Qualifying soil moisture heterogeneity and its impact on tomato Solanum lycopersicum transpiration response under water stress at pot scale

Details

Supervisors

Couvreur, Valentin

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

Water is essential for crops, ensuring good growth and productivity. As climate change is projected to increase severity and frequency of droughts, threatening the cultivated tomato Solanum Lycopersicum, understanding plants response mechanism in water deficit is crucial. Soil water heterogeneity gained significant importance recently with the advent of irrigation method that proved to increase plants water use efficiency when under heterogeneous spatial soil water repartition. In this exploratory study the mechanisms of soil water heterogeneity and its relations with plants are observed. Two groups were set: bare soil pots and plant pots. Both were put under increasing water stress. Soil water heterogeneity was measured with four sensors in each pot measuring matric potential continuously. Transpiration weas measured continuously through weighing scales. Results showed that heterogeneity for plants behaved following a concave curve with decreasing matric potential. For bare soil, heterogeneity increase linearly, which does not fit with standard literature findings and could be explained by measurements errors or short range of matric potential. Overall, less heterogeneity in plants than bare soils was observed through each level of decreasing matric potential, thereby suggesting a homogenizing effect of plant. Horizontal and vertical heterogeneity revealed equivalent among bare soil pot and plants pot which raised the question of the pot effect that would reduce natural horizontal heterogeneity for bare soil and increase the overall root density for plants. Transpiration seemed to be more responsive to higher water potential in the pot. Further measurement of leaf water potential and assessment of the osmotic potential impact could increase the accuracy of this result. Waterings revealed to impact heterogeneity depending on antecedent matric potential state and watering amounts, most heterogeneity was created after a medium watering (40g water/liter pot) at medium matric potential (-400 to -800kPa). Overall, this study highlighted various aspects of heterogeneity dynamics in relation with plants and proposed several improving factors for further experiments especially for getting reliable matric potential measurement with one sensor.