摘要:

Many methods of evaluating organic soil nitrogen (N) mineralization and N availability indexes have been proposed. Chemical methods are more rapid but they do not measure the soil microorganisms and plant root activities. Incubation‐leaching procedure may remove some of the readily mineralizable soil organic N compounds. Continuous‐incubation procedure may sometimes increase soil acidity or cause toxins accumulation. The objective of this study was to determine, in a greenhouse experiment, the relative capabilities of 10 soils with organic matter (O.M.) content ranging from 2.38 to 8.63% to supply plant‐available N by combining two procedures, i.e., soil incubation and plant N‐uptake. In method one (M1), N‐uptake by 3 successive oat crops of 8 weeks each, without soil preincubation was studied. Method two (M2) involved a soil preincubation of 8 weeks, and the subsequent determination of N‐uptake by two successive crops of oats (Avena sativaL.) of 8 weeks each. No soil‐leaching was used. The results show that there was a large difference in plant N‐uptake according to soil organic matter. The highest correlation between soil O.M. and plant N‐uptake (r = 0.91**) was given by the first crop following incubation. The N‐uptake by the first crop in M1(without soil incubation) was much less correlated with soil O.M. (r = 0.74*) and was significantly influenced by soil initial NO3and NH4‐N. The results of this study show that the preincubation of soil samples minimized the influence of soil initial mineral N and that a preincubation was necessary before the plant N‐uptake measurement, even on a 8‐week cropped soil period.

ISSN:0010-3624    

DOI:10.1080/00103628309367379

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Coarse textured soils were analysed for extractable boron, cobalt, copper, iron, manganese, molybdenum and zinc contents. Correlation studies showed significant differences between (i) pH values and extractable copper, manganese, iron and cobalt; (ii) organic matter and zinc, cobalt and boron and (iii) clay content and manganese, iron, zinc, cobalt, boron and molybdenum. Comparison of the extractable trace element contents of coarse and fine textured soils indicated different extraction correlations between these two soil types. Generally the quantities of trace elements extracted were higher in the 0–15 cm horizon.

ISSN:0010-3624    

DOI:10.1080/00103628309367380

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The application of FeSO4alone or in combination with gypsum increased the chlorophyll and Fe2+content of leaves and total dry matter production of sugarcane grown on saline calcareous loam soil irrigated with saline or non‐saline water. Treatment of sugarcane with FeSO4independent of gypsum significantly increased leaf chlorophyll which was strongly and positively correlated with leaf Fe2+, DTPA extractable Fe of soil and. dry matter production.

ISSN:0010-3624    

DOI:10.1080/00103628309367381

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

High vater table sandy soils present special problems when establishing soil pH variables under field conditions. In order to examine the response of a coarse‐textured soil to lime and HC1 acid treatments, data are reported for soil pH and extractable Ca and Mg for a field experiment where Mn treatments on soybeans was the primary objective. Three treatments included HC1 acid, control, and lime. Acid (742 liters/ha 3NHC1) was added only at the beginning of the experiment but dolomitic lime treatments were added each year (2240, 2740, and 2900 kg/ha). The lime and acid were applied to the soil surface and incorporated to a depth of 10 to 13 cm. Soil samples were taken every 2 to 3 months at 3 depths (0 to 15, 15 to 30, and 30 to 45 cm) and analyzed for pH and extractable Ca and Mg. Acid treatment decreased the pH by 0.2 units below the untreated soil at the 0 to 30 cm depth and the effect lasted the entire 3 years of the study. Calcium values were lowered only slightly by the acid treatment. Lime additions caused steady increases in soil Ca. Magnesium values increased several months after each of the first and second lime applications. Lime raised the subsoil (30 to 45 cm) pH after 4 to 6 months. Seasonal variations in pH were very wide with the untreated soil pH varying from 6.1 to 6.8. The high pH level of 7.0 was not maintained for an entire season until the third year of the experiment. Soil pH as well as extractable Ca and Mg showed fluctuations that were the result of seasonal variations and soil moisture content at the time of sampling. Soil pH variables on a sandy soil should be established at least a year in advance of starting an experiment and must be closely monitored in order to maintain the desired pH levels.

ISSN:0010-3624    

DOI:10.1080/00103628309367382

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The results of three years of experimentation on the effect of the addition of dolomitic lime to pine bark‐sand media shows thatPhotinia‘Fraseri’ responds positively to lime additions. This response was not due to pH changes, since for two of the three years only a small change was observed in pH and lime requirement values. It is more likely that the increased growth is due to an improved magnesium environment. Not only was the magnesium content of the foliage increased with lime addition, but the K:Mg ratio was decreased to a level where potassium‐magnesium antagonism was not important.

ISSN:0010-3624    

DOI:10.1080/00103628309367383

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The influence of soil moisture on endomycorrhizal infection in black walnut was studied using four groups of potted seedlings watered at different time intervals. Seedlings watered every day or every second day had much longer lateral roots but fewer infected root segments than seedlings watered every third or fourth day. These results suggest that controlling the soil moisture level may alter the conditions that affect competition for colonization between introduced and indigenous mycorrhizal fungi.

ISSN:0010-3624    

DOI:10.1080/00103628309367384

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The available Cu extracted by DTPA, EDTA, 0.1NHC1 and 0.05NHC1 was determined in 51 diverse soil types under dry and flooded conditions. The latter two solutions did not extract Cu from dry soils having high pH or high organic carbon content. Under flooded soil conditions, the number of soils giving extractable Cu by DTPA, EDTA and 0.1NHC1 decreased, while 0.05NHC1 did not extract Cu from any of the flooded soils. DTPA and 0.05NHC1 extractable Cu from dry soil gave good correlation with plant Cu content of 2 rice cv. Since these two reagents are now commonly used for determining available Cu in soils for growing rice, the pH and organic C content of soils may be taken into consideration while choosing between the two.

ISSN:0010-3624    

DOI:10.1080/00103628309367385

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Ten extractants were used for measuring the available phosphorus (P) in 24 tropical soils, and the extractable P values were correlated against plant parameters obtained from a 170‐day continuous cropping experiment and a 50‐day response experiment. The Olsen method was the ‘best’ for the continuous cropping experiment and the Hislop resin method the ‘best’ for the response experiment. When the 24 soils were separated into groups on the basis of organic carbon levels, soil classification, or mineralogy, a higher set of correlation coefficients was obtained than when a single extractant was used for all the soils. The increased precision was thought to justify the extra work involved.

ISSN:0010-3624    

DOI:10.1080/00103628309367386

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Basic cation fractions, total, exchangeable and nonexchangeable of five Pennsylvania soils were measured by chemical dissolution or extraction. Although the soils differed in the magnitude of the fractions due to differences in previous management history, texture and mineralogy, the patterns for the fractions of each cation were: Ca ‐ total > exchangeable > nonexchangeable, Mg ‐ total > non‐exchangeable > exchangeable and K ‐ total > nonexchangeable ≥ exchangeable. For the cations relative to each other the‐ patterns were: total ‐ K > Mg > Ca, nonexchangeable ‐ Mg > Ca > K and exchangeable ‐Ca > Mg > K. Acid soluble cations (boiling 1 N HC1, 1:3.5 soil to solution ratio) generally increased through four hours of boiling. Comparisons of the quantities of exchangeable cations calculated to be in a soil surface to the potential quantities taken up by alfalfa or corn grain emphasize the importance of resupply mechanisms and/or contributions from the subsoil for K and Mg, especially when alfalfa is grown.

ISSN:0010-3624    

DOI:10.1080/00103628309367387

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628309367378

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor