摘要:

Soybean (Glycine max(L.) Merr. cv Bragg) plants were grown in the greenhouse using a low‐Mn Leefield sand amended with 0, 2.5, 5, 20 and 50 yg Mn/g. The plants were inoculated and were primarily dependent on symbiotically fixed N. Measurements of DTPA‐extractable soil Mn, soil pH, leaf tissue Mn, top weight, top N content, and nodule weight, volume and number were made at 27, 42, 56, 63 and 69 days after planting. The DTPA extrac‐tant was a good predictor of leaf tissue Mn giving a highly significant (P = 0.01) overall correlation coefficient of 0.704 for this comparison. Because of an unexpected decline in soil pH from 6.8 to 6.0 and an associated increase in DTPA‐extractable Mn from 0.14 to 0.24 yg/g during preparation and handling prior to the first harvest time, Mn in the leaf tissue of the controls was never less than 21 yg/g. Since this concentration of Mn is above the deficient level, no significant responses in top growth, nitrogen fixation or nodule measurements were obtained from the addition of low rates of Mn. The highest Mn rate was only mildly toxic in terms of top growth and top N content, producing leaf tissue having Mn concentrations ranging from 171 to 180 yg/g at the last three harvest periods.

ISSN:0010-3624    

DOI:10.1080/00103627809366842

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Ammonium nitrogen can be determined in silage samples using an ammonia electrode. Dilute hydrochloric acid (0.1N HCl) is used to extract the ammonium nitrogen from the fresh silage samples. The electrode method is rapid, simple and precise, and gives quantitative recoveries of added ammonium. Results agree closely with distillation of the silage sample.

ISSN:0010-3624    

DOI:10.1080/00103627809366843

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Zinc availability was studied using five soils from Hawaii which had histories of massive phosphorus applications. Heavy phosphate fertilization usually increased extractable Zn, irrespective of the extractant used. The extra extractable Zn associated with the added P probably came from Zn as an accessory element in the fertilizer. Treble superphosphate commonly used in Hawaii contains about 1400 ppm Zn. The Zn content of phosphate fertilizers must be considered before making statements about the effect of fertilizer P on Zn solubility and availability in soils.

ISSN:0010-3624    

DOI:10.1080/00103627809366844

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A buffer is generally a mixture of a weak acid and a salt of the same weak acid. Hence it can neutralize both acids and bases, and thus resists marked changes in pH of a system. Yet systematic change in pH of a buffer caused by addition of an acidic substance can be used to indicate the total acidity represented by the change in buffer pH. Since acid soil is itself a buffer, when it is added to a buffer mixture for the purpose of measuring its acidity or lime requirement (LR), the resulting double‐buffer suspension (soil‐buffer) is a relatively complex system. Much of the complication in interpreting the changes in buffer pH brought about by mixing soil and buffer stems from the facts: i) that much of the acidity is pH‐dependent, and ii) that quick‐test methodology involves reaction of only a fraction of the total soil acidity with the buffer. Marked change in relative amounts of H ions dissociating from the soil‐SMP‐buffer system at soil‐buffer pH 6.9 and above accounts for relatively wide variations between buffer‐indicated and CaCO3incubation‐measured LR of low LR soils. Similarly, decreased reactivity of H+in high organic matter soils and increased reactivity of H in acid‐leached soils cause errors in buffer‐indicated LR. Awareness of these principles helps avoid pitfalls of existing buffer methods, and has led to incorporation of the double‐buffer feature for improving the SMP method.

ISSN:0010-3624    

DOI:10.1080/00103627809366845

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Long filtration time, accumulation of salt residue on the atomic absorption or flame emission burner slot, and contamination of P and K in the sodium acetate are three problems encountered when using sodium acetate‐acetic acid or Morgan's solution (MS) for extracting P, K, Ca, and Mg from soil samples. Thus an ammonium acetate‐acetic acid (AA‐AA) solution was compared with MS for 144 soil samples which, although ranging in pH from 4.4 to 7.9, were all derived from calcareous glacial till. A highly significant linear correlation was obtained between the two methods for each of the four elements. Filtration time for the AA‐AA solution was 30–45 minutes shorter than that for MS. No salt residue accumulated on the atomic absorption burner slot when using AA‐AA. Because of these advantages, we have replaced MS with AA‐AA for samples analyzed in our laboratory.

ISSN:0010-3624    

DOI:10.1080/00103627809366846

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Differential responses were noted among several corn (Zea maysL.) inbreds for Ca when grown in nutrient solutions at varied Ca stresses. Properties of one of the more “Ca‐efficient”; inbreds (Oh43) compared to one of the more “Ca‐inefficient”; inbreds (A251) are reported.

ISSN:0010-3624    

DOI:10.1080/00103627809366847

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A laboratory experiment was conducted to study kinetics of sorption of orthophosphate (OP) and pyrophosphate (PP) from dilute solutions by three ammoniated tropical soils. Milligrams of P sorbed by soil (?P) and shaking time (t) showed a linear relationship: ?P = a + b√t. The data suggested two diffusion — controlled processes during P sorption. In general, due to ammoniation, initial sorption rate of OP (in linear region I) increased while that of PP decreased. PP was sorbed more than OP. Sorption rate of OP and PP in linear region II showed a tendency to decrease with increasing ammoniation levels.

ISSN:0010-3624    

DOI:10.1080/00103627809366848

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Electro‐ultrafiltration (EUF) of soils ‐ a combination of electrodialysis and ultrafiltration ‐ which works on the principle of extraction of nutrient ions from soils under an external electric field, can be employed as a useful method in soil fertility work to characterize the desorption parameters of soil nutrients.

ISSN:0010-3624    

DOI:10.1080/00103627809366849

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Two cultivars of cotton(Gossypiumspp.) were grown in solution culture in a glasshouse to determine phytotoxicity effects of excesses of Ni and Cd. Leaf yield was depressed 94% by 10‐4MNiSO4(with 198μg Ni/g leaf) in Acala SJ‐2 and 93% (with 167μg Ni/g) in Plma PS‐5. The Ni gradient was roots > stems > leaves in both cultivars. At 10‐5M, CdSO4gave more phytotoxicity than NiSO4. The 10‐4MCdSO4resulted in about the same amount of phytotoxicity as did the Ni for both cultivars. The Pima PS‐5 plant parts, however, contained less Cd than did the Acala SJ‐2 at the highest Cd concentration. At 10‐5MCdSO4the reverse held in leaves and stems. Interactions held for both metals but the inverse effect between Cd and Mn was less pronounced than for other species. Many other interactions were present.

ISSN:0010-3624    

DOI:10.1080/00103627809366850

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Two cultivars of cotton(Gossypiumspp.) were grown in Yolo loam soil in a glasshouse to determine phytotoxicity effects of excesses of Ni and Cd. A 200 μg/g level of Ni in soil reduced yield by 60% in Acala SJ‐2 and by 83% in Giza 45. The leaf Ni concentrations, respectively, were 146 and 165 μg/g‐ The 300 μg/g level of Cd decreased leaf yields by 60% and 75% for the two cultivars, respectively. Leaf concentrations of Cd, respectively, were 43 and 63μg/g. There was a stem to leaf gradient of Cd for all cases. High Cd did not depress Mn concentrations in plants . as in other species but there were many mineral element interactions.

ISSN:0010-3624    

DOI:10.1080/00103627809366851

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor