Effect of decomposition intensity of incorporated chickpea manure on stability and saturated hydraulic conductivity of a clay loam and clay soil

Abstract

The role of organic matter (OM) in soil aggregation and saturated hydraulic conductivity (Ksat) has long 
been recognised but their depedence on the intensity of decay is less studied. The objective of this 
study was to determine the effect of decomposition intensity of incorporated chickpea manure on soil 
aggregate stability and Ksat. Samples of a clay loam and clay soil were collected from the top 15 cm 
layer and amended with chickpea green or mature dry manure and incubated at 30°C and ~60% water 
holding capacity. Decomposition intensity was determined by measuring CO 2 evolution using NaOH 
traps, aggregate stability by wet sieving and Ksat by the constant head method. All determinations were 
made 3, 7 and 30 days after incubation and the data analysed following the general linear model for a 2 
x 3 × 3 factorial in randomised complete block design. Evolution of CO2 in both soils and manure was 
highest on day 7 compared to day 3 and 30. In both soils >60% of the soil aggregates were 
macroaggregates >0.5 mm but the relative proportion of microaggregates <0.5 mm increased from ~10 
to ~20% in the control and to ~15% in the amended cay loam soil in the day 30 treatments. 
Decomposition intensity was increased by incorporating chickpea manure which resulted in improved 
soil aggregate stability and Ksat especially in soil with low clay content. CO2 which is a simple product 
of decomposition may be used as a rapid indicator of soil aggregate stability and water movement in 
agricultural soils.