Assessing of the influence of organic and inorganic amendments on the physical-chemical properties of a red soil (Ultisol) quality

Abstract Many highly weathered soils in subtropical environments have low organic matter contents that limit the aggregation, plant available water (PAW) and have acidity issues, increasing the risk of erosion and limiting plant growth. The objective of this study was to determine the influence of gypsum, lime, fused calcium-magnesium phosphate (fertilizer) (CaMgP), and biochar on soil physical and chemical properties in two types of red soil (Ultisol). In a laboratory study, two types of red soil aggregate stability, PAW, the saturated hydraulic conductivity (Ksat), pH, and Fe/Al oxides were measured after 21, 60, 180, and 365 days application. The soil amendments increased soil pH and the amount of amorphous Fe/Al oxides for two soils. The clayey red soil amorphous Fe/Al oxides (ammonium oxalate extracted oxides) were significantly (P