Microbial activity and nutrient dynamics in earthworm casts (Lumbricidae)

Summary Microbial respiration, microbial biomass and nutrient requirements of the microflora (C, N, P) were studied in the food substrate (soil taken from the upper 3 cm of the mineral soil of a beech wood on limestone), the burrow walls and the casts of the earthworm Aporrectodea caliginosa (Savigny). The passage of the soil through the gut caused an increase in soil microbial respiration of about 90% over a 4-week period. Microbial biomass was increased only in freshly deposited casts and decreased in aging faeces to a level about 10% lower than in soil. Microbial respiration of the burrow walls was only increased over a shorter period (about 2 weeks). The microflora of the soil and the burrow walls was limited by P, whereas in earthworm casts, microbial growth was limited by the amount of available C. In aging faeces the P requirement of the microflora increased and approached that of the soil. Immobilization of phosphate in earthworm casts is probably caused by mainly abiotic processes. C mineralization by soil microflora fertilized with glucose and P was limited by N, except in freshly deposited casts. Ammonium, not nitrate, was responsible for this process. N dynamics in earthworm casts are discussed.     

The earthworm population of a winter cereal field and its effects on soil and nitrogen turnover

The earthworm population in a winter cereal field in Ireland was studied over a 3-year-period and its effects on soil and N turnover were assessed. The mean annual population density was 346–471 individuals m^-2 and the mean biomass was 56.9–61.2 g m^-2. Twelve species were recorded, the most abundant being Allolobophora chlorotica followed by Aporrectodea caliginosa, and 242 mg at 5°C to 713 mg at 10°C in the case of juvenile Lumbricus terrestris. Gut contents (dry mass of soil) comprised 6.7–15.5% of the A. caliginosa live mass, and 9.7–14.7% of the Lumbricus terrestris mass. Annual soil egestion by the field population was estimated as 18–22 kg m^-2. Tissue production ranged from 81.7 to 218.5 g m^-2, while N turnover resulting from mortality was calculated as 1.5–3.9 g m^-2 depending on the year and the method of calculation. Earthworms were estimated to contribute an additional 3.4–4.1 g mineral N to the soil through excretion, mucus production, and soil ingestion. Independent estimates of N output via mucus and excretion derived from ¹⁵N laboratory studies with Lumbricus terrestris were 2.9–3.6 g m^-2 year^-1.     

Effect of different types of organic fertilizers on the chemical properties and enzymatic activities of an Oxisol under intensive cultivation of vegetables for 4 years

The effects of different types of organic fertilizers on the chemical and enzymatic properties of an Oxisol were studied after being fertilized for four consecutive years (26 crops) in a greenhouse under intensive cultivation of vegetables. Seven treatments, consisting of five types of organic fertilizer treatments, one "sequential application" (SA) treatment, and a chemical fertilizer treated plot were compared. The organic fertilizers used were dairy cattle dung compost (DCDC), hog dung compost (HDC), chicken dung compost (CDC), pea residue compost (PRC) and soybean meal (SBM). After 4 years of cultivation, the soils were analyzed for their chemical properties and enzymatic activities. The microbial carbon (C) and nitrogen (N), basal respiration and nitrification rate were also measured. The results showed that the SBM significantly lowered the soil pH, and that the HDC and DCDC raised the soil pH. The SBM and CDC resulted in the lowest soil electrical conductivity. The SBM had no significant effect on soil organic C and total N contents when compared with the CF plot. However, the DCDC resulted in the highest contents of soil organic C and total N. The organic fertilizers applied did not significantly affect the soil available copper, zinc, cadmium, lead and nickel. The effects of the different organic fertilizers on soil enzymatic activities depended on the types of organic fertilizers applied. The SBM and CDC often resulted in a lower microbial C (or N) and respiration rate, while in contrast DCDC and PRC resulted in high measurements. Most of the measured soil enzymatic activities in the SBM treatment, except for acid phosphatase, were the lowest. Differing contents of different heavy metals in the organic fertilizers resulted in different Mehlich III extractable heavy metal contents in the soils. From the point of view of the soil chemical and enzymatic properties, SBM is not an appropriate organic fertilizer for continuous application to an Oxisol.     

Soil microbial biomass and activity in organic tomato farming systems: Effects of organic inputs and straw mulching

Organic farming is rapidly expanding worldwide. Plant growth in organic systems greatly depends on the functions performed by soil microbes, particularly in nutrient supply. However, the linkages between soil microbes and nutrient availability in organically managed soils are not well understood. We conducted a long-term field experiment to examine microbial biomass and activity, and nutrient availability under four management regimes with different organic inputs. The experiment was initiated in 1997 by employing different practices of organic farming in a coastal sandy soil in Clinton, NC, USA. Organic practices were designed by applying organic substrates with different C and N availability, either in the presence or absence of wheat-straw mulch. The organic substrates used included composted cotton gin trash (CGT), animal manure (AM) and rye/vetch green manure (RV). A commercial synthetic fertilizer (SF) was used as a conventional control. Results obtained in both 2001 and 2002 showed that microbial biomass and microbial activity were generally higher in organically than conventionally managed soils with CGT being most effective. The CGT additions increased soil microbial biomass C and activity by 103-151% and 88-170% over a period of two years, respectively, leading to a 182-285% increase in potentially mineralizable N, compared to the SF control. Straw mulching further enhanced microbial biomass, activity, and potential N availability by 42, 64, and 30%, respectively, relative to non-mulched soils, likely via improving C and water availability for soil microbes. The findings that microbial properties and N availability for plants differed under different organic input regimes suggest the need for effective residue managements in organic tomato farming systems.     

Impact of simulated erosion on the abundance and activity of indigenous vesicular-arbuscular mycorrhizal endophytes in an Oxisol

Summary The influence of simulated erosion on the abundance and activity of indigenous vesiculararbuscular mycorrhizal (VAM) populations was evaluated in an Oxisol. Surface-soil losses in excess of 7.5 cm were generally associated with significant decreases in the numbers of total and active VAM propagules and in the symbiotic effectiveness of the active propagules. Surface-soil removal not exceeding 7.5 cm was associated with decreased propagule abundance without adverse effects on VAM colonization of roots and symbiotic effectiveness of the fungi. The extent of VAM colonization of roots and the degree of symbiotic effectiveness observed at this level of simulated erosion were significantly higher than those observed in the soil not subjected to simulated erosion. This stimulation is attributed to the removal of antagonistic biotic factors as the top 7.5 cm of soil was removed. It is concluded that propagules lost during erosional soil losses must be replaced before legumes grown on relatively highly weathered and severely eroded tropical soils could appreciably benefit from the VAM symbiosis.Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3234     

Effect of organic and mineral fertilizers on some soil properties

Abstract

NPK was applied to a Haynie, very fine, sandy loam as 89.6 MT/ha (40 T/ac) of OF (organic fertilizer as feedlot manure at 45% water content) and as MF (mineral fertilizer) with nutrients equivalent to the manure during 18 months.

Organic fertilizer increased soil organic matter content 0.25% more than the MF and 0.2% more than the control. Organic fertilizer increased the CEC 0.3 m.e./100 g more than the MF and 0.4 m.e./100 g more than the control. Organic fertilizer increased exch. Mg by 32 kg/ha while MF decreased exch. Mg slightly.     

Assessing the organic phosphorus status of an Oxisol under tropical pastures following native savanna using 31P NMR spectroscopy

³¹P nuclear magnetic resonance (NMR) spectroscopy, P fractionation, and a P sorption experiment were used to follow the changes in P in the A horizons (0–10 cm) of acid savanna soils, Colombia, after little P fertilization and 15 years' continuous growth of a grass (Brachiaria decumbens) and a grass/legume (B. decumbens+Pueraria phaseoloides) pasture. Ready P supply as analyzed by Bray P was low under native savanna (1.3 mg kg^-1 soil) and responded moderately on pasture establishment. Concurrently, the affinity of the soil for inorganic P declined slightly after pasture establishment. ³¹P NMR spectroscopy revealed that P associated with humic acids was dominated by monoester P followed by diester P. Smaller proportions were observed for phosphonates, teichoic acid P, orthophosphate, and pyrophosphate. P associated with fulvic acids had lower proportions of diester P and higher contents of orthophosphate. Under native savanna the reserves of labile organic P species (phosphonates and diester P including teichoic acid P) associated with humic and fulvic acids were 12.4 and 1.1 kg ha^-1, respectively, and increased to 18.1 and 1.8 kg ha^-1 under grass pasture, and to 19.5 and 2.3 kg ha^-1 under grass/legume pasture. These data emphasize the importance of labile organic P species in the P supply for plants in improved tropical pastures, and further indicate that humic acid P in particular responds to land-use changes within a relatively short time-scale. Earthworm casts were highly abundant in the B. decumbens+P. phaseoloides plot and were enriched in labile organic P species. We conclude that earthworm activity improves the P supply in soil under tropical pastures by creating an easily available organic P pool.Dedicated to Professor J.C.G. Ottow on the occasion of his 60th birthday     

Effects of organic manure on nitrification in arable soils

Summary The production of nitrate by the process of nitrification is highly dependent on other N-transforming processes in the soil. Hence, changes in the type of N compound applied to enrich agricultural soils may affect the production of nitrate. The size and activity of the chemolithotrophic bacterial community were studied in an integrated farming system, with increased inputs of organic manure and reduced inputs of mineral nitrogenous fertilizer, versus conventional farming. The integrated farming had a positive effect on potential nitrifying activity, but not on the numbers of chemolithotrophic nitrifying bacteria as determined by a most probable number technique or by fluorescence antibody microscopy. Cells of the recently described nitrite-oxidizing species Nitrobacter hamburgensis and Nitrobacter vulgaris were just as common as the cells of the well known species Nitrobacter winogradskyi. It was concluded that nitrification is stimulated by integrated farming, presumably by an increased mineralization of ammonium which is not immediately consumed by the crop or immobilized in the heterotrophic microflora of the soil. Since nitrifying bacteria are involved in the production of NO and N₂O, integrated farming with the application of manure may favour the production of noxious N-oxides.Communication no. 40 of the Dutch Programme on Soil Ecology of Arable Farming Systems     

Nitrogen mineralization and reorganization in casts of the geophagous tropical earthworm Pontoscolex corethrurus (Glossoscolecidae)

Summary Mineral N concentrations ranged from 133.1 to 167.8 g g^-1 dry soil in fresh casts of the endogeic earthworm Pontoscolex corethrurus fed on an Amazonian Ultisol; this was approximately five times the concentration in non-ingested soil. Most of this N was in the form of NH _inf4 ^sup+ . N also accumulated in microbial biomass, which increased from a control value of 10.5–11.3 to 67.5–74.1 g g^-1 in fresh casts. During a 16-day incubation, part of the NH _inf4 ^sup+ -N was nitrified and/or transferred to the microbial biomass. Total labile N (i.e., mineral+biomas N) decreased sharply at first (ca. 50% in the first 12 h), and then more slowly. The exact fate of this N (microbial metabolites, denitrification, or volatilization) is not known. After 16 days, the overall N content of the casts was still 28% higher than that of the control soil. Incubation of the soil before ingestion by the earthworms significantly increased the production of NH _inf4 ^sup+ in casts. We calculate that in a humid tropical pasture, 50–100 kg mineral N may be produced annually in earthworm casts. Part of this N may be conserved in the compact structure of the cast where the cast is not in close contact with plant roots.     

Inorganic and organic phosphorus pools in earthworm casts (Glossoscolecidae) and a Brazilian rainforest Oxisol

We compared differences in soil phosphorus fractions between large earthworm casts (Family Glossoscolecidae) and surrounding soils, i.e., Oxisols in 10 year-old upland agroforestry system (AGR), pasture (PAS), and secondary forest (SEC) in the Central Brazilian Amazon. AGR and PAS both received low-input fertilization and SEC received no fertilization. We found that earthworm casts had higher levels of organic hydroxide P than surrounding soils, whereas fertilization increased inorganic hydroxide P. Inorganic P was increased by fertilization, and organic P was increased by earthworm gut passage and/or selection of ingested materials, which increased available P (sum of resin and bicarbonate fractions) and moderately available P (sum of hydroxide and dilute acid fractions), and P fertilizer application and land-use increased available P. The use of a modified sequential P fractionation produced fewer differences between earthworm casts and soils than were expected. We suggest the use of a condensed extraction procedure with three fractions (Available P, Moderately Available P, and Resistant P) that provide an ecologically based understanding of the P availability in soil. Earthworm casts were estimated to constitute 41.0, 38.2, and 26.0 kg ha⁻¹ of total available P stocks (sum of resin and bicarbonate fractions) in the agroforestry system, pasture, and secondary forest, respectively.     

Impact of the earthworm Lumbricus terrestris on the degradation of Fusarium-infected and deoxynivalenol-contaminated wheat straw

When conservation tillage is practised in agriculture, plant residues remain on the soil surface for soil protection purposes. These residues should be widely decomposed within the following vegetation period as microbial plant pathogens surviving on plant litter may endanger the currently cultivated crop. Important soil-borne fungal pathogens that preferably infect small grain cereals belong to the genus Fusarium. These pathogens produce the mycotoxin deoxynivalenol (DON), a cytotoxic agent, in infected cereal organs. This toxin frequently occurs in cereal residues like straw. So far it is unclear if DON degradation is affected by members of the soil food web within decomposing processes in the soil system. For this purpose, a microcosm study was conducted under controlled laboratory conditions to investigate the degradation activity of the earthworm species Lumbricus terrestris when exposed to Fusarium-infected wheat straw being contaminated with DON.Highly Fusarium-infected and DON-contaminated straw seemed to be more attractive to L. terrestris because it was incorporated faster into the soil compared with straw infected and contaminated at low levels. This is supported by a greater body weight gain (exposure time 5 weeks) and smaller body weight loss (exposure time 11 weeks) of L. terrestris, respectively, when highly contaminated straw was offered for different time periods.Furthermore, L. terrestris takes part in the efficient degradation of both Fusarium biomass and DON occurring in straw in close interaction with soil microorganisms. Consequently, earthworm activity contributes to the elimination of potentially infectious plant material from the soil surface.     

Enzymatic hydrolysis of organic phosphorus in extracts and resuspensions of swine manure and cattle manure

Animal manure can be a valuable resource of P for plant growth. Organic phosphates (P_o) are considered bioavailable if they can be hydrolyzed to inorganic P (P_i). Therefore, investigation of the susceptibility of manure P_o to hydrolysis may increase our understanding of manure P_o bioavailability. In this study, we demonstrate that three orthophosphate-releasing enzymes, acid phosphatase from wheat germ, alkaline phosphatase from bovine intestinal mucosa, and fungal phytase from Aspergillus ficcum, were able to hydrolyze certain amounts of P_o in animal manure. A scheme of sequential enzymatic release of P_o in manure was developed and then used to investigate changes in swine and cattle manure P distribution after storage at –20°C, 4°C or 22°C for about a year. Assuming that the P distribution in manure maintained at –20°C remained unchanged (i.e., similar to fresh manure), bioavailable P (P_i and enzyme-hydrolysable P_o) in swine manure remained relatively constant [72.8–76.3% of total P (P_t)]. Soluble but enzymatically unhydrolysable P_o (P_ue) increased from 7.2% to 32.1% of P_t during storage at 4°C. In cattle manure, bioavailable P decreased from 71.6% to 62.9% of P_t, and P_ue increased from 21.7% to 37.2% of P_t during storage at 22°C. These data indicated that the major change during the storage of animal manure for a year was the increase in P_ue, so manure P solubility may increase with storage, but the increase would not produce more bioavailable P in the manure. The effects of storage on the bioavailability of manure P should be further investigated to develop an efficient manure-P management strategy.Trade or manufacturers' names mentioned in the paper are for information only and do not constitute endorsement, recommendation, or exclusion by the USDA-ARS     

Effects of earthworms on soil enzyme activity in an organic residue amended rice–wheat rotation agro-ecosystem

The effect of earthworms on soil hydrolases (protease, urease, invertase, and alkaline phosphatase) and dehydrogenase activities was investigated in maize residue amended rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and an untreated control. The application of maize residues to soil without earthworms significantly enhanced the five soil enzyme activities compared with the control treatment during rice and wheat cultivation. The presence of earthworms further significantly enhanced protease activity in the soils with both incorporated and mulched maize residues during two cultivation seasons, but only significantly increased alkaline phosphatase activity in the soil with incorporated maize residue during the rice cultivation season. Invertase activity was significantly enhanced by the presence of earthworms in the soil with maize residue incorporation during two cultivation seasons. There were no changes in dehydrogenase activity when earthworms were present. Additionally, the five enzyme activities in earthworm casts were significant higher than those in the surrounding soil, especially dehydrogenase and invertase activities. Whatever the treatment, the values obtained for the enzyme activities in both soil and casts, except for dehydrogenase activity in earthworm casts, were significantly higher under wheat than those in rice-cultivated soil. These results indicate that the presence of earthworms strongly affected soil enzyme activities, depending on the method of organic residue application, and the enhanced enzyme activities of earthworm casts probably contributed to the surrounding soil enzyme activities.     

Organic manure stimulates biological activity and barley growth in soil subject to secondary salinization

A pot experiment was performed to compare the impact of organic manure on soil enzymatic activity, respiration rate and the growth of two barley cultivars (Hordeum vulgare L.) differing in their salt tolerance under a simulated salinized environment. A plastic pot with a hole (2 cm in diameter) in the center of bottom was filled with an anthropogenic (paddy) soil and placed in a porcelain container containing NaCl solution (3.0 g L⁻¹) such that a secondary salinization process was simulated via upward capillary water movement along the soil profile. A treatment with neither organic manure nor simulated soil salinization was taken as a control (CK1). The organic manure was applied either inside or outside rhizobag made of nylon cloth (40 μm of pore size). The soil was treated with: 20 g kg⁻¹ rice straw (RS), 20 g kg⁻¹ pig manure (PM), or 10 g kg⁻¹ rice straw plus 10 g kg⁻¹ pig manure (RS+PM). No organic manure was added in an additional control treatment (CK2). The results indicated that the placement of organic manure both inside and outside rihzobags significantly increased the activity of urease, alkaline phosphatase and dehydrogenase, as well as respiration rate in both rhizosphere and bulk soils. Also, nutrient uptake by barley plants was enhanced in the treatments with organic manure amended either inside or outside rhizobags. The activity of these enzymes along with the respiration rate was higher in rhizosphere than in non-rhizosphere when organic manure was supplied inside rhizobags, while the opposite was found in the case of manure incorporated outside rhizobags. Among all the treatments, RS+PM treatment had most significant stimulating effects on enzymatic and microbial activity and shoot dry weight of barley, followed by PM and RS. Moreover, more significant stimulating effects on both enzyme activity and plant growth were achieved in the treatments with manure amended inside rhizobags than outside rhizobags. The results of the present study confirmed the view that incorporation of organic manure especially into soil-root zones is an effective low-input agro-technological approach to enhancing soil fertility and minimizing phytotoxicity induced by secondary salinization.     

Effects of green manure and coral lime on corn growth and chemical properties of an acid Oxisol in Western Samoa

Effects of local green manure (GM) and lime on soil productivity in a low-input agricultural system were evaluated by growing three successive crops of sweet corn (Zea mays) on an acid Oxisol (Typic acrorthox, Togitogiga series) in Western Samoa. The soil was amended with coral lime at 0, 5, and 10Mgha^–1 and with cowpea GM at 0, 7.5, and 15Mgha^–1. Commercial NPK fertilizers at 50kgha^–1 each of N, P, and K were included for comparison. The amendments were applied only once prior to planting of the first crop. Response parameters measured included nutrient composition of leaves at tasseling and grain yield of each crop, and selected soil chemical properties at each planting. Yields of the first crop were nearly tripled with GM additions and doubled with lime additions. Such yield increases were caused mainly by better K nutrition and to a lesser extent by enhanced P nutrition. Yields of subsequent crops were much lower than those of the first, and the declines were much steeper for the GM treatments than for the lime treatments. Thus, the enhancement effect on K nutrition did not last beyond one crop. Poor growth of the second and third crops was caused by K deficiency; probably coupled with Mn toxicity. Significant yield reductions were found when Mn-to-K ratios in leaves exceeded 0.010. As for effects on soil, soil pH was increased significantly by lime but only slightly by GM. Given the variable charge property of this Oxisol, each unit pH increase corresponds to a cation exchange capacity (CEC) increase of 5cmol_ckg^–1. Having greater CEC, the amended soil retained K more effectively, thereby causing yield increases, especially of the first corn crop, which required at least 0.75cmol_ckg^–1 of exchangeable soil K or 7% of CEC for adequate growth. Received: 15 April 1996     

Nematode faunal response to long-term application of nitrogen fertilizer and organic manure in Northeast China

Nematode faunal response to the long-term (20-year) application of nitrogen fertilizer and organic manure was monitored in a Hapli-Udic Cambosol of Northeast China, where no fertilizer (C), nitrogen fertilizer (N), organic manure (M) and nitrogen fertilizer plus organic manure (N + M) treatments were compared. The obtained results showed that total nematode abundance responded positively to the M and N + M treatments. The numbers of Acrobeloides increased in the M and N + M treatments at maize jointing and booting stages, and those of Aphelenchoides were higher in the N + M treatment than in the N treatment at maize ripening stage. Early in the growing season, the numbers of bacterivores of cp-1 (cp, colonizer-persister) and cp-2 guilds were higher in the M and N + M treatments than in the N treatment, while those of bacterivores and fungivores of cp-4 guilds were higher in the C treatment than in the N, M and N + M treatments. Except at maize seedling stage, the numbers of fungivores of cp-2 and herbivores of cp-3 guilds were higher in the N + M treatment than in the C treatment. Ratios of the weighted abundance of representatives of specific functional guilds were used as indicators of food web structure, enrichment and decomposition channels. Values of the enrichment index (EI) at maize seedling and jointing stages were higher in the M and N + M treatments than in the C and N treatments, while an opposite trend was observed in the channel index (CI). Higher EI and lower CI suggest an enriched soil food web dominated with bacterial decomposition channels in the M and N + M treatments.     

Effects of plant species on microbial biomass phosphorus and phosphatase activity in a range of grassland soils

Soil P transformations are primarily mediated by plant root and soil microbial activity. A short-term (40 weeks) glasshouse experiment with 15 grassland soils collected from around New Zealand was conducted to examine the impacts of ryegrass (Lolium perenne) and radiata pine (Pinus radiata) on soil microbial properties and microbiological processes involved in P dynamics. Results showed that the effect of plant species on soil microbial parameters varied greatly with soil type. Concentrations of microbial biomass C and soil respiration were significantly greater in six out of 15 soils under radiata pine compared with ryegrass, while there were no significant effects of plant species on these parameters in the remaining soils. However, microbial biomass P (MBP) was significantly lower in six soils under radiata pine, while there were no significant effects of plant species on MBP in the remaining soils. The latter indicated that P was released from the microbial biomass in response to greater P demand by radiata pine. Levels of water soluble organic C were significantly greater in most soils under radiata pine, compared with ryegrass, which suggested that greater root exudation might have occurred under radiata pine. Activities of acid and alkaline phosphatase and phosphodiesterase were generally lower in most soils under radiata pine, compared with ryegrass. The findings of this study indicate that root exudation plays an important role in increased soil microbial activities, solubility of organic P and mineralization of organic P in soils under radiata pine.     

Effect of mineral fertilizer,pig manure,and <Emphasis Type="Italic">Azospirillum rugosum</Emphasis> on growth and nutrient contents of <Emphasis Type="Italic">Lactuca sativa</Emphasis> L.

Benefits from the application of plant growth-promoting bacteria in agriculture largely depend on the complex interactions between several factors including the nature of fertilizers selected. This study was designed to determine the fine tuning between the inoculated bacteria and different fertilizers and their effect on the growth of lettuce plants (Lactuca sativa L.). Plant growth promotion by a novel species of the genus Azospirillum, namely A. rugosum IMMIB AFH-6, was tested by biochemical, bioassay, and greenhouse studies. The treatments used in the greenhouse study were; unfertilized control (Blank), half recommended dose of chemical fertilizer (1/2CF), full recommended dose of chemical fertilizer (1CF), pig manure fertilizer (PMF), pig manure fertilizer + half recommended dose of chemical fertilizer (PMF + 1/2CF), and pig manure fertilizer + full recommended dose of chemical fertilizer (PMF + 1CF). All these treatments when inoculated with A. rugosum IMMIB AFH-6 inoculation were, respectively, In-Blank, In-1/2CF, In-1CF, In-PMF, In-PMF + 1/2CF, and In-PMF + 1CF. Significant increase in plant biomass and shoot N, P, Ca, and Fe was shown in the In-Blank treatment. Plant growth in soil amended with PMF and A. rugosum IMMIB AFH-6 was significantly lower than in soil treated with the chemical fertilizer, but inoculation combined with chemical fertilizer significantly elevated the plant biomass. The In-PMF + 1/2CF treatment showed the highest yield. A. rugosum IMMIB AFH-6 facilitated the accumulation of trace minerals in higher concentrations when PMF was combined with 1CF. To examine the benefits of inoculation by A. rugosum IMMIB AFH-6, we have proposed a new type of data analysis which considers both biomass and nutrient content of plants. This new type of analysis has shown the importance of the mineral content of plant.     

Effects of long-term mineral fertilization on microbial biomass,microbial activity,and the presence of <Emphasis Type="Italic">r</Emphasis>- and <Emphasis Type="Italic">K</Emphasis>-strategists in soil

Long-term effects of mineral fertilization on microbial biomass C (MBC), basal respiration (R _B), substrate-induced respiration (R _S), β-glucosidase activity, and the r–K-growth strategy of soil microflora were investigated using a field trial on grassland established in 1969. The experimental plots were fertilized at three rates of mineral N (0, 80, and 160 kg ha⁻¹ year⁻¹) with 32 kg P ha⁻¹ year⁻¹ and 100 kg K ha⁻¹ year⁻¹. No fertilizer was applied on the control plots (C). The application of a mineral fertilizer led to lower values of the MBC and R _B, probably as a result of fast mineralization of available substrate after an input of the mineral fertilizer. The application of mineral N decreased the content of C extracted by 0.5 M K₂SO₄ (C _ex). A positive correlation was found between pH and the proportion of active microflora (R _S/MBC). The specific growth rate (μ) of soil heterotrophs was higher in the fertilized than in unfertilized soils, suggesting the stimulation of r-strategists, probably as the result of the presence of available P and rhizodepositions. The cessation of fertilization with 320 kg N ha⁻¹ year⁻¹ (NF) in 1989 also stimulated r-strategists compared to C soil, probably as the result of the higher content of available P in the NF soil than in the C soil.     

Effect of earthworm casts on protein synthesis inAgaricus bisporus

Summary When earthworm casts were used as a casing, an early fructification, a greater stimulation in fruitbody formation, an increase in the carpophore protein content and in L-¹⁴C-leucine incorporation were observed inAgaricus bisporus. The protein-synthesizing capacity of the carpophore and its protein content were tested on samples collected 28 and 35 days after the casing. An increased L-¹⁴C-leucine incorporation of about 34% and an increased protein content of about 25% were recorded.