Optimization of irrigation schemes in 'Conference' pear orchards using Worldview multispectral imagery

Well considered drip irrigation increases pear fruit size in Belgian pear orchards. Irrigation scheduling, using soil moisture sensors, plant sensors or soil water balance models focus often on one specific location per orchard. However, significant heterogeneity in soil water content can be expected in orchards situated on variable soil profiles, planted on slopes with variation in planting regimes, tree age, irrigation efficiency and management strategies. To come to irrigation scheduling which accounts for this spatial variation Worldview-2 multispectral imagery was compared to soil water content, stem water potential (Ψstem) and fruit yield in an irrigated ‘Conference’ pear orchard. Correlation analysis revealed a relationship between soil texture and varying available water content (R2=0.47). Soil water content correlated to Ψstem and reference evapotranspiration (ETo) in a linear multivariate regression in 2011, 2012 and 2013 (R2=0.64, 0.52 and 0.59). Ψstem correlated to fruit size in 2011 (R2=0.57) and fruit weight in 2013 (R2=0.34). Ψstem correlated to the Rededge Normalized Difference Vegetation Index (ReNDVI) derived from multispectral imagery (R2=0.68) (Van Beek et al., 2014). These insights in the relationship between Ψstem, soil properties and irrigation contribute to a new approach for irrigation scheduling which accounts for the spatial variation in the orchard.