No abstract

This paper presents the results of a pot experiment aimed at the assessment of the fertilizer value of struvite, a precipitation product obtained from a liquid fraction of the digestate. The effects of struvite (STR), struvite + ammonium sulphate (STR + N) and ammonium phosphate (AP) treatments were examined on maize and grass cultivation on silty loam and loamy sand soil. The crop yields were found to depend on both the soil type and experimental treatment. Crop yields produced under STR and STR + N exceeded those under the control treatments by respectively 66% and 108% for maize, and 94% and 110% for grass. Crop yields under STR + N were similar or greater than those under the AP treatment. The nitrogen recovery by maize and grass reached respectively 68% and 62% from the struvite and 78% and 52% from AP. The phosphorus recovery by maize and grass reached 7.3% and 4.8%, respectively, from struvite (i.e., STR and STR + N), which was lower than that from the AP (18.4% by maize and 8.1% by grass).

Biogas is an alternative source of energy for fossil fuels. In the process of transforming organic materials into biogas significant amounts of valuable digestate are produced. In order to make the whole process sustainable digestate should be utilized this is a constraining factor in the development of the biogas industry. Consequently, there is an on-going search for new technologies to process digestate, allowing to broaden the range of possible ways of digestate utilization. One of such possibilities is technology of nitrogen (N) and phosphorus (P) recovery from the anaerobic digestate. In this study results of physicochemical analysis of materials flowing through the farm-scale bio-refinery producing struvite (STR) and ammonium sulphate (AS) are presented. Struvite was precipitated from the liquid fraction of digestate (LFDS). Ammonia was bound by sulphuric acid resulting in obtaining ammonium sulphate. The STR obtained was of medium purity and contained other macronutrients and micronutrients that further enhanced its agronomic value. The P recovery effectiveness, counted as the difference between the Ptot content in the material before and after STR precipitation was 43.8%. The AS was characterized by relatively low Ntot and Stot content. The Ntot recovery efficiency reached 43.2%. The study showed that struvite precipitation and ammonia stripping technologies can be used for processing digestate however, the processes efficiency should be improved.

The research aimed at the assessment of N 2 O emission from agricultural soils subject to different fertilization conditions. It was carried out on a long-term experiment field in Skierniewice in Central Poland maintained with no alterations since 1923 under rye monoculture. The treatments included mineral (CaNPK), mineral-organic (CaNPK + M) and organic (Ca + M) fertilization. Measurements were conducted during the growing periods of 2012 and 2013. N 2 O emissions from the soil were measured in situ by the means of infrared spectroscopy using a portable FTIR spectrometer Alpha. N 2 O fluxes over the measurement periods showed high variability with range 0.13-11.20 g N 2 O-N/ha/day (median 2.87, mean 3.16) from mineral treated soil, 0.23-11.06 g N 2 O-N/ha/day (median 3.64, mean 3.33) from mineral-organic treated soil and 0.25-12.28 g N 2 O-N/ha/day (median 3.14, mean 3.55) from organic treated soil. N 2 O fluxes from manure-treated soils were slightly higher than those from soils treated exclusively with mineral fertilizers. N 2 O fluxes were positively correlated with soil temperature, air temperature, and content of both, NO 3 -and NH 4 + , in the soil (0-25 cm) and, to a lesser degree, negatively correlated with soil moisture. Based on the measured N 2 O flux and its relationship with environmental factors it can be concluded that both, nitrification and denitrification the are important sources of N 2 O in mineral soils of Central Poland, where the average soil water-filled pore space during the growing period range from 22-35%. Under the climate, soil and fertilization conditions in Central Poland, the N 2 O emission from cultivated soils during the growing period is approximately estimated as 0.64-0.73 kg N/ha.

Risk aversion is an important research area in the field of agricultural economics in the last years. Creating effective and efficient risk management tools in an increasingly volatile economic and natural environment requires proper recognition of farmers’ behavior and attitudes towards risk. In this context, the main aim of the paper was to estimate farmers’ attitudes towards risk and identification of farm’s and farmer’s characteristics in dependency on risk aversion level. The assessment of farmers’ preferences towards risk was based on hypothetical games in a representative sample of 600 Polish farms—participants of Farm Accountancy Data Network (FADN). Based on the interviews with farmers, a relative risk aversion coefficient has been estimated. Results revealed that on average Polish farmers have quite a strong risk aversion. Their attitudes towards risk are strongly linked with their self-assessment regarding their way of making decisions under risk. Some relations between farmers’ risk aversion and perception of selected risk factors could also be observed. The results revealed that the application of specified risk management tools by farmers and their potential reaction to a significant income drop are related to risk aversion level.