The nutrient management plan at farm level.

At European level, people and policy makers are very concerned with environment issues, one of the main problems being the nitrates contamination of groundwater. The agricultural activities are the main nitrogen supply in soil, due to the application of the mineral and organic fertilizers doses. In the last decades, worldwide there was an increasing tendency for using nitrogen based fertilizers, being well known that it represents an essential nutrient for conservation and/or amelioration the soil fertility state and for agricultural production, which has to satisfy the food needs of increasing population. The presence of the high nitrogen concentrations, exceeding the maximum admissible concentrations may have a negative impact of the environment through the possible losses in the ground and surface waters and/or atmosphere. In order to optimize the crop production and avoid the environmental contamination with nitrates, a nutrient management plan (NMP) at farm or village level has been developed. The need of such a tool is given by the fact that the polluted groundwater, mostly in the nitrates vulnerable communes (NUTS4 level), is used for potable water through the public or individual wells, most of them being placed not far from households. The management plan for (organic and mineral) nitrogen fertilizers is based on the description of N cycle in soil-planthydrosphere system, taking into account the following soil N forms: inorganic nitrogen (nitrates), organic nitrates from vegetal residues incorporated in soil, organic nitrates in active and stable form associated with soil humus stock, organic nitrates from organic manure. The nitrogen alteration processes between different N forms (humus mineralization, vegetal residues decomposition and the associated mineralization, denitrification and immobilization) are described through equations for chemical kinetic associated, the reaction speed being influenced by temperature, soil moisture, and the different nitrogen amount from each form types. Mineral nitrates flux percolating under the roots depth (leaching) is calculated as function of water drained flux and average nitrates concentration on soil profile. The nutrient management plan application has been developed as a MS Excel file, using VBA language. The NMP components, its inputs and outputs data, and the main worksheets are described. A case study for a commune is presented, highlighting the accessibility of the application and its usefulness for the farmers and other local stakeholders, as well as for local authorities. Rezumat: La nivel European, publicul larg si factorii politici sunt preocupati de problemele de mediu, una din cele mai importante fiind contaminarea cu nitrati a apelor freatice. Activitatile agricole sunt principalul contributor al azotului din sol, datorita aplicarii fertilizantilor minerali si organici. In ultimele decenii, peste tot in lume a crescut tendinta de a utiliza fertilizanti pe baza de azot, deoarece acesta este un nutrient essential pentru conservarea si/sau ameliorarea starii de fertilitate a solului si a recoltei, care trebuie sa satisfaca necesitatile hrana ale unei populatii in crestere. Prezenta unor concentratii ridicate de azot, peste maximul admisibil poate avea un impact negativ asupra mediului prin posibilele pierderi catre apele de suprafata si de adancime si/sau atmosfera. Pentru a optimiza recolta si pt a evita contaminarea mediului cu nitrati, a fost dezvoltat un Plan de Management al Nutrientilor la nivel de ferma. Nevoia dezvoltarii unui astfel de plan a fost data de utilizarea apei freatice, mai ales in comunele vulnerabile la nitrati ca apa potabila, prin fantanile publice sau individuale, multe din acestea fiind plasate in apropierea grajdurilor. Planul de management al fertilizantilor (organic si minerali) se bazeaza pe descrierea ciclului de azot in sistemul sol-plantaatomosfera), prin luarea in consideratie a mai multor forme de azot: azotul anorganic (nitratii), Research Journal of Agricultural Science, Vol. 41 (2), 2009 93 azotul organic din reziduurile vegetale incorporate in sol, azotul organic in forma activa si stabile asociate cu rezerva de humus, precum si cel din gunoiul de grajd. Procesele de alterare a azotului intre diferitele forme (mineralizarea humusului, descompunerea rezidurilor vegetale si mineralizarea asociata, denitrificarea si imobilizarea) sunt descrise prin ecuatii chimice, viteza de reactie fiind influentata de temperatura, umiditatea din sol, si de cantitatea diferita de azot in diverse forme. Fluxul de nitrati minerali care percoleaza sub adancimea de inradacinare este calculat ca functie de fluxul drenat de apa si de concentratiile medii de nitrati pe profilul de sol. Planul de management al nutrientilor a fost realizat ca o aplicatie intr-un fisier MSExcel, utilizand limbajul VBA. Sunt descrise in lucrare componentele NMP, datele de input si output, precum si principalele worksheet-uri. Este prezentat un studiu caz pt o comuna din judetul Timis, evidentiind accessibilitatea aplicatiei, precum si utilitatea pentru fermieri si alti stakeholder locali, ca si pentru autoritatile locale.