Saline water for irrigation

Salinity and sodicity of the irrigation water affect the growth and yield of crops. Even different varieties of the same crop may give differential responses under such conditions. Hence, the selection of salinity tolerant crops, cultivars and their specific strains are some of the important factors for the proper utilisation of saline irrigation water. Chillies need frequent and light irrigation to meet their water requirements and under such circumstances high amount of salts will accumulate in the root zone. Therefore, it becomes imperative to devise ways and methods for the better utilisation of such waters to obtain optimum yield.

In a pot study to determine the influence of saline water (electrical conductivity ranging from 1 to 6.95 msKm) on the growth of chilli, it was observed that Relative Growth Rate (RGR) decreased with increasing salinity and was related to the retardation of Net Assimilation Rate (NAR). The leaf area ratio did not decrease with increasing salinity. The leaf expansion rate was inhibited by salinity. Salinity did not influence the growth balance between leaves and other organs. The retardation of NAR was related to the obstruction of stomatal conductance and transpiration (Hirota et al., 1999).

Use of different ratios of fresh water, treated urban waste water and saline ground water (mixed to obtain six levels of electrical conductivity (EC) ranging from 0.3 to 15ds/m) for irrigation of pepper in a mediterranean environment indicated that pepper showed a high growth rate with a lower mortality during establishment (Borin et al., 1997).

In a study on the use of brackish water in raising chillies in red soil, the addition of gypsum (1 t/ha) to the irrigation water showed the best results with the highest pod yield, in comparison to soil applied gypsum and the application of various manures (Sundaravadivel et al., 1996).

At a higher osmotic concentration of saline water (300 mm/20,000 ppm) the germination percentage was lower and the time taken to germinate was longer (Hashem et al., 1991; Palma etal., 1996).

In afield study on the use of non-saline water (0.25 ds/m) and saline water (0.76-1.0ds/m) for the irrigation of chilli crops grown for dry chillies, it was observed that two applications of nonsaline water alternating with one of saline water was the most promising treatment for using saline water to supplement the limited supply of canal water (Srinivas et al., 1991).

Through drip irrigation satisfactory yields of Capsicum (up to 2.1 kg/m2) were achieved with saline (brackish) water, having an EC value upto 6.0 ds/m (Chattopadhyay and Mairi, 1990).

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