Inositol phosphate esters in some surface soils of Bangladesh

Concentrations of inositol mono-, di- and tri-, tetra-, penta- and hexaphosphate ranged from 5.0 to 12.5, 10.0 to 27.6, 20.0 to 45.0, 22.5 to 64.6, and 20.0 to 275.4 ppm, respectively, in samples of soils that were poorly drained and mostly derived from alluvium. Multiple correlation suggested that the amounts of esters of inositol phosphate other than inositol monophosphate were significantly correlated with organic phosphorus, total phosphorus, organic carbon, total nitrogen, inositol phospate, clay, exchangeable iron and aluminium, and pH. Individually, inositol hexa-, penta-, and di- and triphosphates were significantly correlated with organic phosphorus, total phosphorus, organic carbon, total nitrogen, inositol phosphate, and exchangeable iron and aluminium; inositol tetraphosphate with organic carbon, total nitrogen, inositol phosphate, and exchangeable iron and aluminium; inositol monophosphate with none.     

DISTRIBUTION OF INOSITOL PHOSPHATES, PHOSPHOLIPIDS, AND NUCLEIC ACIDS AND MINERALIZATION OF INOSITOL PHOSPHATES IN SOME BANGLADESH SOILS

Concentration of inositol phosphates, phospholipids, and RNA and its derivatives of ten Bangladesh soils varied between 17.5 and 150 ppm, 0.5 and 11.0 ppm, and 0.22 and 1.30 ppm respectively. Variation in inositol phosphates was related to total phosphate and organic phosphate contents. Variation in phospholipids was associated with total phosphate, organic phosphate, and organic matter contents whereas the variation in RNA and its derivatives was related to total phosphate contents of the soils. Maximum mineralization of inositol phosphates was obtained in the first 30 days either when incubated with lime or when submerged under water. A moderate rate was observed in the subsequent 30-day incubation periods. The mineralization was greater in soil which contained more organic matter and inositol phosphates. Mineralization also increased with pH. Liming enhanced mineralization as it induced conditions for the proliferation of phosphate transforming organisms.     

CONTENT OF INOSITOL PENTA- AND HEXAPHOSPHATES IN SOME CANADIAN SOILS

The combined amounts of inositol penta- and hexaphosphates in a number of Canadian soils of differing origin have been measured. The esters were precipitated as barium salts from alkali extracts and purified by anion-exchange chromatography; their identity was confirmed by paper-partition chromatography. An alternative method involving precipitation of the esters as ferric salts in acid medium was found to give much lower values, probably because of incomplete precipitation. Values for eighteen surface soils ranged from 20 to 71 and for twelve subsoils from 18 to 43 ppm P. The amounts found were related to the contents of both total phosphate and total organic phosphate, and accounted, on average, for 6 per cent of the former and 17 per cent of the latter. A correlation of +0.67 (P < 0.01) was found with orthophosphate retention capacity but correlations with soil N and C contents were poor. Amounts of the esters were higher in forest soils than in grassland soils.     

Inositol penta- and hexaphosphate content of some cocoa soils in Ghana

The inositol penta- and hexaphosphate content of some typical cocoa soils in Ghana was measured by anion exchange chromatography with HCOONH₄ as eluant. The values which ranged from 6 to 35 ppm P (average 18 ± 8 ppm P) and accounted for 6% to 40% (average 14%) of the organic phosphorus are within those ranges reported for Canadian, Nigerian, but much lower than those for Scottish soils. The penta- and hexaphosphate content of the soil significantly correlated with total P, organic P, organic C, total N, Fe and P retention capacity. Incubation of soil for 11 weeks did not alter the inositol penta- and hexaphosphate content of the soil. Inorganic P adsorption could be decreased by adding inositol hexaphosphate. These data support the suggestion that a role of the esters in nutrition of crops is probably through the indirect effect of blocking of retention sites and agents which would otherwise be free to bind inorganic phosphorus.     

SOME EFFECTS OF FERTILIZERS AND FARMYARD MANURE ON THE ORGANIC PHOSPHORUS IN SOILS

The amounts of P applied cumulatively to a neutral arable soil (pH 7.1–7. in 0.01M CaCl₂) at Rothamsted, as farmyard manure, alone or with superphosphate, which were converted to organic P in 100 years ranged from 18 to 44 μg P/g of soil (0–23 cm). Superphosphate alone (3300 kg P/ha) slightly lessened the total organic P in the soil. Neither farmyard manure nor super-phosphate significantly changed the amounts (38 to 42 μg P/g) of inositol penta- and hexaphosphate in these soils. In the surface layers (0–7.5 cm) of soils from permanent grassland at Rothamsted, superphosphate (3370kg P/ha) increased organic P by 134 μg P/g at pH 4.5 and 19 μg P/g at pH 6.5, about 6 and 1 per cent respectively of the P remaining from superphosphate applied cumulatively since 1858. In the sub-surface layers (7.5–23 cm) superphosphate increased organic P by 93 μg P/g at pH 4.5 and 62 μg P/g at pH 6.2, about 18 and 10 per cent respectively of the P remaining from superphosphate. The sum of inositol penta- and hexaphosphates accounted for 32 per cent at pH 4.5 and 21 per cent at pH 6.5 of the increases in organic P in the surface layers and 45 per cent and 26 per cent in the sub-surface layers at pH 4.5 and 6.5 respectively. Superphosphate (1260–2100 kg P/ha) applied intermittently or cumulatively increased total organic P by 19 to 52 μg P/g and inositol penta- and hexaphosphates by 13 to 17 μg P/g in acid tea soils (pH 3.2–3.4) from Georgia, U.S.S.R. Rock phosphate (510–1020kg P/ha) applied cumulatively had no effect on either the total organic P or the inositol P in acid tea soils (PH 3.6–3.7) from Ceylon.     

CONTENT OF INOSITOL PHOSPHATES IN SOME ENGLISH AND NIGERIAN SOILS

The mono-, di-, tri-, tetra-, penta-, and hexaphosphates of inositpl accounted for between 11·2 and 30·4 per cent of the organic P in three English and four Nigerian soils. M yoinositol hexaphosphate was the component present in greatest amount in all soils. The lower esters (mono-, di-, and triphosphates) accounted for less than 3 per cent of the organic P in all soils, with the lowest amounts in the soils from Nigeria. For the penta- and hexaphosphates the ratio of myo- plus dl- isomers to scyll oinositol varied from 2·9 to over 10, the highest ratio occurring in the soils from Nigeria. Examination of the techniques showed that they gave approximately correct estimates of the inositol phosphates. The organic P in soil which was not estimated as inositol phosphate occurred in other forms.     

CHARACTERIZATION OF THE INOSITOL PENTA- AND HEXAPHOSPHATE FRACTIONS OF A NUMBER OF CANADIAN AND SCOTTISH SOILS

The nature of the inositol pentaphosphate and hexaphosphate isomers in a number of contrasting Canadian and Scottish soils has been examined. The mixed esters were extracted from the soil with alkali and separated from other soil phosphates by anion-exchange chromatography using HCOONH₄ as eluent. The composition of the mixture was established by anion-exchange chromatography using a gradient of HC1 as eluent, followed by paper chromatography of the esters thus separated, and by paper chromatography of the hydrolysis products. Esters of myo- and scylloinositol together constituted more than 90 per cent of the mixture in most cases. Relatively small amounts of dl-inositol and neoinositol were detected in hydrolysates and it was estimated that esters of these cyclitols did not exceed 10 per cent and 1 per cent, respectively, of the total. The ratio of myo-+dl-inositol hexaphosphates to scylloinositol hexaphosphate ranged from 1.1 to 2.7 in the Canadian soils and 1.8 to 4.6 in the Scottish soils. The ratio of hexaphosphates to pentaphosphates ranged from 0.9 to 2.4 in the Canadian soils and 3.0 to 4.3 in the Scottish soils. The three soils with the highest pH values contained relatively large amounts of scyllo- relative to myoinositol hexaphosphate, but one very acid soil also contained a high proportion of this isomer and no consistent relationship was noted between the constitution of the inositol polyphosphate fraction and any other soil property.     

Macromolecule‐P associations and inositol phosphates in some chilean volcanic soils of temperate regions

Abstract

Total organic P, humic and fulvic acid‐P associations and inositol phosphates in nine volcanic soils of southern Chile were determined. The concentration of organic P (Po) ranged from 654 to 1942 ppm accounting for 49% to 64% of total soil P. Phosphorus associated to humic (HA‐P) and fulvic acids (FA‐P) accounted for 51–68% and 32–49% of Po, respectively. Inositol penta‐ and hexaphosphates represented 42% to 67% of Po suggesting that significant amounts are associated with both humic and fulvic acids. Po content was significantly correlated to organic C, total soil P and HA‐P. HA‐P and FA‐P fractions obtained from the most representative soil were examined by dyalisis and gel filtration. While approximately 96% of HA‐P presented a molecular weight higher than 100,000 daltons, 53% of FA‐P had a molecular weight under 12,000 daltons. It is suggested that these more labile organic P forms would be more easily mineralized, thus increasing the available P pool.     

Long-term effect of chemical fertilizer,straw, and manure on labile organic matter fractions in a paddy soil

To assess the effect of long-term fertilization on labile organic matter fractions, we analyzed the C and N mineralization and C and N content in soil, particulate organic matter (POM), light fraction organic matter (LFOM), and microbial biomass. Results showed that fertilizer N decreased or did not affect the C and N amounts in soil fractions, except N mineralization and soil total N. The C and N amounts in soil and its fractions increased with the application of fertilizer PK and rice straw. Generally, there was no significant difference between fertilizer PK and rice straw. Furthermore, application of manure was most effective in maintaining soil organic matter and labile organic matter fractions. Soils treated with manure alone had the highest microbial biomass C and C and N mineralization. A significant correlation was observed between the C content and N content in soil, POM, LFOM, microbial biomass, or the readily mineralized organic matter. The amounts of POM–N, LFOM–N, POM–C, and LFOM–C closely correlated with soil organic C or total N content. Microbial biomass N was closely related to the amounts of POM–N, LFOM–N, POM–C, and LFOM–C, while microbial biomass C was closely related to the amounts of POM–N, POM–C, and soil total N. These results suggested that microbial biomass C and N closely correlated with POM rather than SOM. Carbon mineralization was closely related to the amounts of POM–N, POM–C, microbial biomass C, and soil organic C, but no significant correlation was detected between N mineralization with C or N amounts in soil and its fractions.     

Preparation and characterization of model humic polymers containing organic phosphorus

The nature of organic P in soil organic matter was studied by evaluating the incorporation of serine, phosphoserine, ethanolamine, phosphoethanolamine and glycerophosphate into model humic polymers prepared by chemical oxidation of polyphenols. Elemental and functional group analysis indicated that the composition of model humic polymers ranged as follows: organic C, 50.6–56.8%; total acidity, 7.86–11.87m-equiv g^?1; carboxyl, 1.42–2.00 m-equiv g^?1; total hydroxyl, 6.79-10.0 m-equiv g^?1; ash, 6.4–13.9%; E₄/E₆ ratio, 5.34–6.19; organic N, 0.70–1.65% and organic P, 0.254–0.942%. These values are within the ranges reported for soil humic substances. The only non-phenolic compounds incorporated into model humic polymers were those containing free amino groups. The P content of model polymers was not increased by the presence of KH₂PO₄, glycerophosphate, serine or ethanolamine whereas phosphoserine and phosphoethanolamine resulted in model polymers containing 0.254 and 0.942% P, respectively. Further characterization studies of the model polymer containing phosphoethanolamine (HA-PE) showed that most of the C (83.2%), N (79.8%) and P (75.3%) was in the humic acid fraction. Gel filtration of HA-PE showed that 0.5% of the polymer was present in high molecular weight (mol. wt) components (mol. wt > 100,000) and 74.8% of the polymer was in two components of mol. wt 10,000–50,000. The majority of the organic P in HA-PE was associated with the medium molecular weight fractions (79.2%) while 16.8% of the P was associated with materials possessing mol. wt < 10,000. Attempts to demonstrate the presence of organic P functional groups contained in HA-PE by infrared spectroscopy was limited by the relatively small amounts of organic P incorporated into the model humic polymers. The results obtained show that a portion of the unidentified organic P in soil humic substances may arise from the incorporation of organic compounds containing both amino and phosphate ester functional groups during oxidative polymerization of polyphenols.     

上海郊区河流沉积物N、P释放的初步研究

A laboratory study was conducted to observe the release of nitrogen and phosphorus from the sedimentsunder both anaerobic and aerobic conditions. The samples used were five creek sediments and a fish-pondsediment (as a comparison) obtained from suburban Shanghai. High loads of nitrogen and phosphoruswere found in the creek sediments. Total nitrogen of the sediments ranged from 1.17 to 5.95 g kg^-1; totalphosphorus from 608.63 to 2 033.95 mg kg^-1. Making up more than 90% of the total nitrogen, organicnitrogen was the dominant nitrogen fraction in the sediments; where as inorganic phosphorus was the dominant phosphorus fraction, which made up more than 85 percent of the total phosphorus. Cabound phosphorus fraction dominated inorganic phosphorus, which occupied more than 50% of the total. A large amount of ammonium was released from the sediments under both aerobic and anaerobic conditions, and the anaerobic releases were slightly greater than the aerobic. In addition, ammonium contents in the aerobic waters decreased sharply after reaching the peaks because of strong nitrification, compared with the relatively maintained ammonium peaks in the anaerobic waters. Anaerobic phosphate releases were much greater than the aerobic and the released ortho-phosphate was mainly from Fe-bound phosphorus. Ammonium and ortho-phosphate releases from the sample of the dredged creek were the lowest, showing that creek dredging could effectively remove contaminants from the surface of sediments and weaken the release potentials of nitrogen and phosphorus. Ammonium and ortho-phosphate releases from the fish-pond sediment were greater than those from the creek sediments though its total nitrogen and phosphorus were not the highest, which was probably due to the larger amount of biologically degraded organic matter in the fish-pond sediment.     

Nitrogen transformations in particle size fractions from a second rotation pine forest soil

Abstract

A second rotation forest sand (Mt Burr sand) was separated by a combination of dry sieving and winnowing into different particle sizes rich in either soil or organic matter. These fractions were analysed for % loss on ignition, % organic carbon, total organic nitrogen and mineral nitrogen. Mineralization of soil organic nitrogen and nitrification of ammonium sulphate added to these fractions were studied. Amongst the heavier fractions obtained by sieving, the <125 μm fraction (the finest) contained the highest concentration of organic and exchangeable nitrogen and was the most active in nitrogen transformations. Amongst the lighter fractions obtained by winnowing, the 125 to 500 μm fraction had the highest organic nitrogen content but mineralization of nitrogen was greatest in the 500 to 2000 μm. Nitrification of native and applied ammonium nitrogen was similar in both the 125 to 500 μm and 500 go 2000 μm organic matter fractions.     

31Phosphorus‐Nuclear magnetic resonance analysis in extracts of a phosphorus‐enriched volcanic soil of Chile

Abstract

The nature of organic and inorganic phosphorus (P) in fertilized and unfertilized samples of Vilcun soil, a Chilean medial mesic typic Dystrandept which was studied through ³¹phosphorus‐nuclear magnetic resonance (³¹P‐NMR) analysis carried out on a single alkaline extraction. The total P contents ranged from 1,506 mg P kg^‐1 (B horizon, unfertilized soil) to 7,541 mg P kg^‐1 (A horizon, fertilized soil). The magnitude of the P signal (SEM‐EDAX results) appears to be related to that of the iron (Fe) signal. Signals of ³¹P‐NMR spectra are attributable to inorganic orthophosphate, and orthophosphate monoesters and diesters. No important differences between horizons were observed. Apparently in this soil, P are mainly associated with iron oxides and organic matter. The organic P forms were not readily subjected to mineralization.     

Organic Matter and Mineralizable Nitrogen Relationships in Wetland Rice Soils

Abstract

Soil nitrogen (N) supply plays a dominant role in the N nutrition of wetland rice. Organic matter has been proposed as an index of soil N availability to wetland rice. This is based on the finding that mineralizable N produced under waterlogged conditions is related to soil organic carbon (C) and total N. The relationship between organic matter and mineralizable N is a prerequisite for determining the N requirement of wetland rice. However, no critical analysis of recent literature on organic matter–mineralizable N relationships has been made. This article evaluates current literature on the relationships of mineralizable N or ammonium N production with soil organic C in wetland rice soils. A number of studies with diverse wetland rice soils demonstrate a close relationship of N mineralized (ammonium‐N) under anaerobic conditions with organic C or total N. However, a few recent studies made on sites under long‐term intensive wetland rice cropping showed that strong positive relationships of mineralizable N with organic C or total N do not hold. Clearly, both quantity and quality of organic matter affect N mineralization in wetland rice soils. Future research is needed to clarify the role of quality of organic matter, especially its chemistry, as modified by the chemical environment of submerged soils, on the mineralization of organic N in wetland rice soils.     

长期有机培肥模式下黑土碳与氮变化及氮素矿化特征

土壤氮的矿化是土壤氮素肥力的重要指标,是影响作物产量至关重要的因素。本研究依托黑土长期定位试验,通过取样分析研究了32 a不同培肥模式下黑土碳、 氮及主要活性组分的变化,采用淹水培养法研究了不同施肥模式下黑土氮素的矿化特征。结果表明,施肥显著提高黑土可溶性碳（DOC）、 氮（DON）的含量及其比例。在氮、 磷、 钾化肥的基础上配施有机肥,显著降低了土壤微生物量氮（SMBN）占土壤总氮的比例,提高了土壤微生物量的C/N比值（SMBC/SMBN）,促进了土壤氮的生物固持。施肥32 a后,单施常量和高量有机肥处理的土壤氮的矿化量（Nt）显著提高,分别相当于不施肥的8.2倍和10.2倍,而单施氮或氮磷钾化肥对黑土氮素矿化量无明显影响。施用有机肥显著提高了土壤氮素的矿化率（Nt/TN）,但有机肥配施化肥（氮或氮磷钾）的处理与单施有机肥相比,黑土氮的矿化率显著降低,降低幅度分别为23.5%~32.1% 和14.1%~17.8%。土壤氮素矿化量与土壤有机质、 全氮储量、 活性碳、 氮组分均呈极显著线性相关,但氮素的矿化率随着有机质和全氮含量的提高而提高至0.4% 后基本稳定。表明尽管土壤氮的矿化与有机质的含量直接相关,但土壤有机质的品质同样决定着土壤氮素的矿化能力。施有机氮是提高土壤供氮能力的重要途径。     

改土物料混用对酸性土壤pH和烤烟生长及物质积累的影响

为明确不同酸碱度生物有机肥配施石灰、绿肥改良酸性植烟土壤的效果,本研究采用盆栽试验,研究了石灰(T1)、石灰+绿肥(T2)、酸性生物有机肥+石灰+绿肥(T3)、碱性生物有机肥+石灰+绿肥(T4)等组成的4种不同改土物料组合对酸性植烟土壤pH值、烤烟生长和干物质与氮磷钾积累分配的影响。结果表明,酸性植烟土壤施用不同改土物料组合,可使土壤pH值提高0.79~1.12,改善烤烟农艺性状,促进烤烟根系生长,使烟叶SPAD值增加0.42~2.76,烟株干物质积累提高18.05%~61.42%;除T3外,烟株氮积累总量提高1.42%~14.07%;磷积累总量提高29.76%~98.08%;钾积累总量提高22.48%~105.47%;同时促进了干物质与钾向烟叶中分配。与其他处理相比,石灰和绿肥配施碱性生物有机肥(T4)更有利于提高酸性土壤pH值,有利于烤烟干物质和氮、磷、钾养分的积累;但石灰和绿肥配施酸性有机肥(T3)更有利于增加烤烟根系数量,有利于增加氮、磷、钾养分在烟叶中的分配比例。本研究表明石灰、绿肥和生物有机肥配合施用可提高酸性土壤改良效果,以石灰+绿肥+碱性生物有机肥最好,其次是石灰+绿肥+酸性生物有机肥。本研究结果为湖南省湘西酸性植烟土壤改良提供了理论依据。     

The profile distribution of total and extractable zinc in selected Nigerian soils

Abstract

The profile distribution of total, DTPA‐ and 0.1 N HC1‐extractable Zn was determined in 11 Nigerian soil profiles formed on various parent Materials including the coastal plain sands, shales, basalt, granite and banded gneiss.

The total content ranged from 9 to 84 ppm. Generally soils developed on igneous rocks contained more Zn than those on sedimenatary deposits. Among the soils on sedimentary rocks, those on shale had more total Zn than those on sandstones. Total Zn was weakly correlated with organic matter but strongly associated vith clay content and free oxides of iron and manganese.

The amounts of Zn extracted by DTPA and 0.1 N HC1 ranged from 0.01 to 10.98 and from 0.23 to 6.25 ppm, respectively. The dilute acid generally removed more Zn from the soils than did the DTPA. The amounts extracted generally decreased vith depth especially vith DTFA extractant. Soils developed on basalt and shales contained the highest amounts of 0.1 N HCl‐extractable Zn while those on basement complex rocks gave the highest values of DTPA‐extractable Zn. Extractable Zn from soils on coastal plain sands remained relatively lev. The extractable Zn was more associated vith organic matter than vith clay content.     

昆阳磷矿植被修复土壤理化与生物学性状的典型相关分析

深入了解昆阳磷矿植被修复土壤理化性状指标与生物学各个性质指标之间的关系,可为进一步筛选土壤质量评价指标提供参考依据。选择了昆阳磷矿旱冬瓜人工林6个不同植被恢复年限样地,研究其土壤厚度、容重、孔隙度、毛管孔隙度、含水量、pH值、有机质、碱解氮、全氮、有效磷、全磷、速效钾、全钾和土壤微生物生物量碳（MBC）、微生物生物量氮（MBN）、氮矿化速率、β-葡萄糖苷酶、酸性磷酸酶、脲酶的关系,综合土壤13个理化性状指标和6个生物学性状指标的典型相关分析得到4对典型变量,其典型相关系数分别为0.997 0,0.988 9,0.879 9,0.856 8,均达到极显著水平（p≤0.01）,说明土壤理化性状和生物学性状存在显著相关关系,而这两组性状的显著相关主要是由土壤碱解氮、有机质、有效磷、全磷、pH值和微生物生物量碳（MBC）、微生物生物量氮（MBN）、氮矿化速率、脲酶的密切相关引起的,其中有机质与微生物生物量碳（MBC）、微生物生物量氮（MBN）、脲酶之间呈极显著相关,有效磷、全磷与氮矿化速率、微生物生物量氮（MBN）、微生物生物量碳（MBC）也呈极显著相关,碱解氮、pH值与微生物生物量碳（MBC）、微生物生物量氮（MBN）、脲酶呈极显著相关,全氮与β-葡萄糖苷酶、氮矿化速率、微生物生物量氮（MBN）呈极显著相关。     

土壤残渣有机质与固定态铵之间的关系

采集了全国不同类型的土壤40个,分析了土壤全氮、有机质、固定态铵、剩余有机质（KOBr处理后的土壤有机质）、残渣有机质（KOBr-HF处理后的土壤有机质）含量.结果表明,以2∶1型粘粒矿物为主土壤的残渣有机质含量与固定态铵含量之间呈极显著正相关（r=0.831^＊＊）,晶格之间存在的有机质（即残渣有机质与剩余有机质之差值）含量则与固定态铵含量之间也呈极显著正相关（r=0.832^＊＊）,而以1∶1型粘粒矿物为主土壤的残渣有机质含量和晶格有机质含量与固定态铵含量不相关;土壤剩余有机质、残渣有机质的含量分别为2.59 g kg^-1、3.70 g kg^-1,分别占土壤有机质的10%和16%.土壤残渣C/N比（平均值为16.69）明显高于原土壤（平均值为5.37）.     

Effects of lime and phosphate additions on changes in enzyme activities,microbial biomass and levels of extractable nitrogen,sulphur and phosphorus in an acid soil

Summary The effects of adding lime and/or phosphate to an acid, phosphate-deficient soil on microbial activity, enzyme activities and levels of biomass and extractable N, S and P were studied under laboratory conditions. Following rewetting there was, as expected, an initial flush in microbial growth and activity, as shown by large increases in CO₂ evolution, in levels of biomass N, S and P and by accumulation of extractable mineral N and sulphate in the soil. Following rewetting, additions of lime and phosphate further stimulated mineralization of C, N and S. In the first 4 weeks of incubation, the mineralized N accumulated in the soil as ammonium N and there was a concomitant rise in soil pH. After this initial period, nitrification increased substantially and soil pH decreased again. Additions of lime generally increased protease and sulphatase activities but decreased phosphatase activity. Additions of phosphate decreased the activities of all three enzymes. The positive effect of liming on protease and sulphatase activities persisted for the duration of the experiment while accumulation of mineral N and sulphate effectively ceased after about 4 weeks. Furthermore, although phosphate additions decreased the activities of protease and sulphatase they increased the accumulation of mineral N and sulphate. Thus, protease and sulphatase activities were not reliable indicators of the relative amounts of mineral N and sulphate accumulated in the soil during incubation. Some uncertainty surrounded the validity of biomass S and P values estimated by the chloroform fumigation technique because differing proportions of the sulphate and phosphate released from the lysed cells may have been extracted from the different treatments.