Correlation of Cationic Indices with Clay Dispersion Degree of Two Soils from Brazil Fertilized With Chicken Manure

Aims: The aim of this work was to evaluate ESR (Exchangeable Sodium Ratio), MCARex (Monovalent Cation Adsorption Ratio) and CROSSex (Cation Ratio of Soil Structural Stability) as indices, using exchangeable cations in calculations, to predict clay dispersion behavior in two soils with chicken manure application.
Study Design: Pots were completely randomized, with 10 replications per treatment.
Place and Duration of Study: A Red Latosol and a Red-Yellow Ultisol from Brazil were sampled. Pots were conducted in a greenhouse in Londrina - Paraná during 90 days.
Methodology: Chicken manure doses (0, 4, 8, 16 and 32Mg ha-1) were applied and mixed with the soils. After 90 days of irrigation, samples were analyzed for Ca2+ex, Mg2+ex, K+ex, Na+ex, organic matter, pHwater, pHKCl (1N) and water dispersible clay. Clay dispersion degree, point of zero charge, ΔpH, ESR, MCAREX and CROSSEX were calculated. ANOVA was calculated and the better-fit regression equation was shown.
Results: No accurate relationship was found between ESR, MCAREX or CROSSEX with clay dispersion degree.
Conclusion: ESP, MCARex and CROSSex did not have enough correlation with clay dispersion of studied soils. More information about soil net charge, organic matter, Fe and Al (hydr) oxides are needed to a high scope index of soil structural stability.