Selection of site and farmers:
Selection of project sites were made based on two major criteria: a well designed and working drainage/sewerage system to collect water discharged from household, commercial establishment, industries and storm water; a peri-urban farmers community already using wastewater for irrigation to produce vegetable crops. Thus the site selected for this project was Terokhadia, a peri-urban area of Rajshahi city and Debidwar upazila under Comilla district. In both areas, farmers are cultivating vegetable crops by using municipal wastewater for many years. So, farmers who are already using wastewater for growing vegetable crops were selected.
Field trials:
Field trials have been set up at farmers’ field of Terokhadia under Rajshahi municipality and at Debidwar upazila under Comilla district with leafy vegetables like spinach and Indian spinach, with salad crops like tomato and with root crop like potato in order to investigate the role of municipal wastewater on yield and quality of these crops. Changes in wastewater irrigated soil and nutrient requirement of crops under wastewater irrigation will also be investigated.
Experimental with leafy vegetables:
Field experiment on Indian spinach and spinach has been set up at the farmer's field in Terokhada village, which is at the outskirt of Rajshahi City Corporation. The soil was silty clay loam having a bulk density of 1.44 gm/cc and field capacity of 29.57%. The experiment was designed in a split plot with two irrigation methods as a main factor and three fertilizer doses as sub-factor that replicated thrice to identify effect of wastewater on the yield and quality of leafy vegetables (Indian spinach and spinach), a intensively cultivated vegetable in sub-urban area of Rajshahi. The treatments were as follows:
Irrigation method:
I1 = Flood irrigation with wastewater
I2 = Broad bed furrow irrigation with wastewater
Fertilizer dose:
F1 = 100% of recommended fertilizer dose
F2 = 80% of recommended
F3 = 60% of recommended
For spinach, six treatment combinations were made using two irrigation methods and three fertilizer doses. An additional treatment of freshwater irrigation with 100% fertilizer dose was kept as a control. Then these seven treatments replicating thrice were assigned in 21 elementary plots in a randomized complete block design. The standard dose of fertilizers was calculated with the help of Fertilizer Recommendation Guide (FRG, 2012) considering soil nutrient status as 92, 20, 20, and 5 kg/ha of N, P, K, and S, respectively, for spinach and 115, 20, 50, and 18 kg/ha of N, P, K, and S for Indian spinach. The entire amount of these fertilizers under specific doses, except nitrogen, were applied and incorporated into soil at the time of final land preparation. Nitrogen was applied in two equal split for spinach: half at final land preparation and rest half at 25 DAS; and for Indian spinach in three equal splits: one-third each at final land preparation, and at 25 and 45 DAP as top dressed. Seeds of spinach were sown on 7 December 2017 at a spacing of 20 cm line to line while Indian spinach were planted on 12 December 2017 with a spacing of 25 cm x 15 cm in a elementary plot of 5 m x 4 m. Each elementary plot was separated by a 0.5 m buffer to avoid any interference of fertilizers from one plot to another one.
Experimental with potato and tomato:
Field experiment on potato, a popular vegetable crop to wastewater farmers, was laid out in Randomized Complete Block Design (RCBD) with seven treatments and three replications. The treatments were as follows:
T1 = Furrow irrigation by fresh water with 100% of recommended fertilizer (standard practice)
T2 = Furrow irrigation by wastewater with 100% of recommended fertilizer
T3 = Furrow irrigation by wastewater with 80% of recommended fertilizer
T4 = Furrow irrigation by wastewater with 60% of recommended fertilizer
T5 = Alternate furrow irrigation by wastewater with 100% of recommended fertilizer
T6 = Alternate furrow irrigation by wastewater with 80% of recommended fertilizer
T7 = Alternate furrow irrigation by wastewater with 60% of recommended fertilizer
Potato was irrigated four times-just after planting and at 25, 45 and 65 days after planting (DAP).
Experiment with tomato was laid out in Randomized Complete Block Design (RCBD) with the following four irrigation methods replicated thrice.
I1 = Traditional furrow irrigation at 10 days interval with wastewater
I2 = Alternate furrow irrigation at 10 days interval with wastewater
I3 = Broad bed furrow irrigation at 10 days interval with wastewater
I4 = Drip irrigation at 3 days interval with wastewater. Recommended fertilizers doses was 138 kg N, 30 kg P, 90 kg K, 12 kg S, 1 kg Zn and 1 kg B/ha for potato and 140 kg N, 34 kg P, 50 kg K, 18 kg S/ha for tomato. The entire amount of these fertilizers under specific doses, except nitrogen, were applied and incorporated into soil at the time of final land preparation. Nitrogen was applied in two equal split for potato: half at final land preparation and rest half at 25 DAP; and for tomato in three equal splits: one-third each at final land preparation and at 25 and 45 DAP as top dressed. Cut tubers of sprouted potato were planted on 5 December 2017 at a spacing of 60 cm x 15 cm in a unit plot of 6 m x 4.2 m while 30 days old of tomato seedlings were planted on 3 December 2017 with a spacing of 60 cm x 40 cm in an elementary plot of 4.8 m x 4 m. Each elementary plot was separated by a 0.5 m buffer to avoid any interference of fertilizers from one plot to other ones.
Statistical analysis of data:
The collected data were evaluated statistically by the analysis of variance (ANOVA) in MSTAT software. The parameter means were separated by Duncan’s multiple range tests.