Determination of Leafy Vegetables Need in Water and Nitrogen Use Efficiency by Using the Diviner 2000 and the Isotopes Techniques: Case of Amaranth (Amaranthus cruentus)

A study was conducted to determine how the nitrogen (N) in the fertilisers can be quantified and what amounts of fertilizers should be given to leafy vegetables to achieve their requirements. This study also aimed to determine the efficient use of water by the plant. The experiment was laid out in a randomized complete block with three replicates and three levels of urea (T₀ = 0 kg/ha, T₁ = 43.5 kg/ha, T₂ = 65 kg/ha). Estimation of growth parameters and biomass yield revealed that the treatments produced statistically identical values. But numerically, T₁ (43.5 kg of urea/ha) gave the highest yields and T₂ (65 kg of urea/ha) produced the lowest. It was the same for the determination of the water use efficiency (WUE) by the plant where T₁ produced the highest values compared to T₂. The yield curve as a function of the applied urea dose allowed the identification of the urea dose that corresponds to optimal yield in amaranth. From the dose of 65 kg of urea/ha, any increase becomes harmful to the plant. This results in a decrease in yield in the amaranth plant. (author)