Laboratory and field evaluation of two extractants (NH4OAc and CaCl2) and determine their suitable concentrations to available potassium for rice plant (Oryza Sativa)
2010
Shokri Vahed,Hassan . | Davatgar,Naser . | Shahdy,Abbas . | Darighgoftar,Farahnaz .
Availability and movement of plant nutrients to roots is mainly controlled by the concentration of the given nutrients. In the case of potassium, it is depending on the equilibrium of in soil solution and the easily and slowly or none exchangeable forms in the soil. Availability of nutrients is mainly affected by the extent of roots, soil moisture, clay and humus content, the soil pH and others. Even with knowing these soil properties, it is rather complicated to calculate the precise potassium requirement of crops through the whole vegetation period. The amount of potassium released to the plants and by various extracting solutions differs greatly. The aim of this research was to determine the available potassium (K) content of the 22 paddy soils of Guilan and most suitable concentration of two chemical extraction method includes CaCl2 and NH4OAc in four concentrations (0.01M, 0.25M, 0.5M and 1M). The treatments included two K levels [0 and 150 kg K2O h-1 as potassium sulfate (K2SO4)] and 22 soils in experiment in a randomized block design. The results indicated that K application increased grain and straw yield, K concentration, and K uptake of rice. Potassium extracted by 1M NH4OAc and 0.25M CaCl2 showed higher correlation with relative yield, straw yield and total K uptake (0.54*,0.56**,0.49*) and (0.54*,0.50*,0.50*), respectively. A multiple stepwise regression analysis model revealed that 93% of K extracted with 1M NH4OAc variation was accounted by K/CEC and Clay. This factor was for CaCl2 56% by CEC.
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