Spatial Distribution of Soil Water Content, Soil Salinity and Root Length Density in a Drip Irrigated Nectarine Orchard under Plastic-Mulched and Bare Soils

This study characterizes the spatial distribution of Gravimetric soil Water Content (GWC), soil saturation extract Electrical Conductivity (ECe) and Root Length Density (RLD) in the wetted area by the emitter in a drip irrigated nectarine orchard cultivated in bare and plastic-mulched soils. To this aim, 150 soil cores were sampled in a 0.25 m by 0.25 m grid spacing at three soil depths in one m(2) area with an emitter located in the center and a tree in a corner of the area in the bare and plastic-mulched soils. The 0-60 cm soil profile mean GWC was 15% higher and the mean ECe 42% lower in the mulched than in the bare soil, whereas the mean RLD was similar in both treatments. Root growth was preponderant at the 0-20 cm soil depth, where RLD accounted for 66% of the total RLD. The root weighed GWC (GWC(rw)) was somewhat higher and the root weighed ECe (ECerw) somewhat lower than their arithmetic means, indicating that root growth was preponderant in regions with higher moisture and lower salinity. This conclusion was supported by the positive RLD-GWC correlation, and the RLD-ECe upper boundary line analysis showed that root growth decreased above a threshold ECe of about 4 dS m(-1). Overall, plastic mulching benefited water conservation and soil salinity control, but did not promote nectarine root growth.