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  • Author or Editor: Carl J. Rosen x
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Current techniques used in genetic transformation can result in variation of numerous traits in addition to the transformed trait. Backcrossing to the standard genotype can eliminate this variation, but because of the heterozygous nature of potatoes (Solanum tuberosum L), backcrossing is not effective. Therefore, the chances of obtaining altered performance in transformed potato are high. `Superior' potato plants were recently genetically modified to resist attack and damage by the Colorado potato beetle [Leptinotarsa decemlineata (Say)]. The transformed clone, `NewLeaf Superior' (`NewLeaf'), has been shown in previous field trials to be more vigorous than the standard clone. The objective of this 2-year study was to evaluate the performance of `NewLeaf' relative to that of the standard clone at various fertilizer nitrogen (N) levels. The two clones were randomly assigned as subplots to main plots consisting of four N levels (28, 112, 224, or 336 kg·ha-1). Based on regression analysis, total yield was higher for `NewLeaf' than for `Superior' at N rates below 92 kg·ha-1 in 1997. At higher rates, however, `Superior' had higher yields than the transgenic clone. In 1998, the clon×N rate interaction was significant, but there was no consistent trend to the response of the two clones to N application. At the 112 kg·ha-1 N rate, total yield was higher for `NewLeaf' than for `Superior', but yields were similar for the two clones at other N rates investigated. Nitrogen and biomass accumulation in vines increased more for `NewLeaf' than for `Superior' as N rate was increased from 28 to 336 kg·ha-1. At equivalent N rates, these traits were higher for the transformed than for the standard clone within the range of N rates investigated. However, harvest index at equivalent N rates was higher for the standard clone than for `NewLeaf'. `Superior' and `NewLeaf' produced similar tuber dry weight yields per unit of N supplied and per unit of N absorbed by the plant. Nitrogen uptake efficiency (NUE) was 16% higher for `NewLeaf' than for the standard clone at the low N rate (112 kg·ha-1), whereas at higher N rates NUE was either lower for `NewLeaf' or similar for the two clones. This observation, together with the finding that yield for `NewLeaf' was maximized at lower N levels than the standard clone, suggests that `NewLeaf' may require lower N input than the standard clone. Results from the study indicate that the greater efficiency of `NewLeaf' at lower N levels was associated with acquisition of N from the soil rather than utilization of absorbed N in metabolism.

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Two on-farm field studies were conducted in 1996 and repeated in 1997 to determine the effects of soil amendments and scape (flower stalk) removal on yield, dry matter partitioning, and storage quality of hardneck garlic (Allium sativum L.). One study site was on a loamy sand soil with low organic matter and fertility and the other site was on a sandy loam soil with high organic matter and fertility. Soil amendment treatments tested at both sites were: 1) no amendment, 2) composted manure, and 3) inorganic fertilizer according to soil test recommendations. A fourth treatment, dried, composted turkey-manure-based fertilizer, was included at the low organic matter site. Scapes were removed at the curled stage from plants in half of the harvest rows. Scapes from the remainder of the harvest row plants were allowed to mature until harvest. In 1997, bulbs from each treatment were stored at 0 to 3 °C or 19 to 21 °C for 6 months. Soil amendment treatments had no effect on total garlic bulb yield, dry mass partitioning, or stored bulb weight loss at the sandy loam, high organic matter site. Manure compost, fertilizer, and composted turkey manure soil amendments reduced the yield of smaller bulbs compared with the control at the loamy sand, low organic matter site. The proportion of bulbs >5 cm was highest with the manure compost treatment. At the low organic matter site, scape removal resulted in a 15% increase in bulb yield and an increase in bulb size compared with leaving scapes on until harvest (P = 0.05). At the high organic matter site, scape removal increased bulb yield by 5% (P = 0.10). Scape removal increased dry matter partitioning to the bulbs, but had no effect on total (scape + shoot + bulb) aboveground dry matter production. The increase in bulb dry mass when scapes were removed was offset by an increase in scape dry mass when scapes were left on. Bulb weight loss in storage was less at 0 to 3 °C than 19 to 21 °C. Soil amendments only affected bulb storage quality at the loamy sand, low soil organic matter site. The effect of scape removal on bulb weight loss was nonsignificant at either location.

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An important aspect of establishing critical sap nutrient concentrations for diagnostic purposes is to determine the accuracy of the analytical method used. We compared a Cardy flat membrane NO3 electrode, a Hach portable NO3 electrode, and a Wescan N analyzer for their ability to determine NO3 concentrations in sap of potato (Solanum tuberosum L.) petioles. The Hach and Wescan instruments require diluted sap, while nondiluted sap can be used with the Cardy. Nitrate-N concentrations in nondiluted petiole sap measured with the Cardy electrode were 90 to 120 mg·L–1 higher than the other two methods. Using sap diluted with 0.075 m aluminum sulfate tended to lower Cardy NO3 readings to concentrations closer to the other methods, but made the procedure more complicated for practical use. We also compared a Cardy K electrode with flame emission spectroscopy for determining K concentrations in sap. Using nondiluted sap with the Cardy procedure resulted in K concentrations 200 to 2500 mg·L–1 lower than those determined by flame emission, depending on K concentration of the sap. Diluting sap with 0.075 m aluminum sulfate or deionized water for use with the Cardy electrode resulted in K concentrations similar to those determined by flame emission.

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An important aspect of establishing critical sap nutrient concentrations for diagnostic purposes is to determine the accuracy and precision of the analytical method used. We compared a Cardy flat membrane NO3 electrode, a Hach portable NO3 electrode, and a Wescan N analyzer for their ability to determine NO3 concentrations in sap of potato petioles. The Hach and Wescan instruments require diluted sap, while nondiluted sap can be used with the Cardy. Nitrate-N concentrations in nondiluted petiole sap measured with the Cardy electrode were 100 to 200 mg·liter–1 higher than the other two methods. Using sap diluted with 0.15 M Al2(SO4)3 tended to lower Cardy NO3 readings to concentrations closer to the other methods, but made the procedure more complicated for practical use. We also compared a Cardy K electrode with flame emission spectroscopy for determining K concentrations in sap. Using nondiluted sap with the Cardy procedure resulted in K concentrations 1000 to 1700 mg·liter–1 lower than those determined by flame emission. Diluting sap with 0.15 M Al2(SO4)3 for use with the Cardy electrode resulted K concentrations similar to those determined by flame emission. Implications for using the electrodes for diagnostic purposes will be discussed.

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Abstract

Nutrient solution experiments were conducted to characterize the absorption of K+ and NH 4 + , as affected by plant K+ status and solution concentrations of K+ and NH 4 + , for tomato (Lycopersicon esculentum Mill. cv. UC823) and ‘French’ prune scions (Prunus domestica L.) on Myrobalan 29C rootstocks (P. cerasifera Ehrh.). Prune and tomato plants pretreated in solutions adjusted daily to 1000 μm K+ had significantly higher K+ concentrations in leaves and roots than those plants pretreated in nutrient solutions adjusted on alternate days to 100 μm K +. NO differences in total N concentrations of roots or leaves due to pretreatment were detected. Potassium uptake rates of prune and tomato plants of high K+ status were significantly lower than those of low K+ status. For both plant species, NH 4 + uptake by roots was independent of plant K+ status. On a relative basis, the presence of solution NH 4 + inhibited K+ uptake to a greater extent in K+-loaded plants than in K + -starved plants. Potassium status of the plant had no effect on the extent of NH 4 + uptake inhibition due to solution K +. Ammonium-induced efflux of K+ from plant roots to initially K+ -free solutions was greater from roots of high K+ status than from roots of low K+ status. Increasing solution NH 4 + concentrations from 100 μm to 1000 μm significantly lowered the K+ uptake rates. The effect was much more dramatic in prune than in tomato. Increasing solution K+ concentrations from 100 μm to 1000 μm had no significant effect on the NH 4 + uptake by either plant species.

Open Access

Root sections of cranberry (Vaccinium macrocarpon Ait. cv. Searles) were microscopically examined to document the typical anatomy of cranberry roots and changes in root anatomy in response to N-form and solution pH. Cranberry cuttings were rooted, then established in hydroponic conditions with three N and two pH regimes. The three N regimes with equal N levels were 1) NH4-N alone, 2) NH4/NO3-N in combination, or 3) NO3-N alone. pH was maintained at 4.5 or 6.5. Root apical regions were examined using phase contrast, bright field, and epifluorescence microscopy. The cranberry root tip develops with a closed apical organization with the tetrarchal vascular cylinder, cortex, and root cap traceable to independent meristem cell layers. The most obvious treatment difference was an accumulation of unidentified “granules” in the subepidermal layer, readily visible with epifluorescence microscopy with NO3-N alone. Roots produced at pH 4.5 branched less than those at 6.5 and had more “quiescent” root initials; at pH 6.5, these developed more frequently into branch roots.

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The effects of pH and N form on growth and nutrition of blueberry (Vaccinium corymbosum L. × V. angustifolium Ait. cv. Northblue) and cranberry (V. macrocarpon Ait. cv. Searles) were tested in separate greenhouse hydroponic experiments. A factorial treatment arrangement of two pH levels (4.5 and 6.5) and three N forms (NO3-N, NH4-N, and NH4-N/NO3-N) was used for each clone. Blueberry shoot growth and final dry weight were greatest at pH 4.5, regardless of N form. In contrast, cranberry fresh weight accumulation and final dry weight were higher with NH4-N/NO3-N or NH4-N than with NO3-N alone. Cranberry plants receiving NO3-N alone accumulated low levels of tissue N and grew relatively poorly at both pH levels. Differences in N response by these two species may be due partially to the environments in which they were selected. Soil from the site where `Northblue' blueberry was selected contained relatively high NO3-N and low NH4-N levels; soil from commercial `Searles' cranberry bogs had relatively low NO3-N and high NH4-N levels. Both species accumulated relatively high levels of root Fe, regardless of pH or N form. Levels of Fe in the root were as much as 100 times higher than in the shoot. Based on X-ray microanalysis of cranberry roots, most of the Fe appeared to be precipitated on the root surface as iron phosphate. Concentrations of Mn in shoots and roots depended on N form and pH. In general, root Mn was highest at pH 6.5 and apparently was precipitated with Fe.

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Although laboratory analyses of nitrogen (N) release from polymer-coated urea (PCU) are available for most brands of PCU, data are lacking for release patterns under field conditions. Release rate studies for PCU are often time-consuming and expensive as a result of the need for multiple chemical analyses. We compared the N release using a weight loss method with a direct chemical analysis method for two types of PCU (Agrium PCU, Agrium U.S. Inc.; Kingenta PCU, Shandong Kingenta Ecological Engineering Co., Ltd.). The PCU prills were placed in a mesh bag and N loss from the prills over time was determined indirectly by loss in weight. The N content of the prills was determined by the combustion method to verify the weight method technique. A second study was conducted to determine if the type of mesh bag material affects the percentage of N released. For this study, mesh bags were constructed from two different materials with two different hole sizes and total amount of open area. Overall, regression analysis suggested that the percentage of N released as estimated by the weight method and combustion method was not significantly different over the growing season for two types of PCU. The mesh bags made of the material with smaller holes and less open area resulted in significantly less N release than the material with more open area and larger holes. Overall, these results suggest that the weight method can be reliably used as a substitute for chemical analysis to determine N release characteristics of PCU, but mesh bag materials must be taken into consideration to reduce errors. The best technique to determine N release may be one that does not include a mesh bag; however, until that method is developed, using a larger hole size is recommended.

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The effect of N form and solution pH on the carboxylic and phenolic acid content of cranberry (Vaccinium macrocarpon Ait. cv. Searles) shoots and roots was determined in a greenhouse experiment. The predominant carboxylic acids measured were malate and citrate. Protocatechuic acid was the dominant phenolic acid detected. Total organic acid concentrations were unaffected by N form supplied. In shoots, higher total concentrations of organic acids were found at pH 4.5 than at 6.5 in the shoot, but there was little pH effect in the roots.

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Sweet corn silage waste is ≈18% dry matter and contains 1.2% N and 0.26% P on a dry-weight basis. Silage waste in rates of 0 to 448 T·ha–1 was applied to a previously harvested sweet corn field in late summer. Beginning the following spring, soil samples were periodically collected to follow the rate of N mineralization. Field corn was planted to the site the following spring as the test crop. At harvest, grain, stover, and silage yields were recorded and N removal from the system was followed through grain and tissue sampling. Additional studies were also conducted to evaluate the impact of primary tillage method on subsequent N mobilization from sweet corn silage waste and to assess the residual N release potential beyond the first year following silage waste application. Results suggest that land application of sweet corn silage waste at 224 T·ha–1 would be environmentally responsible, provided that adequate nitrogen credit from the silage waste is integrated into the total nitrogen needs of the subsequent crop. Greater mineralization is achieved when the silage waste is moldboard plowed compared to chisel plowing. Chisel plowing could result in greater residual N carryover during the year following silage waste application. Seedling emergence rates were faster and grain yield was superior in some years in moldboard-plowed plots compared to chisel-plowed plots. Further calibration of additional N fertilizer on land that received silage waste is necessary for improved production efficiency and sweet corn silage waste use in production systems.

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