Attila Tomócsik

Digestate: A New Nutrient Source - Review

Digestate contains a high proportion of mineral nitrogen (N) especially in the form of ammonium which is available for plants. Moreover, it contains other macroand microelements necessary for plant growth. Therefore the digestate can be a useful source of plant nutrients, it seems to be an effective fertilizer for crop plants. On the other hand, the organic fractions of digestate can contribute to soil organic matter (SOM) turnover, influencing the biological, chemical and physical soil characteristics as a soil amendment.

Changes in physical properties of sandy soil after long-term compost treatment

Abstract Studying the long-term effect of composted sewage sludge application on chemical, physical and biological properties of soil, an experiment was established in 2003 at the Research Institute of Nyíregyháza in Hungary. The applied compost was prepared from sewage sludge (40%), straw (25%), bentonite (5%) and rhyolite (30%). The compost was ploughed into the 0-25 cm soil layer every 3rd year in the following amounts: 0, 9, 18 and 27 Mg ha−1 of dry matter. As expected, the compost application improved the structure of sandy soil, which is related with an increase in the organic matter content of soil. The infiltration into soil was improved significantly, reducing the water erosion under simulated high intensity rainfall. The soil compaction level was reduced in the first year after compost re-treatment. In accordance with the decrease in bulk density, the air permeability of soil increased tendentially. However, in the second year the positive effects of compost application were observed only in the plots treated with the highest compost dose because of quick degradation of the organic matter. According to the results, the sewage sludge compost seems to be an effective soil improving material for acidic sandy soils, but the beneficial effect of application lasts only for two years.

EFFECT OF A BIOGAS-DIGESTATE AND BENTONITE ON SOME ENZYME ACTIVITIES OF THE AMENDED SOILS

Almost all the measured soil chemical parameters have been changed on the treatments, and this complex alteration has an apparent influence on the enzyme activities, studied. Among the three enzymes, however not all proved to be sufficient for the soil characterization or to estimate the soil fertility level, like to earlier findings of Trasar-Cepeda et al. (2000). The applied digestate seems to be favourable only for the dehydrogenase activities, while the other two enzymes have higher activities more particularly in the water-treated soil samples. The application of both the digestate and the bentonite has enhanced on the other hand simultaneously the crop yield (data not shown). In a short term bases there are positive (i.e the incresing pH level), and negative (i.e Na-content increase) changes in soil characteristics. Soil is a continuously changing, complex, multifactorial system, further studies are necessary, therefore to understand the short and long-term effects of the used soil amendments, and their consequences on the most-typical soilbiological parameters.

Effect of a Long-Term Compost Treatment on the Water Management of Sandy Soil

Background: The large part of sandy soils in Hungary has unfavorable water management properties. Studies have shown that the sewage sludge compost, due to its high organic content, is suitable for improving structure and water management of these soils. The aim of our study was to determine the effects of the application of sewage sludge compost on physical properties of sandy soil. Materials and Methods: The experiment was established in 2003 at the Research Institute of Nyíregyháza of the University of Debrecen in Hungary to study the utilization of sewage sludge compost in agriculture. In this study, however, the changes of water retention and erodibility of soil were measured for three periods. The soil type of the experiment is Arenosol (Dystric Lamellic Arenosol). The applied compost contained sewage sludge of 40%, straw of 25%, bentonite of 5% and rhyolite of 30%. The compost is applied every 3 year in the following amounts: 0, 9, 18 and 27 Mg ha of dry matter. Results: The compost treatment had a beneficial effect on soil structure thereby reducing the runoff and sediment loss under high intensity rainfall (130 mm h). However, in the control plot there was significantly higher water erosion. The water retention of soil was slightly increased after compost application. Conclusions: The compost application improved the water management properties of sandy soil, which is connected with organic matter addition into soil. The compost treatment had a beneficial effect on soil structure thereby reducing the runoff and sediment loss.

EFFECT OF SEWAGE SLUDGE COMPOST TREATMENT ON CROP YIELD

Due to the increasing number of sewage cleaning plants, the amount of sewage sludge also increases. We have to solve the environmentally sound disposal of the sludge. Results of many experiments show that sewage sludge and sewage sludge compost can be recycled as nutrient suppling material in agriculture. Municipal sewage sludge compost could cause the occurrence and accumulation of toxic elements in the soil. A small-plot experiment with sewage sludge compost was established in the spring of 2003. The applied compost contains 40% sewage sludge, 25% straw, 30% rhyolite, 5% betonite. The small-plot experiment was retreated in the autumn of 2006, 2009, 2012and 2015. There are 4 treatments in five blocks, where the sewage sludge compost was applied at a rate of 0, 9, 18 and 27 tha-1 and then ploughed into the soil. Triticale as autumn cereal, maize and green pea as spring crops were sown in crop rotation every year. Plant samples were collected before harvesting. In this paper the results of crop yield between 2010- 2012 are presented. Crops of triticale and maize were higher in the treated plots than in control one in 2010 and 2011. Treatment effect was not observed on green pea yield.The results show that the effect of applied compost doses depends on plant species and time. Our aim is to maintain this unique long-term experiment for studying the composted sewage sludge as a nutrient and organic matter source, applying it similarly to the farmyard manure.