Assessment of Cassava Water Footprint in Farmers’ Fields

Abstract

Water footprint is used as a tool to measure both direct and indirect water uses by crops or products. Cassava fresh root yield has a wide range of uses in many local downstream industries. Water footprint (WF) of cassava had mostly been reported from secondary data- due to limited availability of field-based publication. WF of cassava fresh root yield in farmer's fields was investigated from 4 consecutive growing seasons from 2017/18 to 2020/21 in 26 provinces. Results showed that WF varies for each region due to differences in soils, weather and management. Most cassava were grown under rainfed conditions and KU50, R5 R72 and R11 were the major cultivars. The growing season started from March to May, earlier in eastern region and later in the northern region, thus varied from 10.4  to 19 months long. The average fertilizer application rate was 7.2 kg.N/rai The average yield was 4.1 ton/rai.  Average yield from Udon Thani province was the highest at 6.5 ton/rai and Pitsanulok was the lowest at 2.9 ton/rai. The WF assessment showed that water uses per 1 ton of fresh root product was 268 m³ whereas 226 m³ is WF_green and 42 m³ is WP_grey. Uthai Thani province was the highest at 402 m³ and Udon Thani was the lowest at 138 m³_. The water footprint was found to be positively correlated with the amount of fertilizer used but was the opposite for cassava fresh root yield. The month of the year at harvest, number of months after planting and planting year tend to increase water footprint, whereas cultivar was not found to be related to water footprint.