Développement d'une approche intégrée d'irrigation en production de pommes de terre

Authors: Matteau, Jean-Pascal
Advisor: Gumière, Silvio J.
Abstract: Water scarcity is increasingly recognized as the most pressing limitation to improvement in agricultural production over the upcoming decades. It is expected that the world population will reach 8.6 billion by 2030 and 9.8 billion by 2050, increasing the demand for both food and agriculture production. Therefore, increasing overall water productivity is one of the most critical challenges of the twenty-first century. Potato isthe fourth most cultivated food crop behind wheat, maize, and rice. Among the major crops, potato is the most efficient in calory production by water liter, but potato yields are recognized as sensitive to water stress. Therefore, the precise control of the amount of irrigation water, water application timing, and prevailing micro-meteorological conditions are critical factors that influence the plant health and yield. However, the increasing pressure on agricultural systems can endanger soil health, as several soil health indicators are affected by agricultural production, like soil structural stability, bulk density, hydraulic conductivity, and soil organic carbon. Maintaining soil healthis critical to preserve soil ecosystemic functions like water infiltration, filtration andstorage, nutrient cycling, and carbon storage, impacting plants productivity, and wateruse efficiency. The objective of this thesis was to create an integrated irrigation approach for the potato crop, allowing optimal potato yield, water use efficiency, and minimizing the environmental impact of irrigation. Through six green house experiments using an automatic irrigation system managed using a soil sensors network, the effect of irrigation management on the potato varieties, potato yield, water use efficiency, tuber spatial distribution, and soil organic carbon dynamics has been analyzed and temporalized. The second and third chapters of this study evaluated the effect of precision irrigation thresholds on the potato yields of four varieties with different maturity classes (Envol: very early, Kalmia: early, Goldrush: mid-season, and Red Maria: mid-late). Anoptimal comfort zone between −10 and −24 kP a has been identified. The optimal irrigation thresholds identified were not dependant on maturity class, plant height, or tuber potential production. The −24 kP a is the precision irrigation threshold that allowed higher yields and water use efficiency. The time spent in the comfort zone was identified as critical for the potato yield. The analysis of the irrigation thresholds'temporal effect made in the third chapter showed that precise irrigation managementis needed early in the season and should be maintained throughout all the growingseason as the critical period identified corresponded to the leaf expansion and tuber initiation stage. An appropriate irrigation management of potato crops has been shownto increase yield by a 25 to 40% margin. The fourth chapter evaluated the impact of four soil matric potential (−10, −20, −30,and −45 kP a) on potato tubers’ spatial distribution using an X-ray CT scanner. Alinear relationship between irrigation thresholds and potato tuber depth was identified.The deepest tuber distribution was observed with the −10 kP a treatment. Potato irrigation management using a SMP threshold between −20 and −30 kP a could reduce the harvest depth. Reducing the harvest depth could decrease the negative impacts of soil disturbance on soil structural stability. In the −45 kP a treatment, the tubers were too close to the soil surface, which could lead to a greater preponderance of tuber diseases like late blight or greening. The precision irrigation threshold used in this study affected the decomposition rate of soil organic carbon, evaluated in the fifth chapter. Faster decomposition of labile organic carbon was promoted by water excess (−15 kP a). The dryer (−30, −45, and −60 kP a) precision irrigation thresholds did not show any differences. The difference between the precision irrigation thresholds was made in the second quarter of the growing season,between 38 and 53 days after planting. This critical period occurred in a stage of strong vegetative growth and rapid irrigation cycles, the tuber initiation and tuber bulking stages. The determination of an integrated irrigation management approach will allow potato growers to adapt their farm management processes to integrate more sustainable water management practices and to achieve higher yields and water use efficiency. Improving soil water management may also optimize tuber spatial distribution, enhance harvest efficiency, reduce greenhouse gas emissions, soil carbon degradation, and soil disturbance in the cropping systems to benefit global soil health conservation.
Document Type: Thèse de doctorat
Issue Date: 2021
Open Access Date: 12 July 2021
Permalink: http://hdl.handle.net/20.500.11794/69585
Grantor: Université Laval
Collection:Thèses et mémoires

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