The administration of large quantities of chemical fertilizers may strongly diminish the plant diversity of semi-natural grasslands. In the Apuseni Mountains (Romania), the chemical fertilization is rarely used, but, considering the population’s decrease and the livestock diminish, this might have a greater importance in the future. The maintenance of semi-natural grasslands within the mountainous landscape depends greatly on fertilization. Our paper’s goal is to assess the influence of mineral fertilizers upon semi- natural grassland’s plant diversity. Mineral fertilizers complex NPK 20:10:10 ratio was applied in three quantities: 50N 25P 25 K, 100N 50P 50K, and 150N 75P 75 K. The large quantities of mineral fertilizers generated a considerable decrease of the plant diversity.

More accentuated intensi ication of management from areas with high biodiversity may act to reduce the level of mycorrhizal colonization, while producing a reduction in plant resistance to stress factors. In the context of current climate drought is an common phenomenon, and depreciation of hyphal networks produced by mycorrhizae in root systems of plants increases their susceptibility to drought. In these circumstances, application of zinc over fertilization can increase the mycorrhizal colonization with increasing plant resistance to drought. The main objective of this paper was to analyze the potential for stabilization of colonization based on zinc application as a base for grassland ecosystems balance preservation under changes in the way of fertilization applied to these surfaces. The level of colonization was analysed in roots of Festuca rubra, during 2010-2011, samples being collected from an experiment with 6 graduations of mineral and organic fertilization located in Garda de Sus village, on each variant being additionally applied a zinc sulphate treatment. Application of zinc sulphate over fertilization with manure acts to reduce the level of frequency of colonization in the root system of plants of Festuca rubra, at the end of the growing season. At the same sampling period, a similar phenomenon is recorded under conditions of Eurofertil mezocalc fertilization. The intensity of the colonization varies greatly under the experimental conditions, higher values were observed at the end of the growing season for fertilization based on chemical nitrogen. During the period of plant maximum activity successful fertilizer recipes were without chemical nitrogen supplements in 2010, and NPK fertilization in 2011, these options ensuring the highest levels of colonization intensity.

The maintenance of semi-natural grasslands within the mountainous landscape is deeply influenced by fertilization. Application of fertilizer will cause changes in the chemical composition of the plant and will increase the palatability, decreasing the denials. One should apply fertilizers taking into account the way of exploitation of the grassland. If the grasslands are grazed, much of the nutrients return into the meadow by manure, fattening being more important than on mowed lawns where all the nutrients taken from plants are exported. The aim of this paper was to assess the influence of organic and mineral fertilizers upon semi-natural grassland’s plant diversity on different soil types. The research was carried out in Apuseni Mountains, in an experimental field with one experience with organic fertilizers  ( T1 control, T2 10 t ha-1manure, T3 20 t ha-1 manure, T4 30 t ha-1 manure ) . Mineral fertilizers complex NPK 20:10:10 ratio was applied in three quantities: 50N 25P 25 K, 100N 50P 50K, and 150N 75P 75 K. The results showed that the largest quantities of mineral fertilizers generated a considerable decrease of plant diversity. For future management actions that are meant to maintain plant diversity in Apuseni Mountains, the organic fertilization with 10 t ha-1 manure quantities administrated annually or once on two years. In conclusion is justified to make organic treatments on Preluvosol Rodic soil type and mineral treatments on Eutricambosol Rendzinic soil type.

In general, in the West European countries, countries with a developed growing animals sector, the surfaces covered by seeded meadows is in continuous growth (Rotar,2010,2011). Carlieretal. (1998), underlines the fact that seeded meadows have valuable attributes, unequaled by those registered by other forage crops.  Among these stands, first of all, the high yields, this can be 3-5 times larger than those achieved by permanent grasslands. Our study followed the behaviour of Medicago sativa and Bromus inermis  fertilized with gulle and manure, on an experience located in Cobatesti village, Odorheiul Secuiesc area. Our experience was installed after the subdivided parcels method, on a loamy soil. The mixture showed different reactions, according to the type of fertilizer applied. The highest yield registered on the experiences fertilized with manure was 12.59 t/ha DM, when 30 t/ha manure were applied, and the highest yield registered on the experiences fertilized with gulle was 14.26 t/ha DM, when 5 t/ha gulle were applied.The mixture consisting in Medicago sativa and Bromus inermis showed to be very productive and suitable for drought areas.

Organic fertilizers have an influence on the floristic composition of grasslands. Fertilizing with manure favours the phytodiversity of grasslands. The objective of the study was to follow the influence of mulching and organic fertilizing in small quantities and at various time intervals upon dry matter yield and phytodiversity of Agrostis capillaris L. - Festuca rubra L. grassland type in the Apuseni Mountains. Seven treatments  ( witness  ( mowed 1/year ) ; mulch 1/year; mulch 1/year + 5 t/ha manure /year; mulch 1/year + 5 t/ha manure/2 years; mulch 1/year + 10 t/ha manure/2 years; mulch 1/year + 10 t/ha manure/3 years; abandonment )  were evaluated experimentally. Organic fertilizing in low quantities could be a way to maintain the floristic diversity of oligotrophic grasslands in Apuseni Mountains.