Soil drying combined with nitrogen (N) deficiency poses a grave threat to agricultural crop production. The rate at which nitrate (NO3−) is taken up depends partly on the uptake and transpiration of water. Rapid changes in nitrate assimilation, in contrast to other N forms, may serve as a component of the plant stress response to drought because nitrate assimilation may lead to changes in xylem pH. The modulation of xylem sap pH may be relevant for stomata regulation via the delivery of abscisic acid (ABA) to guard cells. In several factorial experiments, we investigated the interactions between nitrate and water availability on nitrate fate in the plant, as well as their possible implications for the early drought-stress response. We monitored the short-term response (2–6 days) of nitrate in biomass, transport to shoot and reduction in Pisum sativum, Hordeum vulgare, Vicia faba, and Nicotiana tabacum and correlated this with sap pH and transpiration rates (TRs). Cultivation on inorganic substrate ensured control over nutrient and water supply and prevented nodulation in legume species. NO3− content in biomass decreased in most of the species under drought indicating significant decline in NO3− uptake. Hordeum vulgare had the highest NO3− concentrations in all organs even under drought and low NO3− treatment. This species can likely respond much better to the combined adverse effects of low NO3− and water scarcity. Nitrate reductase activity (NRA) was reduced in both roots and leaves of water deficient (WD) plants in all species except H. vulgare, presumably due to its high NO3− contents. Further, transient reduction in NO3− availability had no effect on sap pH. Therefore, it seems unlikely that NRA shifts from shoot root leading to the supposed alkalization of sap. We also did not observe any interactive effects of NO3− and water deficiency on transpiration. Hence, as long as leaf NO3− content remains stable, NO3− availability in soil is not linked to short-term modulation of transpiration.
This investigation was conducted to determine the effect of organic fertilizers on the content of chlorophyll a, chlorophyll b, antioxidant activity, crude fibre, and zinc in two onion cultivars, Stuttgarter Riesen and Rote Laaer, during 2016, 2017, and 2018. In this research, the following treatments were used: B-Stimul (contains Azospirillum Tarrand et al., Azotobacter Beij., Bacillus Cohn, Chlorella vulgaris Beij., and Herbaspirillum Baldani et al.), EkoBooster 2 (contains biostimulators and mineral salts of nitrogen, phosphorus, and potassium) and Vermifit A (extract of compost of Californian earthworm). The results showed that the application of biofertilizers to onion resulted in the highest chlorophyll b content in 2017 in Stuttgarter Riesen. EkoBooster 2 positively affected crude fibre content in both cultivars, but only in 2016. Antioxidant activity was not significantly affected by the interaction of experimental factors. The application of the biostimulating fertilizers can have a positive impact on the quality parameters of onion, but the kind of fertilizer must be suited to seasonal conditions and the cultivar.
The aim of this study was to determine the microbiological activity in soil under beans in organic and conventional production. Organic production was conducted on the field in the village Pivnice (Serbia), while conventional production was conducted in the village Curug (Serbia) during 2014 on the chernosem type soil. Cultivars of beans Belko, Dvadesetica, Maksa, Slavonac, Sremac, Zlatko were used. Before sowing, the bean seeds were inoculated by biofertilizers NS-Nitragin. NS-Nitragin contains a mixture of selected strains of symbiotic bacteria Rhizobium leguminosarum bv. phaseoli. The total number of actinomycetes, ammonifiers, Azotobacter, bacteria and fungi were determined. At the end of vegetation period in conventional production the highest number of actinomycetes (5.83) and fungi (4.87) was recorded in cultivar Dvadesetica. In organic production the highest number of ammonifires was in cultivar Sremac (9.91). The highest number of bacteria was in cultivar Dvadesetica (9.08) and the highest number of fungi was in cultivar Zlatko (5.14). The results have shown that number of microorganisms was higher in organic production.
The present study evaluated the effect of different organic fertilizers on the morphological parameters and yield in two different onion cultivars. Proper use of organic fertilizers in appropriate amounts could be helpful to growers from the economic point of view. Field experiments were conducted to study the effect of three different organic biofertilizers on yield and morphological parameters of two onion cultivars ‘Stuttgarter Riesen’ and ‘Rote Laaer’ during 2016 and 2017. The investigated treatments included: B-Stimul® – a mixture of bacterial and algal extracts, EkoBooster 2® – organic matter and NPK, and VermiFit A® – an extract of compost produced by Californian earthworms, peat, nutrients, plant hormones, enzymes, amino acids, and sugars. The following parameters of onion plants were evaluated: number of leaves, bulb diameter, bulb weight, marketable and total yields. The study showed that all the results were affected by the growing season (higher values were recorded in 2016). In ‘Stuttgarter Riesen’, EkoBooster 2® application resulted in the highest bulb weight in 2016 (67.16 g) and in 2017 (55.17 g) and in the highest number of leaves in 2016 (6.66) and in 2017 (6.30), which led to the highest marketable bulb yield in 2016 (3.47 kg m−2) and in 2017 (2.53 kg m−2). In ‘Rote Laaer’ in 2016, EkoBooster 2® application resulted in the highest number of leaves (7.06), bulb diameter (54.32 mm) and bulb weight (79.30 g). In 2017, the largest bulb diameter (54.13 mm) and the highest bulb weight (71.79 g) and marketable bulb yield (2.39 kg m−2) were determined after VermiFit A® application. EkoBooster 2® showed the best effect on parameters such as the number of leaves, bulb weight, and marketable bulb yield of the cultivar ‘Stuttgarter Riesen’ and positively affected the parameters of ‘Rote Laaer’ during 2016, while in 2017 VermiFit A® showed better results as compared to the other treatments.
This paper describes the influence of organic fertilizers on the content of vitamin C, carotenoids, antioxidants and heavy metals (Cd, Cu, Pb) in two onion cultivars, i.e., "Stuttgarter Riesen" and "Rote Laaer". The experiment was done during 2016 and 2017. Treatments B-Stimul (contains Azospirillum, Azotobacter, Bacillus, Chlorella vulgaris and Herbaspirillum), Ekobooster 2 (contains organic matter and NPK stimulates) and Vermifit A (composition nutrients in immediately acceptable forms, plant hormones, enzymes, extract of compost of californian earthworm) were used. The results showed that the cultivar "Stuttgarter Riesen"at the treatment B-stimul in 2016 reached the highest content of vitamin C (35.4 mg kg-1 and carotenoids (14.6 mg kg-1), while in 2017 the highest content of vitamin C (44.4 mg kg-1) and antioxidants were (4.1 mM TE.100 g-1). The cultivar "Rote Laaer" reached the highest content of carotenoids in both years in the treatment Ekobooster 2, 7.5 mg kg-1 (2016) and 22.8 mg kg-1 (2017). In 2016, control showed the highest content of vitamin C (17.5 mg kg-1) and antioxidants (18.5 mM TE. 100 g-1). In both years and in both cultivars, the content of Cd and Pb was in line with European law, and the content of Cu was lower than those recommended by EU standards.
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