211 MONDAL ET AL Environment & Ecology 29 (1) : 211—216, 2011 © Copyright by MKK Publication 2011 ISSN 0970-0420 Effect of Salinity on Growth, Yield and Quality of Sweet Potato (Ipomoea batatus) CHANDAN KUMAR MONDAL*, SHYAM SUNDAR LAKSHMAN LAKSHMAN CHANDRA PATEL AND BHASKAR MUKHERJEE Ramkrishna Ashram Krishi Vigyan Kendra, Nimpith 743338, South 24 Parganas, India *Correspondence Abstract Agriculture faces three way problems in the Sundarban blocks of South 24 parganas district of West Bengal. These are soil salinity, late release of land for rabi crop due to poor drainage system along with low percolation rate, and poor irrigation facility as the ground water is saline. In this perspective, it was imperative to find out a crop which can tolerate salinity to some extent and can grow without irrigation. Sweet potato being a crop which can grow without irrigation, the present investigation was made to find out the threshold salinity level for growing sweet potato in the saline rice fallow of Sundarbans. It was observed that this crop could be grown successfully at a salinity level upto EC 2.37 dS/m. With gradual increase in salinity level, the initial herb growth was well but root development became poor. Although a satisfactory yield and a profitable return was obtained upto a medium soil salinity level. Key words : Salinity, Sweet potato, Sundarban, Yield, Growth. In the southern parts of South 24 Parganas district of West Bengal especially in Sundarbans, the agriculture faces three way hindrances. These are soil salinity, late release of land for rabi crop due to poor drainage system along with low percolation rate, and poor irrigation facility as the ground water is sa- line. The farmers of this region have less mobility in crop selection for the rabi season after aman paddy. In this crop selection process, one should keep in mind that the crop should bear the following charac- ters i.e. it should survive in water stressed condition, can tolerate soil salinity to some extent and can pro- tect the soil from direct sun by covering the soil sur- face, thus minimizing soil salinization process. Keep- ing these in mind, sweet potato was selected to ob- serve its potential performance in this area. Ahn (1) reported that the sweet potato is sensitive to drought at the tuber initiation stage i.e. 50—60 days after plant- ing. But, unlike other crops, sweet potato can grow well in any type of problematic soil with or without irrigation facility as sweet potato is a drought toler- ant crop (2). In sundarban soil, sweet potato has enough scope because sundarban has its own pecu- liarity with respect to its salinity development. It is observed that just after harvesting of paddy particu- larly in the month of December, there is very little or Table 1. Soil nutrient status of eight treatments. Tre- EC N 2 P 2 O 5 K 2 O atm- (dS/ OC (kg/ (kg/ (kg/ ents pH m) (%) ha) ha) ha) T 1 7.04 1.63 0.86 563.6 89.7 443.5 T 2 6.86 1.85 0.78 542.9 79.6 451.6 T 3 6.98 2.06 0.81 556.1 83.4 411.8 T 4 6.82 2.26 0.80 510.7 80.5 403.2 T 5 6.88 2.37 0.84 537.4 78.8 436.2 T 6 7.01 2.49 0.80 513.5 81.3 468.8 T 7 6.92 2.58 0.76 532.2 78.2 423.6 T 8 7.02 2.70 0.85 560.6 85.9 431.7 no salinity in the soil. But with time when the upper surface of the soil starts drying, some of the plots become saline due to the upward movement of saline ground water. In this situation, planting of sweet po- tato vines immediately after harvest of aman paddy, can save both the soil and the crop as well. Sweet potato is a good economic crop in this situation, as it provides some monitory return at that time when no other crop was possible. It is also used as a green fodder during March to May, when scarcity of green fodder is acute in this region. In Sundarbans situa- tion, sweet potato was tried sporadically, particularly by the farmers, for the last five to seven years and huge tuber production was recorded in the less sa-