Abstract
The objective of this study was to examine the effect of compost, rice straw and sawdust amendment on hydraulic and pore characteristics of a clay loam soil. Amendments were applied at an application rate of0.2 m3/m3 (apparent soil volume) in three rectangular plots each comprising an area of3.0 m2. Water retention characteristics were measured by hanging water column and centrifuge method. Hydraulic conductivity was measured by disc permeameter at -15.0, -6.0, -3.0 and0 cmof water pressure heads. Volumetric water content increased in all amended soils, compared with the control. Unsaturated hydraulic conductivity was almost identical for straw and sawdust at all pressure heads, although that for compost amended soils were much higher. Field saturated hydraulic conductivity (Kfs) was higher in organic matter amended soils as were number of macropores (14.7% - 29.2%). Contribution of each pore class to the total saturated flux was evaluated from the hydraulic conductivity and water retention measurement. A new alternative weighed factor (We) was proposed to estimate the actual contribution of macro- and mesopores to the total saturated water flux. The Wg was found to be more representative for calculating pores contribution to saturated water flux than that of hydraulic conductivity measurement. Although there is only a small fraction of the total porosity, amendment increased effective macro- and meso-porosity (qe). Pores in the amended soils were hydraulically active and water movement was dominated by gravity. Collectively, our results demonstrated that organic matter generated as agricultural by-product could effectively be used to improve soil quality
Highlights
Field scale measurement of soil hydraulic properties including quantification of porosity are very important in organically managed soil
The results showed that, at most or all imposed pressure heads water retention characteristics of amended soil had generally increased
Macro and mesopores contribution to the saturated water flux was evaluated from the water retention and hydraulic conductivity measurement
Summary
Field scale measurement of soil hydraulic properties including quantification of porosity are very important in organically managed soil. A number of studies have been reported on the effects of farmyard manure on soil structure and hydraulic properties [3,4,5,6]. Some of these studies have reported that application of manure increases the saturated hydraulic conductivity (Ksat) and infiltration rate [7,8,9]. Very few studies have measured unsaturated hydraulic conductivity in organic matter amended soils [11,12]. We did not find any study that measured unsaturated hydraulic conductivity in compost, straw and sawdust amended soil
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