ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHPLC method for the analysis of the urease inhibitor N-(n-butyl)thiophosphoric triamide and its metabolitesElizabeth A. Douglass and Larry L. HendricksonCite this: J. Agric. Food Chem. 1991, 39, 12, 2318–2321Publication Date (Print):December 1, 1991Publication History Published online1 May 2002Published inissue 1 December 1991https://pubs.acs.org/doi/10.1021/jf00012a045https://doi.org/10.1021/jf00012a045research-articleACS PublicationsRequest reuse permissionsArticle Views444Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Inseason sitespecific nitrogen application has the potential to improve the efficiency of nitrogen use and reduceenvironmental contamination. Identification of withinfield crop nitrogen stress is essential for improved nitrogenmanagement. Corn nitrogen stress is frequently associated with leaf chlorophyll content, which can be characterized byspectral reflectance measurements. Therefore, satellite remote sensing has potential for characterizing corn nitrogendeficiency on a wholefield scale. To evaluate the use of satellite imagery to detect nitrogen deficiency in corn during thegrowing season, this study compared spectral variables extracted from SPOT satellite imagery and digital aerial imagery,and investigated the relationship between spectral variables of the SPOT imagery and the measurement data of a handheldchlorophyll meter (or SPAD meter). SPOT images and aerial images were acquired on one commercial field in 1999 andanother one in 2000.
The correlation coefficient (r) between the NDVIs derived from the SPOT image and the aerial image was 0.73 in 1999,and 0.54 in 2000, respectively. When the field had large spatial variability in crop development in 1999, the spectral variablesfrom the SPOT image were strongly correlated with those from the aerial image. However, when the crop development wasmore uniform in 2000, the correlation between the SPOT image and the aerial image was not as good. The limited range ofavailable digital counts that can be used to represent the reflectance from an individual farm field for the SPOT system limitedits sensitivity in detecting crop stress. Nevertheless, the NDVIs from SPOT images were significantly correlated with SPADdata in both fields, with correlation coefficients of 0.90 in 1999 and 0.68 in 2000. The correlation between SPOT images andSPAD data was similar to that between aerial images and SPAD data, indicating that SPOT imagery may have potential fordetecting chlorophyll levels and nitrogen stress in corn during the growing season.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUse of Chelex-100 to maintain constant metal activity and application to characterization of metal complexationL. L. Hendrickson, M. A. Turner, and R. B. CoreyCite this: Anal. Chem. 1982, 54, 9, 1633–1637Publication Date (Print):August 1, 1982Publication History Published online1 May 2002Published inissue 1 August 1982https://pubs.acs.org/doi/10.1021/ac00246a038https://doi.org/10.1021/ac00246a038research-articleACS PublicationsRequest reuse permissionsArticle Views104Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
We reevaluated selected data describing complexation (including adsorption) of cadmium and other trace metals by natural solid and soluble soil components, using a consistent format to demonstrate the conditional nature of reported selectivity coefficients. In all cases, the determined selectivity values increased substantially as the concentration of trace metals decreased with respect to the concentration of other competing cations. This dependence upon relative metal concentrations is apparently due to the heterogeneous composition of complexing sites in most soil systems and competition among the various cations present for these sites. Most selectivity coefficients have been obtained after the introduction of metal concentrations well above those normally encountered in natural systems, with little attention paid to the concentration and composition of competing cations. Under such conditions, the metal occupied not only the most specific sites, but a large portion of the more numerous nonspecific sites. The use of selectivity values obtained under such conditions, in predictive models, will greatly underestimate metal complexation in natural systems. This demonstrates the importance of determining selectivity coefficients under conditions comparable to those existing in nature, if results are to be applicable to real systems.
Abstract Fertilizer N applied in the fall for the next growing season is often less efficient than N applied closer to the time of plant use. Efficiency might be greatly improved by maintaining the N as NH 4 through the use of the nitrification inhibitor, Nitrapyrin [2‐chloro‐6(trichloromethyl)pyridine] (NI). To evaluate this hypothesis, field trials were established during 1975 to 1977 in south central Wisconsin using 84 to 168 kg/ha N applied as anhydrous ammonia with and without 0.55 kg/ha NI. Nitrogen was applied in early or late fall, or just prior to planting corn ( Zea mays L.). The soil sampling data showed that NI provided excellent control of nitrification on the site from which yields were obtained. By early May more than 50% of the fall‐applied NH 3 was still in the NH 4 form when treated with NI, while more than 80% was nitrified in the untreated bands. Despite the rapid nitrification of untreated NH 4 at this site, little inorganic N was apparently lost from the rooting zone. Therefore no yield or N uptake response by the crop to NI was obtained. Nitrapyrin was much less effective in controling nitrification on a poorly‐drained site adjacent to the yield trials. Soil at this site also had higher pH and organic matter, and we found large inorganic N deficits in the sampled zone. These deficits, which can likely be attributed to denitrification, were significantly reduced by NI treatment.
Abstract In a laboratory study, ammonia (NH3) was trapped from 10 g soil units treated with 10 mg urea‐N, 10 mg urea‐N plus 50 ug N‐(n‐butyl) thiophosphoric triamide (NBPT), or 10 mg urea‐N plus 50 ug phenyl‐phosphorodiamidate (PPD). The soil was a Dothan loamy sand with pH levels adjusted to 6.0, 6.5, and 6.9 prior to N application. After 12 days, NBPT reduced NH3 volatilization 95 to 97%, while PPD reduced it 19 to 30%. Although NH3 loss was positively related to initial soil pH, there was no interaction between pH and urease inhibitor. In a field study, NH3 was trapped in semi‐closed chambers from 134 kg N/ha surface applied to corn (Zea mays L.) 6 weeks after planting. Nine days after N application, NH3 losses were 20.5, 1.5, 1.5, and 0.2 kg N/ha from urea, urea plus 0.25% NBPT, urea plus 0.50% NBPT, and ammonium nitrate, respectively. Covariance analysis showed that percent organic matter was negatively related to NHL losses. The soil properties, initial pH, CEC, and percent sand, did not vary enough to affect NH3 volatilization. In conclusion, in both the laboratory and the field, NBPT exhibited strong control of NH3 volatilization, and could thereby prevent significant loss of surface‐applied urea‐N to crops.
Abstract An araperometric titration method for Cl was suitable for reproducible analysis of equimolar Cl. Br and I in all possible combinations in the range 0.125 to 2.50 millimolar (mM). A solid state Br specific ion electrode exhibited a reproducible Nernstian response to Br over the range 0.005 to 1 mM, with minimal Cl interference. Bromide and Cl added to a lysimeter and a field were quantitatively recovered by estimation of (Cl + Br) amperometrically and Br potentiometrically.
