A study on the mobility of nitrogen in agro-environmental context
A study on the mobility of nitrogen in agro-environmental context: determination of total nitrogen in Ferrara (Emilia Romagna, Italy) heterogeneous cultivated areas, designated as Nitrate Vulnerable Zone Under the Nitrate Directive (91/676/EEC).
The study has been carried out in order to check total nitrogen content and organic carbon on agricultural soil samples collected within an area near Ferrara, in a nitrate vulnerable zone. Monitored soils have heterogeneous characteristics. Results show that in this context, the majority of the soils have a low content of nitrogen, that decreases with increasing depth, and so, is insufficient for crop needs in place. Only when the samples were taken from peat areas, naturally rich in nutrients, the founded amounts are medium to high. The heavy use of nitrogen fertilizer by farmers is therefore in line with the situation emerged from the study and an intervention is often 'forced' to get the yields required by the market, but this manner causes environmental problems, such as nitrate pollution of surface and underground water. The great mobility of nitrogen compounds supplied in the form of soil, can be attributed to the prolonged use of land which has probably damaged the structure of the soil and the ability to retain the nutrients so that these quickly reach water bodies nearby. Therefore, it was decided to conduct a study on a more specific situation: two sub-channels used for irrigation, near Budrio and Molinella, characterized by the presence of aquatic species Lemna minor have been monitored for eight months. On the two sites water samples have been collected monthly, analyzed and compared by the chemical point of view, in order to know how much the fertilization could influence the concentration of their nitrogen compounds. In combination with these investigations and following the same sampling rate, the presence of duckweed in channels was monitored. When plant sampling was possible, it was analyzed the percentage of total nitrogen content in tissues. This result has been correlated to concentrations of dissolved nitrogen found in water, in order to know any capacity absorption of nitrogen compounds by duckweed. It is complex to give a clear assessment on the data obtained, because the trends are highly variable and it has been impossible to collect data of the last half of the season, which closes the cycle. We can just say that, as on both channels the form of founded nitrogen of greatest concern is the ammonium ion, the presence of duckweed depends largely on water flow and that duckweed can absorb dissolved nitrogen compounds but not enough to affect its concentration significantly.