摘要:

An investigation was conducted in a watershed formed by the tributaries of the Little River in South Georgia to study the nature of the humic and inorganic fractions of black water, and their influence on stream water quality. Large amounts of black colored water were sampled during 1983 to 1984 according to streamflow pattern in December, March, June and September. Measurements of air and water temperature and dissolved oxygen were made at the gaging sites, whereas water analysis for conductivity, Cl, NO3‐N, NH4‐N, P, total N, and other macro‐ and microelements were conducted in the laboratory. Fulvic (FA) and humic acid (HA) were isolated from the water samples, and analyzed by infrared and13C NMR spectroscopy. Suspended clay from the water samples were collected and determined by x‐ray diffraction analysis. The results showed that black water was characterized by low conductivity and low ion concentrations indicating satisfactory chemical quality. The Na content was half the amount of other rivers in the Southeastern United States, whereas the ? content was similar to the world average. A seasonal fluctuation was noticed for Ca and Mg concentration. The increase of these ions during high streamflow in spring and summer was attributed to agricultural practices in the surrounding lands. Dissolved organic matter (DOM) concentration was highest in December during low streamflow. As DOM content decreased during high streamflow, water pH increased. A large part of the humified DOM was composed of fulvic acid, which was more aromatic in nature than soil‐fulvic acid as determined by13C NMR. The suspended clay had a composition reflecting the clay mineralogy of Tifton soils in the surrounding uplands. It is believed that the Tifton soil, with its low activity clay and hence low CEC, may not be able to buffer the effect of acid leaching of black water.

ISSN:0010-3624    

DOI:10.1080/00103629009368355

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Total contents of the major and several minor constituents in soils were determined by the titled methods and compared with those obtained by X‐ray fluorescence or atomic absorption spectrometry, which have been successfully used in the authors’ laboratory as the most reliable method in recent years.

ISSN:0010-3624    

DOI:10.1080/00103629009368356

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In a randomized block experiment, NPKCa fertilizers were applied annually for 5 years to a mature sugar maple (Acer saccharumMarsh.) woodlot in southern Ontario. Trees selected from 3 crown classes were fitted with dendrometer bands, tapped for sap and analyzed for foliar starch and nutrients and sap nutrients. Crown classes responded differently to the fertilizers. Trees which responded significantly in diameter growth did not respond the most in sugar yield. Effects of the fertilizer treatments on sugar yield were shown to be significant when the area of crown overlap of competing trees was subtracted from the crown area of crop trees. Foliar analysis and DRIS showed which nutrients were in demand after fertilizer applications. Sap analysis showed significant relations between sap nutrients and between sap nutrients and diameter growth. Starch analysis showed significantly higher foliar starch concentrations after potassium fertilization than after other fertilizer treatments.

ISSN:0010-3624    

DOI:10.1080/00103629009368357

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The occurrence of phosphorus (P) deficiencies in small grain crops are normally predicted through the use of preplant soil analysis and verified by tissue analysis for total ? often at the beginning of reproductive growth. Few studies have addressed the potential use of tissue phosphate (PO4‐P) tests to characterize the ? status of grain crops during early vegetative growth which could allow for correction of ? deficiency in irrigated production systems during the current season. Three field experiments were conducted in southeastern Arizona from 1986–89 to examine the effects of ? applications, and residual soil ? on tissue phosphate (PO4‐P) concentrations and yield of irrigated durum wheat (Triticum turgidumL. var durum cv. Aldura). Fertilizer ? additions resulted in significant increases in basal stem and leaf tissue PO4‐P concentrations at GS 2, 6 and 10. Fertilizer ? applications of up to 40 kg P/ha increased extractable ? levels in the soil by 82% at the beginning of the next growing season but had no significant effect on grain yields or tissue PO4‐P concentrations of the succeeding wheat crop. Band applications of ? resulted in higher tissue PO4‐P concentrations versus broadcast applications. While both basal stem and upper leaf tissue PO4‐P concentrations were responsive to differences in ? availability, routine use of basal stems for nitrate testing and significantly higher PO4‐P levels in basal stems at GS 2 and GS 6 favor its use in diagnosing ? deficiency. Basal stem tissue PO4‐P analysis seemed to accurately reflect ? nutrition of durum wheat from GS 2 to 10. Preliminary critical levels of PO4‐P in basal stem tissue of irrigated durum wheat were 2000, 1200 and 500 mg/kg at GS 2, 6 and 10, respectively.

ISSN:0010-3624    

DOI:10.1080/00103629009368358

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Leaf N and soil nitrate and ammonium levels were monitored in 1986 and 1987 following N fertilization of 8–9 year old highbush blueberries. Urea was applied at 76 kg N/ha in a single application at bud break or in two applications (split) at bud break and petal fall. Controlled release fertilizers (CRF), of two different residual effects (Osmocote 3 mo., Osmocote 8 mo.) were applied at 38 kg N/ha or 76 kg N/ha at bud break. Compared to controls, N applications increased soil ammonium and nitrate levels early in the season and leaf N levels throughout the season. Urea provided a greater increase in leaf N and soil ammonium levels than CRF. Split urea applications increase leaf levels slightly over single urea treatments. Fertilizers increased soil ammonium and nitrate levels below the root zone, indicating that some leaching losses occurred.

ISSN:0010-3624    

DOI:10.1080/00103629009368359

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Phosphorus fertilizer recommendations could be improved mark‐edly if, in addition to the extractable P concentration, some estimate of the P buffering capacity were considered. Measuring the P buffering capacity or its estimate from clay content or surface area, however, is too time consuming for most soil testing laboratories. Soil samples from the southeastern USA and western Spain were analyzed for several properties that either are or could be measured readily. These properties were cation exchange capacity (CEC), sample density (SD), humic matter (HM), and a color index (CHL). Topsoil samples with HM > 20 g/L were eliminated from the set. The P buffering capacity was estimated with a sorption index. This index correlated well with clay content, so clay content was used for comparison with CEC, SD, and CHL. Of these parameters, clay content was best correlated with CHL (r2= 0.81). Since CHL can be determined very quickly under routine laboratory conditions, it could be utilized for refining the P soil test interpretation and improving subsequent fertilizer P recommendations.

ISSN:0010-3624    

DOI:10.1080/00103629009368360

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Field experiments were conducted on calcareous and non‐calcareous Orthic Black Chemozemic soils over a five year period to study the effect of rates and placements of P‐fertilizer on Canadian rape (Brassica napus L. cv Tower) production. Six rates of P as mono‐ammonium phosphate (MAP) were applied at seeding using four placement methods: i) broadcast and cultivated 10 cm into the soil (BC); ii) banded in the seed row with the seed (PWS); iii) banded 2.5 below and 2.5 cm to the side of the seed (PSS); iv) banded 2.5 cm directly below the seed (PBS). Soil type had no significant effect on rape growth, seed yield and P‐uptake. Rape responded best to P‐fertilizer banded with (PWS) or near (PSS, PBS) the seed. But, placing 15 kg/ha P or greater with the seed reduced seedling emergence; with 25 kg P/ha insufficient plants emerged to justify harvesting. The reduced seedling emergence resulted in reduced seed yield and P‐uptake. Maximum yields were obtained when the fertilizer was banded 2.5 cm away from the seed (PSS, PBS). The BC method produced the least growth, yield and P‐uptake responses of the four methods. Only when broadcast rates of P were in excess of 10 kg/ha did rape dry matter, seed and P‐uptake increase. Banding 10 kg/ha with or near to the seed was equivalent to broadcasting 25 kg/ha in terms of seed yield and P‐uptake. Application of P fertilizer also increased seed protein and oil concentrations.

ISSN:0010-3624    

DOI:10.1080/00103629009368361

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Data from experiments conducted in Hawaii, measuring soil surface temperatures in plots cropped with potato, cassava, and maize, were used to estimate soil surface temperatures using a model from the temperate zone. According to this model maximum soil surface temperature under a given vegetative cover can be estimated from maximum air temperature and a factor, Et, that represents the elevation of maximum soil surface temperature over maximum air temperature under that crop cover. Inputs for the model are: maximum air temperatures and plant biomass measurements. A generally good agreement between estimated and observed maximum soil surface temperatures was obtained when Et was arbitrarily set to 0.1 × Et. For potato during summer of 1985, maximum soil surface temperature estimates were within an average of less than 2C of observed surface temperatures and with a deviation of no more than 3.8C. For cassava during summer of 1986, estimates were within 2.3±5.1C; for maize during summer of 1988, estimates were within 2.7±4.4C.

ISSN:0010-3624    

DOI:10.1080/00103629009368362

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Soil physical, chemical, and taxonomic data of about 12,000 pedons from the continental U.S., Hawaii, Puerto Rico, and some foreign countries were used to develop multiple regression equations to estimate sum of exchangeable bases (SUMBAS) and base saturation (BS). Soils were grouped according to their taxonomic classification at order and suborder categories. Multiple regression equations using organic carbon and clay contents, and soil pH in water ratio 1:1 accounted for more than 50% of the variation in SUMBAS in 11 of 35 suborders included in this study. Regression equations using organic carbon and clay contents, pH, 1M KC1 extractable Al or percent Al saturation, and cation exchange capacity accounted for more than 70% of the variation in SUMBAS in 18 of 35 suborders. Percent Al saturation and organic carbon content were negatively related to BS. These two parameters accounted for more than 70% of the variation in BS in 16 of 32 suborders. Regression equations using soil pH alone, in turn, accounted for more than 70% of the variation in BS in 4 of 6 suborders with a formative element Aquic in their taxonomic names.

ISSN:0010-3624    

DOI:10.1080/00103629009368363

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A computer data collection program requiring a minimum of program maintenance and technician training and allowing technician involvement with analytical instrument operation, was developed for a high volume production laboratory. The program, which complemented existing laboratory methodology, was written in top‐down, block‐style format. This structure insured easy maintenance and allowed individual instruments and their calibrations to be easily added to the program for data collection. The program was menu‐driven and limited direct technician involvement with instrument operation to changing samples, monitoring the instrument for calibration, monitoring the final readings, and intervening in the event of an obvious error. A two hour familiarization period requiring no instruction manuals was all that was required of a technician with no prior computer knowledge or training of any kind to become proficient with using the program.

ISSN:0010-3624    

DOI:10.1080/00103629009368364

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor