Physiological Respone of Rice and Wheat to Salinity/Sodicity in Texturally Different Soils During Reclamation

Abstract

In arid and semi-arid regions, salt stress is a major limiting factor for crop production and sustainable development of the agriculture sector. Plants growing on these degraded soils face salt shock that results in altered basic physiological characters and functions in plants. Evaluation of these traits helps in monitoring plant health and indirectly determines stress response. The present research was designed to evaluate plant physiological, growth, and ionic responses as well as soil characteristics as a function of amendment behavior while reclaiming salt-affected soils. First experiment was carried out for the selection of rice and wheat cultivars from existing cultivars tolerant to salt stress. For this purpose, ten cultivars per crop were tested in germination trial at four EC (dS m-1 ): SAR (mmol L-1 ) 1/2 levels (for rice crop, 4:20, 8:40, 12:60 and 16:80, for wheat, 5:8, 10:16, 15:24 and 20:32). In case of rice, Super Basmati showed more tolerance compared to other tested cultivars, while the diminishing response of Kashmir Basmati and Basmati-6129 towards increasing EC: SAR levels was observed, thus declared as sensitive cultivars. Results regarding wheat revealed that Galaxy-2013 was the most tolerant among all the tested cultivars based on salt tolerance index, while PARI-73 was classified as a sensitive cultivar. In the second experiment, growth, physiological, and ionic responses of rice crop were evaluated at different salinity and sodicity levels (ECe: SAR levels 4:20, 8:40, 12:60, and 16:80) of different texture soils [sandy clay loam (SCL) and clay loam (CL)] amended with organic [farm manure (FM) and inorganic (gypsum (Gyp) and sulphuric acid (SA)] amendments in lysimeters. Selected salt-tolerant variety Super Basmati was grown on these treated soils for 3 years in a row. This 3-factor experiment was arranged in completely randomized design with three replications. Data regarding plant attributes, i.e. physiological (transpiration rate, photosynthetic rate, stomatal conductance and total chlorophyll contents), growth (biological yield, plant height, and grain weight), ionic (straw and grain N, P and K and soil characteristics (ECe, SAR and pHs) were recorded. Results showed that in CL soil, overall SA performed best in improving rice physiological, ionic, and growth attributes at higher ECe: SAR levels, whereas at lower levels, FM and Gyp performance was more appropriate. Regarding SCL soil, plant responded best with Gyp at lower ECe: SAR levels while SA remained best at higher ECe: SAR levels. The SA decreased ECe (38%) and SAR (64%) over control in both soils. For third experiment, wheat was used as the test crop. Similar arrangement that was used in 2nd experiment was set for this study except ECe: SAR levels, i.e. 5:8, 10:16, 15:24, and 20:32. Selected salt-tolerant variety, Galaxy-2013, was grown on these treated soils. Parameters regarding plant and soil of this 3-factor factorial experiment, arranged in a completely randomized design, were recorded for 3 years in a row and analyzed statistically. The results revealed that plant physiological, growth, and ionic responses were negatively affected by increasing ECe: SAR levels. Gypsum and SA performed better in combating salinity and sodicity stress and improving physiological, ionic, and growth attributes. Considering soil parameters, overall Gyp showed better performance in improving soil characteristics, i.e. ECe decreased about 21% and SAR decreased about 38% with respect to control. Whereas a significant role of SA was observed in decreasing SAR (about 42% decrease with respect to control) at level 20:32. It can be concluded from the above research work that the use of tolerant cultivars and site-specific reclamation with respect to crops can be a wise option for getting high yield from salt-degraded lands. Plant attributes, i.e. physiological and ionic, were improved with SA at high salinity/sodicity (overall) because of their positive effects on soil properties, whereas FM and Gyp performed better at lower salinity/sodicity.