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  • Author or Editor: Ronald F. Korcak x
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Abstract

Calcifuges, represented by the blueberry and cranberry (Vaccinium spp.) and rhododendrons and azaleas (Rhododendron spp.), are an economically important segment of the horticultural industry. They share the common requirement of an acid soil, about pH 5.5 or below, and minimal nutrition. Indeed, overfertilization, particularly when plants are young, can cause foliar injury. Much nutritional research has been performed on these acid-loving plants from the aspects of fertilizer recommendations and soil management practices. It is not the purpose of this paper to review the nutritional requirements or recommendations of blueberries and other calcifuges. Such information can be found elsewhere (Eck, 1966; Joiner et al., 1983; Kenworthy, 1973; Kofranek and Lunt, 1975; Korcak, 1988; Trevett, 1962). Instead, the two-fold purpose of this paper is to first examine the role of selected elements (Mn, Al, Fe, Ca, and N) on blueberry growth in atypical soil/site environments and, second, to explore the potential variation within Vaccinium that may be beneficial in genetic selection for growth under these new situations.

Open Access

Abstract

Genotypic variation in the capacity of plants to absorb, translocate, and use mineral nutrients has been the subject of many investigations since initial reports in the 1920s and 1930s (5, 6) However, it has only been within the past 15 to 20 years that researchers have made concerted efforts to understand and exploit genetic differences in plant nutrition as a means to improve crop production. Slow progress in this area can be attributed to emphasis on amending soils for plants rather than selecting plants for particular soil conditions (1–3, 7, 17). Lack of a clear understanding of mechanisms involved at cellular, tissue, and whole-plant levels has also impeded progress. Breeding for desirable nutritional traits in plants is, with few exceptions, a complex process, likely to involve more than one gene, and greatly affected by various environmental factors. Despite these challenges, there has been some success in breeding nutritionally improved genotypes (3, 7, 17). The use of soil amendments to replenish nutrients used by plants will always be an integral part of crop production, but it is now recognized that selecting plants for improved nutritional characteristics can be a viable and, at times, necessary alternative for increasing crop pro

Open Access

A 3-year experiment was conducted to determine the optimum fertilizer N requirements of fresh-market tomato (Lycopersicon esculentum Mill.) `Sunbeam' grown on a hairy vetch (Vicia villosa Roth.) or black polyethylene mulch. In 1993 and 1994, four rates of fertilizer N (0, 56, 112, and 168 kg·ha-1) as water-soluble NH4NO3 were applied in 14 equal applications through the trickle irrigation system starting 1 week after planting. Four additional rates (224, 280, 336, and 392 kg·ha-1) were applied in 1995 to assess the plant response to supra-optimal levels of N. Hairy vetch produced 3.3–4.5 t·ha-1 of above-ground biomass and a total N content of 126–169 kg·ha-1 in the above-ground biomass. Leaf N content at 7 weeks after transplanting of tomatoes correlated positively with yield from black polyethylene but did not correlate with yield from the hairy vetch plots where leaf N content was optimal at all N rates. Predicted tomato yields were higher for the hairy vetch than for the black polyethylene treatment at all applied N rates in all years. Tomatoes grown in black polyethylene required N at 130 to 144 kg·ha-1 to achieve yields equivalent to those grown following unfertilized hairy vetch. Tomato yield increased in response to applied N in both mulches in all 3 years; optimum N rates of 89 and 190 kg·ha-1 in hairy vetch and black polyethylene, respectively, were predicted by a linear plateau model, and 124 and 295 kg·ha-1 by a quadratic plateau model. The linear plateau model is recommended because it would allow less N to become available for runoff and leaching.

Free access