We measured the activity and soil microbial biomass in volcanic ash soils from 10 sites under ecological farming (no pesticides, shallow ploughing, mulching, organic fertilizers, crop rotation) and 15 sites under conventional farming (pesticides, mineral fertilizers, deep ploughing). Our aim was to determine the effects of management system on soil quality and soil fertility in tropical Nicaragua in relation to soil type. None of these sites were irrigated. Conventional management led to significantly increased amounts of total soil P and a significantly larger biomass C-to-P ratio compared to ecological management. Almost all of the other microbial properties, i.e. soil basal respiration, ergosterol and biomass C were significantly improved by ecological management. Also the biomass C-to-soil C ratio was significantly increased, but not the metabolic quotient qCO2 or the ergosterol-to-biomass C ratios, indicating that the positive effects of ecological management were mainly due to increased C input rates. Biomass C, ergosterol, and basal respiration rate were significantly larger at the loamy sites than at the sandy sites. The same was true for the biomass C-to-soil C ratio, but the ergosterol-to-biomass C ratio and the metabolic quotient qCO2 were larger at the sandy sites. Our results demonstrate that ecological management is an important tool for soil conservation and sustainable management of arable land in Nicaragua. However, the decline in total P and the low P availability to soil microorganisms need attention as a precaution against P deficiency. The improvement was greatest at the loamy sites, although the effects of management system were in most cases independent of the soil type. For this reason, ecological management should be preferably promoted on loamy soils.

An experiment was conducted to study the estimate of total biomass (shedded leaves plus roots) during bast fibre crop (jute, kenaf and mesta) cultivation and the performance of biomass in soil fertility. The newly released four varieties of Bangladesh Jute Research Institute were used in the trial viz. Deshi jute BJC-83, Tossa jute OM-1, kenaf HC- 95 and mesta HS-24. Each of the new variety produces good amount of biomass and enriches the soil fertility. The highest biomass produced with HC-95 (7.30 t he-1) and lowest BJC-83 (5.23 t ha-1). Appreciable performance recorded with each of the variety in enriching the soil fertility on post harvest soil. Highest organic carbon (1.31 %) nitrogen (0.13%) phosphorus (18 ppm) and potassium (0.183 meq/100) were found with the variety HC-95. The percent increment of organic carbon (OC), nitrogen (N), phosphorus (P) and potassium (K) by the HC-95 were 87.14, 150.00, 63.64 and 30.71 respectively over the initial soil nutrient content. According to the performance of the production of biomass and soil enrichment the varieties were in the order of HC-95 greater than HS-24 greater than OM-1 greater than BJC-83.

Chinese soils that had been cropped to continuous wheat-maize rotation for 10 to 13 years in Guangzhou (tropical red soil), Nanjing (subtropical yellow-brown soil), and Henan (temperate meadow soil) were analyzed to evaluate changes in quantity and quality of soil organic carbon (C) under different fertilization treatments compared to reference soils. Addition of farmyard manure and farmyard manure + NPK fertilizer tended to increase amounts of oxidizable C, microbial biomass C and mineralizable C, while NPK fertilizer only increased microbial biomass C and mineralizable C, and decreased oxidizable C. Among different agroecosystems, oxidizable C, microbial biomass C and mineralizable C in Nanjing were much higher than those in Guangzhou and Henan. When characterized by 13C nuclear magnetic resonance, an influence of fertilization treatment was evident, especially on long chain aliphatic C and carboxylic C. Long chain aliphatic C was the dominant component (34–51%) of the soil organic C. Soil oxidizable C, microbial biomass C and mineralizable C were positively related to carbohydrate C and carboxylic C, and negatively related to unoxidizable C and long-chain aliphatic C.

The purpose of this experiment was to investigate the influence of soil compaction and water content on root development of 6 month old sengon seedling. The experiment was arranged 3 x 3 factorial experiment within a complete randomized design and 3 replications. The factor number one was soil compaction and factor number two was soil water content. The soil compaction factor consists of 3 levels, which are 1,5 g/cm3 (A1), 1,2 g/cm3 (A2), and 0,9 g/cm3 (A3) respectively, while the soil water content also consists of 3 levels, which are 60,41 % (B1), 49,64% (B2), and 42,86 % (B3) for each level. The parameters were counted which are root number, diameter, root length, biomass, surface area, and root length density. The result was that soil compaction treatment has a significant influence to root number, root length, biomass, surface area, and root length density. On the other hand the soil water content treatment on pF 2,54 until 3,5 and interaction soil compaction and water content have no influence to root number, diameter, root length, biomass, surface area, and root length density. Root number, diameter, length, biomass, surface area and root length density were increased accordingly to the age of the seedling, but the increasing of soil compaction has decreased to the number, length, root length, biomass, surface area and root length density. The secondary root was found more larger than the primary and the tertiary root in term of the root length, surface area and root length density.

The relationships between microbial biomass C, organic C, and environmental parameters were studied in soils under corn (Zea mays. L) in the mountainous areas of southwest China. Three yellowish-red (Ultisols), yellow (Ultisols) and yellowish-brown (Alfisols) soils were relatively weathered, leached and impoverished, with most having a low input of aboveground corn residues. Seasonal changes in soil microbial C at 0-10 cm depth were significant at each sampling site, with the highest value (120 g C m(-2)) in winter, and lowest value in summer (21 g C m(-2)). Microbial biomass C was significantly and negatively correlated with site elevation and positively correlated with mean annual temperature. The seasonal change in microbial biomass C was significantly correlated with total soil organic C. The decline in microbial biomass C estimated as a percentage of the total soil organic C was negatively correlated with the elevation above sea level, ranging from 3.9+/-0.9% below 600 m to 1.4+/-0.5% above 1,500 m, suggesting higher turnover rates of soil microbial biomass C at warmer air temperatures. Temperature influenced the decomposition of organic C in soils mainly through its effects on microbial biomass C, and the microbial biomass C/organic C ratio appears to be a sensitive index of the change in organic matter content of soil.

There were no significant differences in the percent mortality and weight of earthworms (Lumbricus terrestris) after 40 days in soil planted with Bt (NK4640Bt) or non-Bt corn or after 45 days in soil amended with biomass of Bt or non-Bt corn. The toxin was present in the guts and casts of earthworms in soil planted with Bt corn or amended with biomass of Bt corn, but it was cleared within 2-3 days from the guts after placing in fresh soil. There were no significant differences in the colony-forming units of culturable bacteria (including actinomycetes) and fungi and in the numbers of protozoa and nematodes between rhizosphere soil of Bt and non-Bt corn or between soil amended with biomass of Bt and non-Bt corn. The Cry1Ab protein in root exudates and biomass of Bt corn appears not to be toxic to earthworms, nematodes, protozoa, bacteria, and fungi. The presence of the toxin in the guts and casts of earthworms confirmed that the toxin released in root exudates and from transgenic biomass was bound on surface-active particles in soil, which protected the toxin from biodegradation, as has been observed in this laboratory with purified toxin.

Soil amended with different proportions of flyash, a solid waste generated from coal-fired thermal power plants, was evaluated as a soil conditioner and nutrient supplement during a field study on the growth of rice, Oryza sativa. Generally, pH and organic carbon (OC) content did not increase significantly (P > 0.05) in flyash amended soil, but significant increases (P < 0.05) in soil conductivity (32%), available phosphorus (48%) and organic matter (OM, 29%) were observed during harvest at the 20 t ha-1 flyash application rate. Amylase, invertase, dehydrogenase and protease activities, and CO2 evolution increased in flyash amended soil over the control. The pigment (chl-a, chl-b, and carotenoid) content in rice plants did not vary significantly (P > 0.05) between different flyash amendments. Total plants biomass and aboveground biomass increased (P < 0.05) significantly (17% and 25%, respectively) at the 20 t ha-1 flyash application. However, there was a retarded growth of underground biomass. Grain and straw yield increased by 21% and 18%, respectively, at 17.5 t ha-1 flyash amendment when compared to the control. Although, a significant increase (P < 0.05) in plant biomass and grain yield in flyash amended soil is encouraging from the point of waste disposal and management, elucidation of reasons for retarded growth in underground biomass will require additional research based on long-term studies.

In vineyards, the long-term use of copper fungicides has increased soil Cu concentrations that can adversely affect the number and activities of soil microorganisms. To better understand this phenomenon and to ameliorate such harmful effects, an incubation experiment was carried out with a sandy loam and a sandy soil to which increasing rates of CuS04 were added. By this treatment, the basal soil respiration (7-55%) and decomposition of added vine branches (46-86%) was inhibited. At the application rate of 500 mg Cu kg-1, soil microbial biomass-C was inhibited (7-66%) in the sandy soil and stimulated (2-10%) in the sandy loam soil. The specific respiration rate was a reliable indicator for Cu stress, and it increased with time and higher Cu concentrations before lime and compost applications. Total number of bacteria and streptomycetes were also strongly inhibited. Fungal population was significantly more tolerant to copper toxicity than the bacteria. A stimulation of fungal population at a dose of 500 mg Cu kg-1 in both soils was observed. A criterion such as "stimulation" lasting for more than 60 days can also be used as indication of Cu contamination of soils. The order of inhibition (on day 125) at a dose of 500 mg Cu kg-1 soil was as follows: A. sandy loam soil (pH> 7.0) - fungi < biomass-C < basal soil respiration < bacteria < streptomycetes; B. sandy soil (pH< 6.0) - fungi < basal soil respiration < biomass-C < bacteria < streptomycetes. The application of lime increased soil recovering ability at a moderate rate (for CO2 production - 22-70% and for biomass-C- 39-156%), but the combination of lime and compost significantly increased soil resiliency (for CO2 production- 16-518% and for biomass-C- 103-693%). The soil resiliency assessed by number of bacteria in compost treatments was 30-120% in sandy loam soil and 92-700% in the sandy soil. Compost and lime application increased the number of streptomycetes from 52 to 500% in sandy loam soil and from 100 to 700% in sandy loam soil. Fungal population was less increased in sandy soil as compared to sandy loam soil. The ecological dose higher than 5% inhibition of microbial processes and microorganisms appears to be suitable to assess Cu contamination of soils. CO2 production, biomass-C and specific respiration rate were less sensitive indicators as compared to streptomycetes and bacteria. It appears that compost application effectively promoted the recovery of soil microbial activity and soil fertility of Cu contaminated soils.