Bi-diretional reflectance spectroscopy to study crop response to soil salinty

Salinisation, which is one of the main causes of decline of soil quality and agricultural productivity in the Mediterranean region, is becoming a serious treat for many coastal areas of southern Italy, because of increasing use of irrigation with saline waters. Early detection of salt accumulation in soils is required to prevent efficiently prevent the process. Spectral data from satellite and airborne platform could contribute noticeably to this end. Where soils are covered by vegetation an indirect assessment of soil salinity status may be possible though the analysis of plant spectral response. This study investigated such hypothesis though a field experiment in the low Volturno plane river. The effects of irrigation with non saline, moderately saline and high saline waters (T0, T0.5 and T1 treatments) was on soil properties, aubergine (Solanum melongena) crop characteristics and plant spectral response were assessed. Aubergine, along with pepper and tomato is a widespread crop in the low Volturno river plane. After five irrigation with saline waters, the investigated heave-textured, swelling soil becomes saline or saline-sodic. Soil salinity/sodicity status affected noticeably aubergine plants characteristics (dry biomass, leaf area index, plant water content and leaf water potential) . Changes in plant characteristics resulted in observable changes in the plant spectral response. Significant relationships were found between plant characteristics and some spectral indexes (normalise difference vegetation index, or NDVI, water index or WI). Indirect relationships were found between soil salinity/sodici parameters (exchangeable sodium percentage, or ESP, effective electrical conductivity, or ECe, pH) and the above spectral parameters. Plant spectral response was, thus, considered a useful criterion for discriminating salt affected from non salt affected soils. The results of present study on aubergine plants (moderately sensitive to soil salinity) confirm a study previously carried out on pepper plant (sensitive, like tomato, soil salinity). Key word: soil salinity/sodicity, aubergine crop, crop spectral reflectance