Spatio-temporal patterns of topsoil moisture content in a Mediterranean rainfed strip-tilled Almond orchard, Southeast Spain

Abstract

It is yet unclear how applying 1,5 2 m wide no till strips in otherwise fully tilled Almond orchards affect s the soil’s hydrological behaviour. This is a relevant knowledge gap, as in recent years this practise has been applied as a means to regenerate the soil, while keeping the partial benefits of tilling in Mediterranean areas. This led to the research questions: i) What is the spatial pattern of topsoil moisture content in a Mediterranean rainfed strip tilled Almond orchard, Southeast Spain? Spain?, ii) What is the temporal pattern of topsoil moisture content in a Mediterranean rainfed strip tilled Almond orchard, Southeast Spain In this research, dielectric conductivity measurements have been used to as an indica tion for the spatial and temporal patterns of topsoil moisture content in a rainfed strip tilled mediterranean almond orchard. Soil compaction testing, point intercept vegetation analysis, soil texture testing, and a Visual Soil Quality assessment all have been performed to give more context to the found patterns. The results showed an increase of mea sured dielectric conductivity (indication soil moisture) away from the almond trees, peaking however not farthest away from the trees but where topsoil compaction was highest (lowest value 28 mV = 2,6 %vol , highest value 172 mV = 14,0 %vol, estimated permanent wilting point = 17,5 %vol). Farthest away from the trees values were still higher than closest to the trees. Standard deviation (indicating change of soil moisture over time) was highest at 0,1m (and the opposite 6,9m), and in the 2,0m 4,5m zone away from the trees, also for the control plot. Sensor readings were off due to influence by touch (0,14 2,26 %vol, media n ~1,0 vol It can be concluded that the topsoil moisture content is lower in the till areas, relative to the no till areas. This report also includes a proposal on how to determine if a dielectric conductivity sensor gives true values, or whether it’s readouts are affected by degree of soil compaction.