Могућности повећања приноса и квалитета биомасе природних травњака брдско-планинских подручја Републике Србије

Abstract

Regardless of their very low forage yields, highland grasslands are extensively cut for hay production. Th e main reasons for low hay yields in these areas include poor quality of the soil used for hay production, inadequate cultural practices, notably fertilization, improper utilization of soil (in meadows – cutting hay too late, in pastures – grazing too early in the spring, and disharmony between the carrying capacity and cattle numbers), high presence of weeds and unfavorable weed species composition. Given their low response to amelioration, highland grasslands must be amended through cultural and other practices as they are the main source of roughage in these regions. Moreover, they play an exceptionally important role in the comprehensive utilization of soil and its protection from erosion. Amendment practices for natural grasslands are more eff ective in lowland good quality soils as they exhibit a good response to management practices in general and fertilization in particular. To improve feed production in these regions, particularly in low uplands at elevations up to 1,000 m, increasing importance is being given to the establishment of sown grasslands. Th e quickest way to improve natural grasslands is through mineral fertilization. Research has shown that hay yields can exceed 8 t ha-1. In production, environmental and economic terms, the main attention should be given to adapting nutrient rates and ratios to each plant community. NPK ratios should be about 3-4:1:1, and NPK rates as follows: 40–120 kg ha-1nitrogen and 30–45 kg ha-1 phosphorus and potassium, respectively. Due to the frequently very low PK levels in the soil, initial rates of P and K fertilizers should be somewhat increased as their eff ect becomes reduced due to partial immobilization. Th e use of a single application of the whole amount of fertilizers in the spring, before the beginning of the growing season, is justifi ed. The floristic abundance of natural grasslands is the result of the presence of numerous species belonging to a range of families and genera. Most grasslands in the hills and uplands have a low presence of Poaceae and Fabaceae species. Mineral fertilizers generally reduce the presence of weed species, while promoting grass development. It would be desirable do transform the grass communities into Agrostietum vulgaris, Festucetum rubrae or their transitional forms. Mineral fertilizers aff ect the chemical composition of forage. Protein levels are generally higher in fertilized grasslands, particularly under nitrogen fertilization. Any increase in nitrogen application rate contributes to increasing protein levels in the dry matter. Th e concentration of phosphorus in the hay is unsatisfactory, and that of potassium is suffi cient in most cases. To justify the economic eff ect of fertilization, knowledge of the production potential of a grassland community is of importance. In highly productive grasslands, the economic eff ects of fertilization are far more pronounced than in low productivity grasslands which have relatively low yield increases. In addition to the impor tance of economic aspects for farmers and end users, special consideration should be given to environment-related aspects. Th e fi rst matter of concern is the loss of nutrients, particularly nitrogen leaching, potentially resulting in water quality deterioration and, hence, subsequent pollution events. Mineral nitrogen fertilization has an important role in ensuring grassland growth conditions. However, the use of a mixture of species, particularly grasslegume mixtures, can be a good option to limit the use of mineral nitrogen fertilizers and, accordingly, avoid adverse side eff ects. Another way to limit the loss of nitrogen is to employ an appropriate grassland utilization pattern, primarily involving the utilization of grasslands for combined cutting and grazing, and adequate grazing periods. Th ere has been an increasing need today to reduce the use of fossil fuels and the emission of harmful gases. Grassland species composition i.e. the presence of legumes off ers the potential to reduce fossil fuel energy consumption, and decrease dietary protein supplementation through reduced nitrogen fertilization. Th erefore, it is important to reach and maintain a high presence of legumes in mixtures, and retain proteins during preservation for storage purposes. Last but not least, grasslands can potentially contribute to preserving the characteristics of the environment through the preservation of biodiversity i.e. the variety of plant and animal species directly associated with grasslands. As regards the preservation of biodiversity, the Serbian policy on the protection and preservation of plant resources (also including natural grasslands) should be harmonized with the EU policy. Importantly, measures to protect and regenerate endangered meadow plant communities in Serbia should be adopted and implemented through “in situ” protection programs, as well as through the inclusion of these habitats in international protection programs.