Spent coffee grounds as organic amendment modify hydraulic properties in a sandy loam Brazilian soil

Abstract

Soil physical and chemical properties can be amended by application of organic residues, such as spent coffee grounds (SCG). In this work we examined SCG effects on the modification of some soil physical-hydraulic properties, such as soil water retention and aeration, investigating beneficial uses for this waste product. Soil properties were evaluated using pots filled with a mixture of a sandy loam soil with the contents of 0, 5, 10, 15 and 20% of SCG. The most relevant soil properties to the purposes were the moisture at container capacity (θcc), readily available water capacity (RAWC) and drainable porosity (ϕD). Additionally, under the hypothesis that SCG can be used as soil conditioner, lettuce crop, cultivar “Mimosa Roxa Roxanne”, was transplanted to the pots where the leaf area index and the cumulative biomass throughout the growing cycle were examined. Comparing to the absence of SCG (0%), soil SCG contents of 5, 10, 15 and 20% presented larger values of θcc and consequently larger RAWC and smaller ϕD. Although the increase of soil water storage from 43.2 (0%) to 53.3 (20%) mm, crop development was prejudiced by the reduction on ϕD from 0.1595 (0%) to 0.0827 (20%) m3 m−3, which affected soil aeration. This greater water availability, obtained with the increase of θcc, was promoted by the residue addition pointing out for a possible use of SCG to increase water retention for other crops.