Growth and Water Footprint Analysis of Three Cassava Varieties under Rainfed Conditions

Abstract

Growth and water footprint assessment of three cassava varieties: Rayong 5, Rayong 72 and Kasetsart 50 under rainfed condition was conducted at Rayong Field Crops Research Center, Muang District, Rayong Province. Cassava were planted in April 2018 and harvested in March 2019. Texture of the soil was loamy sand and 15-7-18 chemical fertilizer was applied at the rate of 50 kg/rai. Throughout the experiment, total rainfall, crop water used water used and effective rainfall were 1,662, 360.4 and 962 mm, respectively. Results showed a rapid increase in height and canopy width at 6 months after planting (MAP). Kasetsart 50 had the highest height and canopy width of 138 and 130 cm, followed by Rayong 5. Dry weight accumulation showed a markedly increased in to[1]tal mass at 4 to 8 MAP. At 4 MAP, Rayong 72 had the highest percentage of root dry weight accumulation at 68%, followed by Kasetsart 50 and Rayong 5 with 59.8 and 54.0%, respectively. At 8 MAP, Rayong 72 still had the highest accumulation up to 86.1% followed by Kasetsart 50 and Rayong 5 with 82.1%, and 76.5 %. Fresh roots yield of 3 cassava varieties showed that Rayong 72 gave the highest fresh roots yield of 5.43 ton/rai, followed by Kasetsart 50 and Rayong 5, gave fresh roots yield of 5.21 and 3.72 ton/rai, respectively. Average water footprint for 1 ton of cassava fresh roots yield was 144.1 m3 accounting for 111.9 m3 of green water footprint, and 32.2 m3 of gray water footprint. In summation, it was found that Rayong 72 had the lowest water footprint of 123.5 m3 , divided into WF green, WF blue and WF grey 95.9, 0 and 27.6 m3 , respectively, whereas Kasetsart 50 had 128.7 m3 /ton,dividedinto WF green WF blue and WF grey at99.9,0and28.8 m3 /ton, respectivelyand Rayong 5 had the highest 180.3 m3 /ton, divided into WF green WF blue and WF grey 140, 0 and 40.3 m3 /ton, respectively. Results showed that cassava varietysuitableforgrowingonloamysandsoil under rainfed condition in Rayong province was Rayong 72because it was more efficient in using water to produce fresh root yield per ton than Rayong 5 and Kasetsart 50.