摘要:

Soil sulfur was determined by inductively coupled argon plasma spectroscopy (ICAP) and SO4‐S by liquid ion chromatography (LIC). Soils from 153 locations across the Great Plains were used in this study. Organic matter in the soils ranged from 0.2 to 3.8%. Inductively coupled argon plasma S was determined on calcium phosphate and ammonium acetate extracts. Liquid ion chromatography was performed on calcium phosphate extracts. Soil SO4‐S analyzed by LIC averaged 21% lower than ICAP‐S. Higher S values from ICAP are probably due to soil S in forms other than SO4‐2. Ammonium acetate extracted 13% more S than calcium phosphate. Soil SO4‐S can be predicted from calcium phosphate ICAP‐S by a linear equation (SO4‐S = ‐3.28 + 0.786(ICAP‐S), R2=0.963). Sulfate‐S can be predicted from ammonium acetate extracted ICAP‐S by another linear equation (SO4‐S =‐2.00 +0.688(ICAP‐S), R2=0.917). Using ICAP, S could be determined in the same ammonium acetate extract used to determine exchangeable cations. Additional forms of S extracted by ammonium acetate and included in ICAP analysis may improve correlations between plant parameters and soil test S levels.

ISSN:0010-3624    

DOI:10.1080/00103629009368333

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Colorimetric determination of soil NO3‐N by transnitration of salicylic acid was compared to an automated cadmium reduction and specific ion electrode methods. Soils from 155 locations across the Great Plains were extracted and analyzed for NO3‐N by each method. Nitrate concentrations in the soils ranged from 1 to 2 34 mg NO3‐N/kg. Almost identical results were obtained by salicylic acid and cadmium reduction methods. Linear regression of NO3‐N determined by salicylic acid and cadmium reduction produced a R2of 0.994. Nitrite was not detected in soils used for this study. The specific ion electrode method gave significantly lower NO3‐N values than the two other methods. Linear regression of NO3‐N determined by salicylic acid and the electrode method produced a R2of 0.985. Transnitration of salicylic acid is a fast method for determination of soil NO3‐N that returns nearly identical results as automated cadmium reduction.

ISSN:0010-3624    

DOI:10.1080/00103629009368334

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A procedure is described for optimizing plant tissue digestion conditions for accurate selenium (Se) analysis. Optimal concentrations of nitric acid, ceric ammonium nitrate, hydroxylamine HCl and the use of vapor trapping funnel were evaluated for total recovery of Se in NIST wheat flour reference material using atomic absorption spectrophotometry with continuous Se hydride generation. During sample digestion, excessive or insufficient amounts of nitric acid (<0.45 M or >1.02 M), ceric ammonium nitrate (<6.7 x 10‐5M or >6.6 x 10‐4M), or hydroxylamine HCl (<0.016 M or >0.398 M) caused a 15–20% reduction in the total Se recovered. Additional losses up to 15% were observed in the same samples without the use of the vapor trapping funnel. These results demonstrated how digestion conditions must be optimized for precise and accurate Se analysis in plant tissue.

ISSN:0010-3624    

DOI:10.1080/00103629009368335

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Cotton (Gossvpium hirsutumL.) yields are limited by K deficiency in extensive areas of California where soils contain minerals that fix K in nonreplaceable forms. A survey study was conducted to evaluate the relationship between seed cotton yield and four soil test methods for K by regression analysis. A total of 38 on‐farm sites over two years were included in the study. Intensity parameters obtained from two soil tests that measure solution‐phase K+concentration in soil/solution suspensions were the best predictors of cotton yield across soils, sites, and years. Quantity parameters based on 1 M NH4‐extractable K or K extracted by 5 N H2SO4were significantly less precise in predicting yield. Three K fixation isotherm methods were also compared for their ability to predict the proportion of added K that is fixed. Only one method that included a soil wetting and drying cycle provided estimates of K fixation and solution‐phase K+concentration that were in reasonable agreement with actual values measured in a 3‐yr field study. These results indicate that K fertilization recommendations would be improved using a solution‐phase K+soil test to identify soils where a response to added K is likely, and an appropriate fixation isotherm method to estimate the fertilizer K requirement.

ISSN:0010-3624    

DOI:10.1080/00103629009368336

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Soil testing and leaf analysis have been used as one of the measures for indicating fertilizer needs on country level, and thus fertilizer allocation. In 1976, a project was initiated to introduce soil testing and leaf analysis as a base for working out specific fertilizer recommendations on farmer's level and as monitoring system for crop nutritional status. Three well equipped laboratories were established and surveys were carried out. In 1981, services were made available to farmers, co‐operatives, farmers organizations, etc. Highly qualified field personnel is advising farmers, interpreting analytical results and working out fertilizer recommendations. Services are partially paid by the beneficiaries. During 1985–1988 service was rendered to about 22,000 farmers. In the meantime, a program was set up to establish service laboratories throughout the country. Eleven were initiated, but still not established to serve the farmers directly. However, they help in indicating fertilizer needs of the country in general. Some universities are running analysis as services for farmers within very limited scope. Gained experience by the project is now under evaluation. A manual of methods to be used in routine analysis has been agreed upon by organizations participating in providing analytical services to farmers. Establishing a network of service laboratories is suggested. Different strategies are given and discussed. Contacts are intensified with developed as well as Arab countries to exchange and share experience.

ISSN:0010-3624    

DOI:10.1080/00103629009368337

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The objective of this study was to characterize the level of Zn, Cu, Mn and Fe in different plant parts of various forage legumes and cole crops grown in Prince Edward Island. The concentration of the four nutrients was consistently highest in leaves and lowest in the stem, except for Zn in cole crops where a greater concentration was found in the upper halves of the plants than in the leaves. The Cu and Zn concentrations were generally higher in the upper halves than in the lower halves of the plants. Manganese and Fe did not follow any specific pattern in the upper and lower halves of the plants. Zinc, Mn and Fe were lower in the forage legumes than in the cole crops, while Cu was higher in forage legumes than in the cole crops. The mean concentrations of Zn, Cu, Mn and Fe in different plant parts of the forage legumes and cole crops investigated ranged from 25 to 48, 6.1 to 8.8, 47 to 149, and 46 to 112 mg kg‐1, respectively. Since leaves generally contained the highest amounts of Zn, Cu, Mn and Fe, it is recommended that wherever possible leaves should be sampled to characterize the micronutrient cations status of crops.

ISSN:0010-3624    

DOI:10.1080/00103629009368338

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The latent mineral‐N residue is the smallest required inorganic nitrogen quantity, at the moment that the maximum N‐amount is present in the crop, to obtain optimum yields. These latent mineral‐N residues vary widely between crops, ranging from 25 kg NO3‐N/ha, for cereals and sugar beet, upto more than 100 kg NO3‐N/ha for some leaf vegetables. Different factors are responsible for these variations.

ISSN:0010-3624    

DOI:10.1080/00103629009368339

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Banding of fertilizers below the seed at planting under reduced tillage conditions is becoming more commonplace. This technique however, can lead to difficulties in obtaining a representative soil sample for determining the status of mobile (N,S) and nonmobile (P,K) nutrients. This study was designed to evaluate three different soil sampling techniques. These techniques included: systematic (taking a series of soil cores perpendicular to band rows), controlled (random soil sampling avoiding the band row), and random soil sampling. All three sampling techniques adequately estimated the mobile nutrient status of soils; however, differences as a consequence of soil sampling techniques were observed for non‐mobile nutrients. The systematic sampling technique provided the highest non‐mobile nutrient values, while the controlled sampling procedure the lowest. Considering time, labor costs and the lack of availability of skilled labor the random sampling technique was the best for sampling fertilizer banded fields.

ISSN:0010-3624    

DOI:10.1080/00103629009368340

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A field experiment was conducted in 1987 on a Vertic Haplustoll on the Island of Oahu (Hawaii) to monitor the dynamics of 1M KCl extractable NH4‐N and NO3‐N, and organic carbon (OC) and total nitrogen (N) contents following the application of increasing rates of N fertilizer as urea (0, 50, 100, and 150 kg N/ha) and subsequent cropping with irrigated cassava. Soil samples were taken at 0–15, 15–30, 30–45, and 45–60 cm soil depths at 60, 120, 180, 240, and 300 days after planting (DAP). Cumulative rainfall values for the periods 0–60, 60–120, 120–180, 180–240, and 240–300 DAP were 151, 0, 156, 142, and 1032 mm, respectively. Two waterlogged periods occurred, one just before 180 DAP and the other after 240 DAP. NH4‐N accumulated to high levels after the first waterlogged period but no NO3‐N was detected. NH4‐N declined sharply after the second waterlogged period. Both OC and total N contents decreased over time and were not affected significantly by N fertilization. Changes in OC and total N contents over time were controlled primarily by temperature and C/N, respectively.

ISSN:0010-3624    

DOI:10.1080/00103629009368341

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A field experiment was conducted in 1987 on a Vertic Haplustoll on the Island of Oahu (Hawaii) to study dry matter production and efficiency of dry matter partitioning of cassava grown under increasing rates of applied nitrogen (N) (0, 50, 100, and 150 kg N/ha). A series of biomass harvests were collected throughout the growing season to examine the effects of differential N regimes on top and root growth. Although plant growth was partially stunted by waterlogging, N fertilization increased significantly top and total plant dry matter production but decreased the proportion of dry matter allocated to roots. The maximum dry matter partitioning ratio for roots (root dry weight/total dry weight) was 0.28 for the 150 kg N rate vs. 0.44 for the control (0 kg N).

ISSN:0010-3624    

DOI:10.1080/00103629009368342

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor