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Carolyn DeMoranville and Joan Davenport

The relationship between yield and applied N in cranberry has been investigated. Cultivar was important in determining optimum seasonal N rate. Sustained production for the hybrid `Stevens' required an annual seasonal total of N at up to 67 kg·ha–1, higher than was optimal for native selections `Early Black' and `Howes'. High N rates were associated with increased fruit rot and vine overgrowth. Optimum N rate varied within cultivar, likely due to variation in soil conditions, but soil N test results have not correlated well with subsequent yield in cranberry. Soil organic matter content can predict potential N release, but plant response must also be taken into account. To refine N rate recommendations, plant characteristics that might predict N requirements/status of cranberry were investigated. A standard of 0.9% to 1.1% N in August tissue has been established for cranberry. To find characteristics that could be used earlier, we surveyed 30 sites for percentage of N in tissue, length of new growth, SPAD chlorophyll meter ratings, fertilizer N use, and yield. Length of new growth could be used as an indicator of cranberry N status from June until bloom, being positively correlated with subsequent yield. The SPAD meter proved to be a viable alternative to in-season monitoring of tissue N during June and July. Readings below proposed standard values indicated the need for N fertilizer if vegetative growth was in the standard range. Thus, the easily determined factors of upright length and SPAD rating could be used to refine fertilizer rates during the active growing season, while tissue testing for percentage of N could be used as a “report card” on the fertilizer program at the end of the season.

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Joan R. Davenport

Potato (Solanum tuberosum L.) is grown extensively throughout the Pacific Northwest as a high-value crop in irrigated rotations with other row crops such as wheat (Triticum aestivum L.) and corn (Zea mays L.)—both field and sweet. Center pivots are predominant irrigation systems. Soil texture ranges from coarse sands to finer textured silt loams and silts and can vary within one field, often with very hilly topography. Site-specific management is being evaluated as an approach to help to optimize inputs (water, seed, agricultural chemicals) to maintain or enhance yield and reduce the potential of negative environmental impacts in these farming systems. Currently variable rate fertilizer application technology and harvest yield monitoring equipment are commercially available for these systems. Variable rate seeding and variable rate irrigation water application technologies are developed but not fully commercialized and variable rate pesticide application equipment is in development. At the Irrigated Agr. Res. and Ext. Ctr. in Prosser, Wash., we have a team of research scientists (both university and USDA/ARS), interested individuals from local industry, and other key organizations (e.g., local conservation districts) who are working together to evaluate different site specific technologies, improve the ability to use available tools, and to improve decision-making ability by conducting research both on farm and in research plots.

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Joan R. Davenport

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Joan R. Davenport

To examine the impact of N fertilizer rates and timing on cranberry (Vaccinium macrocarpon Ait.) yield and the fruit quality factors total anthocyanin, average berry weight, and field and storage rot, plots were established for 3 to 4 years. The cranberries received a total of 0, 22, or 44 kg N/ha over the growing season applied in three, four, or five applications, which varied by growth stage. There were eleven possible treatment combinations in Massachusetts on `Early Black' and `Howes' and in Wisconsin on `Stevens' and `Searles', and seven possible treatments in New Jersey on `Early Black' and in Washington on `McFarlin'. The results showed a nationwide response to N that suggests the experimental middle rate of 22 kg·ha-1 would result in high yields with moderate rot. However, the best timing for applying the fertilizer varied by both state and cultivar, where three late season applications were best on `Early Black' in New Jersey versus four early season applications on the same cultivar in Massachusetts, and applying N fertilizers across five applications was optimal for `Stevens' in Wisconsin.

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Joan R. Davenport and Carolyn DeMoranville

Soluble nitrogen (ammonium and nitrate) is released when soil organic matter is mineralized. The amount of N released by this process depends on the amount of organic matter present and soil temperature. Cranberry (Vaccinium macrocarpon Ait.) grows in acidic soils with a wide range in organic matter content. To evaluate how soil N release is affected by soil temperature, intact soil cores were collected from sites that had received no fertilizer and placed in PVC columns. Four different soil types, representing the range of cranberry soils (sand, sanded organic soil, peat, and muck), were used. Each column was incubated sequentially at six different temperatures from 10 to 24 °C (2.8 °C temperature intervals) for 3 weeks at each temperature, with the soils leached twice weekly to determine the amount of N release. The total amount of N in leachate was highest in organic soils, intermediate in the sanded organic soil, and lowest in the sands. The degree of decomposition in the organic soils was important in determining which form of N predominated. In the more highly decomposed organic soil (muck), most of the N was converted to nitrate. The data from this study resulted in the development of two models—one predicting the N mineralization and the other predicting the proportion of N in each of the two forms. Key factors for N release rate were soil temperature, percentage of clay, and organic carbon content. For predicting the proportion of N as ammonium vs. nitrate, key factors were soil temperature, soil pH, and the distribution of mineral matter in the silt and sand fractions.

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Joan R. Davenport and Carolyn DeMoranville

Native nitrogen is released when soils are mineralized. The amount of N released by this process depends on the amount of organic matter present and soil temperature. Cranberry (Vaccinium macrocarpon Ait.) grows in acidic soils with a wide range in organic matter content. To evaluate release of cranberry soil N at varied soil temperatures, intact soils were collected from sites that had received no fertilizer. Soils were cored and placed in polyvinyl chloride (PVC) columns 20 cm deep × 5 cm in diameter. Four different soil types, representing the array of conditions in cranberry soil (mineral, sanded organic, organic peat, and muck) were used. Additional columns of sand soil (pH 4.5) that had been pH adjusted to high (6.5) and low (3.0) were also prepared. Each column was incubated sequentially at six different temperatures from 10 to 24 °C (2.8 °C temperature intervals) for 3 weeks at each temperature, with the soils leached twice weekly to determine the amount of N release. The total amount of N in leachate was highest in the organic soils, intermediate in the sanded organic, and lowest in the sands. At the lowest temperature (10 °C), higher amounts of N were released in sanded organic and sand than in organic soils. This was attributed to a flush of mineralization with change in the aerobic status and initial soil warming. The degree of decomposition in the organic soils was important in determining which form of N predominated in the leachate. In the more highly decomposed soil (muck), most of the N was converted to nitrate. In the pH adjusted sand, high soil pH (6.5) resulted in an increase in nitrate in the leachate but no change in ammonium when compared to non-adjusted (pH 4.5) and acidified (pH 3.0) treatments. This study suggests that for cranberry soils with organic matter content of at least 1.5% little to no soil-applied fertilizer N is needed early in the season, until soil temperatures reach 13 °C. This temperature is consistent with the beginning of active nutrient uptake by roots. Soil N release from native organic matter was fairly consistent until soil temperatures exceeded 21 °C, indicating that when temperatures exceed 21 °C, planned fertilizer applications should be reduced, particularly in highly organic soils.

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Joan R. Davenport and Nicholi Vorsa

Cranberry (Vaccinium macrocarpon Ait.) has the opportunity to partition resources into sexual and/or asexual (stolons) modes of reproduction. Nitrogen status has been shown to impact the degree of stoloniferous growth. To determine whether there is a genotypic response to varying nitrogen levels, six hybrid and four native cultivars were treated with three annual rates of nitrogen fertilizer (17, 34, or 67 kg·ha-1) for 4 years. Fruit yield was determined each year and asexual vegetative growth (stolons) weight was removed and measured in all but the first year of the experiment. Cultivars exhibited different patterns of yield and stolon weight response over the three nitrogen rates. Not all cultivars exhibited significant yield decreases at the high N levels. Vegetative growth (stolon weight) generally increased with increasing N, however, not all cultivars responded similarly over three N rates. Partitioning between yield and stolon production favored fruit yield at the lower N rates in three of the four native cultivars studied (`Cropper', `Early Black', and `Howes'). Yield over N rates was more stable for four of the six hybrid cultivars, which may be the result of greater heterozygosity in hybrids than natives, and/or genetic gain from one breeding and selection cycle, offering increased tolerance to nitrogen stress. This study indicates that genetic variation exists for yield, yield stability, and stolon production relative to nitrogen level, and that genetic gain in cranberry is possible for these traits. Future studies involving cranberry physiology and nutrition should consider the genotypes used.

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Suphasuk Pradubsuk and Joan R. Davenport

This study investigated the distribution of the micronutrients boron (B), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in 42-year-old ‘Concord’ grapevines (Vitis labruscana Bailey) grown in a calcareous soil to understand seasonal partitioning and distribution of micronutrients throughout various grapevine tissues. In 2006 and 2007, four vines each were excavated at winter pruning, budbreak, the three- to four-leaf stage, bloom, veraison, harvest, and postharvest. Separated plant organs were measured for biomass and analyzed for B, Fe, Mn, Cu, and Zn. The results showed that seasonal patterns of micronutrient concentrations varied considerably with respect to organ and growth stage. Leaf blades, shoot tips, and petioles had the highest concentration of B at bloom and Mn at harvest, whereas Fe, Cu, and Zn concentrations were highest in fine roots but values varied over time each year. Whereas seasonal patterns of Fe, Cu, and Zn contents differed year by year, B and Mn contents had a similar pattern over both years. Translocation of B and Mn from woody tissue to actively growing organs occurred at the beginning of the season. The majority of B uptake occurred between bloom and veraison, whereas that of Mn occurred between bloom and harvest. There were similar B concentrations in shoot tips and leaf blades. Boron remobilization to woody tissues from the leaves occurred between veraison and harvest, suggesting moderate, late-season, phloem mobility of B in ‘Concord’ grapevines. Microsite differences in soil pH likely contribute to variable nutrient availability around the root system, demonstrated by high variability of Fe, Cu, and Zn contents in different vine organs.

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Suphasuk Pradubsuk and Joan R. Davenport

Understanding how grape (Vitis L.) vines store nutrients in permanent tissues, how much nutrient vines take up from the soil, and how nutrients are partitioned and redistributed throughout the plant is critical to the development of sound nutrient management practices. This study investigated the seasonal patterns of macronutrient uptake and redistribution in whole ‘Concord’ grape (Vitis labruscana Bailey) vines. The study was conducted in a 42-year-old own-rooted ‘Concord’ vineyard. The site was a furrow-irrigated fine sandy loam. In 2006 and 2007, four vines were excavated at winter pruning, budbreak, three- to four-leaf stage, bloom, veraison, harvest, and postharvest. Each vine was separated into different organs, dried, and weighed to determine biomass, and then ground and analyzed for C, N, P, K, Ca, and Mg. The results showed that the seasonal dynamics of nutrient contents shared a consistent pattern: translocation of nutrients from woody tissues to actively growing organs at the beginning of the season; nutrient uptake from bloom to veraison (P and Mg in 2006), bloom to harvest (N, P, K, and Ca), or veraison to harvest (P and Mg in 2007); and nutrient movement to woody tissues occurring after veraison until leaf fall with no further nutrient uptake. There was a very high accumulation of Ca in permanent structures of the vine, reflecting the high Ca and CaCO3 found in the soils of the region. As a result, the vines had a higher Ca content than all other nutrients throughout the growing season, which is different from findings in other growing areas.

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Carolyn J. DeMoranville and Joan R. Davenport

It has been speculated that cranberries are susceptible to chloride injury. If this is the case, it is possible that applications of high rates of 0-0-60 (KCl) fertilizer as a K source could be detrimental to cranberry productivity. Grower anecdotes of using 0-0-60 to “shut down the plants” persist. Supposedly, using 225+ kg·ha-1 of this material slows or arrests vegetative growth. In fact, growers have claimed it can overcome the production of rank vegetation that results when too much N fertilizer has been applied. Field plots were initiated to determine the suitability of KCl and to determine if high K rates could overcome the deleterious effects of excess applied N. Plots were set up in a split-block plot design with N doses [three each “normal” (28-34 kg·ha-1 N) vs. “high” (56-67 lb N/A)] in one direction and potassium/chloride treatments in the other direction (KCl or K2SO4 at 115 or 225 kg K2O; CaCl2 to give the equivalent Cl as in the high-rate KCl treatment, and a nontreated control) for a total of 36 2 × 2-m plots per each of three cultivar locations. Plots were treated and evaluated for three consecutive years. There were no significant differences in yield among the K2SO4 and KCl treatments, indicating that at rates as high as 225 kg·ha-1 K2O, 0-0-60 and 0-0-50 perform similarly. Further, treatment with CaCl2 had no significant effect on yield. In the third year, plots receiving no K treatment had significantly lower yield than those receiving either rate or form of K (single degree of freedom comparison, significant at 0.03). These results indicate that at the rates used in this study, KCl is an adequate K source. The effect of N rate was more pronounced than that of the K treatments. In years two and three, the low N rate strips had significantly greater yield compared to that in the high N rate strips. By year two, the high N strips were visually different, with rank overgrowth. There was no significant interaction of N rate and the K treatments. While there was a trend for greater difference between the 0 K and 115 kg K rates in the high N plots compared to the moderate N plots, the addition of K never entirely overcame the negative yield effects of high N rate.