Soil Acid Phosphatase Activity Research Articles

Use of hydrophilic polymers from diapers to aid the establishment of Spergularia purpurea in a mine soil

We used hydrophilic polymers from diapers to aid the establishment of an indigenous plant (Spergularia purpurea (Persoon) G. Don fil.) in a soil from a pyrite mine. Lysimeters were filled with the mine soil with no amendment (control), with a polyacrylate polymer, with a polymer removed from diapers, and with shredded diapers. The establishment of a plant cover was faster in soil amended with polymer from diapers, and 85 days after sowing the soil was completely covered in all treatments except control. The concentrations of trace elements in plant shoots decreased in amended soil. The activities of soil acid phosphatase, beta-glucosidase, protease and cellulase were greatest in soil amended with the polyacrylate polymer or with polymer removed from diapers, while the application of shredded diapers leads to values that were in general intermediate between these treatments and unamended control. Basal- and substrate-induced respirations, and dehydrogenase were greatest in soil amended with polymers, but the presence of a plastic film and fibrous materials from shredded diapers prevented any improvement in these parameters compared with unamended soil. In the second experiment, we evaluated the risk of downward movement of polymers in columns of a sandy soil. Polymer from diapers, with or without Cu, was placed at a 10 cm-depth. Five leaching cycles with artificial rain took place and leachates were analyzed for organic matter and Cu. At the end of the experiment, the soil columns were sliced and each layer was analyzed separately. Some repacking of soil and polymer particles took place, but there was no indication that polymers moved to any great depth in soil columns.

Elevated levels of acid and alkaline phosphatase activity in roots and rhizosphere of cowpea (Vigna unguiculata L. Walp.) genotypes grown in mixed culture and at different densities with sorghum (Sorghum bicolor L.)

The aim of this study was to assess P acquisition efficiency in 5 cowpea genotypes in mixed culture and at different plant densities using assays of acid and alkaline phosphatase activity and measurement of P in organs. Five cowpea genotypes (2 improved cvv. ITH98-46 and TVu1509, and 3 farmer-selected varieties, namely Bensogla, Sanzie, and Omondaw) were grown in the field at 2 planting densities (83 333 and 166 666 plants/ha) under monoculture and mixed culture with sorghum during 2005 and 2006. Fresh plant roots and rhizosphere soils were collected during the 2 years of experimentation, and assayed for acid and alkaline phosphatase activity. P concentrations in root tissue and rhizosphere soil were also determined using inductively coupled plasma-mass spectrometry. The data for 2005 and 2006 were similar, and therefore pooled for statistical analysis. Our results showed that raising cowpea density from 83 333 to 166 666 plants/ha significantly increased both acid and alkaline phosphatase activity in the rhizosphere, just as mixed culture (or intercropping) also increased the acid and alkaline phosphatase activity in cowpea rhizosphere soil. High plant density and mixed culture (or intercropping) also raised the acid phosphatase activity in fresh roots of cowpea plants. The increased enzyme activity in roots and rhizosphere soil resulted in significantly improved P nutrition in cowpea, greater plant growth, and higher grain yield in the farmer-selected varieties, especially cv. Sanzie. This suggests that field-grown legumes can be screened for high P acquisition efficiency by assaying for acid and alkaline phosphatase activities.

Colonização micorrízica e atividade de fosfatases ácidas na rizosfera de cultivares de cana-de-açúcar após aplicação de herbicidas

Objetivou-se com este trabalho avaliar o impacto de herbicidas na colonização micorrízica e na atividade de fosfatases ácidas na rizosfera dos cultivares de cana-de-açúcar RB867515 e SP80-1816. O experimento foi conduzido em campo, em sistema de cultivo convencional, com espaçamento de 1,4 m e 18 gemas m-1. Utilizou-se o delineamento em blocos casualizados, em esquema fatorial 2 x 5, com quatro repetições, sendo o primeiro fator constituído por dois cultivares de cana-de-açúcar (RB867515 e SP80-1816) e o segundo por quatro herbicidas (ametryn, 2.000 g ha-1; trifloxysulfuron-sodium, 22,5 g ha-1; ametryn + trifloxysulfuron-sodium, 1.463 + 37,5 g ha-1, e sulfentrazone, 750 g ha-1), mais uma testemunha sem aplicação de herbicida. A aplicação dos herbicidas foi realizada quando a cultura encontrava-se com três a quatro folhas. O sistema radicular e o solo rizosférico de cana-deaçúcar foram coletados para avaliação da colonização micorrízica e atividade de fosfatases aos 7, 14 e 28 dias após a aplicação dos herbicidas (DAH). Os herbicidas não interferiram na atividade das fosomonoesterases ácidas nas épocas avaliadas. O cultivar RB867515 apresentou maior colonização micorrízica (22,5 e 27,0%), em comparação à testemunha, sem aplicação de herbicidas, aos 7 e 14 DAH, respectivamente. Aos 7 DAH, constatou-se menor valor de colonização (11,50%) para o cultivar RB86-7515 tratado com trifloxysulfuron-sodium + ametryn. O herbicida trifloxysulfuron-sodium estimulou a colonização micorrízica no cultivar SP80-1816 aos 14 DAH (46,3%). Ambos os cultivares avaliados apresentaram maiores valores de colonização quando tratados com ametryn, aos 28 DAH. De modo geral, constatou-se incremento da colonização micorrízica do sistema radicular em função do tempo. A colonização micorrízica foi distinta entre os cultivares e os herbicidas usados.

Improvement in soil and sorghum health following the application of polyacrylate polymers to a Cd-contaminated soil

Contamination of soils with cadmium (Cd) is a serious global issue due to its high mobility and toxicity. We investigated the application of insoluble polyacrylate polymers to improve soil and plant health. Sorghum was grown in a Cd-contaminated sandy soil. Polyacrylate polymers at 0.2% (w/w) were added to half of the soil. Control soil without plants was also included in the experiment. Growth of sorghum was stimulated in the polymer-amended soil. The concentration of Cd in the shoots, and the activities of catalase and ascorbate peroxidase decreased in plants from polymer-amended soil compared with unamended control. The amount of CaCl(2)-extractable Cd in the polymer-amended soil was 55% of that in the unamended soil. The Cd extracted in sorghum shoots was 0.19 mg per plant grown on soil without polymer and 0.41 mg per plant grown on polymer-amended soil. The total amount of Cd removed from each pot corresponded to 1.5 and more than 6% of soil CaCl(2)-extractable Cd in unamended and polymer-amended soil, respectively. The activities of soil acid phosphatase, beta-glucosidase, urease, protease and cellulase were greatest in polymer-amended soil with sorghum. In conclusion, the application of polyacrylate polymers to reduce the bioavailable Cd pool seems a promising method to enhance productivity and health of plants grown on Cd-contaminated soils.

Micellar electrokinetic chromatography after precapillary enzyme assay for the determination of phosphatase activity in semiarid soil

Inorganic phosphorous (P) is an essential plant nutrient that must be added to most soils to maintain plant growth and sustain crop yields. Phosphatase enzymes play a major role in the processes of mineralization of organic P substrates. In the present study we propose a precise and accurate method to determine the alkaline and acid phosphatase activity in soil using adenosine monophosphate (AMP) as a substrate. The adenosine released by the enzymatic reaction was quantified by micellar electrokinetic chromatography (MEKC) method. The background electrolyte (BGE) consisted in 20 mM phosphate buffer, 10 mM sodium dodecyl sulphate (SDS) and 10% acetonitrile (ACN). The LOD and LOQ for adenosine were 2.27 × 10 −4 and 6.4 × 10 −4 mg mL −1, respectively. This sensitive method allowed the use of natural compound as enzymatic substrate, which is commonly found in soil. Moreover, we improve the detection method by diminishing the amount of waste and using a harmless substrate.

Genotypic differences in phosphorus acquisition and the rhizosphere properties of Brassica napus in response to low phosphorus stress

Genotypic differences in acquiring immobile P exist among species or cultivars within one species. We investigated the P-efficiency mechanisms of rapeseed (Brassica napus L.) in low P soil by measuring plant growth, P acquisition and rhizosphere properties. Two genotypes with different P efficiencies were grown in a root-compartment experiment under low P (P15: 15 mg P kg−1) and high P (P100: 100 mg P kg−1) treatments. The P-efficient genotype produced more biomass, and had a high seed yield and high P acquisition efficiency under low P treatment. Under both P treatments, both genotypes decreased inorganic P (Pi) and organic P (Po) fractions in the rhizosphere soil. However there was no decrease in NaHCO3-Po at P100. For the P15 treatment, the concentrations of NaHCO3-Po and NaOH-Po were negatively correlated with soil acid phosphatase activity. The P-efficient genotype 102 differed from the P-inefficient genotype 105 in the following ways. In the rhizosphere the soil pH was lower, acid phosphatase activity was higher, and depletion of P was greater. Further the depletion zones were wider. These results suggested that improving P efficiency based on the character of P efficiency acquisition in P-efficient genotype would be a potential approach for maintaining rapeseed yield potential in soils with low P bioavailability.

Rhizosphere pH and Phosphatase Activity in Orthic Allophanic Soil Under Pinus radiata Seedlings Grown with Broom and Ryegrass

Under Pinus radiata plantations where the tree spacing is wider and most soils are phosphorus (P) deficient, the radiata tree response to P fertilizer is expected to be more influenced by the interaction between the applied P fertilizer, the tree and understorey vegetation. Therefore, a better understanding of the soil P chemistry under radiata pine trees in association with other plants is required. We investigated the effect of broom ( Cytisus scoparius L.) and ryegrass ( Lolium multiflorum) grown with radiata seedlings in Orthic Allophanic Soil treated with 0, 50, and 100 μg P g-1 soil of TSP on the pH and phosphatase activity in the rhizosphere soils under glasshouse condition. The pHs of radiata rhizosphere soils either grown with broom or grass were lower than those in the bulk soils and the bulk and rhizosphere soils of grass and broom, whether they were grown alone or grown with radiata at the applications of 50 and 100 μg P g-1 soil. These results suggest that P application enhanced root induced acidification in a P-deficient Allophanic Soil under radiata. The soils in the rhizosphere of grass and broom, grown in association with radiata, were also acidified by the effect of radiata roots. Acid phosphatase activity in soils under radiata, grass and broom decreased with an increased rate of P application. At all P rates, acid phosphatase activity was higher in the rhizosphere of radiata grown with broom than in the bulk soils. The phosphatase activity in the rhizosphere soil of radiata grown with broom was also higher than that of radiata grown with grass, but it was slightly lower than that in the rhizosphere of broom grown alone. These results suggest that broom may have also contributed to the higher phosphatase activity in the rhizosphere soils than in the bulk soils of broom and radiata when they were grown together

Rhizospheric soil enzyme activity of allelopathic rice at seedling stage

In order to determine the relationship between allelopathic potential of rice and soil enzyme activity in rhizospheric soils, a dry cultivation experiment was conducted on enzyme activity in rhizospheric soil of allelopathic rice "PI312777", "IAC47" and "Iguape", and non-allelopathic rice "Lemont" at seedling stage. The results show that allelopathic rice inhibits dehydrogenase, peroxide, polyphenol oxidase, urease, and cellulose activity and enhances acid phosphatase, alkaline-phosphatase, invertase and catalase activity in rhizospheric soils. Correlation analyses show that urease and polyphenol oxidase activity is significantly negatively correlated with rice allelopathic potential, while acid phosphatase and alkaline-phosphatase activity is significantly positively correlated with rice allelopathic potential. No significant relationship exists between protease and dehydrogenase activity with other enzymes or microbial amount and rice allelopathic potiential. Allelopathic rice decreases polyphenol oxidase activity, increases acid-phosphatase, alkaline-phosphatase and invertase activity, which is beneficial for allelopathic substance accumulation, soil carbon and phosphorus cycle enhancement.

Experimental drought reduced acid and alkaline phosphatase activity and increased organic extractable P in soil in a Quercus ilex Mediterranean forest

A six-year (1999–2005) experiment of drought manipulation was conducted in a Quercus ilex Mediterranean forest (Southern Catalonia) to simulate predicted climatic conditions projected for the decades to come. The aim was to investigate the direct and indirect effects of drought conditions on acid and alkaline phosphatase activity in soil and on P concentrations in soil, leaves and litter throughout the year. Soil acid phosphatase activity was higher than soil alkaline phosphatase activity. Drought reduced acid phosphatase activity in soil in all seasons, including summer and winter, the seasons with less biological activity due to water and cold stress. Reductions of soil water content between 13 and 29% reduced soil acid phosphatase activity between 22 and 27% depending on the season. Drought reduced alkaline phosphatase activity (by 28%) only in winter. Soil acid and alkaline phosphatase activities were positively correlated with soil water content in all seasons. In contrast short-term available-P which increased under drought in several seasons was weakly correlated with soil phosphatase activities. As a result, immediately/short-term available-P concentration ratios decreased in all the seasons (between 10 and 71%). Drought increased foliar P concentration and reduced the C/P concentration ratio in litter fall of the dominant tree Q. ilex. Drought also decreased the ratio between organic C and short-term available-P in soil. The results show that soil phosphatase activity is more directly dependent on changes in water availability than on changes in its substrate, short-term available-P. These effects of drought have several implications: the accumulation in the soil of labile P not directly available to plants, the increase in potential P losses from leaching and erosion during the torrential rainfalls typical of the Mediterranean climate, and changes in plant, litter and soil C:P stoichiometry that may lead to changes in soil trophic chains.

Soil microbiochemical properties as indicators for success of heathland restoration after military disturbance

AbstractDecline of heathlands in Central Europe raises the question of successful restoration of degraded heathlands. We examined the impact of different restoration techniques on soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and enzyme activity on an abandoned military training site in the Lüneburger Heaths. The aim was to determine which technique resulted in typical heathland soil conditions. The training site was in use for about 50 years. Vegetation and soils were degraded in large areas. Restoration actions were: (1) spreading of heath plaggen (sods, containing the organic layer and a few centimetres mineral soil), (2) spreading of heath plaggen and grass seeds (Festuca filiformis Pourr.), (3) spreading of F. filiformis‐seeds and (4) succession (episodical tree removal). Ten years after restoration, we measured pH, bulk density, abundance of roots, soil organic carbon (SOC), nitrogen (Nt), phosphorus (Pt), Cmic, Nmic and acid phosphatase activity (AcP) in the first 10 cm of the mineral soil. Four restoration treatments were compared with one reference site. The reference site is heathland located near the training site, where no military actions took place.At all disturbed sites, bulk density and pH proved to be higher than on the reference site. Relative to the reference site, SOC storage reached from 37 to 91 per cent, regeneration of Nt was slightly lower. In contrast to the advanced development of SOC and Nt, the regeneration of Cmic and Nmic was much lower (15–44 per cent). The succession site showed a low pool of SOC, Nt, Cmic and Nmic, but microbial ratios indicated a less disturbed C‐ and N‐cycle. AcP pronounced differences in nutrient demand between disturbed sites and reference. On this base, recommendations for restoration management were given. Copyright © 2008 John Wiley & Sons, Ltd.

Changes in biological activity of a degraded Mediterranean soil after using microbially-treated dry olive cake as a biosolid amendment and arbuscular mycorrhizal fungi

A field experiment was carried out to assess the effect of a combined treatment involving addition of Aspergillus niger-treated dry olive cake (DryOC) in the presence of rock phosphate, plus pre-transplant inoculation of seedlings with the arbuscular mycorrhizal (AM) fungi Glomus intraradices, Glomus deserticola or Glomus mosseae, on the establishment of Dorycnium pentaphyllum L., in a degraded semiarid Mediterranean area. Associated changes in soil labile C fractions, enzyme activities and aggregate stability were also observed. One year after planting, the combined treatment of fermented DryOC addition and inoculation with AM fungi, particularly with G. mosseae (on average 328% greater than control plants), had the strongest effect on the shoot biomass of D. pentaphyllum. Only the fermented DryOC addition increased assimilable P, total N and aggregate stability, the greatest increase being in the soil available P content (about four-fold higher than in the non-amended soil). Both the addition of fermented DryOC and the mycorrhizal inoculation treatments significantly increased enzyme activities of rhizosphere soil (dehydrogenase, protease-BAA, acid phosphatase and β-glucosidase). The microbially-treated DryOC proved to be an effective amendment for improving the soil quality which, in turn, enhanced the success of revegetation with mycorrhizal D. pentaphyllum seedlings.

Effects of Hg and Cu on the activities of soil acid phosphatase

Comparative study on the activity and kinectic properties of acid phosphatase (ACPase) of three soils amended with Hg and Cu at constant temperature and humidity was carried out. The results indicated that the inhibition on ACPase of the three sample soils by Hg and Cu varied with the content of soil organic matter and pH, where, Soil 1 was the most seriously contaminated due to its lowest content of organic matter and the lowest pH among three samples, Soil 2 took the second place, and Soil 3 was the least contaminated. Except Soil 3, the activity of soil ACPase tended to increase along with the contact time under the same type and the same concentration of heavy metal. In particular the Vmax values of ACPase in all three samples decreased with increasing Hg and Cu concentration, whereas the Km values were affected weakly. According to the change of Vmax and Km values, Cu and Hg had the same inhibition effect on soil ACPase. Both of them may be a type of compound of non-competitive and anti-competitive inhibition. Statistic analyses indicated that activities of soil ACPase and Vmax values could serve as bioindicator to partially denote the heavy metal Hg and Cu contamination degree.

Factors affecting soil P dynamics in temperate volcanic soils of southern Argentina

During volcanic soil development, factors controlling plant-available P shift from hydrolysis of P bound to primary Ca compounds to mineralization of organic P, and an increasing role of amorphous materials in P retention. Monospecific forests of the Andean–Patagonian region are distributed in a narrow strip characterized by young volcanic soils and decreasing west–east precipitation. We analyzed sequential P fractionation, P retention, active Al and Fe, and acid phosphatase activity in the superficial soil (0–15 cm) of ten dominant woody species, and related these data to previous results on soil chemical and biological fertility, and green leaf P concentration. Higher plant-labile P (water–Pi + NaHCO 3–Pi) corresponded to soils with higher total P, and this was directly related to the increase of organic P (NaHCO 3–Po + NaOH–Po). Phosphatase activity was mainly explained by the increase of organic C and the decrease of primary minerals (P–HCl). The strongest determinant of P retention was the formation of active Al, which increased with acidification and losses of cations and primary minerals. In the drier extreme of the precipitation gradient, we found the lowest values of active Al and P retention coupled with high exchangeable cations and neutral pH. The effect of plant species increased in wetter areas, and was reflected in differential patterns of SOM accumulation, base cation cycling and active Al formation. When comparing plant functional groups, potential net N mineralization and nitrification, phosphatase activity, organic C, organic P (NaHCO 3–Po) and green leaf P were significantly higher in broad-leaf deciduous species than in conifers.

Microbial biomass and enzyme activities in submerged rice soil amended with municipal solid waste compost and decomposed cow manure

We studied the suitability of municipal solid waste compost (MSWC) application to submerged rice paddies in the perspective of metal pollution hazards associated with such materials. Experiments were conducted during the wet seasons of 1997, 1998 and 1999 on rice grown under submerged condition, at the Agriculture Experimental Farm, Calcutta University at Baruipur, West Bengal, India. The treatments consisted of control, no input; MSWC, at 60 kg N ha −1; well decomposed cow manure (DCM), at 60 kg N ha −1; MSWC (30 kg N ha −1) + Urea (30 kg N ha −1); DCM (30 kg N ha −1) + U (30 kg N ha −1) and Fertilizer, (at 60:30:30 NPK kg ha −1 through urea, single superphosphate and muriate of potash respectively). Soil microbial biomass-C (MBC), MBC as percentage of organic-C (ratio index value, RIV), urease and acid phosphatase activities were higher in DCM than MSWC-treated soils, due to higher amount of biogenic organic materials like water soluble organic carbon, carbohydrate and mineralizable nitrogen in the former. The studied parameters were higher when urea was integrated with DCM or MSWC, compared to their single applications. Soil MBC, urease and acid phosphatase activities periodically declined up to 60 day after transplanting (DAT) and then increased after crop harvest. The heavy metals in MSWC did not detrimentally influence MBC, urease and acid phosphatase activities of soil. In the event of long term MSWC application, changes in soil quality parameters should be monitored regularly, since heavy metals once entering into soil persist over a long period.

Microbial Enzyme Activities in a Freshwater Marsh after Cessation of Nutrient Loading

Accurate assessment of perturbation and recovery from anthropogenic nutrient inputs in wetland ecosystems is important for resource management decisions. Nutrient availability affects detrital decomposition and sediment accumulation rates, contributing to and helping to maintain changes in plant community structure. In this paper we report patterns of microbial enzyme activities as indicators of change in areas of a subtropical wetland 8 yr after cessation of nutrient loading. Select enzyme (acid phosphatase, β‐glucosidase, and dehydrogenase) activities were assayed on detrital material and surface soils collected from different vegetation communities within impacted and reference (unimpacted) areas. Acid phosphatase activity (APA) did not vary as dramatically as total P (TP) in soil, but was distinctly different in detritus of impacted and reference vegetation communities. The APA in soil and detritus was greatest in the reference sites, particularly in the Panicum area. Beta‐glucosidase activity was highest in Typha areas and demonstrated significant temporal variation. Differences in the timing and length of inundation may play a role in observed trends, since the NW Panicum and Cladium reference sites flooded and reached anaerobiosis later in the growing season than did impacted areas. Data from this study indicate ongoing changes in biogeochemical cycling of nutrients in soils and detritus associated with vegetation communities in areas of historic nutrient loading.

Acid phosphatase role in chickpea/maize intercropping.

Organic P comprises 30-80 % of the total P in most agricultural soils. It has been proven that chickpea facilitates P uptake from an organic P source by intercropped wheat. In this study, acid phosphatase excreted from chickpea roots is quantified and the contribution of acid phosphatase to the facilitation of P uptake by intercropped maize receiving phytate is examined. For the first experiment using hydroponics, maize (Zea mays 'Zhongdan No. 2') and chickpea (Cicer arietinum 'Sona') were grown in either the same or separate containers, and P was supplied as phytate, KH2PO4 at 0.25 mmol P L(-1), or not at all. The second experiment involved soil culture with three types of root separation between the two species: (1) plastic sheet, (2) nylon mesh, and (3) no barrier. Maize plants were grown in one compartment and chickpea in the other. Phosphorus was supplied as phytate, Ca(H2PO4)2 at 50 mg P kg(-1), or no P added. In the hydroponics study, the total P uptake by intercropped maize supplied with phytate was 2.1-fold greater than when it was grown as a monoculture. In the soil experiment, when supplied with phytate, total P uptake by maize with mesh barrier and without root barrier was 2.2 and 1.5 times, respectively, as much as that with solid barrier. In both experiments, roots of both maize and chickpea supplied with phytate and no P secreted more acid phosphatase than those with KH2PO4 or Ca(H2PO4)2. However, average acid phosphatase activity of chickpea roots supplied with phytate was 2-3-fold as much as maize. Soil acid phosphatase activity in the rhizosphere of chickpea was also significantly higher than maize regardless of P sources. Chickpea can mobilize organic P in both hydroponic and soil cultures, leading to an interspecific facilitation in utilization of organic P in maize/chickpea intercropping.

Phosphorus mobilization in agroforestry: Organic anions, phosphatase activity and phosphorus fractions in the rhizosphere

In agroforestry systems on Ferralsols in the tropics, maize crop yields are low owing to a lack of P. However, some agroforestry tree species adapted to P-fixing soils may be able to utilize less available P sources and concurrently increase P availability to adjacent crops. Adaptations for enhanced P acquisition from P-fixing soils include exudation of low molecular weight (LMW) organic anions (OA) and phosphatase enzymes. We identified major organic anions, and measured acid phosphatase activity and P fractions in the rhizosphere soil of maize (Zea mays L.), as well as in the perennial species Grevillea robusta A. Cunn., Cassia spectabilis DC. (syn. Senna spectabilis (DC.) H.S. Irwin and R.C. Barneby), Tithonia diversifolia (Hemsl.) A. Gray, Eucalyptus grandis W. Hill ex Maiden and Cedrella serrata Royle. Maize and trees were grown simultaneously at field sites and in large pots. Rhizosphere soil of C. spectabilis contained at least 29 μmol oxalate g−1 soil, derived from a high exudation rate in the range of at least 5–10 μmol oxalate m−1 root day−1. Incubation of Ferralsols with much lower concentrations of citrate increased labile P fractions, but there was no clear relation between OA concentration and an increase in labile P fractions in rhizosphere soils, where P mobilization and P uptake occur at the same time. Acid phosphatase activity in rhizosphere soil of all species was two to five times greater in rhizosphere soil compared with bulk soil, and correlated in rhizosphere soil of G. robusta with a shift from organic P to inorganic P in soil P fractions. We conclude that organic anion exudation and acid phosphatase activity of tree roots may increase mobilization of P in the rhizosphere, the extent of which depends on the species, the organic anion and pH. However, it is unlikely that the extent of P mobilization will benefit adjacent crop plants unless crop roots exert insufficient P-mobilization effects themselves, and grow in the rhizosphere of tree roots.

Influence of toxic metals on activity of acid and alkaline phosphatase enzymes in metal-contaminated landfill soils

A study was conducted to determine the effect of toxic metals on soil acid phosphatase (EC 3.1.3.2) and alkaline phosphatase (EC 3.1.3.1) enzyme activities in landfill soils. The enzyme activities were consistently higher in the landfill soils than in an uncontaminated alluvial soil. The landfill soils contained higher concentrations of metals (iron, manganese, cadmium, lead, zinc, copper) than did the alluvial soil. Enzyme activities were negatively correlated with the metals, with inhibition increasing with the bioavailability of the metals. It is suggested that the metals affected enzyme activities by behaving synergistically or additively with each other. Although the landfill soils had higher enzyme activities than the alluvial soil due to higher organic matter concentrations, the ratios of enzyme activity/organic carbon indicated that inhibition of enzyme synthesis and stability had occurred due to metal stress.

Residual effect of municipal solid waste compost on microbial biomass and activities in mustard growing soil: Restwirkung von müllkompost auf die mikrobielle biomasse und mikrobielle aktivitaten in boden mit senfbewuchs

Residual effect of municipal solid waste compost (MSWC) on microbial biomass and enzyme activities of mustard after submerged rice paddies was studied. Experiments were conducted during the two consecutive winter seasons of 1997 to 1998 on mustard grown at the Agriculture Experimental Farm, Calcutta University, Baruipur, West Bengal, India. The treatments consisted of control, no input and MSWC, at 60 Kg N/ha and well rotted cow dung manure (CDM), at 60 Kg N/ha and MSWC (30 Kg N/ha) + Urea (U, 30 Kg N/ha) and CDM (30 Kg N/ha) + U (30 Kg N/ha) and F (at recommended dose at 60 : 30 : 30 NPK/ha through urea, single super phosphate and muriate of potash respectively). Soil microbial biomass-C (MBC), urease (UR) and acid phosphatase (AP) activities were higher in CDM than MSWC-treated soils, due to the qualitative differences between the two materials. The studied parameters were higher when urea was integrated with CDM or MSWC than when applied singly. The MBC, UR and AP activities of soil periodically declined up to day 60, and then increased after harvest. The appreciable amounts of heavy metals in MSWC produced no evidence of any detrimental influence on MBC, UR and AP activities of soil. This indicated the suitability of MSWC as an alternate source of organic matter in mustard.

Effect of MSW Compost on Microbiological and Biochemical Soil Quality Indicators

This laboratory incubation study was conducted to evaluate the effect of municipal solid waste compost (MSWC) as a soil amendment on soil quality indicators, such as microbial biomass, and their activities. The MSWC was compared against cow dung manure (CDM), a traditional organic supplement. The comparative study was carried out in water regimes of 60% water holding capacity (WH) of soil and under waterlogged (WL) condition. MSWC was applied to an alluvial soil (Typic Fluvaquent) at the rates of 0, 2.5, 10, 20 and 40 and CDM at 0, 20 and 40 t/ha. Microbial biomass-C (MBC), glucose induced soil respiration (SR), urease and acid phosphatase activities in soil were analyzed following 15, 30, 45, 60, 90 and 120 days of incubation. The parameters studied were significantly higher in CDM-treated than in MSWC-treated soils. Increase in graded doses of MSWC from 2.5 to 40 t/ha substantially increased the MBC, SR, urease and phosphatase activities in the soil. In 60% WH regime, MBC and SR increased for the first 30 days of incubation and then declined. Under the WL regime, the MBC declined while SR increased from 15 days till 120 days of incubation. Urease and phosphatase activities of soil increased for up to 60 days during incubation in 60% WH regime and then decreased. Activities of both the enzymes under WL regime decreased progressively during incubation. There were no negative impacts on the soil quality indicators from high application rates of MSWC.