Uticaj ozimih međuuseva na dinamiku mineralnog azota, prinos i kvalitet silažnog kukuruza / The influence of winter cower crops on the dynamics of mineral nitrogen, yield and quality of silage corn

A modern agricultural production must respond to increasing demands in terms of environmental protection, reduction of production costs and an increased demand for high quality, safe and healthy products. In such conditions, one of the responses of agricultural producers to the challenges posed is also cultivation of winter cover crops, because they can provide different advantages in agricultural production in terms of ecology and production. Therefore, the aim of the research is to examine which plant species can be cultivated as winter cover crops in our agroecological conditions, their impact on the soil, the benefits of their application as animal feed or green fertilizer, and the impact they have on the subsequent crop. The field experiment was conducted on three locations using the random block design with replications. The research was carried out in two production cycles, from October 2011, when the winter cover crops were sown, to September 2013, when corn was reaped for silage. Herbaceous species used for winter cover crops are hairy vetch (Vicia vilosa Roth., variety NS-Sirmium), winter triticale (x Triticosecale Wittm. Ex A. Camus, Odyssey variety) and their mixture. In addition to variants with winter cover crops, variants with fertilization with mineral nitrogen according to the N-min method up to 120 kg/ha of nitrogen (N1) and up to 160 kg/ha of nitrogen (N2), as well as a control, are included in the field experiment. Winter cover crops sown in the first block were used for fodder, while the winter cover crops sown in the second block were ploughed. Depending on weather conditions of the tested plant species and their mixture grown as winter cover crops, they can achieve high yields. Their ploughing can significantly improve the content of mineral nitrogen in soil and provide a significant increase in voluminous fodder production in farms. The dynamics of mineral nitrogen in soil is highly dependent on winter cover crops and the nitrogen content is the lowest after their harvest. Out of the tested species, the highest nitrogen uptake was by triticale, then winter forage mix and the smallest by winter vetch. In the period from sowing to harvest of silage corn, the content of mineral nitrogen in soil increases with all treatments. The content of mineral nitrogen at the end of the vegetation is higher with treatments where the green mass of the cover crops were taken away from the plot. However, the remaining quantity of nitrogen (ARNS) after corn harvest was, statistically speaking, significantly higher in treatments where winter cover crops were ploughed, from the treatment where they were taken away from the plot and ranges from 66 to 150 kg N ha-1 ; the largest nitrogen content was measured after winter forage mix. The green mass yields of corn in subsequent sowing after winter cover crops are lower compared to fertilized variants and the control and range from 6.6 t ha-1 to 22 t ha-1 , while the quality of silage meets the energy potential, as well as the content of proteins and minerals for quality livestock feed on farms.