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Dairy manure applications are common practice in southern Idaho. Questions have arisen regarding the salt accumulations commonly associated with dairy manure applications on salt-sensitive crops like potatoes. The objective of this 2-year study was to evaluate the impact of dairy manure, dairy compost, dairy lagoon water and fertilizer application on salt accumulation and tuber yields in south-central Idaho based on grower-reported nutrient applications and yields. Soil samples and grower-reported tuber yield information were collected midseason (during time period of July 1st-July 30th) from 84 cooperator potato fields in south-central Idaho in both 2009 and 2010. Soil samples were collected to a 30 cm depth and analyzed for soil electrical conductivity (EC), soluble K, Na, Ca, Mg, and pH. Information on manure application, cultural management practices, and total tuber yield was collected for each field. Average reported application rates (wet basis) of these amendments were: 128 Mg ha⁻¹ dairy manure (28 fields), 29 Mg ha⁻¹ dairy compost (11 fields), 415,000 l ha⁻¹ dairy lagoon water (9 fields), or no manure applied (33 fields) over the 4 year period prior to the study. Mean soil soluble K for dairy manure (1.6 mmolc L⁻¹) and dairy lagoon water fields (1.4 mmolc L⁻¹) were significantly greater than dairy compost (0.6 mmolc L⁻¹) or fertilizer fields (0.4 mmolc L⁻¹). Manure application history had no significant treatment effect on soil electrical conductivity (EC), sodium adsorption ratio (SAR), soluble Na, Ca, or K, soil pH, or grower-reported total tuber yield. These overall findings suggest that current dairy manure, compost, and lagoon water application practices to potato production systems in south-central Idaho are not significantly influencing tuber yield or soil salt accumulations. However, significant soluble K accumulations in the soil suggest that dairy manure and dairy lagoon water applications should still be monitored to avoid potential salt accumulations and yield losses.

The use of accent lighting in retail stores has focused illumination on potatoes for greater consumer awareness. Unfortunately, this directed light on displayed potatoes may impact the rate or level of tuber greening. The objective of this study was to evaluate the influence of various retail accent light sources on greening and quality of illuminated tubers. Two separate experiments exposed ‘Russet Burbank’ potato tubers to fiber optic, ceramic metal halide, fluorescent, fluorescent with filter lighting (experiment 1) and fiber optic, halogen, and fluorescent lighting (experiment 2). In each experiment, tubers were exposed to a consistent light intensity (1390 lx in experiment 1 and 1300 lx in experiment 2) in addition to a dark control. Tubers were illuminated for 22 h per day at an ambient room temperature of 22 C. Six randomly selected tubers were evaluated for level of greening, chlorophyll concentration, and weight loss at day 0, 2, 4, 7, and 9. Total glycoalkaloid content was analyzed at days 0 and 9. In experiment 1, the fiber optic and fluorescent illuminated tubers showed significantly lower chlorophyll content compared to the ceramic metal halide light source. There was no significant difference in chlorophyll level or greening rating between the fluorescent light source and fluorescent with filter. In experiment 2, the fiber optic illuminated tubers had lower chlorophyll content and less visual greening compared to the halogen illuminated tubers. Total glycoalkaloids were not significantly impacted by light source. The use of fiber optic lighting or a combination of fiber optic lighting with standard fluorescent lighting would retard the progression of greening in the retail store yet potentially highlight the commodity for consumer eye-appeal.

Russet Burbank is the predominant potato ( Solanum tuberosum L.) cultivar grown and stored for fresh market and frozen processing (French fry) use in North America. Multi-year assessments of potato tuber quality under different storage regimes can provide information about a cultivar’s ability to retain process quality when challenged with seasonal variations across multiple years. The objective of a 15-year study initiated in 1999 was to evaluate the quality of Russet Burbank tubers grown and stored at the Kimberly Research and Extension Center. Potatoes were measured for specific gravity at harvest and stored for eight months under three temperatures (5.6, 7.2 and 8.9 °C) and periodically sampled throughout the storage season to determine dormancy length, sugar content, fry color and mottling severity (a quality issue), and weight loss. The year in which the crop was grown significantly ( p  < 0.001) affected all quality characteristics except specific gravity (average ranged between 1.071 and 1.081). Tubers held during the 2011–2012 and 2013–2014 storage seasons exhibited generally higher glucose, darker fry color, more severe mottling, and higher weight loss. Average sucrose content at 7.2 °C and 8.9 °C across the 15 years significantly decreased over the eight-month storage while average glucose content remained consistent after first month of storage. Average percent weight loss across the 15 years was 6.1 % after eight months in storage. This 15-year study emphasized that variation of post-harvest storage quality from year to year was likely a result of variable seasonal growing conditions. Storage temperatures between 7.2 and 8.9 °C were the optimum range for storing fry processing Russet Burbank potatoes and the warmer temperature of 8.9 °C appears to ameliorate the seasonal effects on glucose content and fry color to maintain better processing quality throughout storage.

Chlorpropham (CIPC) is a highly effective potato (Solanum tuberosum L.) sprout inhibitor. Some export regulations require CIPC or other sprout inhibitor to be applied to potatoes as a general phytosanitary measure. In addition, due to trucking and temporary storage issues, seed potatoes may be inadvertently exposed to CIPC. The objective of this 2-year study was to document the effects of several low rates of CIPC application or contamination on emergence, yield, and grade of the subsequent crop. CIPC was sprayed on whole ‘Russet Burbank’ seed tubers at rates of 0, 1.3, 2.5, 5.0, and 10.0 ppm CIPC. Seed tubers were cut, planted and grown under typical commercial practices for Idaho. Low rates of CIPC (1.3 and 2.5 ppm) applied to tubers resulted in significant delays in emergence compared to the untreated control. Some plants failed to emerge from seed treated with 5 or 10 ppm CIPC. CIPC treatment resulted in total yield decreases of 26 % (2.5 ppm CIPC) to 78 % (10 ppm CIPC) in 2009 and 36 % (1.3 ppm CIPC) to 94 % (10 ppm CIPC) in 2010 compared to the untreated controls in each respective year. Harvested tuber size profile was significantly altered by CIPC applications with higher rates producing smaller potatoes. These dramatic reductions in yield reinforce the importance of avoiding all potential for CIPC contamination of seed. The study also documents the severe consequences of planting commercial potatoes exported for consumption that have been treated with CIPC.

2,4-D has been used since the 1950’s to enhance color in red-skinned potatoes, but there is little research on the potential use of other plant growth regulators to improve tuber skin color in the wide range of specialty potatoes now available on the market. Field trials conducted at Parma, ID in 2009 and 2010 evaluated the effect of foliar applications of 2,4-D, NAA, and LPE on plant height, foliar injury, tuber yield, size distribution, and skin color of six specialty potato cultivars. Skin color was rated visually and via HunterLab colorimeter at harvest, and again after storage (132 days in 2009 and 93 days in 2010) at 4 °C and 95 % R.H. 2,4-D caused slight foliar injury and reduced tuber size in all cultivars. It also increased visual skin color rating in the red-skinned cultivars ‘Red LaSoda’ and ‘TerraRosa’ at harvest and after storage, and influenced incidence of pink coloration around the eyes of ‘Yukon Gem’ tubers, but did not affect color of blue/purple-skinned cultivars. NAA and LPE did not consistently influence plant growth, yield, tuber size or visual skin color in any cultivar. Colorimetric evaluations mostly agreed with the visual ratings, and indicated that storage significantly altered skin color in all cultivars, regardless of growth regulator treatment.

Potato growers in Idaho and other dairy producing regions often grow potatoes on fields that have had a history of fresh and composted manure applications. Growers remain uncertain of the impacts that previous manure applications will have on tuber yield and quality, as well as diseases, physiological disorders, and contamination by human pathogenic bacteria such as E. coli. The focus of this study was to determine the long term effects of manure, compost, and chemical phosphorus (P) fertilizer applications on tuber yields, tuber quality, nutrient uptake, tuber disorders and diseases, and soil nutrient concentrations. Russet Burbank potatoes were grown in 2008 and 2009 on plots that had received dairy manure, dairy compost, P fertilizer, or no P source (control) at the same target P rate in 2003, 2004, and 2005. Compared with the P fertilizer treatment, applications of manure and/or compost significantly increased total yields, soil potassium (K), soil nitrate (NO 3 -N), early season petiole P, and late season petiole K in at least one year of the two-year study. There were no significant differences between P fertilizer, manure, and compost treatments on soil test P, late season petiole P, early season petiole K, E. coli populations on tuber surfaces, common tuber diseases and disorders, and tuber quality. Based on our findings, tuber yields significantly increased three years after applications of fresh and composted dairy manure, while tuber diseases, disorders, and quality were not affected.

A major component of managing potato quality in storage is effective sprout inhibition. Sprouting causes increased weight loss, reduced tuber quality and impedes air movement through the potato pile. The primary method to control sprouting in storage is with postharvest applications of isopropylN-(3-chlorophenyl) carbamate (chlorpropham; CIPC). CIPC inhibits sprout development by interfering with cell division. However, a recent Environmental Protection Agency mandate, from the requirements of the Food Quality Protection Act (FQPA) of 1996, resulted in a reduction in allowable CIPC residue on fresh potatoes in the United States from 50 ppm to 30 ppm. This mandate coincides with tolerance reductions or restrictions for use of CIPC in other parts of the world. CIPC is an effective sprout inhibitor although factors such as storage conditions, application technology, and cultivar can impact that effectiveness. Alternative sprout inhibitors to CIPC continue to be evaluated. Essential oils (e.g., caraway, peppermint, spearmint, clove) or their components (e.g., s-carvone, eugenol), and hydrogen peroxide-based materials, physically damage the developing sprout and suppress sprout elongation. However, repeated or continuous application of these compounds may be necessary for efficacy. Substituted naphthalenes (e.g., dimethyl naphthalene, diisopropyl naphthalene) may help reduce the amount of CIPC applied and/or our dependency on CIPC for sprout suppression in storage. The objective of this review is to summarize the current use of CIPC for potato sprout inhibition in storage and to review the status of current research on other postharvest applied compounds or materials that may be used as alternatives for CIPC.

A 2001 survey indicated that many growers are reluctant to adopt research-based recommendations because of a perception that it is not practical or applicable to their specific farming operation. Other growers, however, appear to adopt these practices successfully. Highlighting \"model\" growers is a method that can be used to field-test research findings and facilitate grower adoption. The objectives of this project were to: 1) establish field demonstrations with potato (Solanum tuberosum L.) growers who generally follow research-based best management practices (BMPs); 2) establish plots within each field to compare BMPs with a high input, maximum yield management (MYM) approach; and 3) enhance grower confidence regarding research-based BMPs. Fourteen field trials were conducted in the Pacific Northwest during 2002-2005. Five replicates of BMP and MYM plots were established in each field. The BMPs consisted of sampling, scouting, and use of prediction models to aid in determining rate and timing of inputs to maximize returns. In contrast, the MYM approach was based on tradition and calendar timing, with a near zero tolerance for pest and nutrient limitations. The MYM plots had 1.7 to 13.2% more fertilizer and pesticide costs than the BMP plots. The MYM treatments resulted in significant marketable yield increases in three fields and decreases in two fields, with the remaining nine fields and the combined average of all 14 fields being statistically equivalent. When factoring in estimated costs, only two fields resulted in a monetary advantage with MYM treatment. In contrast, the BMP treatment resulted in significant increases in net crop value of five fields, as well as the combined average of all 14 fields ($200 ha^sup -1^ or 3.2%). These field demonstrations, along with associated field days and grower meetings, have resulted in many documented changes in grower practices towards BMPs, with many more undocumented changes probable. [PUBLICATION ABSTRACT]

The post-harvest application of chlorine dioxide (CIO2) was evaluated as a disease suppressant for stored potatoes. Chlorine dioxide was prepared by acidifying a buffered sodium chlorite solution with a food grade acid. In vitro studies verified the effectiveness of CIO2 at low concentrations (ED50 = 2 to 122 ppm) against Erwinia carotovora (soft rot), Fusarium spp. (dry rot) and Helminthosporium solani (silver scurf). Evaluations of tubers inoculated with Phytophthora infestans (late blight) and Fusarium spp. or infected with H. solani and then treated with CIO2 either going into storage or through the humidification system resulted in a lack of disease suppression. Inconsistent performance of CIO2 in storage appeared to be a result of several contributing factors. Chlorine dioxide concentrations varied greatly (up to six-fold), depending upon the method of activating and diluting sodium chlorite solutions. Chlorine dioxide is a gas soluble in water and, therefore, is easily released from solution (25%-75% loss) into the air when applied as an aqueous spray. Chlorine dioxide reacts quickly with the tuber and associated organic matter, thereby reducing the effectiveness. Applying higher than currently registered rates may be necessary to achieve measurable disease suppression.