摘要:

Four procedures (desorption by anion resin, Olsen, ammonium oxalate and calcium lactate), to determine the available P in soils, were compared in a greenhouse study. Five rates of P (0, 55, 110, 165 and 220 mg/kg) were applied to 18 calcareous soils from Syria and yield response of perennial ryegrass (Lolium multiflorum L.) to applied P was measured. Dry weight of tops correlated very well with the anion resin‐P or Olsen‐P procedures while lactate P and oxalate P results were poorly correlated. Similarly, total P uptake were significantly correlated with both anion resin P (R2=0.85) and NaHCO3‐P (R2=0.82) and less so for the oxalate P (R2=0.63) and lactate P (R2=0.32) methods. All 4 soil test procedures were effective in classifying soils into responsive and non‐responsive to P. Critical soil P levels were 18.5, 11.5, 9.5 and 7.4 mg/kg for the anion resin, Olsen, lactate and oxalate soil test procedures respectively. The Olsen method is our recommendation for calcareous soils since it is a simple, rapid, and reproducible method that is well correlated with plant response.

ISSN:0010-3624    

DOI:10.1080/00103628809367926

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An experiment was conducted over two years on a Typic Haplaquoll and an Aquic Argiudoll to determine the effect of tillage on the response of two corn hybrids(Zea mays) to soil K fertility. Four tillage systems were used: moldboard plow, chisel plow, disk, and no‐till. The soil K treatments were 336 and 560 kg exchangeable K/ha and 336 kg exchangeable K + 73 kg banded K/ha. Increase in exchangeable soil K increased midseason leaf K each year. Banded K increased leaf K only in the drier year. Tillage affected grain yields only in the growing season with the higher precipitation. The lowest grain yields were obtained with the no‐till system, the highest with the chisel system. Potassium treatment did not affect grain yields. It was concluded that K fertility recommendations developed for moldboard plow systems are adequate for reduced tillage systems.

ISSN:0010-3624    

DOI:10.1080/00103628809367927

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Agricultural soils in northern Idaho have become acidified in the last 20 years due to heavy use of ammonium‐based N fertilizers. There is, however, a lack of information on the performance of lime requirement tests on these soils. This study was undertaken to evaluate several of the more commonly used lime requirement tests on some northern Idaho soils. Latahco silt loam soil (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll) was selected to represent these closely related soils in this study. Latahco soil was incubated under controlled environmental conditions with 0, 1,2, and 4 Mg ha‐1Ca(OH)2for five weeks. The results were compared to “quick” lime requirement tests using linear regression equations. All lime requirement tests were highly correlated with incubation‐indicated lime requirement (r 0.89 at target pH 6.0). However, only Woodruff and Improved Woodruff buffer methods provided acceptable estimates of the actual lime requirement over the pH range evaluated (5.0 to 5.8). The SMP buffer method overestimated lime requirement over all pH values (5.0 to 5.8). A modification in the Woodruff buffer method was suggested to further improve its predictive ability. The modification was to use a buffer pH adusted to 6.0 (Woodruff‐pH6) rather than 7.0. The Woodruff‐pH6 appears to provide the most accurate lime requirement value among methods evaluated in this study.

ISSN:0010-3624    

DOI:10.1080/00103628809367928

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Phosphate and sulfate were shown to interfere in the analysis of aqueous molybdenum (Mo) standards by graphite furnace atomic absorption spectroscopy (GFAAS) when either peak area or peak height was used to measure absorption signals. Lanthanum (La) addition to the standards eliminated interferences from PO4=and SO4=when absorption signals were measured as peak area but not when measured as peak height.

ISSN:0010-3624    

DOI:10.1080/00103628809367929

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Cumulative patterns of Al release upon exhaustive leaching of E, Bh1 and Bh2 horizons of a podzol with M, 0.1Mand 0.01MKC1 were found to be markedly dependent upon KC1 concentration. Comparison ‘bulk’ extracts, equilibrated for both 16 h and 7 days, in most instances gave pH‐1/3pAl values which lay between 2.6 and 3.0, close to the value for the solubility of gibbsite. Results are discussed with reference to whether exchange processes or solubility processes controlled the extraction of Al. Differences in behaviour of the E horizon are related to a specific difference in its mineralogy.

ISSN:0010-3624    

DOI:10.1080/00103628809367930

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Soil bulk density markedly influences hydrolysis of surface‐applied granular urea that is vulnerable to serious ammonia volatilization losses. In order to decrease the ammonia losses by retarding urea hydrolysis, several chemicals have been tested for their soil urease inhibition properties. Phenyl phosphorodiamidate (PPDA) is a potent soil urease inhibitor. Laboratory studies using soil column incubations were conducted to investigate the effect of soil bulk density on inhibition of hydrolysis of surface‐applied urea granules (=20 mg of urea/granule) containing 1% PPDA in unsaturated soils. The increase in soil bulk density (from 0.69 to 1.50 Mg/m3) markedly increased the rate of hydrolysis of surface‐applied urea granules and significantly decreased the apparent urease inhibition by PPDA present in the granules. These results are attributed to the probable spatial separation of urea and PPDA because of the differences in diffusive transports in unsaturated soils caused in part by differences in their solubilities in water.

ISSN:0010-3624    

DOI:10.1080/00103628809367931

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A micro‐Kjeldahl method suitable for use with a commercial block digestor is described which minimizes NO3‐N reduction during digestion and also reduces foaming. One hundred mg plant tissue are pretreated with 3 ml H2O2at 100° C for 15 min. This is followed by addition of concentrated H2SO4, K2SO4, and catalyst, and digestion at 360° C for 1 hr. With H2O2added after the H2SO4, 40% of the NO3‐N was reduced over a range in the tissue from 0.25% to 1.5% NO3‐N. With the H2O2pretreatment essentially none of the NO3‐N was reduced. Total nitrogen, (reduced N determined by the proposed method plus nitrate, measured separately) was analyzed for 9 species ranging in NO3‐N from 0 to 0.73% and in total N from 1.4 to 4.4%. The results agree well with the AOAC method 2.052 (1).

ISSN:0010-3624    

DOI:10.1080/00103628809367932

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A laboratory column study was conducted to determine the influence of eluent ionic strength on Fe transport and DPTA‐Fe levels in a coarse‐textured soil. Leaching solutions consisted of either 10‐2, 10‐4mol L‐1KC1 or distilled H2O, adjusted to pH 4.8. Approximately, two pore volumes, 750 ml of solution, were applied to the soil columns., after which the columns were analyzed for pH and DPTA‐Fe with depth. Soil leached with 10‐2mol L‐1KC1 exhibited lower DPTA‐Fe levels compared to the 10‐4mol L‐1KC1 and H2O treatment. Dissolved organic carbon (DOC), inositol hexaphosphate and Fe in collected leachates increased with low ionic strength treatments. Changes in the distribution pattern of DPTA‐Fe in the soil columns and in leachate Fe were attributed to increased dissolution of Fe oxides by soluble organic acids and inositol hexaphosphate.

ISSN:0010-3624    

DOI:10.1080/00103628809367933

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We have shown that the traditional Kjeldahl method applied to clay soils of the Duero Basin (Spain) is not effective; so, it is necessary to add HC1 + HF to free trapped ammonium. This fixed ammonium has been measured by two methods which give significantly different results. The level of fixed ammonium in cultivated clay soils is relatively high (it ranges from 180 to 490 ppm). Fixed ammonium is significantly correlated to clay content and total inorganic nitrogen of the soil. A proposed method of analysis for total N is given.

ISSN:0010-3624    

DOI:10.1080/00103628809367934

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628809367925

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor