Water and nitrogen effects on lettuce evapotranspiration

Abstract

The purpose of this work was to evaluate the evapotranspiration of lettuce (Lactuca sativa) cv “Verônica” to water and nitrogen levels. The experiment was conducted on the greenhouse of Centro Técnico de Irrigação, at Universidade Estadual de Maringá campus (state of Paraná, South of Brazil), from March 16 to April 25, 2001. It was conducted in a 4 x 4 factorial scheme, with 16 treatments. The experimental design was completely randomized with four levels of water (W₁ = 62.5; W₂ = 75.0; W₃ = 87.5 and W₄ = 100% of the water retention capacity of the soil) and four levels of nitrogen (N₁ = 75; N₂ = 150; N₃ = 225 and N₄ = 300mg dm³) subdivided in five identical applications during the studied period in the plant cycle. Experimental unity was a vase with 2kg of soil and one plant of lettuce. The replacement of water occurred when the mass of water evapotranspiration of each treatment reached 50% of the water retention capacity. Within the greenhouse was also measured the evaporation by a pan (evaporimeter) with 60cm diameter and 25cm height. The lettuce evapotranspiration was influenced by water and nitrogen treatment. Lettuce evapotranspiration was linearly affected by nitrogen and quadratic affected by water levels. If soil water is no limiting, lettuce evapotranspiration decreases when nitrogen level increases.