Micronutrient cations and their availability in soils from the major corn-producing regions of Thailand /
by Weerapun Chotivanich
- Los Baņos, Laguna : Cavite State University- Main Campus, 1986.
- 128 pages : illustrations ; 28 cm.
Thesis (Ph.D. - - Soil Science) Univesity of the Philippines, College, Laguna.
Includes bibliographical references.
WEERAPUN CHOTIVANICH, University of the Philippines at Los Banos, September 1986. Micronutrient Cations and Their Availability in Soils from the Major Corn-Producing Regions of Thailand. Major Professor: Dr. Diosdado A. Carandang
Twenty-four profiles and forty surface soil samples were obtained from the major corn-producing regions of Thailand. The purpose of the study was to evaluate the amount, distribution and availability of micronutrient cations in the soils. As a consequence of the study an experiment was conducted to determine the form and method of zinc application for corn grown on zinc-deficient soils.
The total Fe, Mn, Zn, and Cu vary from 1.60 to 12.60 percent, 110 to 6175 ppm, 12 to 87 ppm, and 14 to 180 ppm, respectively.
The DTPA-extractable Fe, Mn, Zn, and Cu range from 0.40 to 66.00, 0.20 to 68.00, 0.14 to 4.74, and 0.20 to 11.62 ppm, respectively. The available Fe in the soil profiles increases with an increase in CEC but available Mn increases with organic matter and decreases with clay content. Available Zn increases with an increase in either organic matter and/or CEC. Available Cu has no correlations with other soil characteristics. In general, the total quantities of these elements are relatively uniformly distributed throughout the soil profiles but the available forms decreased with depth.
The double pot technique for the diagnosis of micronutrient deficient soils was used using corn (Zea mays L.) as the test plant. The critical levels for corn using the SQ procedure reported herein are: 0.841 for Fe, 0.692 for Zn, and tentatively 0.81 for Mn and 0.82 for Cu. The SQ compares favorably with the visual deficiency symptoms and the DTPA soil test. The advantage of this method is that it is handy, cheap, and simple.
Zn-application significantly increased the dry weight of corn on zinc deficient soils. The commercial sources of Zn were ZnSO, and Zn0. 2nSo, is superior to ZnO in corn grown on Zn-deficient soils. Zinc mixed with the soil at the rate of 5.0 ppm is beneficial to corn, The most effective Zn application for calcareous soils is foliar spray at the rate of 0.15 g Zn/L H,0 and seed coating with 0.01% Zn solution.