Protective Effect of Humic acid and Chitosan on Radish (Raphanus sativus, L. var. sativus) Plants Subjected to Cadmium Stress

BackgroundHumic acid or chitosan has been shown to increase plant growth, yield and improving physiological processes in plant, but its roles on alleviating the harmful effect of cadmium on plant growth and some physiological processes in plants is very rare. Pot experiments were conducted to study the role of 100 and 200 mg/kg dry soil from either humic acid or chitosan on counteracted the harmful effects of cadmium levels (100 and 150 mg/kg dry soil) on radish plant growth and some physiological charactersResultsCadmium at 100 and 150 mg kg-1 soil decreased significantly length, fresh and dry weights of shoot and root systems as well as leaf number per plant in both seasons. Chlorophyll, total sugars, nitrogen, phosphorus, potassium, relative water content, water deficit percentage and soluble proteins as well as total amino acids contents were also decreased. Meanwhile, cadmium concentration in plants was increased. On the other hand, application of chitosan or humic acid as soil addition at the concentration of 100 or 200 mg kg-1 increased all the above mentioned parameters and decreased cadmium concentrations in plant tissues. Chitosan at 200 mg kg-1 was the most effective than humic acid at both concentrations in counteracting the harmful effect of cadmium stress on radish plant growth.ConclusionIn conclusion, both natural chelators, in particular, chitosan at 200 mg/kg dry soil can increase the capacity of radish plant to survive under cadmium stress due to chelating the Cd in the soil, and then reduced Cd bio-availability

Evaluation of humic substances fertigation through surface and subsurface drip irrigation systems on potato grown under Egyptian sandy soil conditions

The aim of this study was to evaluate the effect of humic substances application in sandy soil under surface and subsurface drip irrigation systems on potato tubers yield quantity, quality, nutrients concentration in tubers and soil fertility after harvesting. For this purpose, field experiment was carried out at the experimental farm of the Agricultural Research Station, National Research Center, El-Nubaria district, Egypt during the winter season of 2007/2008. The used experimental design was split plot design with three replicates, main treatments were presented irrigation systems, i.e. surface and subsurface drip irrigation, while subtreatments were presented rates of humic substances additives which were 0, 60 and 120kgha-1. Results showed that increasing humic substances application rates up to 120kgha-1 enhanced tubers yield quantity, starch content and total soluble solids. The increase of humic substances application rates was associated with the decrease of nutrients leaching, which was reflected on increasing macro- and micronutrients concentration in potato tubers, as well as increasing concentration of these nutrients in soil after tubers harvesting. Subsurface drip irrigation system was found to be more efficient than surface drip irrigation system on improving tubers yield quantity, quality parameters and nutrients concentration content, in addition to soil fertility after harvesting.Humic substance Fertigation Surface drip irrigation Subsurface drip irrigation Potato Sandy soil