Abstract
Water scarcity and soil salinization affect large semiarid agricultural areas throughout the world. The maintenance of agricultural productivity implies better agricultural practices and a careful selection of resistant crops. A proper monitoring of the physiological status of plants can lead to better knowledge of plant nutritional requirements. Visible and near-infrared (VNIR) radiometry provides a non-destructive and quantitative method to monitor vegetation status by quantifying chemical properties using spectroscopic techniques. In this study, the capability of VNIR spectral measurements to detect salinity effects on melon (Cucumis melo L.) plants was tested. Melon plants were cultivated under multiple soil salinity conditions (electrical conductivity, (EC)1:5: 0.5, 1.0 and 2.5 dS m-1). Spectral data of leaves were transformed into vegetation indices indicative of the physiological status of the plants. The results showed differences for N (p < 0.05), K and Na content (p < 0.01) due to salinity suggesting different degrees of salt stress on the plants. Specific leaf area increased with salinity levels (p < 0.001). The capabilities of VNIR radiometry to assess the influence of soil salinity on melon physiology using a non-destructive method were demonstrated. A normalized difference vegetation index (NDVI750-705), and the ratio between water index (WI) and normalized difference vegetation index (WI/NDVI750-705) showed significant relationships (p < 0.01) with the salinity. Therefore, this method could be used for in-situ early detection of salinity stress effects.
Highlights
Mediterranean ecosystems are characterized by the aridity of the climate and the persistent scarcity of water resources
An increment in the soil salinity generally tends to induce a decrease in leaf reflectance in the near infrared spectral region (Leone et al, 2007; Peñuelas et al, 1997b), but an increase in near infrared reflectance with salinity was observed in this study
Zhang et al (2011) observed a rise in near infrared reflectance for salt-tolerant species growing on moderately saline soils in a wetland environment
Summary
Mediterranean ecosystems are characterized by the aridity of the climate and the persistent scarcity of water resources. Agriculture with high water requirements under increased occurrence of extreme drought events have forced irrigation with poor quality water from both irrigation drainage and groundwater sources, causing processes of degradation, reduction of the production capacity, and soil salinization (Pérez-Sirvent et al, 2003; Ashraf et al, 2007). Salt stress is the most widespread abiotic stress that limits plant growth, physiology and productivity mainly affecting the ionic balance and plant water relations (Dogan et al, 2010). The effects of soil salinity depend on the plants' level of tolerance and the salinity level, since there are differences between species in terms of ability to maintain nutrient concentrations for growth under salt stress (Munns et al, 2002; Melgar et al, 2008)
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