Changes in water retention properties due to the application of sugar foam in red soils

► Sugar foam is a relatively abundant waste, rich in organic matter (7%) and calcium carbonate (40%). The application of this type of organic waste to the soil is a widespread practice. This addition may affect some of the soil characteristics. In this work, the influence of the application of sugar foam on water retention properties in two red soils (an original soil versus a soil with addition of sugar foam) in the La Mancha region of Spain is studied. ► The sugar foam applied to the soil altered its chemical properties. An increase in contents of organic matter (3.5% versus 1.4%), calcium carbonate (40.8% versus 0%) and pH (8.2 versus 6.3) are observed in the superficial horizon of the studied soils, although there is no such significant increase in electrical conductivity (0.33 dS/m versus 0.25 dS/m). ► The physical properties of the soils are changed too: the depth of horizon A increases (32 cm versus 12 cm), the stoniness reduces (5% versus 25%), the structure is well developed, due to the texture becomes finer (silty versus sandy clay loam), and, finally, the bulk density reduces (0.79 g cm−3 versus 1.19 g cm−3). ► The gravimetric moisture at field capacity was 49% in the soil altered with sugar foam, versus 12% in the non-altered soil; the gravimetric moisture in the permanent wilting point was 14.5% versus 8% and the available water retention capacity was 34.5% and 4%, respectively. ► The most influential factors in this change are the increase of calcium carbonate, the increase of organic matter and the reduction of bulk density. The scientific novelty is that the hydro-behaviour of the soil due to the addition of sugar foam improves the characteristic values of moisture and this fact is very interesting from an agricultural and environmental point of view. This work describes the influence of the application of sugar foam (an organic residue from sugar beet industry) on water retention properties, over an extended period of time (>25 years), in two red soils in the La Mancha region of Spain. The properties of gravimetric moisture at field capacity, gravimetric moisture in the permanent wilting point and available water retention capacity both in the original soil – without the addition of sugar foam – and in the soil affected by the addition of sugar foam are compared. For this purpose, the profiles are characterised macro morphologically. Chemical, physical–chemical and mineralogical parameters are determined, in addition to determining the wat