Nitrogen deficiency influences importantly the plant photosynthetic capacity and crop productivity. Here, we employed the rapid, non-invasive measurements of chlorophyll a fluorescence kinetics for calculation of the integrative fluorescence parameters related to the leaf photosynthetic performance. In pot experiments with winter wheat (Triticum aestivum L.) we cultivated plants during the whole growing period in the soil substrate supplied with four different doses of nitrogen. The leaf nitrogen and chlorophyll content as well as the plant dry mass were analyzed after chlorophyll fluorescence records in three growth stages. Our results indicate that the commonly used parameter F v /F m (the maximum quantum yield of photochemistry) was almost insensitive to nitrogen treatment. In contrary, the performance index (PI abs ) and total performance index (PI tot ) were much more responsive and significant differences among plants of different nitrogen treatments as well as between the youngest and third leaf from the top were observed. Parameter PI tot was shown to express only small diurnal changes, thus being more reliable and more useful for comparison of different samples in field conditions than more frequently used parameter PI abs .

ABSTRACT. The progressive increase in the size and weight of farm machinery causes concerns due to the increased risk of soil compaction that arises from non-organized vehicle traffic. Controlled traffic farming (CTF) offers

Nitrogen deficiency strongly influences crop photosynthetic performance and biomass production. In this study, we applied rapid, non-invasive records of chlorophyll a fluorescence kinetics for evaluation of wheat (Triticum aestivum L.) leaf photosynthetic performance. Plants were grown during the whole season in big pots filled with the soil substrate and they were supplied by different doses of nitrogen nutrition. The plant nitrogen and leaf chlorophyll content as well as the plant aboveground biomass were analyzed after chlorophyll fluorescence records in three growth stages. Our results confirmed that the maximum quantum yield of photochemistry frequently used in previous studies was almost insensitive to nitrogen treatment, if measured in young, non-senescent leaves. On the contrary, the performance index was much more responsive. The performance index values derived from parallel measurements in the youngest and third leaf from the top were used to calculate performance index leaf ratio, which correlated well with the plant nitrogen content. Moreover, this parameter was not sensitive to midday depression, which significantly affected the values of other chlorophyll fluorescence parameters. Although the optimum performance index leaf ratio values decreased continuously in the second part of the growing season, the optimum and critical values for each growth stage can be easily identified. Thus, we suggest performance index leaf ratio as the simple parameter for the rapid evaluation of the wheat photosynthetic performance and an early indicator of insufficient nutrition level. Unlike some other approaches, suggested method seems to be useful also in conditions of a moderate nutrient deficiency.

Abstract:The risk rate of sugar beet growing was analyzed by using the algorithm for modelling and generating the random numbers based on the conditions determined in advance and the statistical distribution of sugar beets yield, the total costs, earnings and gross profit. on the bases of results of the analysis of economic risks of sugar beet production in years 1995-2009, it follows that the sugar beet growing in all regions is highly risky in the czech republic. The subsidy SAPS and ToP-UP per 1 hectare of sugar beet have a positive impact on its economics though not sufficient enough. in practice, it means that it is highly probable that the break-even point will not be achieved and thereby it is highly probable that the fixed costs are not covered and the update of machines is significantly limited. This happens mainly in the marginal regions. if the agricultural companies count on the separate sugar payment, the sugar beet growing is in all regions of the czech republic with acceptable risk.

Galambošová J., Rataj V., Prokeinová R., Prešinská J., 2014. Determining the management zones with hierarchic and non-hierarchic clustering methods. Res. Agr. Eng., 60 (Special Issue): S44-S51.Delineation of the management zones of a field is commonly used in precision agriculture technology. There are many techniques used to identify management zones. The most used technique is k-means clustering, where the number of clusters is managed by the user. The paper deals with clustering the yield data and electromagnetic data of a 17 ha field using the Ward's method followed by the k-means clustering method. The cubic clustering criterion was used to determine the number of clusters. Based on results, it can be concluded that it is beneficial to combine the k-means clustering method with the hierarchic method (Ward's method).