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Doctoral thesis, 2016

Nutrient economy in annual and perennial crops

Pourazari, Fereshteh


Nitrogen use efficiency (NUE) of agricultural crops is related to crop nitrogen (N) uptake and thereby the amount of N that is removed from agro-ecosystems through crop harvest. As the N removal through harvest is linked to the fertilization requirements and the risk of N leaching, the crop NUE is an important aspect of sustainability in agriculture. Crops with different life strategies, photosynthetic pathways, and selection and breeding histories are expected to have different NUE; and the N content of the harvested crop fractions (e.g. total aboveground, grain or tuber) is linked to the N removed from the agro-ecosystem. Therefore, crop traits and desired end use (e.g. fodder, energy or industry use), are expected to impact the NUE and sustainability of crop production (sensu N removal). The aim of this thesis was to evaluate the variation in NUE between and within several crops commonly grown in Sweden, and to identify the most N efficient crops for specific end uses. Various NUE components of maize, winter wheat, mixed perennial ley and potato crops were compared in field and pot experiments. In wheat and potato, the NUE was further investigated by comparing different varieties. The yield output per harvested N (i.e. N removal from agro-ecosystem) was assessed in relation to different end uses, i.e. crude protein and energy output (wheat, maize and ley) or amylose content (two potato varieties). In wheat, the concentration of plant N was further investigated in relation to the concentrations of other elements (P, K, Ca, Mg, S, Mn, Fe, Cu, Na) during two growth periods with different weather and after different preceding crops. On a growing-season basis, the highest and lowest harvested biomass was found in potato and wheat, respectively. Ley produced moderate yields with moderate N concentrations coupled with a low N uptake, making ley the most sustainable (sensu N removal) crop for fodder production. In contrast, moderate biomass production in maize was associated with high N uptake and low yield N concentration, making maize the most sustainable crop for energy production. A potato line genetically modified (GM) for high tuber amylose content had a higher tuber yield and N uptake efficiency than its non-GM parent. Ancient wheat varieties responded weakly to increased N availability and had a higher N uptake efficiency and grain N concentration than modern varieties; suggesting that those varieties can be interesting material for breeding. Element concentration pattern in wheat was strongly affected by developmental stage and weather, but not by preceding crop; N displayed a strong influence on the concentration pattern for all elements. Overall, the assessment of the functional links between crop yield, yield quality and N removal from the agro-ecosystem can contribute to the development of a more sustainable agriculture.


nitrogen use efficiency; sustainability; stoichiometry; wheat; maize; ley; potato

Published in

Acta Universitatis Agriculturae Sueciae
2016, number: 2016:70
ISBN: 978-91-576-8642-8, eISBN: 978-91-576-8643-5
Publisher: Department of Crop Production Ecology, Swedish University of Agricultural Sciences

Authors' information

Pourazari, Fereshteh
Swedish University of Agricultural Sciences, Department of Crop Production Ecology

UKÄ Subject classification

Agricultural Science

URI (permanent link to this page)