Improving traditional leafy vegetables production through water use efficiency and fertilizer microdosing technology in Benin Republic

In most developing countries, water and fertilizer management pose serious problems to vegetables production. This study aimed at determining the fresh leaf yields and Water Use Efficiency (WUE) under microdosed fertilizer technology of two main traditional leafy vegetables (TLVs) (Amaranthus cruentus L. and Solanum macrocarpon L.) that are consumed in Benin. A field experiment was carried out at Centre de Recherche Agricole d'INA, Northern Benin, under sprinkler irrigation at maximum evapotranspiration (MET) calculated from Cropwat 8.0. The study was laid out in a randomized complete block design with four replications and two factors: 1) urea (46% N) applied at D0, D20, D40, D60, D80 (kg ha^-1) and 2) urea application timing at d1: early application (10 days after transplanting, DAT) and d2: later application (15 DAT). Following the MET (6.6 mm day^-1), plants were irrigated twice a day (morning and evening) at 3.3 mm per watering. This irrigation rate was applied by operating the sprinklers with 0.078 mm min^-1 of water flow for 44 min. Soil moisture and drainage were measured every week using TDR (time domain reflectometry) probe and micro-lysimeters respectively. The water balance was calculated using the trapezoidal method. WUE was determined using the ratio of dry biomass yields and real crop evapotranspiration (RET). Data were analyzed with R software following analysis of variance (ANOVA) and Pairewise t test at 0.05 level of probability. Quadratic regression was used to model TLVs response to fertilizer rates. At D60d1 and D40d2 we recorded the highest RET (35-42.45 mm week^-1), highest fresh biomass yields (4.5-4.7 t ha^-1 for eggplant and 9.9-10.5 t ha^-1 for amaranth) and highest WUE (2.5-4 kg ha^-1 mm^-1), respectively. Microdosed fertilizer technology may be therefore used to improve TLVs production and WUE because it may contribute to reduce fertilizer use by 2.5-10 times for urea and to 50% irrigation water while increase fresh leaf yield by 30-64%.