Characterization and amelioration of lowland rice soils affected by volcanic ejecta from Mt. Pinatubo [Philippines]
1992
Mateo, L.G.
X-ray diffraction analyses indicated that Angeles clay loam soil (fine-textured soil) was dominantly montmorillonitic while volcanic ejecta (coarse-textured soil) was made up of primary minerals such as feldspar and microline. X-ray flourescence on light and heavy metals showed that K, Ar, and S were higher while Zn, Cu, Ni, Fe, Mn amd Ti, were lower in volcanic ejecta than Angeles clay loam soil. The total N; exchangeable bases (Ca, Mg, K and Na), CEC, and extractable cations (Zn, Fe, and Mn) were likewise lower in volcanic ejecta than Angeles clay loam soils. The adverse effects of increasing depth of volcanic ejecta on lowland rice grown on Angeles clay loam soil applied with 80 kg N/ha were manifested on the production of total number of tillers, number of productive tillers, number of grains per panicle and consequently grain and straw yields of the crop. At 3 and 9 cm depth of volcanic ejecta, significant reductions were observed in the number of grains per panicle and the number of productive tillers, respectively. Also, grain yield, was significantly reduced by 20% occurred at 6 cm depth of volcanic ejecta. Increasing the rate of inorganic N application was effective in counteracting the detrimental effects of volcanic ejecta on lowland rice grown on Angeles clay loam soil. Results in the use of organic and inorganic fertilizers as ameliorant indicate that at 1.88 cm depth volcanic ejecta, application of equivalent amount of chicken manure alone produced the best effect in terms of the growth, yield and yield components of the crop. At higher depth of volcanic ejecta and application of equivalent amount of organic fertilizer with or without inorganic fertilizer proved to be detrimental on the crop
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