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doi: 10.1080/01904168809363921pmid: N/A
Abstract Iron (Fe) chlorosis induced by heavy phosphate (P) fertilizations is a serious problem for macadamia (Macadamia integrifolia) in Hawaii. To address this problem, a study was conducted to quantify the effects of P‐Fe interaction on macadamia leaf composition and chlorosis. The soil used was a limed Oxisol (Tropeptic Eutrustox, Wahiawa Series), pH 5.5. Phosphate was added as treble superphosphate at 0, 150 and 500 mg P/kg. The 150 mg P/kg rate was designed to yield approximately 0.04 mg P/L in the soil solution, a level considered adequate for macadamia growth. The 500 mg P/kg rate was intended to produce approximately 0.2 mg P/L, a level required by many horticultural crops but considered excessive for macadamia. Iron was added as Fe‐DTPA at 0, 5 and 10 mg Fe/kg soil, and factorially imposed on the P treatments. Color Index, a numerical rating based on hue, value and chroma from a Munsell Color Chart for Plant Tissues, was correlated with leaf chlorophyll concentration and used as an indicator of chlorosis. Phosphate concentrations in leaves increased with increasing P application rates as expected, but decreased remarkably with increasing Fe rates (at a constant P rate). Plant Fe unexpectedly remained unchanged with increasing Fe rates but decreased with increasing P rates. The results suggest that (1) soil‐solution Fe was not a limiting factor to macadamia growth as is often incorrectly assumed for high P‐fertilized soils, (2) Fe uptake was restricted not because soil‐solution Fe was low but because plant P was excessively high, and (3) Fe translocation from roots to leaves may have been hampered by high P in the plants. Consequently, Fe chlorosis was intensified primarily by P fertilization (actually, by high plant P concentrations) and secondarily by P‐Fe interactions. Chlorosis, as measured by Color Index, can be diagnosed by a leaf Fe/P ratio < 0.06, and predicted by a soil‐solution 3√Fe/P ratio < 15.
Korcak, R. F.; Zimmerman, R. H.; Miller, S. S.
doi: 10.1080/01904168809363922pmid: N/A
Abstract Nutrient concentrations in leaves of self‐rooted apple trees propagated by tissue culture (TC) were compared to the same cultivars budded on seedling, MM 106, and M.26 rootstock planted at two sites, Beltsville, MD and Kearneysville, WV. Leaf samples were monitored annually for 3 years after planting for N, P, K, Ca, Mg, Mn, Fe, Cu, B, Zn and Al from ‘Ozark Gold’ and ‘Stayman’ apples at both sites and ‘Northern Spy’ at Beltsville only. Leaf K and Mn concentrations tended to be higher in trees on M.26 and MM 106, while Ca was higher in TC or seedling trees. Foliar Mg was lower in trees budded on MM 106. Variation in P concentrations was greatest over years, while leaf N and Fe displayed only slight variation among rootstocks. Leaf B and Zn did not exhibit any consistent trends and Cu and Al were not affected by year, rootstock, cultivar or site.
doi: 10.1080/01904168809363923pmid: N/A
Abstract An almond X peach seed line, ‘Titan’ X Nemaguard (T X NG), which is tolerant to lime‐induced chlorosis, was compared to a susceptible seedling rootstock, Nemared, under alkaline conditions. The tolerant rootstock's growth was not affected by Fe stress, whereas the susceptible rootstock showed chlorosis which corresponded to approximately a 20% chlorophyll loss in the new foliage during the 18‐week stress period, a 62% decrease in shoot dry weight and a 22% decrease in plant height.
Lindgren, D.T.; Schaaf, D.M.; Shearman, R.C.
doi: 10.1080/01904168809363924pmid: N/A
Abstract Mineral element concentrations of twelve Kentucky bluegrass (Poa pratensis L.) cultivars grown in alkaline soil (pH = 7.8) were determined. The range of average mineral nutrient concentrations among cultivars was 22.8 to 28.2 mg g‐1 for N, 3.7 to 4.8 mg g‐1 for P, 16.8 to 20.2 mg g"1 for K and 157 to 259 ug g‐1 for Fe. Leaf color was influenced by year and N concentration but not by Fe concentration using a stepwise regression analysis procedure.
Nobel, P. S.; Quero, E.; Linares, H.
doi: 10.1080/01904168809363925pmid: N/A
Abstract Nutrient effects on the growth of Crassulacean acid metabolism plants have received little attention. Agave deserti and A. lechuguilla were therefore selected for study because their rate of leaf unfolding from the central spike relates closely to growth, thus providing a convenient means for monitoring the effect of nutrient applications. The greater fractional influence of nitrogen fertilization on leaf unfolding for A. deserti can be explained by its lower soil level of N than for A. lechuguilla; high application levels of N near 500 kg ha‐1 proved slightly inhibitory compared with 100 kg N ha‐1 during the first year after application but not during the second year for A. deserti. Agave deserti occurred in soils much higher in phosphorus, potassium, and boron than for A. lechuguilla; consistent with this, application of these three nutrients in the field had little influence on the rate of leaf unfolding for A. deserti tut could significantly increase the leaf unfolding rate for A. lechuguilla. Applications of nutrient levels that greatly stimulated leaf unfolding for A, lechuguilla, such as 100 kg N ha‐1 or 500 kg P ha‐1 , led to large increases in net COg uptake over 2k h; applications of 500 kg K ha‐1 or 100 kg B ha"1 led to lower enhancements in CO2 uptake and in the leaf unfolding rate, but again prevented any major decrease in net COg rate during the night. In agreement with studies on other CAM plants, the macronutrients N, P, and K and the micronutrient B can enhance the growth of agaves, depending on the relative level of these nutrients in the soil.
Pew, W.D.; Abbott, J.L.; Gardner, Bryant R.; Tucker, T.C.
doi: 10.1080/01904168809363926pmid: N/A
Abstract Cabbage (Brassica olearacea var. capitata L.) yield differences from added P were highly significant up to the predicted response level of 0.4 mg 1 . The increases in yield were basically due to larger head sizes. No statistical differences were found after the soil P levels were adjusted above 0.4 ppm, as determined by P isotherms constructed from initial soil samples. Slight differences occurred between years, but likely were due to cultivar growth differences. Data show that the isotherm predicted level fits rather closely the P requirements for cabbage as related to crop yields. Since extraction methods measure only the intensity factor of P, these methods could lead to incorrect P fertilization recommendations. The absorption of P is progressively reduced as the temperature goes down.
doi: 10.1080/01904168809363927pmid: N/A
Abstract A corn cultivar × P × K factorial experiment was conducted to evaluate differential responses of selected parameters to P and K soil fertility. Yield along with leaf nutrient concentration of some nutrients differed among cultivars and nutrient concentration of some elements was affected by soil fertility. Leaf K and Mg were more consistently affected by K fertility than other variables studied. Fertility effects upon micronutrient leaf concentration were not consistent among cultivars or between years.
Barker, A. V.; Ready, K. M.; Mills, H. A.
doi: 10.1080/01904168809363928pmid: N/A
Abstract Ammonium nutrition of radish plants (Raphanus sativus L.) suppresses their accumulation of Ca. The objective of this study was to determine the critical Ca concentration of radish in order to assess if NH4 + nutrition induces Ca deficiency in this crop. Cultivar Cherry Belle was grown in sand culture in a greenhouse. Nitrogen was provided as nitrate or ammonium salts, and Ca was varied from 1 to 200 mg/liter in solution. With N03’ nutrition, plant growth increased curvilinearly with increased Ca in solution. Calcium accumulation in shoots was a good index of relative root (edible radish) growth. The critical Ca concentration in shoots for optimum root growth was 2% of the dry matter. With NH4+ nutrition, plant growth declined linearly with increased Ca in solution and with Ca accumulation in the shoots. A critical Ca concentration could not be determined for plants grown with NH4 + nutrition. The antagonism between Ca and NH4 + nutrition could not be explained by deficiencies or toxicities of other elements.
doi: 10.1080/01904168809363929pmid: N/A
Abstract Silicon is a necessary element in the development of sane plants. Its presence is known to affect the elongation of jute (Corhorus capsularis) fibers. The concentration of silicon in developing cotton fiber (Gossypium hirsutum L. and Gossypium barbadense L. ) is high during the elongation phase of fiber development and decreases as the fiber matures. Thus, silicon concentration may have an effect on the development of the cotton fiber.
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