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81.
82.
Quantifying microbial biomass phosphorus in acid soils 总被引:10,自引:0,他引:10
J. Wu Z.-L. He W.-X. Wei A. G. O'Donnell J. K. Syers 《Biology and Fertility of Soils》2000,32(6):500-507
This study aimed to validate the fumigation-extraction method for measuring microbial biomass P in acid soils. Extractions
with the Olsen (0.5 M NaHCO3, pH 8.5) and Bray-1 (0.03 M NH4F–0.025 M HCl) extractants at two soil:solution ratios (1 : 20 and 1 : 4, w/v) were compared using eight acid soils (pH 3.6–5.9).
The data indicated that the flushes (increases following CHCl3-fumigation) of total P (Pt) and inorganic P (Pi) determined by Olsen extraction provided little useful information for estimating the amount of microbial biomass P in the
soils. Using the Bray-1 extractant at a soil:solution ratio of 1 : 4, and analysing Pi instead of Pt, improves the reproducibility (statistical significance and CV) of the P flush in these soils. In all the approaches studied,
the Pi flush determined using the Bray-1 extractant at 1 : 4 provided the best estimate of soil microbial biomass P. Furthermore,
the recovery of cultured bacterial and fungal biomass P added to the soils and extracted using the Bray-1 extractant at 1 : 4
was relatively constant (24.1–36.7% and 15.7–25.7%, respectively) with only one exception, and showed no relationship with
soil pH, indicating that it behaved differently from added Pi (recovery decreased from 86% at pH 4.6 to 13% at pH 3.6). Thus, correcting for the incomplete recovery of biomass P using
added Pi is inappropriate for acid soils. Although microbial biomass P in soil is generally estimated using the Pi flush and a conversion factor (k
P) of 0.4, more reliable estimates require that k
P values are best determined independently for each soil.
Received: 3 February 2000 相似文献
83.
84.
Summary Total populations of bacteria and fungi, dehydrogenase activity (as a measure of total potential microbial activity), and urease and phosphatase activities were determined in earthworm casts and surrounding laterite soils planted to pineapple. The casts contained higher microbial populations and enzyme activities than the soil. Except for fungal populations, statistically significant (P = 0.05) increases were found in all other parameters. Microbial populations and enzyme activities showed similar temporal trends with higher values in spring and summer and lower values in winter. The earthworm casts contained higher amounts of N, P, K and organic C than the soil (P = 0.05). Selective feeding by earthworms on organically rich substrates, which break down during passage through the gut, is likely to be responsible for the higher microbial populations and greater enzyme activity in the casts. 相似文献
85.
As repeatedly reported, soil flooding improves the availability of P to rice. This is in contrast with an increased P sorption in paddy soils. The effects of soil flooding on the transformation of Fe oxides and the adsorption/desorption of P of two paddy soils of Zhejiang Province in Southeast‐China were studied in anaerobic incubation experiments (submerging with water in N2 atmosphere). Soil flooding significantly increased oxalate‐extractable Fe (Feox), mainly at the expense of dithionite‐soluble Fe (FeDCB), as well as oxalate‐extractable P (Pox), but decreased the ratio of Pox/Feox. Flooding largely increased both, P adsorption and the maximum P adsorption capacity. The majority of newly sorbed P in the soils was Pox, but also more newly retained P was found to be not extractable by oxalate. Flooding also changed the characteristics of P desorption in the soils. Due to a decrease of the saturation index of the P sorption capacity, P adsorbed by flooded soils was much less desorbable than that from non‐flooded soils. There are obviously significant differences in the nature of both, the Feox and Pox fractions under non‐flooded and flooded conditions. The degree of the changes in Feox, Pox, P adsorption and P desorption by flooding depended on the contents of amorphous and total Fe oxides in non‐flooded soils. Our results confirm that the adsorption and desorption behavior of P in paddy soils is largely controlled by the transformation of the Fe oxides. The reasons of the often‐reported improved P availability to rice induced by flooding, in spite of the unfavorable effect on P desorbability, are discussed. 相似文献
86.
施磷对限水灌溉小麦根冠及产量的影响研究 总被引:7,自引:0,他引:7
试验研究结果表明 ,盆栽限水灌溉时施P明显促进小麦幼穗、根系和株高的早期生长发育 ,而对叶片含水量和叶绿素含量的影响较小 ;施P明显提高小麦地上部干物质量和产量 ,且以限水处理效果最明显 ,提高了限水处理“温麦 6”根干物质量以及“温麦 6”和“冀麦 36”穗数 相似文献
87.
豫北蔬菜保护地土壤磷素形态及其空间分布特性研究 总被引:15,自引:2,他引:15
采用蒋柏藩、顾益初无机P分级方法研究了豫北褐土多年棚龄蔬菜保护地土壤P素形态及其空间分布特性。结果表明,蔬菜保护地0 ~ 20cm土层全P、无机P、有机P、Olsen-P的含量分别为:1385.6 ~ 2896.5、1097.1 ~ 2365.7、270.0 ~ 606.9、109.8 ~ 302.4 mg/kg,Ca2-P、Ca8-P、Al-P、Fe-P、O-P、Ca10-P分别占无机P的百分比平均为:12.5 %、37.2 %、10.8 %、5.8 %、13.3 %、20.5 %,Olsen-P占全P的百分比高达4 % ~ 15 %,平均为10.6 %;土壤各形态P素主要积累在0 ~ 20 cm土层,随着深度的增加土壤全P、有机P、Olsen-P、各形态无机P均减少。 相似文献
88.
89.
两种氮水平下CO2浓度升高对冬小麦生长和氮磷浓度的影响 总被引:16,自引:0,他引:16
预计到 2 1世纪末期大气CO2 浓度将会比目前水平增加 1倍 ,约 70 0 μmolmol- 1 左右。因此CO2 浓度升高对作物的影响研究十分重要。本文探讨在两种氮 (N)水平下 ,CO2 浓度升高对冬小麦 (TriticumaestivumL cv Xinong 872 7)生长和地上部N、磷 (P)浓度的影响及原因。试验设 3 5 0 μmolmol- 1 和 70 0 μmolmol- 1 两种CO2 浓度水平和 45kghm- 2 和 90kghm- 2 两种N肥施用水平。结果表明 ,CO2 浓度升高 ,冬小麦株高和叶面积指数 (LAI)均增加 ,净同化率 (NAR)值增加 ,叶面积比率 (LAR)下降 ,比叶重 (SLW )不增加。高CO2 浓度对相对生长率 (RGR)的影响因施N水平而异 ,低N时RGR不增加 ,高N时明显增加。CO2 浓度增加 ,小麦抽穗提早 7~ 8d ,叶鞘、茎杆和地上部干物重提高 ,叶片、叶鞘和茎杆N、P浓度降低 ,但叶片、叶鞘和茎杆N、P吸收量增加均不明显。CO2 浓度升高 ,氮磷利用效率 (NUE和PUE)提高 ,而对相对氮磷累积速率 (RNAR和RPAR)影响不大。高CO2 浓度冬小麦体内N、P浓度下降是由于稀释效应以及NUE和PUE提高之故。 相似文献
90.