Nitrogen Form in Root Nutrition of Sunflower
N. MITREVA and I. MITOVA
Institute of Soil Science and Agroecology "N. Poushkarov", BG-1080 Sofia, Bulgaria
MITREVA, N. and I. MITOVA, 1999. Nitrogen form in root nutrition of sunflower. Bulg. J. Agric. Sci., 5: 877-886
The article reflects the results of testing the influence of fertilizer nitrogen source on dry matter accumulation and assimilation of macro- and microelements by sunflower in field and pot experiments, the cation-anion balance, tissue pH and nitrate reductase activity of the organs, supplied with NO3– and NH4+ in different ratios and concentrations as well as different development stages. The ions NO3– and NH4+ are a basic unit of the system of sunflower plant functioning during assimilation and transportation of other nutrient medium ions to the aboveground plant organs. The maximum supply of NO3-N (pH=5.5) secures larger dry matter accumulation than the maximum supply of NH4-N (pH=7). The application of ammonium fertilizers or nitrification inhibitors right after sowing would be harmful to sunflower.
Key words: sunflower, nitrate, ammonium, absorption