Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Aqueous Nitrogen Dynamics in Irrigated Cropping Systems : Improving precision agriculture and environmental performance for the Australian cotton industry

Auteur : Latimer, James

Université de soutenance : Australian National University

Grade : Doctor of Philosophy (PhD) 2021

Description partielle
The Australian cotton industry is an archetypal example of precision agriculture in action, having achieved significant efficiency gains in yield (kg lint ha-1) and water use (kg lint ML-1) over the past 50 years through sustained research and development investment. Unfortunately, nitrogen fertiliser use efficiency (NFUE) has not experienced the same gains over this period, and has instead declined. Australian irrigated cotton production requires high nitrogen (N) inputs to maintain its high yields. N application rates (kg N ha-1) have increased over recent decades due to a range of factors, including low fertiliser costs and grower risk appetites. Average yields have also increased over this period ; however, they have not been proportional to the rise in N applications, resulting in steadily declining NFUE. While significant research describing N dynamics in Australian cotton systems already exists, there remain many research gaps to be filled. This thesis aims to address four research gaps to provide additional management levers for the Australian cotton industry to improve NFUE. The four topics explored herein are : (1) the effectiveness of aqueous N application (fertigation or water-run) ; (2) the mechanisms driving surface runoff N losses in flood irrigation ; (3) the reaction rates and residence times of aqueous N ; and (4) the degree of plant access to different soil N molecules. A series of field, laboratory, and glasshouse experiments were used to address these questions. Three field experiments measuring fertigation application efficacies were conducted on private farms in the Riverina, New South Wales (NSW) over the 2016-17 summer season. Another field experiment was performed at the Australian Cotton Research Institute (ACRI) in Narrabri, NSW over the 2017-18 season, measuring N runoff variations in alternate furrow irrigation configurations.

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