Determination of Nan contents in wet and dry soil samples and their relation to yield of sunflower | Stanovenie obsahov Nan v mokrej a suchej vzorke pôdy a ich vzťah k úrode slnečnice ročnej

The field experiment was performed on the brown soil with slight-acid to neutral soil reaction and medium content of Nan in locality of Velké Ripňany. Impact of natural drying of soil samples on Nan content in the soil and sunflower seed yields was investigated. The relationship between determined Nan content and production characteristics (achene yields, thousand seed weight), respectively, was examined by linear regression analysis. Values of Nan content in soil at the beginning of vegetation (BBCH 14-16) showed a positive correlation with yield of sunflower and thousand seed weight. Higher content of Nan in soil in the later growth stage (BBCH 35-38) significantly decreased yields of sunflower. However, it was caused mainly by increased content of N-NO3+. The relationship between content of NU determined in dry soil at the beginning of vegetation and achene yields and thousand seed weight, respectively, was stronger than the samé relation when Nan was determined in a fresh soil sample sampled at the samé time. Conversely, the relationship (correlation) between content of Nan determined in dry soil in the later growth stage to yield of sunflower seeds was negative. The fresh soil sample was found to be more suitable than dry soil sample for the Nan content determination serving for calculation of nitrogen fertilizer rates suitable for sunflower growing on the soil where there the mineralization effect is low. As a result the higher rates of nitrogen fertilizers will be calculated. Oppositely, when sunflower is grown on fertile soil with high microbiological activity sufficient amount of Nan will be released during vegetation period and in this čase the dry soil sample will be more appropriate for Nan and nitrogen rate determination. In opposite to the above stated situation, this calculation will result in lower nitrogen rate determination.