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Wageningen University (2009)

Detecting the effect of sodic soils on alfalfa crop performance in Saratov, Russia

Croes, J.

Titre : Detecting the effect of sodic soils on alfalfa crop performance in Saratov, Russia

Auteur : Croes, J.

Université de soutenance : Wageningen University

Grade : Master of Science (MS) 2009

According to the Millennium Ecosystem Assessment (MEA, 2005) the percent of drylands affected by degradation lies between 10% to 20% MEA (2005). This process, if based on the total number of people threatened by it, ranks among one of the greatest contemporary environmental problems (MEA, 2005). In the semi-arid climate of Saratov, Russia, land degradation, especially in the form of alkaline salinity, plays an active role in the region where agriculture is very important to the regions population. It is therefore of essence to be able to understand the effects of salinized land on crop performance. This research project is a joint effort, which focuses on the performance of alfalfa, when the effects of soil salinity and the crop water stress are taken into account. This thesis focuses on the former, while the latter is discussed in Beets (2009). The experimental design comprised of measuring : the EC, pH and soil moisture at different depths in the soil. The measured characteristics of crop performance consisted of : above ground biomass, root biomass to 40 cm depth in 20 cm partitions, maximum plant height, plant density, leaf area index (LAI) and plant water content (plant H2O). The statistical techniques performed on these variables were kept simple due to a small sample pool and included pair wise correlations and partial correlations to discover the strongest relationships between the variables. The results of the different analyses indicated that the root biomass, in general, was significantly correlated with EC as well as pH. Plant water content was in turn negatively correlated with EC. Plant H2O, fresh biomass and LAI were all positively correlated with soil moisture, as expected. The other plant characteristics did not produce any significant correlations. These results indicated that both EC and pH had a positive effect on the alfalfa root biomass, which is normally unlikely in salinized soils. For EC, this was due to saline levels not being high enough. The positive correlation between pH and root biomass at such high pH (basic) levels, however, is a relationship that has not been observed before and more research is required to be able to explain this occurrence. The negative correlation between plant H2O and EC is explained by an increase in soil water potential and osmotic stress.

Mots clés  : medicago sativa / lucerne / sodic soils / alkaline soils / land degradation / russia


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