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Veverka K., Štolcová J., Růžek P. (2007): Sensitivity of fungi to urea, ammonium nitrate and their equimolar solution UAN. Plant Protect. Sci., 43: 157-164.The sensitivity of oomycota, saprophytic and pathogenic fungi to urea, ammonium nitrate and UAN (urea plus ammonium nitrate in equimolar solution) was studied in laboratory trials. The compounds were applied in agar in concentrations of 0.06, 0.19 and 0.6M. The most toxic was urea. Ammonium nitrate inhibited the growth of fungi only in higher concentrations. In contrast, the growth of Gaeumannomyces graminis was stimulated by even the highest concentration of 0.6M ammonium nitrate. The fungi most sensitive to urea and UAN were alternaria tenuissima, Botrytis cinerea, cladosporium cladosporioides and Pseudocercosporella herpotrichoides. No synergistic effect between the two compounds in UAN was found. Urea was toxic also to colletotrichum acutatum which does not produce urease. Likewise, the urease inhibitor NBPT did not decrease the toxicity of urea to fungi; the urea degradation product ammonia should, therefore, not be assumed to be the only toxic agent. Application of urea in agricultural practice can decrease the population of a pathogen not only by the stimulation of antagonists, but also by the direct toxic effect. The tested concentrations of 0.06-0.6M correspond to 0.36-3.6% (w/w) solution of urea and to 0.64-6.4% UAN used in agricultural practice as a 75% water solution. If the dilution and metabolisation under natural conditions is taken into account, the concentration of urea 0.06M (0.36%) was too low to have an effect of practical importance on fungi. While after application of urea on plants or on plant debris its concentration is increasing due to water evaporation, the concentration of the extremely hygroscopic UAN is decreasing. Therefore, the control effect will depend more on the applied rate than on the concentration.Keywords: urea; ammonium nitrate; UAN; fungi; urease inhibitor NBPT The nutrients in both inorganic and organic fertilisers are able to influence the incidence and severity of biotic plant diseases, pests and weeds populations and their impact on the crop. Most of the information on this aspect deals with the effect of nutrients via plant. Individual elements have different roles; in general it can be said that they change the losses caused by pests by influencing plant resistance, alter plant growth and in this way the microclimate in the stand. Increased nutrition used to be prescribed as the first measure to control plant diseases. The most important aspect of this is an increase in the ability of the crop to compensate the losses. The effect of indi-

The field experiment with different soil tillage treatments has been carried out in Prague-Ruzyně locality (Czech Republic) since 1995. Data of two growing cycles in the years 2007-2010 and 2011-2014 were evaluated. Tillage technique was decisive for changes in soil characteristics and crop yields. Bulk density, organic carbon (C org ) and microbial biomass C (C mic ) were more equilibrated throughout all tested soil layers (0-0.1; 0.1-0.2 and 0.2-0.3 m) in conventional tillage (CT). In reduced tillage (RT) and no-tillage (NT) treatments significant accumulation of C org and increase of C mic in the surface layer were found, compared to CT. No significant differences in C org and C mic between two growing cycles were determined; however, mostly higher values were obtained in the top layer of NT during the second growing period. Higher bulk density under conservation tillage techniques did not negatively affect soil characteristics and should be taken in consideration for data evaluation as it can alter interpretation of their changes in the soil profile. Crop yields were comparable in CT and RT. Yield decrease in NT was mostly observed for winter wheat and pea. Beneficial effects of RT and NT conserving soil moisture on crop yield were not observed in dry years.

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The climate changes and increased drought frequency still more frequent in recent periods bring challenges to management with wheat straw remaining in the field after harvest and to its decomposition. The field experiment carried out in 2017–2019 in the Czech Republic aimed to evaluate winter wheat straw decomposition under different organic and mineral nitrogen fertilizing (urea, pig slurry and digestate with and without inhibitors of nitrification (IN)). Treatment Straw 1 with fertilizers was incorporated in soil each year the first day of experiment. The Straw 2 was placed on soil surface at the same day as Straw 1 and incorporated together with fertilizers after 3 weeks. The Straw 1 decomposition in N treatments varied between 25.8–40.1% and in controls between 21.5–33.1% in 2017–2019. The Straw 2 decomposition varied between 26.3–51.3% in N treatments and in controls between 22.4–40.6%. Higher straw decomposition in 2019 was related to more rainy weather. The drought observed mainly in 2018 led to the decrease of straw decomposition and to the highest contents of residual mineral nitrogen in soils. The limited efficiency of N fertilisers on straw decomposition under drought showed a necessity of revision of current strategy of N treatments and reduction of N doses adequately according the actual weather conditions.