Effect of zeolite, clay and peat on salt stress tolerance of lettuce (Lactuca sativa L.)

A. Karlsons* and A. Osvalde

Institute of Biology, Faculty of Medicine and Life Sciences, University of Latvia, 4, O. Vaciesa Street, Riga, LV−1004, Latvia
*Correspondence: andis.karlsons@lu.lv

Abstract:

The present study aimed to investigate the effects of natural zeolite, clay and peat amendments on the growth and NaCl absorptions of lettuce (Lactuca sativa L.) under gradually increasing salinity. Four different growing media based on quartz sands with 10% additions of zeolite, clay and peat were tested. The worst effect of NaCl on plant biomass was evident at the highest salinity levels for zeolite applications. While adverse salinity impact on leaf and root biomass was least pronounced in treatments with peat additives. As expected, the lowest Na concentrations in plant tissues were found in the growing media supplemented with zeolite. In the case of Cl, however, it was the opposite – lettuce leaves accumulated significantly higher chloride concentrations in the zeolite variants in salinity treatments above 20 mM NaCl. In the control, clay and peat treatments, as the substrate salinity increased, the Cl level in the plant increased similarly. Adverse changes in leaf chlorophyll concentration (SPAD) and photosynthetic rate (µmol m^-2 s^-1) parameter appeared under salinity concentrations above 20 mM and were more pronounced in zeolite and sand substrate. According to the obtained results, peat additives can effectively mitigate the harmful effects of excessive salts by binding and immobilizing them as well as improving the water-holding capacity and nutrient availability. The study also concluded that natural zeolite successfully immobilizes cationic sodium, but the harmful effect of chlorine significantly reduced plant growth and photosynthetic performance. Clay additives to the growth medium showed the potential to reduce the adverse effects of salinity on lettuce, however, under the experimental conditions implemented, the effect was small.

Key words:

The dependence of COx and NOx emission concentrations on the excess air coefficient during combustion of selected agricultural briquetted by-products

J. Malaťák*, J. Bradna and J. Velebil

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: malatak@tf.czu.cz

Abstract:

The issue of CO, CO₂ and NO_x emissions is very extensive and important. The aim of the paper is the experimental determination of the CO, CO₂ and NO_x emission dependencies on the amount of excess air. Materials used for the experiments were several types of briquetted biomass. Crops used were Czech knotweed (Reynoutria × bohemica), Rumex hybrid OK 2 (Rumex patientia × Rumex tianschanicus), meadow hay and timothy grass (Phleum pratense). For all samples proximate and elemental analyses were performed (semiautomatic calorimeter LECO AC-600 elemental analyser CHN628 + S and analyser LECO TGA-701) and stoichiometric calculations of combustion were made. Combustion device used in combustion tests was a hot air stove with a grate fireplace and with manual fuel supply. The combustion process was monitored by analyser Madur GA-60. Parameters monitored during the combustion tests were primarily the flue gas temperature and the emission levels of carbon monoxide, carbon dioxide and nitrogen oxides.
Analyses and calculations of plant biomass samples indicate their good properties for energy use. The gross calorific value was as high as 19.55 MJ.kg^-1 in the sample of Rumex OK 2. Limiting factor is the high quantity of ash in plant material. The briquettes from timothy grass achieved 5.77% wt. ash in the dry matter. The excess combustion air had positive influence during combustion test. On the other hand, this caused heat loss by departing flue gases, wherein the flue gas temperature reached high values. The excess air coefficient also significantly affected the emission levels of carbon dioxide and monoxide and nitrogen oxides in the flue gases. Results were statistically analysed and complemented by regression equations, which in practice can be used to optimize the combustion process in boilers with manual fuel supply.

Key words:

calorific value, combustion device, combustion gases, heat loss, plant biomass