More peach [Prunus persica (L.) Batsch.] trees survived when planted in killed bahiagrass (Paspalum notatum Flugge `Paraguayan-22') sod growing between previous orchard tree rows (98%) than when planted in previous tree sites (81%) or in previous tree rows, but halfway between previous tree sites (79%). The previous orchard was removed Nov. 1986, and new trees were planted Feb. 1987. Surviving trees in the killed sod grew better than trees at the other two sites. Tilling the sites before planting did not affect nematode populations or tree survival and growth. Soaking the tree roots in a fenamiphos solution (1 g·liter-1) for 20 minutes before planting resulted in 79% tree survival vs. 93% survival for the nonsoaked trees. Fenamiphos sprayed under the trees at a rate of 11.2 kg·ha-1 during the spring and fall of the planting year did not change nematode populations, tree survival, or tree growth. The fenamiphos sprays reduced the increase in trunk cross-sectional area by 3 cm2 for trees in the sod. Other than leaf Zn concentration, which was low, concentrations of the elements were within the sufficiency range for Georgia for all treatments. Trees planted in the killed sod had an increased leaf K concentration and decreased leaf Mg concentration when compared with trees planted in the rows. Chemical name used: ethyl 3-methyl-4-(methylthio)phenyl (1-methylethyl)phosphoramidate (fenamiphos).
Soilless root media have little capacity to retain PO4 or K, and this contributes to leaching of these nutrients during greenhouse crop production. The objective of this research was to evaluate the suitability of precharged alumina as a sole source of PO4 and K during greenhouse production of potted chrysanthemum [Dendranthema ×grandiflora Kitam. (syn. Chrysanthemum ×morifolium Ramat.)]. Phosphate and K adsorption and desorption curves were created at 25 °C for two particle sizes (0.5 to 0.9 and 1.8 to 3.2 mm) of alumina (Al2O3; acid-washed and unwashed), and a medium of 7 peat: 3 perlite (v/v) using solutions of KH2 PO4 (P at 0 to 20,000 mg.L-1). Based on these curves, 1.8 to 3.2 mm, unwashed alumina was selected for use in the studies. Precharged alumina was tested in two greenhouse studies at 10% and 30% (v/v) of a peat-perlite medium used to produce `Sunny Mandalay' chrysanthemum. Phosphate, K, and pH were determined on unaltered root medium solutions collected throughout the 10-week cropping cycle, and foliar analyses were conducted on tissue collected at the middle and end of the cycle. Potassium release was adequate to meet chrysanthemum demand for 4 weeks, but inadequate for the remainder of the production cycle. Precharged alumina retained and released PO4 at sustained concentrations (P at <2 mg·L-1) over the course of a 10-week cropping cycle. Growth of plants receiving PO4 from precharged alumina was not significantly different from the controls receiving liquid fertilizer (P at 46.5 mg·L-1) at each watering when precharged alumina comprised 30% of the medium, and only slightly less when precharged alumina comprised 10% of the medium. A phosphorus budget showed that while 36% (103 mg) of the applied PO4-P was lost in the leachate of the controls, only 0.1% (2 mg) was lost from plants produced with alumina-P. This research demonstrates that in a soilless medium with physical properties similar to standard commercial mixes, low but adequate PO4 concentrations can be achieved and sustained using current production practices.
Optimum N and K rates were established for ‘Schwabenland Red’ Rieger begonia for weekly fertilization and for application with each watering. Weekly application of 400 ppm N or more and 150 ppm or less resulted in undesirable plant size reduction regardless of K level; 200 ppm was marginal and 250 and 300 ppm N were best. Weekly applications of 60 to 200 ppm K were best and equal when applied with 250 ppm N while levels of 250 ppm K and greater caused smaller final plant size. The best rates of N for application with each watering were 100 and 150 ppm; 75 ppm and lower and 200 ppm and higher had deleterious effects. K levels from 50 to 125 ppm were best for application with every watering while levels of 150 ppm and greater were undesirable.
Analysis of deficiency symptoms and foliar analyses of canopy leaves (youngest leaves 5 cm of wider) of Rieger elatior begonias (Begonia X hiemalis Fotsch cv. Schwabenland Red) indicated that the minimum critical levels for K, Mg, and B lie in the ranges of 0.93 to 0.95%, 0.22 to 0.25%, and 13.0 to 14.0 ppm, respectively.
Symptoms for 7 nutrient deficiencies were established for elatior begonia ‘Schwabenland Red’ (Begonia X hiemalis Fotsch.). These are summarized in the form of a key as follows:
a. Chlorosis is a dominant symptom.
b. Chlorosis interveinal.
c. Interveinal chlorosis on older leaves followed by light tan necrotic spots within chlorotic areas which expand until leaf dies........................................................................................................................Mg
cc. Interveinal chlorosis on younger leaves.....................................................................................................Fe
bb. Chlorosis not interveinal.
c. Lower leaves uniformly yellow then purplish yellow and finally necrotic.................i.....................N
cc. Margins of canopy leaves yellow, then murky green-brown, and finally necrotic; all symptoms spread toward the leaf center......................................................................................................................Ca
aa. Chlorosis not a dominant symptom.
b. Necrosis begins along the margin of lower leaves and progresses inward....................................................K
bb. Plants stunted but normal green..........................................................................................................................P
bbb. Rust color, striations and cracks develop on young leaf petioles and peduncles perpendicular to their axes; internodes shortened and lateral shoots prolific; young leaves brittle crinkled around rust color spots which turn necrotic; chlorosis and necrosis spreading inward from the margin of young leaves...B
Bahiagrass (Paspalum notatum Flugge cv. Paraguayan-22) growing under newly planted peach [Prunus persica (L.) Batsch.] trees severely stunted the trees. Neither supplemental fertilizer nor irrigating with two 3.8-liters·hour-1 emitters per tree eliminated tree stunting emitters were controlled by an automatic tensiometer set to maintain 3 kpa at a depth of 0.5 m under a tree in bahiagrass. Preplant fumigation with ethylene dibromide at 100 liters·ha-1 increased tree growth, but not tree survival. Fenamiphos, a nematicide, applied under the trees each spring and fall at a rate of 11 kg-ha -1 had no positive effect on tree survival, tree growth, or nematode populations. Bahiagrass tended to suppress populations of Meloidogyne spp. under the trees., Meloidogyne spp. were the only nematodes present that had mean populations > 65 per 150 cm3 of soil. Leaf concentrations of several elements differed between trees growing in bahiagrass sod and in. bare ground treated with herbicides. Leaf Ca was low for all treatments in spite of a soil pH near 6.5 and adequate soil Ca. The severe stunting of trees grown in bahiagrass, irrespective of the other treatments, demonstrated that bahiagrass should not be grown under newly planted trees. The low populations of parasitic nematodes in bahiagrass showed that bahiagrass has potential as a preplant biological control of nematodes harmful to peach trees. Chemical name used: ethyl 3-methy1-4-(methylthio) phenyl (1-methylethyl) phosphoramidate (fenamiphos).
Soilless root media retain very little phosphate. This characteristic necessitates continual application of phosphate, which leads to excessive application and leaching. The phosphate desorption characteristics of synthetic hematite (a-Fe2O3), goethite (a-FeOOH), allophane (Si3Al4O12*nH2O), and a commercial alumina (Al2O3), previously determined for their maximum adsorption capacities, were evaluated to determine their potential for providing a low, constant soil solution phosphate supply with low phosphate leaching from soilless root media. The desorption isotherms of the clay minerals were obtained by introducing 10 mM KCl solution at 0.2 ml/min flow rate into a stirred flow reaction chamber loaded with clay adsorbed with phosphate at maximum adsorption capacity. The suspension in the reaction chamber was held at pH 6.4 during desorption. Effluent solutions were collected for phosphorus analysis until the equilibrium concentration of phosphorus in solution reached 0.05 mg•L-1. Adsorbed phosphorus at 0.05 mg•L-1 equilibrium concentration in solution was in the order allophane (19 mg•g-1) > alumina™ goethite (8 mg•g-1) > hematite (1.3 mg•g-1). The equilibrium concentration of phosphorus in solution over time showed that allophane releases phosphate for a longer time than the other clay minerals at a desirable soil solution concentration for plants, less than 5 mg•L-1. Among the clay minerals tested, allophane showed the most favorable potential to supply phosphate to plants in soilless root media.
Forcing azalea (Rhododendron sp. cvs. Redwing, Mission Bells and Gloria were subjected to sufficient and low levels of N, K, and Ca, and the difference in concentration of these nutrients was measured and termed “differential”. Immature, recently mature, and old leaves were sampled periodically from current shoots during development. Ca differential was not related to sample position. N differential was exhibited in a similar manner but was best expressed in older leaf tissue during late growth. The magnitude of the K differential was related to both sample position and sample date; the largest expression occurred in young leaf tissue during early growth and on older leaf tissue during late shoot development. The best single sample position for foliar analysis of these nutrients was the most recently mature leaves on current shoots.
A soil material high in metal oxides collected from the Bw horizon of a Hemcross soil in the state of Oregon was charged with phosphate, added to a soilless root medium, and evaluated for its potential to supply phosphate at a low, stable concentration during 14 weeks of tomato cropping (three successive crops). Three rates of phosphate were charged on the soil material, 0, 2.2, and 6.5 m P/g soil material and the soil material was incorporated into a 3 peatmoss: 1 perlite (v:v) medium at 5 % (40 g) and 10 % (80 g) of the volume of a 13.6-cm pot (1.0 L of medium). Uncharged soil material incorporated into soilless root medium at 5% and 10% reduced soil solution phosphate to deficient levels for 2 and 7 weeks, respectively. Phosphate was adequately supplied for 7, 10, 12, and more than 14 weeks in the 2.2P-5%, 2.2P-10%, 6.5P-5%, and 6.5P-10% treatment, respectively, as determined by symptoms of P deficiency. Phosphate and K levels in soil solution were highest at the beginning of crop 1 and tended to decline thereafter. Incorporation of soil material into soilless root medium improved pH stability whether it was charged with phosphate or not. The loss of the phosphate-charged soil material was negligible, 0.3% for the 6.5P-5% treatment and 1.2% for the 6.5P-10% treatment. The minimum critical concentration of soil solution phosphate for tomato in a 3 peatmoss: 1 perlite (v:v) medium as determined by the pour-through extraction procedure was found to be 0.3 mg·L–1 or slightly less.
Pesticides were applied to ‘Rio Grande’ peach [Prunus persica (L.) Batsch] trees at recommended rates from bloom to harvest using three sprinkler configurations on a center pivot and an air-blast sprayer. Fruit scab infection rates with a patented sprinkler configuration (Piggy-back) that has spray nozzles mounted on a lower truss rod of the center pivot were equivalent on 12 and 23 June 1987 to those with the air-blast sprayer. Scab infection rates for standard impact-nozzles and for a deflector nozzle configuration were equivalent to each other, and tended to be lower than the infection rate for the unsprayed fruit, but higher than the rate for the air-blast sprayer or piggy-back configuration. Brown rot, bacterial spot, and insect catfacing (the other fruit defects observed at harvest) were independent of the method of pesticide application. It may be feasible to chemigate peach orchards with center-pivot irrigation systems.