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Chilean Journal of Agricultural Research
Instituto de Investigaciones Agropecuarias, INIA
ISSN: 0718-5820
EISSN: 0718-5839
Vol. 75, No. 3, 2015, pp. 284-290
Bioline Code: cj15038
Full paper language: English
Document type: Research Article
Document available free of charge

Chilean Journal of Agricultural Research, Vol. 75, No. 3, 2015, pp. 284-290

 en Over fertilization limits lettuce productivity because of osmotic stress
Albornoz, Francisco & Lieth, J. Heinrich

Abstract

It is customary that growers apply high doses of nutrients to the soil in order to achieve high yields, with detrimental consequences for the environment; but no information exists with regards to the crop response to high fertilization levels. To evaluate the physiological response of lettuce ( Lactuca sativa check for this species in other resources L.) to various root zone nutrient concentrations (expressed as electrical conductivity, from 0.6 to 10 dS m-1), a replicated experiment was conducted using increasing concentrations of macronutrients applied to the root zone in an aeroponic system. Leaf photosynthesis and chlorophyll fluorescence were measured using a portable infrared gas analyzer attached with a fluorometer. Leaf nutrient content was analyzed by mass spectrometry and NO3-N was determined by flow injection analysis. Leaf photosynthetic rates increased when the solution concentration was raised from 0.6 to 4.8 dS m-1, but further increases in solution concentration did not result in any differences. The enhancement in photosynthetic rates was related to higher concentrations of N, P, Mg, and S in leaves. Leaf K content was correlated with stomatal conductance. Maximum growth was achieved with solution concentrations between 1.2 and 4.8 dS m-1 while at 10.0 dS m-1 leaf production was reduced by 30%. It is concluded that at high concentration of nutrients supplied in the root zone, yield reduces because of a combination of decreased stomatal conductance and leaf area.

Keywords
Aeroponics; chlorophyll fluorescence; Lactuca sativa; leaf nitrate content; nutrient accumulation; tissue nutrient concentration

 
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