Abstract
Coffee grounds (CG) improved some soil physical properties (dry density, g d; porosity, n ; aggregation; hydraulic conductivity, K s ; and infiltration rate, IR). Effects on other properties were inconsistent (e.g., sorptivity, S), or unfavorable (e.g., available water, AW). g d decreased and n increased with CG. CG decreased K s in sand. In calcareous soil, maximum increase was associated with 10% and 15% CG before and after wetting-and-drying cycles (WDC), respectively. K s increased with CG in clay, with greatest increase attained at 10% CG. IR decreased with CG in sand. In calcareous and clayey soils, IR decreased with CG before WDC but increased after WDC where maximum increase in clay was linked to 10% CG. No solid trends of soil sorptivity, S , were identified. Before WDC, S had the order: sand > calcareous > clay. For most cases, adding CG increased total water holding capacity (WHC). However, after WDC, the increase in water content at field capacity (FC) with CG was accompanied by a greater increase in wilting point (WP) and therefore a decrease in AW. CG improved soil structure and aggregation and increased non-water-stable aggregates in calcareous and clayey soils. Mean weight diameter (MWD) indicated increase in water-stable aggregates in sand at 5% and 10% CG. In clay, MWD increased only at 5% CG. Although results did not show coherent responses with some tested properties, they, mostly, indicate some beneficial effects of CG, particularly in relation to improving aggregation and water flow.
Highlights
Organic amendments are major sources of many physical, biological and chemical reactions in soils
More substantial decrease was seen in clay before Wetting-and-drying cycles (WDC) (-16.5%, compared with -12.6% in sand and -8.6% in the calcareous soil (Table 3))
Adding coffee grounds (CG) enhances aggregate formation and improves soil structure. It has been reported (Thompson and Troeh 1978, Marshall and Holmes 1988) that structures of heavy-textured soils such as clays can benefit from the application of organic matter through enhancing aggregate formation
Summary
Organic amendments are major sources of many physical, biological and chemical reactions in soils. They interrelate in the soil complex system in the processes of formation and degradation of soil aggregates (Emerson 1959, Harris et al 1966). The role played by microorganisms in improving aggregate formation is a direct function of the nutrient status of the soil substrate, among several other factors such as soil moisture, temperature and pH (Alexander 1977). Adding organic matter helps all poor soils, whether they are too sandy or made of too much clay. One of the oldest sources of organic matter for increasing crop productivity is the recycling of agricultural waste such as straws, stalks, husks, etc. Rice husk was used as a partial substitute of the expensive traditional medium components for producing high quality greenhouse and nursery crops (El-Torky and Bedaiwy 1998) as well as many other crops (Cerff et al 1985, Sawan et al 1986)
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