Abstract: After scrutiny of the pertinent literature analytical and tracer experiments with 65Zn along a toposequence of rice paddies in Tiaong, Quezon Province, Philippines are described. The higher catena member is moderately Zn deficient, the lower member extremely Zn deficient. Soil analysis reveals Tiaong soil to be slightly alkaline, smectitic, strongly humic, of high CEC and base saturation, of low plant available Zn (Bray method). The higher catena member (H) leads in Si, Al, K, Na, Zn, Cu, Ni, Co, Cr, Ba, the lower member (L) in C, Ca, Mg, Mn, P. The very high deficiency in (L) corresponds with higher humus-, Ca, Mg, and P concentrations, all potential agents to Zn fixation. Clay minerals are higher in less deficient (H). This, and studies of VAN BREMEN et al. (1980) would point to strong Zn organic fixation. However, DTPA-, dithionite- and oxalate-extracts represent only 2.5–25% pedogenic zinc, the rest is lithogenic and insoluble. Previous combustion scarcely increases these rates. This points against Zn organic linkages as predominating Zn fixation mechanism. Partial correlation, applied to VAN BREMEN's data also annihilates the high correlation between zinc and organic matter, which is replaced by strong ZnMg and Znbicarbonate correlations. Field tests with 65ZnSO4 in plastic tubes of 35 and 25 cm diameter, inserted in the rice fields, showed, that mobility, i.e. lateral and vertical translocation of the zinc was much more pronounced at (H) than at (L). After air drying the removed soil cores replanting was accompanied by much less Zn deficiency than in loco in the rice field. Drainage and at least temporary oxidation seems to be the primary requirement for soil rehabilitation.Adsorption — desorption isotherms followed the Freundlich relation. Kvalues were very high, especially in (L), indicating strong adsorption of Zn. Kvalues of the DTPA desorption extracts were quite low, representative for easy desorption by chelate solution, whereas the 0.1 M HCl extract after DTPA elution had again high K-values as a sign of strong adsorption of the non DTPA extractable Zn. For rehabilitation mixed rice — fish farming with fishponds in the lowest points of the relief seems to be best with propagation of azolla as Ngreen manure for the rice and feed for the fish.

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   |wiki=    Wicri/Terre
   |area=    NickelMaghrebV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     ISTEX:17C247A6B63E8463607C3CEB1AF2A5B9C3C409E6
   |texte=   Zinc deficiency in a soil toposequence, grown to rice, at Tiaong, Quezon province, Philippines
}}