Henry G. Taber

Extraction of silicon from plant tissue with dilute HCl and HF and measurement by modified inductive coupled argon plasma procedures

Detection of silicon (Si) in a dilute acid extract (1 M HCl+2.3 M HF) by inductive coupled argon plasma (ICAP) procedures was equivalent to the traditional silicomolybdous blue (colorimetric) method (r=+0.99). The glassware, nebulizer, spray chamber, and torch assembly of the ICAP instrument consisted of HF resistant materials. Comparison of HCl–HF extraction with autoclave-induced digestion (AID) for selected leaf reference materials indicated good agreement for corn stalks and bluegrass clippings, but not for apple or peach leaves. Recovery of added Si to various leaf tissue prior to HCl–HF extraction was excellent, ranging from 96.5 to 103.3%. Recovery of Si added to a closed nutrient solution by muskmelon plants varied from 97 to 100%. The dilute HCl–HF extraction of Si from rapidly growing plant tissue and measurement by ICAP methodology provides a rapid procedure, minimal chemicals, and a low correction factor reducing potential errors.

PETIOLE SAP NITRATE SUFFICIENCY VALUES FOR FRESH MARKET TOMATO PRODUCTION

Two tomato (Lycopersicon esculentum Mill.) cultivars, Mtn. Spring and Jet Star, were grown on black polyethylene-mulched beds of a loam soil with an organic matter content of 2.4% for two seasons, 1996 and 1997, to evaluate preplant N rate effects on fruit yield and leaf blade total nitrogen (N) and petiole sap NO3-N concentration. Four rates of N fertilizer (0 to 136 kg ha−1), as urea, were rotovated into the bed prior to laying the plastic mulch. Samples of the most recently matured leaves were taken every two weeks for N and NO3-N content. Fruit yield and quality were associated with early season, 4 and 6 week, petiole sap NO3-N concentration. Mtn. Spring required 1050 ppm sap NO3-N compared with 900 ppm for the Jet Star cultivar. In 1996, Mtn. Spring achieved maximum yield at 31 kg N ha−1 whereas Jet Star required 67 kg N ha−1. Maximum yield occurred at 67 kg N ha−1 for both cultivars in 1997. Nitrogen rates above the optimum decreased early yields in 1996, but not in 1997. Soil N mineralization data showed > 112 kg N ha−1 by mid-July in the top 30 cm of the soil profile. On the prairie soils of the upper Midwest soil N management should be similar for both determinate and indeterminate fresh market tomatoes. *Journal Paper No. J-19063 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project no. 3706, and supported by Hatch Act and State of Iowa funds.

Use of Diluted Tomato Petiole Sap for Potassium Measurement with the Cardy Electrode Meter

Abstract Tomato petiole sap from potassium (K) rate experiments conducted on prairie loam and river coarse sand soils from 1998 to 2002 was used to measure K concentration via the battery‐operated portable Cardy flat membrane electrode meter and inductive coupled plasma (ICP) laboratory instrumentation. In 1998, for undiluted sap levels less than 3000 mg kg−1 the linear Cardy–ICP correlation was r=0.94, but when K was more than 3000 mg kg−1, r was only 0.53. Diluting the sap with water (1∶1) improved the linear range to 6000 mg K L−1 (r=0.87, n=190). Petiole sap K, measured by either Cardy or ICP, was highly correlated to whole‐leaf K concentration all years, r=0.8 to 0.91. Even through the slope of the regression lines were similar for the years, the intercepts were significantly different (P<0.01). The Cardy electrode can be reliably used for tomato petiole K determination provided the sap is diluted and the usual handling precautions are taken to prevent petiole moisture loss and maintain stability in electrode readings.

Boron Analysis of Mehlich No. 3 Extractant with Modified Inductive Coupled Argon Plasma Techniques to Eliminate Iron Interference

Abstract Correlation of Mehlich No. 3 (M-3) soil-extracted boron (B) to the traditional hot-water method has been high enough (r = 0.82) to warrant further investigation. The problem has been a lack of suitable analytical procedures to detect 0.01–0.02 ppm B in the extract with high precision. Instrumentation consisted of a dual-view, photodiode array charge-injection device fitted with a SeaSpray nebulizer with a mass controller set at 0.71 L/min. The plasma power was 1150 W, the pump speed was set at 100 rpm, and the integration time was at 15 s. These settings allowed the simultaneous measurement of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), B, and zinc (Zn). The photodiode detection array has three sensitive B wavelengths that could be utilized; 208.959, 249.678, and 249.773 nm. The 249.678 and 249.773 lines are two to three times as sensitive and have twice the detection limit of the 208.959 line. Preliminary studies showed that iron (Fe) (249.782 line) interfered on the B 249.773 line, causing an inflated B extract reading of 0.06 µg/mL. The relative standard deviation for B concentrations <0.1 ppm in M-3 extractant (16 runs) was 1.17, and 1.15% for the 208.959, and 249.678 lines, respectively. Recovery of added B from 0.02 to 0.09 ppm ranged from 100 to 112%. Either of the two lines proved satisfactory, but the 249.678 line was more sensitive to low B concentrations. A field-soil greenhouse experiment showed that M-3 extracted B, measured by either the 208.959 or the 249.678 lines, correlated at r = 0.85, 0.84, and 0.67 with shoot-tissue B concentration for cauliflower, sweet corn, and tomato, respectively.

Nitrogen Source and Concentration Affect Growth and Performance of Bedding-Plant Impatiens

ABSTRACT Impatiens (Impatiens wallerana Hook. f.) is the most important annual bedding plant in the United States, based on wholesale dollar volume. Production of high-quality plants requires optimization of the nutrition regimen during growth, especially the total nitrogen (N) concentration and the ratio of N sources. The objective was to determine the N concentration and the nitrate (NO3 −−N):ammonium (NH4 +−N) ratio of N source that optimized bedding-plant impatiens growth and flower development. Four N concentrations (3.5, 7, 10.5, and 14 mmol N · L−1) were used in factorial combination with four ratios of NO3 −−N:NH4 +−N (4:0, 3:1, 1:1, and 1:3). Application of treatments was made for 30 d. Then for 10 d only deionized water was applied to reduce salt buildup. Substrate pH was lowest (4.9) with the NH4 +−N source and electrical conductivity (EC) highest, but never > 2.4 dS m−1. Nitrogen concentration and N source displayed an interaction for most growth parameters. Shoot fresh and dry weights and flower bud number were maximized at the 1:3 NO3 −−N:NH4 +−N ratio with a N concentration of 10.5 mmol L−1. However, plant diameter, leaf number, and leaf chlorophyll content responded quadratically to N form ratio, with the 1:1 ratio optimum at a concentration of 10.5 mmol N· L−1.

Determination of nitrate in unfiltered extracts of muskmelon tissue by ion‐selective electrodes

Abstract Nitrate (NO3‐N) determination with ion‐selective electrodes (ISE) on muskmelon (Cucumis melo L.) leaf petiole tissue was equivalent to the cadmium (Cd) reduction method provided that the aluminum sulfate [Al2(SO4)3] buffer solution was >0.04M to eliminate ionic strength effects from varying NO3 and chloride (Cl) concentrations. Recovery of added NO3 was better with the HACH ISE, 98.8%, as compared with Orion ISE, 93.6%. The addition of silver sulfate (Ag2SO4) did not significantly improve NO3 recovery with either ISE. The addition of carbon depressed the detected NO3 concentration by 9.7%. The HACH ISE offers the advantage of a inexpensive, easy‐to‐use, single body electrode with a durable membrane allowing the filtration step to be eliminated.

Effect of Excessive Calcium Applications on Growth and Postharvest Performance of Bedding-plant Impatiens

ABSTRACT Application of excessive amounts of calcium (Ca) during the production cycle improves the quality and postharvest life of several florist crops. Most bedding plants are fertigated with Ca at 100 to 200 mg L− 1throughout the production cycle, but we do not know the effects of higher Ca concentrations. The objective was to evaluate the effect of application of excessive Ca (≥ 280 mg L−1) supplied during the production cycle on the growth, development, and subsequent postharvest performance of bedding-plant impatiens (Impatiens wallerana Hook. f. ‘Super Elfin White’) under simulated retail conditions. Calcium was applied at 120, 200, 280, 360, and 440 mg L−1 during each fertigation during the growing cycle. The total nitrogen (N) concentration was 150 mg L−1, and the nitrate (NO3 −)-N to ammonium (NH4 +)-N ratio was 1:1. Application of excessive Ca began 30 d after sowing (22 d after germination) and continued until 60 d after sowing. From day 60 to day 65 only deionized water, as a leach, was applied. From day 65 to day 90, plants were held under shade cloth and irrigated with tap water. Excessive Ca applied during the production cycle decreased shoot dry weight, shoot fresh weight, leaf number, and shoot tissue K concentration at the end of the production cycle. Excessive Ca applied during the production cycle also decreased shoot dry weight, leaf number, and shoot tissue potassium (K) concentration at the end of the postharvest period. Plant height, plant diameter, number of open flowers, and number of unopened flower buds at the end of the production cycle and at the end of the postharvest period were not affected by the amount of Ca applied during the production cycle. It was concluded that excessive Ca applied to bedding-plant impatiens during the production cycle did not benefit plant performance during either the production cycle or the postharvest period.

Nitrogen effect on yield and kernel protein content of sweet corn grown on sandy soils

Abstract Early spring application of N to Iowa sandy, leachable soils results in reduced sweet corn yields and kernel protein content. Normally, split N applications are used to coincide with crop N demand. Our objectives were to determine if nitrapyrin, a nitrification inhibitor, applied with urea would provide high yields and kernel protein levels when applied at planting. Nitrogen rate increased yield, ear leaf N concentration, and kernel protein content in 1976 and 1978, with the optimum rate dependent on the year and soil N residual. Urea, with or without nitrapyrin, significantly enhanced yield 13%, early leaf N concentration 17%, and kernel protein content 9% as compared with Ca(NO3)2 for both years. High leaching loss of NO3‐N occurred with the Ca(NO3)2 source as compared with urea alone. Kernel protein concentration correlated well with ear leaf N concentration (r = .74) and yield (r = .61). Ear leaf K content was not affected by N rate or source, but Ca(NO3)2 enhanced uptake of Ca and Mg as comp...

Method of nitrogen application for muskmelons 1

Abstract Muskmelons (Cucumis melo L.) were transplanted through clear plastic mulch on May 22, 1981, with 45, 90, 135, or 180 kg N/ha applied either preplant broadcast incorporated or injected through the trickle system. Seventy percent of the N rate was injected by flowering (June 23) and the remaining 30% from June 23 to July 27, just prior to first harvest. Muskmelon petiole NO3‐N concentration increased linearly with increasing N rates on all sampling dates for both application treatments. Trickle injected N resulted in a significantly higher plant N03‐N petiole concentration on June 22. Later in the season, July 13 and August 3, there were no petiole NO3‐N concentration differences between the application methods. Marketable early and total yields were not affected by the N rate or application method; but the broadcast method, as compared with trickle injection, increased total fruit per plant by 12%. Soluble: solids and fruit size were not affected by the Nirate on application method; but the broadc...