Nur Okur

Evolution of enzyme activities during composting of tobacco waste

Main characteristics of tobacco waste generated during the processing of tobacco for cigarette manufacture are a high content of nicotine and total organic C. Composting is a way for decreasing the levels of nicotine and total organic C in tobacco waste and for disposal of this kind of agro-industrial waste. Changes in pH and electrical conductivity and activities of dehydrogenase, protease, alkaline phosphatase and β-glucosidase were determined during composting of tobacco waste (TW) and mixtures of TW + grape pomace (GP) and TW + olive pomace (OP). The nicotine in the tobacco waste was completely decomposed by composting. In the final composts, total organic C content and C : N ratio decreased, whereas the contents of total N, P and K increased. The pH of the composts increased rapidly at first and then more slowly and the electrical conductivity first decreased and then increased during composting. Mixing the tobacco waste with the other compost materials decreased the electrical conductivity level by 32 and 46% in the final TW + GP and TW + OP composts, respectively. The highest activities of the studied enzymes were observed on the third week of the composting process for dehydrogenase, the fifth week for protease and β-glucosidase and the ninth week for alkaline phosphatase. All enzyme activities stabilized about in 4 months.

Effect of organic manure application and solarization on soil microbial biomass and enzyme activities under greenhouse conditions

ABSTRACT The temporal behaviour of soil microbial biomass C (SMBC) and the protease, urease, phosphatase and dehydrogenase activities were measured in the organic production of tomato and cucumber crops under greenhouse conditions. Soil was fertilized with either farmyard manure or poultry manure. Manures were applied either alone or with two biological preparations, E2001 and Allgrow Bioplasma. The effect of solarization on microbial activity was also studied. Soil samples were taken three times in each growing season. Activities of protease, urease and phosphatase decreased by 26% and dehydrogenase by 50% after solarization. In both crops, the highest amounts of organic C and SMBC were determined in soils with applied poultry manure. Protease and urease activities showed a strong increase after the first manure application. After the second manure application, enzyme activities stabilized at lower levels than in the first 6 months. Low temperature in the winter season may have limited phosphatase activity. Dehydrogenase activity was very low in all treatments, probably because the greenhouse soils were intensively fertilized with nitrogenous fertilizers before the experiment. Among the organic sources used, poultry manure had a long-term effect on enzyme activity.

A comparison of soil quality and yield parameters under organic and conventional vineyard systems in Mediterranean conditions (West Turkey)

Soil chemical and microbial parameters are commonly used as soil quality indicators to evaluate sustainable land management in agroecosystems. The objective of this research was to evaluate the impact of organic and conventional management strategies on biological, chemical and yield parameters in vineyards (Vitis vinifera cv. Sultani seedless). Organic plots received a mixture of barley, vetch and broad bean (25+35+75 kg seed ha− 1) as green manure, and farmyard manure (15 t ha− 1) every year. Inorganic fertilizers (NPK) and pesticides were used in the conventional managed vineyards. Conventional and mulch tillage methods were used in conventional and organic plots, respectively. Microbiological and chemical soil properties were determined in the soil samples which were taken four times in 2004, 2005, 2006 and 2007. In addition, the yield and some quality parameters of vineyards were also determined. Soil microbial biomass, and dehydrogenase, β-glucosidase and alkaline phosphatase activity were significantly higher in organic management than in conventional management. Higher Cmic/Corg and lower qCO2 values were found with the organic management. The response of the chemical indicators (Corg, Nt and available nutrient content) of the soils to different management systems appeared after a longer time than with the biological indicators. In the transition zone between continental and Mediterranean climates of West Turkey, soil quality of organically managed vineyards improved after 2 years of the transition period prescribed for organic certification. However, soil quality improvements in organic plots did not result in higher yield.