Differential Responses in Potassium Absorption and Use Efficiencies in the Halophytes Catapodium rigidum and Hordeum maritimum to Various Potassium Concentrations in the Medium

The changes in biomass production, root length, mineral nutrition, potassium absorption efficiency (KAE), and potassium use efficiency (KUE) of the halophytes Catapodium rigidum and Hordeum maritimum in response to potassium availability were assessed under natural conditions. Plants were cultivated in the greenhouse of the experimental station of the Biotechnology Centre of Borj Cédria (a Mediterranean coastal area) 30 km south-east of Tunis for four months from the autumn to winter of 2007–2008. H. maritimum biomass production was not significantly affected by the K+ concentration, but C. rigidum growth was increased significantly with increasing K+ concentration in the medium. Root/shoot dry weight ratio remained constant in C. rigidum, but decreased significantly at 1000 and 3000 µM K+ in H. maritimum. KAE increased but KUE decreased significantly with increasing K+ concentration in the medium in both species. However, KAE was higher in H. maritimum than in C. rigidum showing a contrasting response to K+ concentration between the two species. Overall, the maintenance of a cationic balance may be explained by cation antagonism. The lower K+ requirement of H. maritimum to express its optimal growth can be attributed to its higher efficiency to acquire and transfer K+ to shoots

Effects of two composts and two grasses on microbial biomass and biological activity in a salt-affected soil

The effectiveness of compost supply at several doses (0, 50, 100, and 150 t/ha) to a saline soil was studied using municipal solid waste (MSW) and palm waste (PW) composts. The experiment was carried out in pots under cultivation of Polypogon monspeliensis (halophyte forage species) and Hordeum vulgare (common forage species) and lasted three months. The investigation focused on some selected soil physico-chemical properties, soil microbial biomass, and ten soil enzymatic activities; Arylsulfatase (ARY), dehydrogenase (DEH), β-glycosidase (β-GLU), protease (PRO), urease (URE), invertase (INV), Fluorescein diacetate hydrolase (FDAH), catalase (CAT), acid and alkaline phosphatases (PHO). Both amendments improve markedly the saline soil quality. They ameliorate the physico-chemical properties. The increase of soil pH is regarded as an interesting fact and is usually proportional to the compost application rate. Electrical conductivity increased proportionally to the applied rates. Soil carbon and nitrogen amounts were also improved and the highest raise (7.5-folds) was noted for carbon. According to the substantial increase of the organic matter, levels of measured microbial biomass and several enzyme activities in saline soil were improved. DEH activity which proposed as a measure of overall microbial activity exhibited a significant increase only at dose 2 (100 t/ha). Consequently, One hundred tones of composts per hectare, under which some enzymes exhibited an optimal of activity and metal accumulation can be minimized, appeared an interesting rate for saline soil amendment

Effects of 5-year application of municipal solid waste compost on the distribution and mobility of heavy metals in a Tunisian calcareous soil

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