In a paper published in the July 2014 issue of Agricultural Water Management), Panigrahi et al. found that it was possible to utilize deficit irrigation of mandarin orange groves while achieving near maximum fruit yield. A level of irrigation that resulted in 50% evapotranspiration (relative to full irrigation) resulted in significant water savings while providing yield that was within 2-4% of the full irrigation yield; fruit quality was a good or better than that achieved with full irrigation.

Deficit irrigation is a watering strategy that manages irrigation at a level that is below what is necessary to maintain maximal rates of evapotranspiration but that maintain near-full crop yield. Using a Malvern Panalytical’s ASD FieldSpec spectroradiometer, the authors were able to monitor several spectral indices that provided indicators of drought stress. Both the normalized difference water index (NDWI, Gao 1996) and moisture stress index (MSI, Hunt and Rock 1989) provided the means to track moisture stress levels associated with varying levels of deficit irrigation.

Malvern Panalytical’s ASD FieldSpec spectroradiometer is widely used to non-destructively monitor vegetation status for deficit irrigation studies with over 600 peer-reviewed papers published on this subject. In one of the more recent papers on this subject, González-Fernández et al. (2019) developed a method using Malvern Panalytical’s ASD FieldSpec spectroradiometer to determine grapevine water stress level, a parameter needed to optimize irrigation scheduling in vineyards.

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