon pea consumption could increase locally, and exporting opportunities for shipping pigeon pea to alternative markets could be expanded.
Jenny C. Moore and Annette L. Wszelaki
Plasticulture systems with polyethylene (PE) mulch and drip tape are common for production of peppers (Capsicum annuum L.) in the United States because of their soil warming, moisture conservation, and other advantageous effects. However, disadvantages include disposal costs and plastic pollution of the environment and temperature stress in warm climates with black mulch. Use of biodegradable plastic mulches (BDMs) is becoming more common, as they provide the same benefits of PE mulch without the disposal problems. In 2017 and 2018, we conducted experiments in Knoxville, TN, comparing production of pepper fruit with five different BDM [one white-on-black (WOB) and four black], one black PE mulch, one brown creped, paper mulch, and bare ground control treatments. We also measured the durability and effectiveness of weed suppression of the different mulches over the growing season compared with a hand-weeded bare ground control. Most mulches were degraded, with 40% to 60% of the soil exposed by the end of the season, with the exception of the paper mulch, which was completely degraded at the end of both seasons. Yields were similar among treatments in 2017, with the exception of Naturecycle, which had the lowest yield. Weed pressure was severe, especially in 2018, largely due to early penetration of all mulches except paper by nutsedge. Due to the early and season-long weed pressure and heat stress in black mulches, there were fewer healthy plants in all black-colored mulch treatments in 2018, leading to reduced yields in these treatments. Paper mulch was the only treatment that prevented nutsedge growth; therefore, this treatment and the hand-weeded bare ground treatment had the greatest yields in 2018. WOB also had yields comparable with paper and bare ground plots in 2018, likely due to the cooling effect of the white mulch. The results suggest that in hot climates and in fields infested with nutsedge, paper mulches perform best for midseason pepper cultivation due to the cooling effects and superior weed control.
Matthew Kleinhenz, Annette Wszelaki, Sonia Walker, Senay Ozgen, and David Francis
Successful organic farming requires synchronizing soil-based processes affecting nutrient supply with crop demand, variable among and within crops. We report here on two studies conducted in transitional- (TO) and certified-organic (CO) systems containing subplots that, annually, were either amended with compost or not amended prior to vegetable crop planting. Dairy-manure compost was added at rates providing the portion of a crop's anticipated nitrogen requirement not provided by a leguminous rotation crop and/or carryover from previous compost application. In the TO study, potato (2003), squash (2004), green bean (2005), and tomato (2006) were planted in main-season plots in open fields and high tunnels, and beet, lettuce, radish, spinach, and swiss chard were planted in high tunnels in early spring and late fall. Long-term CO open-field plots (±compost) were planted to multiple varieties of lettuce, potato, popcorn, and processing tomato in 2004–2006. Drip irrigation was used in all TO plots and CO lettuce and processing tomato plots. Treatment effects on crop physical and biochemical variables, some related to buyer perceptions of crop quality, were emphasized in each study. Yield in TO, compost-amended plots exceeded yield in unamended plots by 1.3 to 4 times, with the greatest increases observed in high-tunnel-grown mesclun lettuce and the smallest response observed in potato. Similar results were found in CO plots, although compost effects differed by crop and variety. The data suggest that: 1) compost application and the use of specific varieties are needed to maximize yield in organic vegetable systems in temperate zones, regardless of age; and 2) production phase management may influence buyer-oriented aspects of crop quality.
Annette Wszelaki, Jeannine Delwiche, Sonia Walker, Rachel Liggett, Joseph Scheerens, and Matthew Kleinhenz
Sensory evaluations (triangle tests) were used to determine if panelists could distinguish, by tasting, cooked wedges of potatoes grown organically, either with or without compost, and conventionally. Mineral and glycoalkaloid analyses of tuber skin and flesh were also conducted. When the skin remained on the potatoes, panelists detected differences between conventional potatoes and organic potatoes, regardless of soil treatment. However, they did not distinguish between organic treatments (±compost) when samples contained skin or between any treatments if wedges were peeled prior to preparation. Glycoalkaloid levels tended to be higher in organic potatoes. In tuber skin and flesh, potassium, magnesium, phosphorus, sulfur, and copper concentrations were also significantly higher in the organic treatments, while iron and manganese concentrations were higher in the skin of conventionally grown potatoes.
Shuresh Ghimire, Arnold M. Saxton, Annette L. Wszelaki, Jenny C. Moore, and Carol A. Miles
Biodegradable mulches (BDMs) provide a unique advantage to growers in that they can be tilled into the soil after use, eliminating disposal costs that include time, labor, and equipment needs. Biodegradation of BDMs in the soil can be assessed by the presence of visible mulch fragments; although this is not a direct measure of biodegradation, it provides an initial estimation of mulch biodegradation. We carried out three field experiments to develop a protocol for quantifying BDM fragments in the soil after soil incorporation of mulch. Expt. 1 was done at Mount Vernon, WA, and Knoxville, TN, using five BDMs in four replications, including a polyethylene (PE) mulch reference treatment (three replications and at Mount Vernon only), and a ʽCinnamon Girl’ pumpkin (Cucurbita pepo) test crop. At the end of the growing season, mulches were tilled into the soil to a depth of 6 inches and within 16 days, five soil samples were collected with a golf hole cutter (4 inches diameter and 6 inches deep). Fifty-nine percent of the PE mulch fragments were recovered from the reference treatment. Among the remaining treatments, there was a high plot-to-plot variation as to the percent of the BDM recovered (3% to 95% at Mount Vernon, 2% to 88% at Knoxville). To exclude the possibility of mulch degradation impacting mulch recovery, in Expts. 2 and 3 (at Mount Vernon only), one BDM was laid, then tilled into the soil and sampled using the same sampling core as in Expt. 1, but all in 1 day. In Expt. 2, 15 soil samples were collected per plot, which recovered 70% of the mulch, and in Expt. 3, the entire plot was sampled by collecting 128 soil samples per plot, which recovered 62% of the mulch. In summary, sampling with a relatively large core recovered less than 70% of tilled-in mulch, there was high variability between plots within each treatment because of uneven distribution of the mulch fragments in the plot, and even 50 samples per plot did not provide an accurate estimate of the amount of mulch remaining in the field. Thus, soil sampling with a large core was ineffective, and new sampling methods are needed to assess the amount of BDM remaining in the field after soil incorporation.