Assessment of methods to determine the loss of water and nitrate in a lettuce crop grown in organic soil

• Published in: Acta horticulturae no. 889; pp. 403 - 408
• Main Authors: Bergeron Piette, E, Caron, J, Theroux-Rancourt, G, Rekika, D, Gosselin, A, Parent, L.E
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01.01.2011
• Subjects: evapotranspiration; fertilizers; groundwater; growers; irrigation management; leaching; lysimeters; nitrates; normal values; nutrient uptake; organic soils; prices; romaine lettuce; solutes; water balance; Quebec
• ISSN: 0567-7572
• DOI: 10.17660/ActaHortic.2011.889.50

Lettuce growers in organic soils have encountered numerous problems related to irrigation and fertilization. Water is becoming in short supply and fertilizer prices are going up while solute leaching to groundwater is a growing environmental concern. Growers are thus looking for improved irrigation and fertilization strategies with respect to high crop productivity, efficient water and nutrient uptake and solute leaching. The first objective of this project is to compare three methods of water flux estimation in terms of accuracy and relevance to water and nutrient use and leaching in a lettuce crop. Romaine lettuce was grown in organic soils of Southwestern Québec, Canada. Four pan lysimeters were installed at four sites at the depth of field drains. The pans were connected to a bucket. This provided reference values for water flux to the groundwater (first method). A second method to estimate the flux was based on the daily evapotranspirative demand. A third method was based on water balance, computed from changes in water storage and evapotranspiration demand. Water fluxes were combined with nitrate water concentration to determine the flux of solutes to groundwater. Nitrate concentration was measured in samples collected using a suction lysimeter. The three methods were compared for four irrigation strategies: one based on the evapotranspirative demand, another on a non-irrigated control and two others based on matric potential threshold values of -30 and -50 kPa. Our data suggest substantial nitrate leaching to lower depths, between 3.4 NO3- ha-1 and 171.0 kg NO3- ha-1 depending on the estimation method and the irrigation treatment. No effect on leaching was observed from irrigation treatments. Additional work is ongoing to reduce nitrate leaching in lettuce cropping on organic soils.