Experimental study on suitable type of water for growing hydroponic lettuce

Abstract

By 2025, Bangladesh will have to feed about extra 90 million people than today. To meet the food demand will be very challenging in future. Moreover, climate change will affect traditional agriculture adversely. In addition to that, Bangladesh is a land scarce country where agricultural land is getting reduced by 1% per year. To overcome these challenges, hydroponics as a managed culture technique could turn into a good alternative food growing system in a Deep Water Culture system. In this context, an experiment was carried out at Bangladesh Agricultural Research Institute (BARI) on hydroponic culture for Lettuce (Lactuca sativa). Lettuce is a short growing (nearly 30 days after transplantation) leafy vegetable and a cash crop. The suitability of water had been studied using 3 types of water – rain, ground and distilled water for the experiment. The best water was selected mainly by counting the number of adjustment of nutrients with water, where the range of EC was 1-1.5 for 14 days after transplanting (DAT) and 1.5-2.0 for 15-30 DAT. The range of pH was maintained 6.5-7.0 during the total length of growing stage of lettuce. Each type of water showed almost similar suitability in terms of pH and EC management but ground water came out as the most suitable in terms of production, availability and cost of groundwater. The Benefit-Cost Ratios (BCR) are 1.32, 1.11 and 1.15 for ground water, distilled water and rain water respectively. All BCRs are greater than 1 and all might be acceptable. Crop co-efficient (Kc) - the ratio between reference evapotranspiration (ETo) and crop evapotranspiration (ETc) was also determined. The ETc of lettuce in hydroponic system was estimated by Lysimeter method while ETo was determined by CROPWAT software. The acceptable Kc was found as 0.73 for Lettuce. The study will be helpful for hydroponic farmers to select suitable water type and to estimate irrigation water requirement (IWR) and nutrient solution requirement for each crop cycle easily. BCR demonstrates a higher value which is encouraging for a hydroponic farmer. Hydroponic bears a great potential in Bangladesh.