Influence of evapotranspiration and irrigation on potato crop

A field study on the influence of evapotranspiration (ET) and irrigation on potato production was carried out from 1994 through 1997 at Bangladesh Agricultural Agricultural Research Research Institute (BARI), Joydebpur (24.01°N, 90.43°E), Gazipur. The actual ET was studied through a well designed metallic drainage type lysimeter containing 4 tanks, each with 1 m2 surface area and 1 m effective depth. Irrigation need was studied in the field surrounding the lysimeter. The variety of the crop was cardinal. Dry tuber (y) and tuber plus shoot (Y) in t ha1 were found to be related with ET or consumptive use in cm according to the following equations: Y = -1.3625+0.48486ET Y = 0.5+0.55ET 2.44 cm≤ET≤43.83 cm An average standard seasonal ET obtained in lysimeter was found to be 310 mm with a maximum daily ET being about 5.68 mm/day at around 50 days after planting (DAP) for a yield of around 65.5 t ha1 at 80% m.c. (d.b.). The daily ET (DaET) in mm may be represented by the following equation. DaET = 1/(.00084x.9242-DAP + 0.0869 +2.2576x.9242DAP) Crop coefficient referred to Penman-Monteith, FAO corrected Penman, Hargreaves, FAO radiation, FAO corrected Blaney Criddle and Pan evaporation are presented in graphs. Highest crop coefficients were at around 55 DAP. At this stage of growth Kc (PnMon) was around 2.25 as the highest of all methods and the lowest one (1.45) was in Hargreaves methods. Growth of dry potato in a in a standard irrigation practice (applied every 10 days up to 80 DAP) can be fitted to the following equations: Y = 1/(0.1176+107.641x0.8978 DAP), y = 1/(1.2x10-6x0.8978-DAP+2.18x10-3+0.9982x0.8978 DAP) where Y and y stand for cumulative and daily growth of dry potato in t ha1 and Kg ha1, respectively. The single best lysimeter (1 m2) yield was about 82 t ha1 and the single best plot (29.7 m2) yield was about 49 t ha‍1. The highest leaf area index (LAI) was about 3.4 at 70 DAP. Daily growth was maximum at 40 DAP which was about 0.09 d1. The relations of LAI and its daily growth (DaLAI) with DAP were as follows: LAI 1/(0.3219+43.2743x0.89144 DAP) 1=3 DaLAI = 1/(.02083x.89144-DAP +5.6015+376.581x.89144 DAP) -1 Irrigations at 15, 30, 40, 50, 60 and 75 DAP (total 6 applications) were found most suitable for potato production. Dry potato yield (Y, t ha1) was related to the product of amount (A) and number of irrigation (NI) application per season (ANI) as follows: 0.141858 Y = 2.4288x (ANI) r = = .9370 Final yield response functions were as follows: When stressed at stolonisation, Ya When stressed at tuberization, Ya -- 1=3 When stressed at bulking, Ya = Y{1-1.1371 (1-ET2/ET)} Ym{1-.9316(1-ET2/ETm) } Ym{1-.7567 (1-ET2/ETm) } Planting of potato at the 4th week of November appears better than planting about a fortnight earlier from the view point of yield.