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Effect of varied nitrogen sources and type of cultivation on the yield and physicochemical parameters of flowering Chinese Cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee)
The aim of our study was to determine the effect of various nitrogen sources (NH4NO3 (N, 34%), Ca(NO3)2 (N, 15.5%; Ca, 18%), Mg(NO3)2 (N, 11%; Mg, 12%), NaNO3 (N, 15%; Na, 25%) and urea (N, 46%)) and increasing the intensity of N nutrition with these fertilisers (50, 70, and 90 mg N·dm−3) on the yield and quality of flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee). The plants were grown in two different soilless systems, namely pot cultivation (substrate system—mixture of peat and sand) and hydroponic cultivation. The quality of plants was expressed as macro- and microelement contents, pigment contents, antioxidant activity and phenolic content. It was observed that the yield of flowering Chinese cabbage was about 43–70% higher in the hydroponic system than in the substrate. The N source and N nutrition affected the yield volume. The highest mean yield was observed in pot cultivation after fertilisation with Mg(NO3)2 and in hydroponics with Ca(NO3)2. We found a rather high tolerance of flowering cabbage to sodium and an excessive content of ammonium in the nutrient solution. The nitrogen source and N doses modified plant contents of macro- and microelements (N, P, K, Ca, Mg, Na, Fe, Mn, Zn and Cu) and other quality parameters of plants. In pot cultivation, the highest element contents as well as the highest antioxidant activity were obtained after fertilisation with Mg(NO3)2 at N-70 and N-90. The highest pigment contents (chlorophylls and carotenoids) were obtained in the samples treated with urea at the N-90 dose. Those samples were also characterised by a high Mn content. Generally, the pigment content in the pot system positively correlated with the Mn content in leaves, the microelement which is involved in the process of photosynthesis, but it did not correlate with colour coordinates. In the hydroponic system, the highest pigment contents were observed in the samples treated with Mg(NO3)2 at the N-70 dose. Generally, in hydroponics, chlorophyll levels positively correlated with Ca levels in the aboveground parts of the plants. Additionally, the content of Chl b inversely correlated with L* and b* values. In hydroponic systems, the highest DPPH (2,2-diphenyl-1-picrylhydrazyl) activity was observed after treatment with NH4NO3 at the N-70 and N-90 doses and it did not correlate with phenolic content but rather with pigment content. In conclusion, both the intensity of N nutrition and the fertiliser applied can significantly modify the yield of plants and their quality parameters. For pot cultivation, the most effective fertiliser was Mg(NO3)2 at the N-70/N-90 doses, while for hydroponic cultivation, it is difficult to indicate the most effective fertiliser as the responses varied depending on the method of fertilisation.
Sustainable Use of Organic Matter Obtained from the Bottom of a Post-Mining Pit Reservoir—A Case Study on the Creation of Raduszyn Lake in Poland
According to historical sources, a watermill existed in the valley of the Trojanka River on the north-western shore of Raduszyn Lake from the 15th century. Its dams lasted for centuries causing the water flow through the Raduszyn reservoir to slow down and deposit various mineral fractions in it. The aim of paper was to develop a scientific background for the sustainable management of organic matter extracted from the peat top and from deeper layers that are unsuitable for direct use, that is, decomposed peat. A SWOT (strengths, weaknesses, opportunities, threats) analysis was used to describe ways of restoration of the water reservoir alongside the characterization of organic matter and the financial condition of the studied enterprise. For the use of the studied material as a homogeneous substrate for plant cultivation, the contents of nitrogen, phosphorus, potassium, and copper were insufficient, whilst calcium was excessive. Microbiological analyses of the organic materials intended as an additive for horticultural substrates confirmed the presence of plant growth-promoting bacteria. The occurrence of such microorganisms in the substrate can limit the use of mineral fertilizers and chemical plant protection products. The results of the research can be an example for enterprises restoring or creating water reservoirs by extraction of organic matter, which is often considered as waste that generates costs and does not bring financial benefits. Such a measure can be used to improve the efficiency of water reservoir restoration enterprises and at the same time contribute to sustainable land development.
Application of Salicylic Acid Derivative in Modifying the Iron Nutritional Value of Lettuce (Lactuca sativa L.)
The present experiment addressed the effects of foliar sprays of different iron (Fe) concentrations (mg L−1), i.e., 2.8 (Fe I), 4.2 (Fe II), and 5.6 (Fe III), as well as an ionic derivative of salicylic acid (iSal) in two doses (10 and 20 mg L−1) on lettuce yield, chlorophyll and carotenoids content, and fluorescence parameters. Chemicals were used individually and in combinations two times, 23 and 30 days after the plants were transplanted. This experiment was carried out in a climate chamber. The Fe and iSal applications generally (except Fe I iSal, 10 mg L−1; Fe I iSal, 20 mg L−1; and Fe III iSal, 20 mg L−1) did not influence the fresh and dry matter content. The concentration of chlorophylls and carotenoids was reduced for all treatments in comparison to the control (without spraying). The Fe content in leaves was promoted in the Fe-treated plants (+70% for Fe III + iSal, 10 mg L−1, and Fe I). The iSal treatment promoted the Mn content. For most combinations, the Zn and Cu accumulations, as well as the fluorescence parameters, decreased after the foliar spray applications. Overall, our study revealed the effectiveness of Fe-DTPA chelate, but not iSal, in increasing the Fe content of lettuce grown in soilless cultivation systems.
The Influence of Foliar Nutrition of Apple Trees with Silicon on Growth and Yield as Well as Mineral Content in Leaves and Fruits
Enhancing Lettuce Drought Tolerance: The Role of Organic Acids in Photosynthesis and Oxidative Defense
The aim of this study was to investigate the effects of maleic acid (MA), salicylic acid (SA), and citric acid (CA) on alleviating the drought stress of a lettuce (Lactuca sativa L.) hydroponic culture. The effect of these organic acids was tested under stress conditions induced by polyethene glycol (PEG 6000) at 5% and 7.5% concentrations. Drought stress reduced the fresh and dry matter yields of plants. The acid treatment caused increasing tendencies in the fresh weight yield:control (SA, MA), PEG 7.5% (SA, MA, CA)) and dry weight yield (control (SA, MA), PEG 5% (MA), PEG 7.5% (SA, MA)). The acid treatment also enhanced the nutrient uptake of stressed plants: SA: N (PEG 7.5%), K (PEG 5 and 7.5%); MA: N, P, K, Ca (PEG 5 and 7.5%). This work found that chlorophyll a and b amounts did not change under applied experimental conditions. Most parameters of chlorophyll fluorescence did not depend on either the level of applied water stress (PEG level) or the type of spraying. Drought stress increased leaf superoxide anion (O2•−) and malondialdehyde (MDA) levels but decreased H2O2. Proline (Pro) and phenolic compounds (TFC), including flavonols (Fla), accumulated more in stressed plants. Drought stress also affected the chlorophyll fluorescence. Our results suggest that acids can improve plant tolerance to drought stress by boosting the antioxidant defence system and reducing the oxidative damage caused by reactive oxygen species.