The Influence of Treated and Untreated Wastewaters on Enzymatic Activity of a Silty Clay Soil Under Laboratory Conditions

The use of industrial wastewater for irrigating farmlands is currently increasing, especially in arid and semi-arid areas because of water shortage for agriculture. The use of industrial wastewater in farmlands could help the sustainable soil fertility through improving the physical, chemical and biological soil characteristics. On the other hand, wastewater may contain toxic elements that are detrimental to soil microorganism and biochemical reactions. The aim of this study was to determine the effects of industrial wastewater either treated or untreated on soil enzyme activities. The wastewater samples were taken from Zobahan, Foolad Mobarakeh Steel Plants and Polyacril plant. Soil samples were moistened at 70% field capacity using wastewaters and then placed at 25 oC for 3months in an incubator. Soil samples were analyzed to examine enzyme activities at monthly intervals. Results showed that during the first two months of incubation enzyme activities increased in wastewater-treated period and sampling time, adding wastewater to the soil increased enzyme activities. The presence of carbon and nutrients in wastewater could lead to an increase in microbial activities and populations, resulted in increasing synthesis and production of enzymes involved

Zinc and Copper Release Kinetics in a Calcareous Soil amended with Manure and Vermicompost

Introduction: Use of organic fertilizers such as vermicompost in agricultural soils with low organic matter content is almost considered as a one way for adding nutrients in these soils. However, application of these fertilizers may affect micronutrient release characteristics. Micronutrient release Kinetics in soils especially in amended soils give information about potential of amended soils to release these elements into solution. Although it is important to study kinetics of micronutrient release from soils to identify soil micronutrients buffering capacity, little attention has been paid to micronutrients desorption rate studies especially in amended soils. The rate of release micronutrients from soil solid phase by considering micronutrients as adsorbed ions or in mineral forms is an important parameter in nutrition of plants by microelements and a dynamic factor that regulates its continuous supply to growing plants; nonetheless, little attention has been paid to micronutrients kinetics inrelease studies. Material and Methods: In this study, kinetics of zinc (Zn) and copper (Cu) were compared in one calcareous soil amended with 0, 0.5, and 1% (w/w) of manure and vermicompost in a completely randomized design and then amended and un-amended soils were incubated at field capacity, for 30 days. After incubation period, amended and un-amended soils were air-dried and were prepared to kinetics study. Kinetics of Zn and Cu release were studied by successive extraction with DTPA-TEA solution. Two grams of the amended and un-amended soils, in triplicate, suspended in 20 ml DTPA-TEA solution were equilibrated at 25±10C for 1, 8, 24, 48, 72, 96, 120, 144, 168, 336 and 504 h by shaking for 15 min. before incubation and 15 min. before the suspensions were centrifuged. Seven drops of toluene were added to each 1000 ml of extractant to inhibit microbial activity. Zinc and copper desorption with time was fitted by using different equations (Zero-order, First-order, Parabolic diffusion, Simplified Elovich, and Power function). Results and Discussion: Results showed that released Zn in soils amended with manure and vermicompost compared to control soil significantly increased (p0.05) and released Cu in soil amended with vermicompost decreased significantly (

Earthworm Effects on Nitrification Rate and Arginine Amonification in a Calcareous Soil Amended with Urban Sewage Sludge

Introduction: Earthworms are among the most important organisms in soil and their activities can be an indicator of soil quality. These organisms may be influenced by organic wastes application such as sewage sludge and subsequently affect soil quality. One of the quick and easy methods for soil quality monitoring is the use of biological indicators such as microbial activity. It is due to their quick response to changes in the environment. The purpose of this study was to evaluate the effect of earthworms on nitrification rate and arginine ammonification as microbial activity in a calcareous soil amended with urban sewage sludge. Materials and Methods: The studied soil was sampled from Shahrekord University land and sewage sludge belonged to the refinery sludge ponds of shahrekord. Based on dry weight, this organic waste had carbon and nitrogen, approximately 67 and 110 times more than tested soil, respectively. The organic waste in terms of quality and heavy metal concentrations was in class A. Experimental treatments were sewage sludge (without and with 1.5% sewage sludge) and earthworm (no earthworm, Eiseniafoetida from epigeic group, Allolobophracaliginosa from endogeic group and a mixture of the two species) as 2×4 full factorial experiment arranged in a completely randomized design with three replications. After applying sewage sludge, the pots were irrigated three months to achieve a balance in the soil. An adult earthworm per kg of soil was added and in the mixed treatments comparison species were 1:1. To prevent the exit of earthworms, the pots was closed with a thin lace. At the end of the experiment, soil was completely mixed. Part of it was stored in the refrigerator to measure the microbiological parameters. Chemical properties were measured by the air-dried soil. The effectiveness of a factor in the observed changes is shown by partial effect size (Tabachnick and Fidell 2012). So, partial effect size (Eta2p) for each source of variation (SS, earthworm and SS×earthworm) was calculated. Results Discussion: According to Eta2p, the role of sewage sludge application to increase total nitrogen was almost twice the earthworm and had a greater effect on the property. Because of low concentrations of heavy metals and high nutrient in sewage sludge, it increased nitrification rate and arginine ammonification by 16.7 and 62.5 percent, respectively. Considering that the indices represent microbial biomass activity, so we can say sewage sludge application increased theri activities. Sewage sludge application increased total nitrogen, because provided the substrate for heterotrophic bacteria. Consequently, ammonium production improved and stimulated activity of Nitrosomonas and Nitrobacter. There was a positive and significant correlation between total nitrogen, arginine ammonification and nitrification rate, that confirmed the occurrence of this process. Earthworm inoculation affected these two indicators (