Symposium no. 14 Paper no. 973 Presentation: poster 973-1

Thirty soils from several areas of Northern Greece were investigated. The available reserves and release K characteristics were determined in soils grown with ryegrass for 335 days and by continuous leaching of the soils with 0.01 N HCl. The available K reserves of the soils ranged from 346 to 2,058 kg ha under ryegrass and from 603 to 3,211 kg ha under continuous leaching, respectively. The rate of release of nonexchangeable K from soils ranged from 27 to 913 kg K ha , and 2/3 of the soils released the non-exchangeable K at a rate < 400 kg K ha . The total amount of potentially available K of the soils taken up by ryegrass , during the 335 days of experimentation, averaged 3% of the total potassium. The HCl-extractable K yielded a high correlation with the total K-uptake (r=0.90 ). The information on the rate of release of non-exchangeable K can be used as an index for the time period needed to cover the available reserves and as a measure for comparing soils with respect to their capacity to supply crops with non-exchangeable potassium

Symposium no. 28 Paper no. 360 Presentation: poster 360-1

Ten surface soils belonging to orders viz., Vertisol, Inceptisol (mixed red and black) and Alfisol derived from diverse parent materials from major sugarcane growing areas of North Karnataka were considered to study the distribution of different forms of potassium and mineralogical composition of clay. The range in contents of various forms of potassium in different soils was 2.0 to 24.20 mg kg of water soluble K, 175.50 to 429.00 mg kg of exchangeable K, 150 to 1250 mg kg of non-exchangeable K ,175 to 450 kg ha of available K, 0.51 to 3.25% of lattice K and 0.58 to 3.3% of total potassium. The soils in general had contained medium to high available potassium with large total K reserve. The soil clays were dominantly smectitic in Vertisols and kaolinitic in Alfisol and Inceptisol. Inceptisol alone had recorded the presence of vermiculite (8.5%) and interestingly one of the Vertisols had contained almost equal amounts of kaolinite and montmorillonite. The potash bearing mineral mica was noticed in all the soil clays. Invariably, all Vertisols had contained about 10.0 percent kaolinite in their clay fractions. The higher available K status of the Inceptisol soil could be attributed to the presence of potash rich minerals. The continuous sugarcane crop has not much reduced the available K status of these soils