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  • Author or Editor: Timothy L. Righetti x
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Nitrogen, boron, and zinc are the major deficiencies encountered in Oregon tree fruit production. Much of our current management strategies are based on studies evaluating the uptake and plant mobility of labeled N, Zn, and B. Because mature trees differ from young plants, most of our experiments are conducted on fully bearing trees. Nitrogen strategies emphasize applying minimal amounts to avoid excess vigor and poor fruit quality. Our goal is to produce moderately vigorous trees with low fruit N, while still maintaining adequate tree reserves for early spring growth. Labeled 15N studies suggest that the later N is applied, the less is partitioned into leaves and fruit, with more N incorporated into storage tissues. Postharvest foliar applications of urea can also produce high bud N levels in combination with moderate vigor and low fruit N. Partitioning differences from various timings also result in different utilization efficiencies, especially if one considers N losses from pruning. Early N applications may have smaller efficiencies because pruning losses are greater. Although plant B is thought to be immobile, foliar-applied B is rapidly mobilized out of the leaf. Postharvest foliar B applications are an excellent way to ensure that buds have adequate B levels the following spring. Unlike N and B, Zn is not mobilized out of the leaf where it is applied. Sprays directly to young tissues in the spring are the only practical ways of increasing Zn levels.

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`Cornice' pear trees (Pyrus communis L.) were fertilized with ammonium nitrate depleted in “N in Spring 1987 and 1988. In Aug., Oct., and Nov. 1988, midleaves on current season shoots were sampled at three positions from the periphery to the center of the canopy. Total N/cm' of leaf area remained almost constant through October, even though percent N concentration declined as specific leaf weight (SLW) increased. Furthermore, there was no substantial net change in either labeled or unlabeled N in either treatment until senescence began in October. Peripheral leaves contained higher levels of both reserve and newly acquired N than did less-exposed leaves. Despite large differences in N/cm2 for October samples, by November leaves from both high (HN) and low N (LN) trees exported similar percentages of their total N. The average N export to storage tissues irrespective of tree N status was 71%, 61%, and 52% for peripheral, medium, and interior leaves, respectively. The export of N was influenced more by the leaf position in the plant canopy than the nutritional status of the tree.

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Agriculture is changing. State-of-the-art computer systems that use GPS (global positioning systems) data, GIS (geographic information systems) software, remotely sensed images, automated sampling, and information analysis systems are transforming growers' ability to produce their crops. Currently, the farm service and agricultural sales industry, rather than the grower direct most information technology applications. Precision agriculture must become an information-driven and grower-driven process. Data evaluation has to be made simpler, less time consuming, and inexpensive. The purpose of this paper is to outline potential strategies and demonstrate how information can be processed and evaluated with readily available and inexpensive analytical tools.

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This study was carried out on mature `Delicious' apple trees (Malus domestica Borkh.) on EM 9 rootstock. Labeled B (99.63 Atom % 10B) was applied as boric acid. Treatments were postharvest foliar B at 375 mg·L–1, postharvest foliar B (375 mg·L–1) plus urea (2.5% wt/vol), and a soil application at the same per-tree rate as the foliar treatments (16 g boric acid/tree). Postharvest foliar B applied with or without urea was efficiently transported from the leaves into storage tissues for the next year's growth. However, soil-applied B remained mostly in the roots while very little was translocated to the above-ground portions of the tree at full bloom. When urea was added to a foliar B spray, the amount of B in the roots and flower clusters increased at full bloom. Although increasing the efficiency of foliar B applications may not be necessary, combining urea and B into a single application is recommended when growers want to apply both N and B. Shoot leaves from all treatments collected late in the season (midsummer) had similar B concentrations, even though treatments altered the amount of added B that was present in different tree tissues early in the season.

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Cranberry (Vaccinium macrocarpon Ait.) is an important crop in Oregon. However, nutrient critical levels have not been established. Since developing nutrient critical levels usually requires time-consuming and expensive field trials, we chose to use the Diagnosis and Recommendation Integrated System (DRIS), which can use survey data to determine critical levels. We analyzed 139 cranberry samples collected from the southern Oregon coastal area over a three-year period. Leaf concentrations for N, P, K, S, Ca, Mg, Mn, Fe, Cu, B, and Zn in bearing uprights collected in mid-August were matched with the corresponding yields. DRIS was employed to obtain norms and critical levels from this survey data. To test our DRIS norms and critical levels, we evaluated two published experiments (Torio and Eck, 1969 and Medappa and Dana, 1969) where fertility treatments altered mineral concentrations and affected yield. Both ratio-based and critical concentration diagnoses were useful. Changes in the Nutrient Imbalance Index was a good predictor of yield response.

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Management of pear (Pyrus communis L.) trees for low N and high Ca content in the fruit reduced the severity of postharvest fungal decay. Application of N fertilizer 3 weeks before harvest supplied N for tree reserves and for flowers the following spring without increasing fruit N. Calcium chloride sprays during the growing season increased fruit Ca content. Nitrogen and Ca management appear to be additive factors in decay reduction. Fruit density and position in the tree canopy influenced their response to N fertilization. Nitrogen: Ca ratios were lower in fruit from the east quadrant and bottom third of trees and from the distal portion of branches. High fruit density was associated with low N: Ca ratios. Nutritional manipulations appear to be compatible with other methods of postharvest decay control.

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Abstract

Forward stepwise multiple regression equations were developed from seasonal leaf and fruit mineral analyses to predict quality parameters for ‘Starkspur Golden Delicious’ apple (Malus domestica Borkh.) during 1980–82. Quality parameters were evaluated both at harvest and after 6 months of 0°C storage. Soluble solids, skin ground color, and titratable acidity were strongly predictable as early as June or July. However, an August analysis was most predictive. For titratable acidity, a combination of both leaf and fruit minerals produced stronger predictions than leaf or fruit minerals alone in each individual year. Soluble solids, skin ground color, and bitterpit were more accurately predicted by fruit analyses. Fruit size was important in regression equations for firmness, but was not essential for other parameters. Although between-year predictions were not as good as within-year predictions, regression equations could successfully place fruit in high or low categories for most quality parameters.

Open Access

Abstract

A diagnostic procedure was developed to identify mineral limitations on pome fruit quality. Fruit mineral levels were useful only when developed on a ranked or percentile (0 to 100) basis. Therefore, procedures were developed using percentile values for both leaf and fruit mineral concentration. An individual can decide which quality parameters are important and whether minimum, maximum, or intermediate values for these quality parameters are most desirable. Multiple regression is used to predict relative rankings for each qualify parameter. A simple sorting program allows the operator to use these rankings to choose which categories of fruit are undesirable. It is then possible to select from among remaining lots those likely to contain fruit having the poststorage quality factors the operator considers most important. The approach is demonstrated with 2 years of data from a high-density ‘Starkspur Golden Delicious’ apple orchard. Selections of fruit with the best poststorage quality were based on mineral content, assuming that maximum firmness, soluble solids, titratable acidity, and yellow color were considered as most desirable. Further ranking evaluations were obtained by evaluating 6 years of data relating quality in ‘d’Anjou’ pears with fruit mineral concentrations. A ranking approach allows meaningful interpretation despite large differences in fruit mineral concentrations reported for different locations and years by a range of analytical laboratories. The procedure is flexible, and fruit could be categorized successfully according to several definitions of optimum quality.

Open Access

Abstract

The Diagnosis and Recommendation Integrated System (DRIS), which uses nutrient element concentration ratios as indicators of nutrient deficiency, was used to evaluate current sufficiency ranges for hazelnut trees. Reference values that were derived from published and unpublished field data were used to calculate DRIS indices for N, P, K, Ca, Mg, Mn, Fe, Cu, B, and Zn. A nutritional imbalance index (NII) was computed as the sum of DRIS indices irrespective of sign, and a threshold NII value (mean NII + 1 SD), above which severe imbalances are expected, was established. DRIS diagnoses were then compared with the sufficiency range approach to determine if relative deficiencies or excesses associated with severely imbalanced trees would have been routinely detected in 624 mineral analyses of hazelnut leaves. A previously published field trial was also reevaluated. DRIS diagnosis generally agreed with the diagnoses made by the sufficiency range method, especially if sufficiency ranges for some elements were made more narrow. However, some nutrients were never identified by DRIS as a major relative deficiency or excess in any of the trees judged severely imbalanced, based on the sum of DRIS indices. Nitrogen and Mg deficiencies were not detected unless lower NII thresholds were used. Unfortunately, lowering NII thresholds enough to detect N and Mg deficiencies identified some high-yielding trees as severely imbalanced. DRIS will not detect all deficiencies or excesses. Therefore, DRIS is best viewed as a supplement to sufficiency range diagnoses that provides additional information when severe imbalances are detected.

Open Access

The effects of 15N-labeled fertilizer applied to mature summer-bearing red raspberry (Rubus idaeus L. `Meeker') plants were measured over 2 years. Four nitrogen (N) treatments were applied: singularly at 0, 40, or 80 kg·ha-1 of N in early spring (budbreak), or split with 40 kg·ha-1 of N (unlabeled) applied at budbreak and 40 kg·ha-1 of N (15N-depleted) applied eight weeks later. Plants were sampled six times per year to determine N and 15N content in the plant components throughout the growing season. Soil also was sampled seven times per year to determine inorganic N concentrations within the four treatments as well as in a bare soil plot. There was a tendency for the unfertilized treatment to have the lowest and for the split-N treatment to have the highest yield in both years. N application had no significant effect on plant dry weight or total N content in either year. Dry weight accumulation was 5.5 t·ha-1 and total N accumulation was 88 to 96 kg·ha-1 for aboveground biomass in the fertilized plots in 2001. Of the total N present, averaged over 2 years, 17% was removed in prunings, 12% was lost through primocane leaf senescence, 13% was removed through fruit harvest, 30% remained in the over-wintering plant, and 28% was considered lost or transported to the roots. Peak fertilizer N-uptake occurred by July for the single N applications and by September for the last application in the split-N treatment. This uptake accounted for 36% to 37% (single applications) and 24% (last half of split application) of the 15N applied. Plants receiving the highest single rate of fertilizer took up more fertilizer N while plants receiving the lower rate took up more N from the soil and from storage tissues. By midharvest, fertilizer N was found primarily in the fruit, fruiting laterals, and primocanes (94%) for all fertilized treatments; however, the majority of the fertilizer N applied in the last half of the split application was located in the primocanes (60%). Stored fertilizer N distribution was similar in all fertilized treatments. By the end of the second year, 5% to 12% of the fertilizer acquired in 2001 remained in the fertilized plants. Soil nitrate concentrations increased after fertilization to 78.5 g·m-3, and declined to an average of 35.6 g·m-3 by fruit harvest. Seasonal soil N decline was partially attributed to plant uptake; however, leaching and immobilization into the organic fraction may also have contributed to the decline.

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