Fluidized bed material (FBM), a dry, high Ca, alkaline waste product which results from combining coal and limestone, was used as the sole source of Ca for ‘York Imperial’ apples (Malus domestica Borkh.) grown in outdoor sand cultures over 3 growing seasons. FBM treatments were compared to gypsum, applied at similar rates based on apple tree Ca requirements, and to a no Ca amended control. Over 3 years, leaf Ca was significantly enhanced by increasing levels of FBM. FBM was a better Ca source compared to gypsum applied at similar rates only during the third year. Fruit flesh Ca and the incidence of cork spot were not significantly or consistently affected by treatments. There were no visual or nutrient deficiencies or toxicities noted from the FBM nor were yields and average fruit size affected.
Bulk A horizon samples of 4 soils, with or without the addition of peatmoss, and 5 blueberry crosses were used in a study of the adaptability of blueberries to upland soil conditions under 3 fertilization regimes and trickle irrigation in outdoor pots. Blueberry progenies ranged from essentially pure highbush (Vaccinium corymbosum L.) to interspecific hybrids containing varying amounts of evergreen (V. darrowi Camp), lowbush (V. augustifolium Aiton), black highbush (V. atrococcum Heller), and rabbiteye (V. ashei Reade) blueberry germplasm. Blueberry growth, as measured by plant volume, initially was greatest on Manor clay loam, a Piedmont soil high in clay (30%), but by the 2nd growing season, growth was superior on Berryland soil. Various fertilizer sources affected small differences in growth. Generally those progenies that contained less highbush (V. corymbosum) parentage produced more vigorous growth. Depth of rooting and estimated root distribution were affected significantly by soil, but the addition of peatmoss had no consistent effect. Berryland sand and Manor loam soils, which represent extremes in clay content, both produced the deepest root systems. Fruiting and fruit characteristic data from the 2nd growing season indicated a significant effect of peatmoss on the Pope and Galestown soils, which resulted in lowered total fruit acidity. The Berryland soil produced fruit with the lowest total acidity. Blueberry plant growth over the first 2 seasons indicates that soil type can have pronounced effects on plant growth and rooting. These growth differences were due to soil characteristics other than particle size distribution, with fertilizer source having minimal effects on growth.
A range of soils, with or without the addition of peatmoss, and seedlings of blueberry progenies were used in an outdoor pot study to examine the adaptability of blueberries to upland soil conditions with controlled fertilizer additions and trickle irrigation. Blueberry progenies ranged from essentially pure highbush (Vaccinium corymbosum L.) to interspecific hybrids containing varying amounts of evergreen (V. darrowi Camp), lowbush (V. angustifolium Aiton), black highbush (V. atrococcum Heller), and rabbiteye (V. ashei Reade) blueberry germplasm. The soils represented the 3 physiographic regions of the eastern United States with Berryland sand used as a comparative control. Leaf analysis for N, P, K, Ca, and Mg showed significant effects of soil, but no consistent effect of peatmoss addition or fertilizer source in the 2 years of the experiment. There were significant differences among progenies. Foliar Fe, B, Al, Zn, and Cu concentrations varied independent of soil material, progeny, or fertilizer source. Leaf Mn was significantly increased from solid 10N-4P-8K fertilizer and a significant soil by progeny interaction existed. Those progenies containing some V. angustifolium tended to have increased foliar Mn levels. The reduced vigor of the blueberry progenies grown on soils other than the Berryland sand was tentatively ascribed to induced nutrient imbalances, involving Ca, Fe, and Mn, possibly being governed by soil cation exchange capacity and organic matter reactivity.
The response of blueberries (Vaccinium spp.) to added Mn was studied in soil, solution, and sand cultures. Weekly additions of up to 0.8 mg Mn to Berryland sand soil (4.3 kg/pot) for 7 months produced the most growth in highbush blueberries, and additions of 6.4 mg Mn/week resulted in growth reductions but no visual toxicity symptoms. Solution culture- (800 ml/bottle) grown ‘Blueray’ highbush blueberries tolerated Mn additions up to 96 μg·ml−1 without significant growth reductions. Under similar conditions, a lowbush clone grew best at high added Mn and had higher foliar Mn concentrations than did ‘Blueray’, the rabbiteye cultivar ‘Tifblue’, or a selection of Vaccinium elliotti Chapman. Lowering solution Ca, Mg, and NO3 levels sharply increased foliar or stem Mn concentrations of all species. Growth of three genetically diverse hybrid blueberry progenies were not signficiantly affected by relatively high levels of applied Mn or Al when grown in sand culture. Increasing Al had a greater effect on increasing root Mn concentrations than did an increase in Mn levels. There were no visual Mn toxicity symptoms expressed in any of the three media from excessive Mn levels.
Fluidized bed material (FBM), a dry, high-Ca, alkaline waste product from the combustion of coal and limestone, was used as the sole Ca source for ‘York Imperial’ apples (Malus domestica Borkh.) grown in outdoor sand cultures for one season. Leaf Ca tended to increase with increasing rates of FBM and flesh Ca was not significantly increased by FBM application, although incidence of cork spot tended to be reduced. The trees showed no visible symptoms of toxicity or altered nutritional levels from the FBM treatments.
The beneficial influences of gypsum on soil improvement and plant growth have been well-documented, Among these benefits are reclamation of sodic soils, alleviation of subsoil acidity problems, and contribution of Ca and S as nutrients. There are three industrial byproducts that contain significant amounts of gypsum. Phosphogypsum is probably the best-known byproduct gypsum source; the others are clean-air technology coal combustion byproducts, namely fluidized bed combustion and flue gas desulfurization residues. This review summarizes the beneficial chemical and physical effects of gypsum on soil properties and the resultant benefits on plant growth. Where applicable, emphasis is placed on potential uses and limitations of byproduct gypsum sources on horticultural crops. The potential for incorporating these materials in artificial mixtures with organic materials is discussed.
Solution cultures altered with polyethylene glycol to induce a water stress of− 1.0 bar decreased net photosynthesis (Pn) and stomatal conductance (Cs) in the leaves of ‘York Imperial’ apple seedlings (Malm domestica Borkh.). Sprays with a complete nutrient solution produced similar responses and further decreased Pn and Cs in water-stressed plants. It appeared from the mesophyll conductance (Cm) calculation that reduction in Pn rate in water-stressed, as well as sprayed trees, was not caused solely by a stomatal factor. It is not known, however, whether nonstomatal limitation of Pn reflects a decreased capacity for CO2 fixation or increased light respiration, since mesophyll conductance was calculated assuming constant (zero) sink CO2 concentration in the leaf. In another experiment, decreasing to − 1.0 bar water potential of nutrient solution reduced daily water consumption and fresh weight of ‘York Imperial’ apple seedlings. Sprays with complete nutrient solution also tended to decrease daily water consumption of plants. Water stress decreased leaf Ca and root K and Mg concentrations, indicating that water stress may lower the absorptive capacity of the roots. However, water-stressed plants contained more Ca in the roots than unstressed plants, suggesting that lower leaf Ca concentration in stressed plants was caused by suppressed transport. Leaf sprays with complete nutrient solution increased Mg concentration in the leaves and stems and Ca concentration in the leaves.
‘York Imperial’ apple seedlings (Malus domestica Borkh.) grown in nutrient solution cultures with decreased water potential to− 1.0 bar by polyethylene glycol (PEG) increased water consumption, photosynthesis rate (Pn), and stomatal conductance (Cs). High light preconditioning of the plants used in this experiment was probably the reason why− 1.0 bar water potential in the nutrient solution was not low enough to induce apple seedling responses typical of water-stressed plants. However, application of PEG stress (−1.0 bar), to K-sprayed (K2SO4, −0.5%) trees lowered seedling water consumption Pn, and Cs. Potassium sprays alone did not significantly affect water consumption, Pn or Cs. When the water potential of the nutrient solution of PEG stressed plants was further decreased to −2.5 bars, unsprayed trees started to wilt within 2 days while sprayed trees did not. It is proposed that earlier stomatal closure of K-sprayed trees when stressed, already at low level of water stress (−1.0 bar), prevented plant water depletion when stress level was increased. This in turn delayed commencement of plant wilting. Potassium sprays also increased root:shoot ratio and root K concentration in PEG-stressed plants. These responses of K-sprayed trees could also contribute to greater tolerance to higher levels of water stress.
Low- and high-K pretreated ‘York Imperial’ apple seedlings (Malus domestica Borkh.) were grown in nutrient solution cultures. Addition of polyethylene glycol (PEG) to the nutrient solution to reduce water potential to −1.0 bar reduced water consumption, fresh weight, specific leaf weight (SLW), and leaf water potential and increased the amount of water consumed per unit of fresh weight gain. High-K pretreatment increased water consumption of unstressed seedlings but decreased water consumption of PEG-stressed plants. Daily sprays with 0.5% KCl applied in early afternoon had no effect on water consumption rate in apple seedlings. However, sprays probably induced wider stomatal opening, since K-sprayed trees had lower leaf water potential when measured at noon than unsprayed trees. This effect was not observed when water potential was measured in the morning (0800 hr). High-K plants had higher leaf water potential than low-K plants in the morning. Potassium pretreatment and PEG stress as well as K-sprays had numerous effects on plant mineral composition. The K-pretreatment or K-sprays did not alleviate the detrimental effects of PEG-induced water stress despite the effects of K-pretreatment and K-sprays on mineral composition and leaf water potential.
The effect of polyethylene glycol (PEG)-induced water stress on stomatal and nonstomatal inhibition of photosynthesis of apple seedlings (Malus domestica Borkh.) grown in solution culture was investigated. Water stress was applied gradually by modifying the nutrient solution water potential daily to a minimum of -8.0 bar. Nutrient solution of less than or equal to water potentials -6 bar decreased net and gross photosynthesis rates. Stomatal and nonstomatal factors were responsible for photosynthetic inhibition. Nonstomatal inhibition of photosynthesis appears to be due to decreased capacity for CO2 fixation and not increased photorespiration. The ratio of gross to net photosynthesis was not affected. A higher level of water stress was required to affect mesophyll resistance than stomatal resistance and/or there was a lag time for mesophyll resistance to respond to stress.