摘要:

Soluble aluminum (Al) exists in a variety of forms in the soil system and is responsible for limiting plant growth in many areas of the world. Some phytotoxic forms of soluble Al have been identified in solution culture experiments, but current soil test methods do not effectively discriminate between toxic and nontoxic forms of Al. Large differences in Al tolerance exist within and among plant species. Efforts to select or breed plants for Al toxic soils have been somewhat successful, but accelerated progress will occur when plant Al tolerance mechanisms are more fully understood.

ISSN:0010-3624    

DOI:10.1080/00103628909368163

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A greenhouse experiment was conducted to evaluate “liming”; potential of different green manures. Ground leafy materials of cowpea (Vigna unguiculata),leucaena (Leucaena leucocephala) and guinea grass (Panicum maximum) were added at 0, 5, 10 and 20 g/kg to an Ultisol having a soil‐water pH 4.0, KCl‐extractable Al = 7.6 cmoLc/kg, Al saturation = 50% and soil‐solution Al = 2.2 mM. Treatments with Ca(OH)2were established for comparison.Sesbania cochinchinensis,an Al‐sensitive tree legume, was grown for 4 weeks as a test crop. Biomass production and chemical composition of the soil indicated that (i) cowpea and leucaena were more effective than guinea grass in detoxifying Al; for example, the additions of 10 g manure per kg soil were equivalent to 1.8 cmol(OH)/kg for guinea grass, 3.4 for cowpea and 4.2 for leucaena (at least on a short‐term basis), (ii) reduction of soluble Al at increased pH as a result of manure additions was the major mechanism for Al detoxification, and (iii) complexation of soluble Al by organic molecules also contributed to the detoxification.

ISSN:0010-3624    

DOI:10.1080/00103628909368164

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Copper sulfate as a catalyst in Kjeldahl digestion of selected ecological materials has been demonstrated to be effective when a salt/acid ratio of 1 g/mL is used. Copper sulfate in combination with zirconium sulfate is no more effective than copper sulfate alone.

ISSN:0010-3624    

DOI:10.1080/00103628909368165

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Overwintering soil temperature may influence crop response to phosphorus (P) and indices of P availability in the humid, temperate, transitional climate of Tennessee. The effects of P fertilization and soil incubation temperature on sorghumsudangrass (Sorghum bicolorxS. Sudanese) grown on a Typic Hapludalf was investigated in a greenhouse study. In order to determine the effect of temperature on P availability, soils were incubated prior to cropping, at a constant temperature of 6°C or an average diurnal temperature of 24 and 36°C. Reagent grade Ca(H2PO4)2.H2O was used as the fertilizer source and applied at rates of 0, 10, 20, and 30 mg P kg‐1for the first test and 0, 20, 40, 60, and 80 mg P kg‐1for the second test. Critical P concentration in the shoots for optimum yield was found to be 1.3 mg g‐1, corresponding to soil solution and labile P concentrations of 5.5 μmol L‐1and 167 μg g‐1, respectively. Optimum yield occurred for applications of >65 mg P kg‐1and was unaffected by soil incubation temperature. Applied P rates affected extractable P by five chemical extractants (Bray I, Bray II, Mehlich I, Mehlich III, and Mississippi), but soil incubation temperature had no affect. The extractants, however, were poorly correlated to plant P uptake and no one extractant appeared preferable to the others as an indicator of P availability.

ISSN:0010-3624    

DOI:10.1080/00103628909368166

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Phosphorus uptake rate, plant top weight, and grain yield were measured for corn (Zea maysL.) planted in field plots with or without fumigation, with different levels of P fertilization, and under conventional till and no till management. Plant growth and grain yield in P‐deficient, unfumigated conventional till and no till plots were significantly higher than those in the corresponding fumigated plots. The heightened responses were attributed to enhancement of P uptake by biological activity. Therefore, the effect of differential microblal activity on P uptake must be considered in estimating the lowest level of P fertilization needed for adequate growth in low P soils.

ISSN:0010-3624    

DOI:10.1080/00103628909368167

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The SKα shift between the valences of sulfur has been used to determine by X‐ray spectrometry the two main forms of sulfur present in plant material, viz: oxidised S (S6+) and covalently bonded sulfur (Sc). S6+and Scwere shown to correlate closely with sulfate, as determined by reduction with hydriodic acid, and cysteine+methionine S, respectively. The method is rapid and reliable provided the X‐ray spectrometer is stable and has high reproducibility in goniometer setting. The use of S6+and Scis recommended as an alternative to chemical methods for assessing the sulfur status of crops and the sulfur amino acid content of diets.

ISSN:0010-3624    

DOI:10.1080/00103628909368168

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Z1nc (Zn) deficiency of corn (Zea maysL.) has been detected in 20 or more states 1n the United States including Georgia. Since soil pH is a major factor in assessing the availability of soil Zn, this measurement has been included with acid extractable soil Zn in developing calibration Zn soil tests in North Carolina and Virginia. The objectives of this study were to develop a reliable soil test for Zn based on soil pH and Mehlich 1 soil Zn for corn gown on coarse‐textured soils and to compare our soil test values with those recently published from North Carolina where Mehlich 3 was the extractant. The study was conducted 1n 1979 to 1981 on a Tifton loamy sand (Plinthic Paleudult) site which had been used to study the influence of lime rates on micronutrient availability since 1970. Treatments consisted of four soil pH levels ranging from 5.3 to 6.6 and soil Zn levels ranging from 0.5 to 4.9 mg/kg. The Zn levels were established from the previous study where 5.6 kg Zn/ha had been applied annually for eight years (residual treatment) and by applying 3.36 or 6.72 kg Zn/ha during 1979, 1980 and 1981.

ISSN:0010-3624    

DOI:10.1080/00103628909368169

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Potassium‐retention characteristics of the topsoil and subsoil of a medial over thixotropic, isomesic, Typic Hydrandept (Puaulu series) was investigated under moist conditions. This soil occurs in high rainfall areas where important losses of K are likely. Exchangeable cations were extracted with 1M NH4OAc pH 7 and Potassium Retention (Kr) was calculated by the difference between initial K (exchangeable, soluble, and added K) and final K. The results indicated that for any given K solution concentration, the amount of K held by the subsoil was twice that retained by the topsoil. The relationship between Kr and Potassium Adsorption Ratio (PAR) was nonlinear. The Gapon selectivity coefficient (KG) sharply decreased with increasing Potassium Saturation (Ep) and then leveled off to an almost constant value at Ep values of 0.25 for the topsoil and 0.15 (mmol‐1L)½for the subsoil. This constant value of =KGwas reached when 5 and 10% of the initial exchange sites were occupied by K retained in the topsoil and subsoil, respectively.

ISSN:0010-3624    

DOI:10.1080/00103628909368170

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Greenhouse and laboratory research studied K and CI nutrition of four soybean [Glycine max(L) Merril] cultivars with differential resistance to Soybean Cyst Nematode (SCN,Heterodora glycinesIchinohe). The cultivars: Forrest (Group V, resistant to races 1 and 3), Bradley (Group VI, resistant to races 1, 3 and 4), Essex (Group V, susceptible), and Davis (Group VI, susceptible*) were used. Potassium treatments were zero K, K2SO4and KCI, and SCN treatment was zero and 500 eggs/100 g of previously sterilized soil. Single plants were grown for 30‐days in 400 g of soil in 3.5 cm pots maintained at 23°C. Plants were separated into roots and shoots for analysis. Post harvest SCN cyst counts were completed to evaluate cultivar‐K treatment effect on SCN population dynamics and treatment effects on root and shoot K, Ca, Mg and CI.

ISSN:0010-3624    

DOI:10.1080/00103628909368171

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The effect of the carbon:nitrogen ratio (C/N) of organic amendments on soil structure modification was studied in laboratory incubation experiments. Variable C/N ratios were obtained through application of carbonaceous substrates (cellulose, starch and wheat straw) and different levels of urea. Optimal responses of soil density and soil aggregate stability were found for the C/N range of 20–40. The levels of sugars extracted with boiling water and those of uronic acids were highest for the same C/N range. The preference of this C/N range substrates is also justified theoretically, considering microbial carbon and nitrogen budgets.

ISSN:0010-3624    

DOI:10.1080/00103628909368172

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor