Lettuce production to water and nitrogen levels

Abstract

The purpose of this work was to evaluate the production 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 N/dm³) subdivided in five identical applications during the studied period in the plant cycle. Every experimental unity was compound of one 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 of the soil. The lettuce production was linearly affected by nitrogen and quadratic affected by water levels. Water and nitrogen are substituting production factors to lettuce, then increasing any of factors on soil, the other can be reduced without changing the production.