Nature and distribution of soil phosphorus as revealed by a sequential extraction method followed by 31P nuclear magnetic resonance analysis

Soil samples from long-term plots annually fertilized with superphosphate since 1952 and also unfertilized (control) plots of an irrigated and intensively grazed pasture in Canterbury, New Zealand, were subjected to a sequential extraction procedure followed by ³¹P nuclear magnetic resonance (NMR) analysis of the soil phosphorus (P) forms present. Overall, 80% of the total organic P (as determined by ignition) was removed from the soil by the sequential extraction procedure. Most of the organic P (90%) detected by NMR was in the monoester fraction. Small quantities of diester and pyrophosphate were also found. Choline phosphate constituted a significant proportion (18–25%) of the monoester P in the acetylacetone and 0.5 M NaOH extracts. Long-term superphosphate additions resulted in almost all of the P accumulated in the monoester P fraction (up to 99%).     

CHANGES IN MOLECULAR WEIGHT DISTRIBUTION OF SOIL ORGANIC MATTER DURING SOIL DEVELOPMENT

Ten different topsoils representing members of three soil chronosequences were pre-treated with 0.1 M HC1 and extracted with neutral 0.1 M Na₄P₂O₇ followed by 0.5 M NaOH. Extracts were purified and fractionated into five different nominal molecular weight fractions using gel filtration. With increasing soil development, the proportion of large molecules (>200 000) in the organic matter decreased with an increase in the proportion of intermediate size molecules (200 000 – 10 000). This effect was more evident in the mild Na₄P₂O₇ extracts than in the subsequent NaOH extracts, and in soils of the Manawatu chronosequence than in those of the other two chronosequences and are attributed to changes in the nature and humification of soil organic matter during soil development.     

Effects of organic and inorganic calcium compounds on soil-solution pH and aluminium concentration

The reactions of two organic (citrate and fulvate) and two inorganic (chloride and phosphogypsum) calcium compounds were studied during leaching of columns of unsaturated acidic soil. The potential of these compounds to decrease the aluminium concentration in the soil solution and remove exchangeable aluminium, and their effects on soil acidity are described. The calcium citrate solution increased the soil solution pH from 5 to a maximum value of 7 in the upper portion of the column. In contrast, the fulvate, calcium chloride and phosphogypsum solutions had little effect on soil-solution pH. Treatment with calcium citrate, or fulvate solution that contained 51 mm Na, removed most of the exchangeable aluminium from the column. The cation exchange sites in the upper portion of the column were saturated with calcium, and the cation exchange capacity of the soil was increased from 35 to c. 80 mmol_c kg^?1 in the calcium citrate treatment. Leachate from this treatment contained low (< 2 mm ) calcium concentrations and high aluminium concentrations. In contrast, the above changes were not shown by the calcium chloride and phosphogypsum treatments. In these treatments the calcium concentration in the leachate was equal to that in the inflowing solution, which indicated that calcium was transported through the entire column. These results suggest that calcium alone was ineffective in displacing aluminium from the cation exchange sites and a strong complexing agent such as citrate or fulvate is needed to mobilize the exchangeable aluminium.     

Distribution of carbon, nitrogen, phosphorus, sulphur, and acidity in two molecular weight fractions of organic matter in soil chronosequences

Ten different topsoils from three soil chronosequences were pretreated with 0.1 m HCl and 0.1 m HCl: 0.3 m HF, then extracted with neutral 0.1 m Na₄P₂0₇, followed by 0.5 m NaOH. Pretreatments and extracts were purified and fractionated into two nominal molecular weight (MW) fractions (> 50000 and < 50000) using gel filtration. The distribution between the two MW fractions of total carbon (C), nitrogen (N), phosphorus (P), sulphur (S), total acidity, and carboxyl (COOH) acidity and their ratios relative to C were determined. Organic matter in the > 50000 MW fraction contained lower N, P, S and acidity ratios relative to C than those of the < 50000 MW fraction. The chemical nature ofthe > 50000 MW fraction remained unaffected by soil development or vegetation, whereas that of the < 50000 MW fraction changed with soil age and appeared to be influenced by vegetation. The results strongly suggest that two chemically different extractable fractions of organic matter can be isolated from most soils, represented by the active fraction (< 50000 MW) and the relatively large (> 50000 MW) and less active (passive) fraction. A three-phase system of organic matter is proposed comprising the two extractable fractions and the non-extractable component.     

CROSS POLARISATION 13C-N.M.R. SPECTROSCOPY OF SOME GENETICALLY RELATED NEW ZEALAND SOILS

Cross polarisation ¹³C-n.m.r. spectra of seven New Zealand soils have been determined. Some of the soils are genetically related. The results show that the aromaticity of a soil may vary widely from soil to soil even when the parent material and vegetation are similar. The youngest of the soils examined (Hokitika, 300 years), was highly aromatic, and the oldest soil (Okarito, 22,000 years) was more aliphatic.     

不同气候对氧化型降解地膜的影响（英文）

【目的】通过在三个不同气候地区的试验,研究气候因素对农用氧化型降解地膜降解的影响,为此类降解地膜在不同地区的应用而调整添加剂配方提供指导。【方法】太阳辐射、温度和湿度是控制降解速度的主要因素,通过红外光谱分析,力学性能和分子量测试来评估他们对降解的影响。【结果】太阳辐射强度对氧化型降解地膜的降解影响最大。经过6个月太阳照射后,含有高浓度添加剂的降解膜,降解速率快。【结论】氧化型农用降解地膜的降解速率主要受太阳辐射强度控制,温度和湿度对降解速率影响较轻。当分子量小于5道尔顿时,降解膜碎片能够被微生物消化。     

Effects of feeding fermented fish on egg cholesterol content in hens

This study was conducted to investigate the effects of feeding fermented fish (FF) to layers on laying performance, and polyunsaturated fatty acid and cholesterol levels in eggs and plasma. A total of 96, 13-week-old Babcock B380 pullets were used in this study. They were randomly assigned to four numerically equal groups with eight replicates per treatment, three birds per replicate. All the birds were housed in individual cages. The dietary treatments were: Control diet, without FF; FF3 diet containing 3% (w/w) FF, FF6 diet containing 6% (w/w) FF and FF9 diet containing 9% (w/w) FF. The study was carried out for 16 weeks inclusive of two weeks of adjustment. Weekly feed intake and egg production were recorded. Blood plasma cholesterol and fatty acid profiles were assayed at the end of the experiment. FF did not enhance ( P  > 0.05) egg mass but ( P  < 0.05) decreased egg weight slightly. However, egg yolk cholesterol and plasma cholesterol concentrations were reduced ( P  < 0.05) by FF. The n-6:n-3 fatty acids ratio in the egg yolk (Control = 7.9, FF9 = 6.2) and plasma (Control = 10.6, FF9 = 6.2) were decreased by feeding FF. Moreover, FF was able to increase ( P  < 0.05) the docosahexaenoic acid (DHA) concentrations in egg yolk and plasma. In conclusion, this study demonstrated that FF increased DHA and reduced egg yolk cholesterol in poultry eggs.     

Studies of litter and acid insoluble soil organic matter fractions using 13C-cross polarization nuclear magnetic resonance spectroscopy with magic angle spinning

Cross polarization carbon-13 nuclear magnetic resonance spectroscopy with magic angle spinning (CP-MASS) was used to analyse for various forms of carbon in soils, a moss peat, hydrochloric acid insoluble residues from soils and peat, and litter from beech and pine trees. The chemical composition of the litters was also investigated by conventional techniques. The results show that hydrolysis with hydrochloric acid extraction removes nearly all oxygenated alkyl carbon from the soils used. It is shown that humification pathways in which carbohydrates are incorporated into humic substances via nonhydrolysable linkages are not important for the soils investigated in this work. CP-MASS data suggest that the percentage of aromatic carbon in pine leaves increases with increase in ageing time. The results for the beech leaves are not sharply defined.     

REMOVAL OF CONTAMINANTS TO IMPROVE THE RELIABILITY OF RADIOCARBON DATES OF PEATS

Peat samples from Timaru Downs, New Zealand were subjected to a wide range of chemical treatments before radiocarbon assay. A step wise procedure was used in which each sample was radiocarbon dated before and after the treatments were applied. The criterion adopted for indicating the removal of young contaminants and thus resulting in the improvement in the reliability of radiocarbon dates is the increase in the radiocarbon age of the sample after treatment. When peat samples were radiocarbon dated without prior chemical treatments the results could not be used to accurately date the time of formation because of young contaminants. Contaminants could be removed by chemical treatment of peats with mineral acids, particularly 70% HNO₃ for the very old peat sample. The improvement brought about by acid treatment was greater than that from the classical humus extraction and fractionation method.     

MOLECULAR WEIGHT DISTRIBUTION OF SOIL ORGANIC MATTER AS AFFECTED BY ACID PRE-TREATMENT AND FRACTIONATION INTO HUMIC AND FULVIC ACIDS

Effects of acid pre-treatment and fractionation on the molecular weight distribution of OIM Na₄P₂O₇ organic matter extracts were investigated in a chronosequence of weakly weathered soils developed on aeolian sand in New Zealand. Acid pre-treatment of soils with OIM HCl followed by OIM HCI:03M HF was found to enhance the polydispersion in the nominal molecular weights of the extracts. The same treatment resulted in significant increases in yield and reduction in ash content. However, prolonged standing of extracts in the acids led to acid-induced polymerization, resulting in a predominance of organic matter in the higher nominal molecular weight ranges. Fractionation of organic matter extracts by acid precipitation into humic and fulvic acids did not separate them according to molecular weight as commonly believed. Instead, fulvic acids from most soils were found to have similar nominal molecular weight distributions to those of their humic acid counterparts. A large proportion of soil fulvic acid compounds was in the > 100 000 nominal molecular weight range.