Eureka! Institutional Repository

The absence of a sufficient number of studies on the release rate of macronutrients (N, P, K) from Control Release Fertilizers (CRF) or Zero Loss Fertilizers (ZLF) is an important field for research. Their technical characteristics given to the user are the laboratory rate of release of their nutrients which is quite different from that in the field, since the soil and climate conditions are not taken into account. This postgraduate dissertation aims at studying the duration and rate of macronutrients release when using stabilized fertilizers under agronomic techniques. To achieve this goal a comparative study of a granular fertilizer (urea) used as a control in relation to five different zero-loss fertilizers was carried out in two different crops. During the 2018 cultivation period, a Randomized Complete Block Design with four replications experiment was installed in 5-liter pots and studied in a greenhouse of International Hellenic University (Sindos, Thessaloniki). The experiment consisted of two different crops of large biological cycle (corn and cotton). The treatments included the same doses of fertilization units for each crop, on a poor nutrients soil, with regular irrigation and one-off fertilization during sowing. After six soil samplings, which started one month after sowing and were carried out every twenty days, NO3-N, P and K were determined in the soil science laboratory of IHU. Data analysis was performed in the IBM SPSS 24 statistical program. The soil analysis gave the following results: nitrate nitrogen concentrations were not significantly different between applied fertilizers (treatments), the lowest phosphorus concentrations were observed in control (urea 46-0-0) without existing important differences between the rest of treatments, while the highest potassium concentrations were noticed in the treatments of 24-6-12+Β+Zn fertilizer with nitrification and urease inhibitors and without existing important differences between the rest of treatments. Crucial factor of the rate of macronutrients’ release from zero loss fertilizers, seems to be the temperature.