The role of active fractions of soil organic matter in physical and chemical fertility of Ferrosols

Abstract

The relationships between fractions of soil organic carbon (C) oxidised by varying strengths of potassium permanganate (KMnO4) and important soil physical and chemical properties were investigated for Queensland Ferrosols. These soils spanned a wide range of clay contents (31-83%), pH values (4·4-7·9; 1 : 5 water), and total C contents (12· 1-111 g/kg). Carbon fractions were derived by oxidation with 33 mM (C1), 167 mM (C2), and 333 mM (C3) KMnO4, while organic C and total C were determined by Heanes wet oxidation and combustion, respectively. Aggregate stability was determined by wet sieving soil from the surface crust after 30 min of high intensity (100 mm/h), simulated rainfall on disturbed samples in the laboratory. The proportion of aggregates <0·125 mm (P125) was used as the stability indicator because of the high correlation between this size class and the final rainfall infiltration rate (r2 = 0qa86, n = 42). The soil organic C fraction most closely correlated with P125 was C1 (r2 = 0·79, n = 42). This fraction was also highly correlated with final, steady-state infiltration rates in field situations where there were no subsurface constraints to infiltration (r2 = 0·74, n = 30). Multiple linear regression techniques were used to identify the soil properties determining effective cation exchange capacity (ECEC, n = 89). Most variation in ECEC (R2 = 0 ·72) was accounted for by a combination of C1 (P < 0·0001) and pH (P < 0·0001). These results confirm the very important role played by the most labile (easily oxidised) fraction of soil organic matter (C1) in key components of the chemical and physical fertility of Ferrosols. Management practices which maintain adequate C1 concentrations are essential for sustainable cropping on these soils.

Spatial variability in the physico-chemical properties of soils affected by animal wastes in Uyo, Akwa Ibom State of Nigeria

“…The same trend was observed in percentage base saturation. There is a positive correlation between organic matter and base saturation as also reported by Bell and Moody (1998).…”

Permanganate Oxidizable Carbon Reflects a Processed Soil Fraction that is Sensitive to Management

“…Lefroy et al (1993), Blair et al (1995), and others (Conteh et al, 1997;Shang and Tiessen, 1997;Bell et al, 1998), built on this work, using varying concentrations of permanganate (0.03-0.33 mol L -1 KMnO 4 ) to measure labile soil C. Studies that have used multiple concentrations of permanganate have consistently reported greater sensitivity to management with more dilute concentrations (0.02-0.033 mol L -1 KMnO 4 ) (Bell et al, 1998, Weil et al, 2003Vieira et al, 2007). Weil et al (2003) further developed and streamlined this method, using 0.02 mol L -1 KMnO 4 to measure the 'active C' fraction of total SOC.…”

The effects of soil organic matter on seedling emergence in sunflower (Helianthus annuus L.)

“…Even in small amounts, organic matter is very important. Organic matter has a profound impact on soil physical, chemical and biological properties (Bell et al 1998, Brussoard 1998, Jonge et al 1999, Six et al 2000, Carter 2002. Organic matter has several functions in soil; it increases nutrient holding capacity of soil, is a pool of nutrients for plants, improves water infiltration, decreases evaporation, increases water holding capacity, reduces crusting, improves aggregation, prevents erosion, and prevents compaction (Carter 2002).…”