摘要:

A field crop of 3‐month old cabbages was sampled every 2 h from 0600 h until 2000 h. At each sampling, an upper, middle and lower leaf were taken from four plants, and their petiole nitrate status measured by three methods (a) “Merckoquant”; test strips (b) specific ion electrode on a fresh macerated extract and (c) the same electrode on an extract of oven dry tissue. All three methods led to similar conclusions:a.there were very big differences in concentration with leaf position, the middle leaf having the highest;b.there were large concentration differences between plants, especially for the lower leaves;c.the effect of time of day was not significant.

ISSN:0010-3624    

DOI:10.1080/00103628309367406

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The kinetics of the formation of MnHPO4and Cd3(PO4)2in solution were studied in order to determine the overall reaction order and the rate constant at various temperatures for each reaction. Known concentrations of cation were added to a saturated solution of monopotassium phosphate (MKP) which was kept at a constant temperature. Aliquots of the reaction solution were removed at various time intervals and analyzed. The reaction temperatures ranged between 20–60°C with the reaction time varied between 3 and 12 hours. Results indicate that both MnHPO4and Cd3(PO4)2are second order overall reactions, with Mn(II), Cd(II), HPO4‐2, and PO4‐3being first order with respect to their appropriate reactions. The rate constant for each reaction was found to increase with temperature and to conform to the Arrhenius equation. The activation energy and the pre‐exponential constant for each reaction was calculated from the Arrhenius equation.

ISSN:0010-3624    

DOI:10.1080/00103628309367407

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Specific sarption of low quantities of Zn in eight gleysolic C horizons in Quebec soils was studied in dilute Cacl2solutions. Initial Zn concentrations were between 5 and 30 ppm. The range of specific Zn sorbed calculated as percentages of Zn added ware very high to moderately high indicating a high affinity sarption for Zn of the sorbed complex surface. Specific Zn sarption was found to agree with the Freundlich and Langmuir isotherms over a large range of concentrations.

ISSN:0010-3624    

DOI:10.1080/00103628309367408

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Simple and multiple regression analyses was used to examine the relationships between cation exchange capacity (CEC) and organic matter, and clay content of 40 surface Philippine soils to determine the contributions of organic matter and clay to CEC.

ISSN:0010-3624    

DOI:10.1080/00103628309367409

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Attention is drawn to the availability of packaged computer programs for calculating nutrient indices for the DRIS (Diagnosis and Recommendation Integrated System) approach to diagnosing nutrient insufficiencies, excesses and imbalances in plant tissue. A brief outline of the subroutines is given together with details of how to obtain and use the programs. The following crops are covered: maize, soybeans, sorghum, potatoes, wheat, rubber, sugarcane, sunflower, alfalfa.

ISSN:0010-3624    

DOI:10.1080/00103628309367410

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The Diagnosis and Recommendation Integrated System, previously applied successfully to many other crops, is shown to be an appropriate foliar diagnostic tool for sorghum (Sorghum bicolorL.) with respect to N, P, K, Ca and Mg. The norms were developed from a data bank comprising 907 observations of tissue composition and yield gathered from the literature and investigators’ files. The total population of observations is divided into a high and low subpopulation on the basis of yield. Those forms of expressing tissue composition which discriminate best between the two subpopulations are used to compute DRIS indices which measure the extent of the deviation from the established norm. An independent set of data from two field experiments is used to show that the norms can validly diagnose nutrient insufficiences which when, corrected result, in yield increases.

ISSN:0010-3624    

DOI:10.1080/00103628309367411

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Boron (B) is the third member of the third periodic group. It is a nonmetal with an atomic number of five and a constant valence of 3+. Boric acid [B(OH)3]and H2Bo3−are the most common geologic forms of B, with boric acid the predominant form of B in agricultural soils. Boron occurs mainly in silicate minerals. The 10 μg/g B concentration of the earth's crust is distributed among common rock types.

ISSN:0010-3624    

DOI:10.1080/00103628309367412

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

When in‐row subsoilers are used to plant crops in no‐tillage systems, starter fertilizers are often applied in the in‐row subsoil track. Although rates applied are small, the actual concentration within the rooting zone can be excessive, and injury to germinating seed and young plants can be severe. The purpose of this greenhouse study was to determine the effect of starter fertilizer placement, rate, and source on germination, growth, and nutrient uptake ef corn (Zea maysL.) seedlings. Fertilizers were surface applied, mixed with the upper 7.5‐cm, 7.5‐ to 15‐cm and the 0‐ to 15‐cm soil depths. Fertilizer rates were equivalent to 15 and 30 kg/ha of field applied P. Sources were diammonium phosphate (DAP, 18–46–0) and ammonium polyphosphate (APP, 10–34–0). Treatments did not affect germination, but the surface application resulted in severe crust formation which had to be mechanically broken. Plant heights and weights and root weights were increased by fertilizer. Nitrogen was primarily responsible for increased plant growth 2 weeks after emergence, but P appeared to have the greatest effect at 4 and 6 weeks. Although seedling death or severe damage to plants did not result from any source, rate, or application zone, some damage did occur. Optimum treatments varied with sampling dates, but after 6 weeks, optimum treatments in terms of greatest root and shoot weights and plant heights were the low rate of APP mixed with the 0‐ to 7.5‐ or the 0‐ to 15‐cm soil depths.

ISSN:0010-3624    

DOI:10.1080/00103628309367413

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The use of kochia (Kochia scoparia(L.) Schrad.) as a forage crop has recently generated considerable interest, but little is known about how fertilization affects yield and quality. Two greenhouse experiments were conducted; the first with a clay loam soil and 0, 67 and 135 kg P/ha, and the second with a sandy loam soil and extremely high rates of P, which were 0, 4.5, 9.0, 13.5 and 17.9 ton P/ha. Both had 0, 84, 168 and 252 kg N/ha in a complete factorial with the P levels. In the first experiment, dry matter yield, root dry matter yield and flowering percentage increased linearly with N, while Ca, P and oxalate percentage decreased quadratically with N. Oxalate levels were low with a mean of 1.98%. Phosphorus levels affected only P percentage, which increased quadratically with P level. No interactions were observed between N and P in the first experiment.

ISSN:0010-3624    

DOI:10.1080/00103628309367414

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Ammonium sulfate and urea were added to three soils of widely different composition. After incubation for 28 days at 20°C, from 13 to 89% of the N from ammonium sulfate, and 8 to 71% of the N as urea were not recovered, and at 40°C, 44 to 95% of the N as ammonium sulfate, and 33 to 81% of the N as urea was not recovered as either ammonium‐N or nitrate‐N. Significantly more N was lost from a soil containing 3% calcium carbonate at pH 8.4 as compared to the two other soils containing 25 and 35% calcium carbonate, which have pH's of 7.7 and 7.5, respectively. An incubation temperature of 40°C appeared quite unfavourable for nitrification.

ISSN:0010-3624    

DOI:10.1080/00103628309367415

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor