The experiment was set-up at the research field of Irrigation and Water Management Division (IWM), Bangladesh Agricultural Research Institute (BARI), Gazipur during the rabi season of 2017-2018. BARI Tomato-14 cultivar is used for this experiment. Six irrigation treatments were used, where each treatment was replicated thrice following randomized complete block design (RCBD). The treatments were as follows:
T1 = Full irrigation (FI) with biochar at a rate of 10 t/ha
T2 = Deficit irrigation (75% of FI) with biochar at a rage of 10 t/ha
T3 = Deficit irrigation (50% of FI) with biochar at a rage of 10 t/ha
T4 = Full irrigation with no biochar
T5 = Deficit irrigation (75% of FI) with no biochar
T6 = Deficit irrigation (50% of FI) with no biochar
** All the treatments were under drip irrigation at applied at 3-5 days interval.
The soil was sandy clay loam with pH 6.44, field capacity 28.6%, wilting point 14.3% (by weight basis) and bulk density 1.51 g/cc. The weather of the experimental site during the crop growing season was colder, where maximum temperature was recorded in April and minimum temperature was in January. The average relative humidity was recorded highest in the month of December and gradually decreased afterwards. A total rainfall 106 mm was recorded during crop season. A summary of the weather information of the experimental location is given.
The unit plot size was kept as 1.8 m × 4 m, where the experimental blocks are separated by 2 m and the plots in each block are separated by a buffer of 1 m. Tomato plants of 28 days were transplanted on 11 December 2018. Plant to plant distance are kept 40 cm and line to line distance are maintained as 55 cm. Biochar, which was made through the pyrolysis of mango and mehgani wood, collected from the Christian Commission for Development in Bangladesh (CCDB). It was then mixed with cowdung at a ratio of 1:1, maintained adequate moisture and left for a week before application in the plot (Blackwell et al. 2009).
Finally, inoculated biochar was evenly mixed with the top soil of the plots (T1, T2 and T3) during final land preparation. Land preparation was done by using tractor, power tiller, etc. Fertilizers were applied in the form of urea, TSP, MP, gypsum, borax, and zinc sulfate (N100P55K120Zn4B1Mg4 kg/ha and cowdung 10 t/ha) following the Fertilizer Recommendation Guide (FRG) 2012. Where, N and K in the form of Urea and MP, respectively, were applied with irrigation water into four splits. The total P in the form of TSP, other micronutrients and cowdung were applied during final land preparation. Irrigation was applied by drip method, where timing of irrigation generally kept within 3-5 days interval (to meet the demand of crop ET) and the amount of water in each irrigation event was determined following the individual treatments. A 200-litres water tank (0.5 m height) placed on an iron stand of 1 m height was used as the water source to the drip system of each treatment. Admire and Bavistin were applied few times to control while fly and fungus. Weeding was done according to necessary. When the fruits got matured, harvesting was started from 12 March 2018 till 20 April 2018, when the plants were uprooted.
The soil moisture content upto root-zone depth (45 cm) in each plot was monitored by using the gravimetric method at seven-day interval started from sowing to harvest.
Finally, water productivity (WP) was calculated as the ratio of fruit yield and water use (SWU).
Both NH4-N and NO3-N were extracted from the soils during the crop growing period to determine the available N in the soil sample (Jackson (2005). Microbial respiration from the soil in different treatments were also assessed periodically by trapping emitted CO2 in NaOH (Anderson 1982). All assays were performed in triplicate. The trapped CO2 was measured by adding 15 mL of 10% w/v BaCl2 to the NaOH to precipitate BaCO3. The remaining NaOH was then back titrated against 1M HCl to the phenolphthalein to neutralize NaOH. Finally, more HCl was added to the methyl orange to dissolve BaCO3.
Data on the yield attributing characters of tomato (plant height, number of branches per plant, number of marketable and curl fruit per plant, fruit length, fruit diameter, unit weight of the fruits, weight of marketable and curl fruit per plant, and marketable and curl yield) were collected during the crop growing season as well as after the harvesting was done.
During the early maturity stage (at 12 March 2018), evenly shaped and ripened fruits were collected for quality analysis between the fully irrigated biochar and non-biochar treatments (T1 and T4). Five tomatoes were drawn from each item (2 Treatments and 3 replications) and dipped for five minutes in the pure water and then washed in clorox (250 ppm) solution, finally, air dried at ambient temperature for 10 minutes. The samples were finally assessed for TSS (°B), titratable acidity (%), total carotenoids (mg/100g) and Vitamin-C content (mg/100g) following the method described by Ranganna (1986).
After the raw data is collected field and the lab, it was then converted and processed to the standard units to make suitable for the analysis. Finally, data analysis was done using Statistix 10 software and tabulated according to the desired format.