J Agronomy & Crop Science 178, 135—140 (1997) ,; ]997 Blackwell Wissenschafts-Verlag, Berlin isSN 0931-2250 OeBartarrtenlo de Suelos, Facultad de Agronomia, Vniversidad de Buenos Aires, Argentina Effects of Waterlogging Followed by a Salinity Peak on Rapeseed {Brassica napus L.) F H- Gutierrez Boem, R. S. Lavado and C. A. Porcelli Authors' address: Dr F. H. Gutierrez Boem, Professor Dr R. S. Lavado (corresponding author) and Dr C. A, Porceili, Avenida San Martin 4453, 1417 Buenos Aires, Argentina With 4figuresand 3 tables Received July 3, 1996; accepted October 3!, 1996 Abstract Due mainly to alterations in plant metabolism, lack of oxygen and excess salts are disturbances that affect crop yields. In different parts of the world crops are subjected to those disttirbances, simultaneously or successively. Our objective was to determine the effects of a winter waterlogging followed by a spring salt peak on rapeseed yield, A pot experiment, combining waterlogging and salinization was carried out. The waterlogging duration was: 0 (control), 3, 7 and 14 days and the sahnity treat- ments were peaks of Electrical Conductivity of 5 and 8 dS m ' and the control. The yield started decreasingfrotn 3 days during waterlogging, mainly due to the lower number of seeds per plant. The salt peak from 5 dS m"' affected the yield only in plants which had suffered a waterlogging lower than 7 days, showing interaction between salinity and waterlogging, Only salinity reduced oil content. The saline peak affected the K, Ca and Na concentration in plant tissues, but the effect of salinity on rapeseed could be more related to soil water potential than specific ion toxicities or imbalance. Keywords; Rapeseed — Brassica napus L. — water- logging — salinity. Introduction Lack of oxygen and excess salts are disturbances that affect crop yields mainly due to plant metab- olism alterations (Drew, 1992; Kalaji and Piet- kiewicz, 1993), When soil becomes waterlogged, the oxygen supply to the roots can quickly decrease. The speed of oxygen concentration decrease depends on soil microorganisms and root respiration rate (Glin- ski and Stepniewski, 1985). The consequences of this process on a crop growth are related, among other factors, to the waterlogging duration and the crop stage of development (Jackson and Drew, 1984). Salinity can affect plant growth either because of the decrease in soil water potential or the mcrease of ion concentration in plant tissues to levels that interfere with metabolism (Kalaji and Pietkiewicz, 1993). Under different conditions different plants are affected by water relations or ion balances (Gal- loway and Davidson, 1993; Munns and Termaat, 1986). Several investigations showed that salt tol- erance can vary with the phenological stage (Hoff- man and Shannon, 1986) and that the effects of saline stress change with its duration (Munns and Termaat, 1986). In several parts of the world crops are affected by waterlogging with salty waters. For instance, coastal swamps and marshes, poorly drained irrigated soils and low lying land subject to primary or secondary salinization (Barret-Lennard, 1986), Plants are, then, subjected to two simultaneous disturbances: anoxia and salinity (Perry and Williams, 1996). In other areas both disturbances occur successively, for instance river floods over salty soils (Galloway and Davidson, 1993). Another example is found within the Argentine Pampas in the area called Flooding Pampa. In that area crops are subjected to winter waterlogging caused by rainfall followed by spring- summer salinization peaks. Those peaks are tem- porary increases in soil salinity because of salts rising from groundwater, later leached by rainfall (Aicon- ada et al., 1993; Lavado and Taboada, 1988). Specific papers about the effects of waterlogging (Cannell and Belford, 1980) or salinity (Francois, 1994) on rapeseed have been published elsewhere. To assess the effect of each of these disturbances under the environmental conditions of the Flooding Pampa, we also carried out several pot experiments. They included winter and spring waterlogging (Gut- ierrez Boem et al, 1996), constant salinity (Gut- ierrez Boem et al., 1994), alkalinity (Gutierrez Boem and Lavado, 1996) and both salinity and alkalinity (Porcelli et al., 1995). Using the above mentioned methodology, our objective was to study the effects •' S. Copyright Cleamnco enter Code S.atonent. 0931-2250/97/7803-01 35 S14.00/0