Abstract :
[en] Thinopyrum intermedium subsp. intermedium is currently proposed as a perennial grain crop. This crop is multifunctional by providing grain for human consumption, forage for livestock and multiples ecosystem services thanks to its year-round soil cover and its extensive root system. In comparison to annual crops, Th. intermedium prevents nutrient leaching (Jungers et al., 2019) or enhances soil biodiversity (Förster et al., 2023). However, the allocation of resources to grains is low with a nitrogen harvest index ranging from 20 to 50% (Fagnant et al., 2024). This work aims to quantify the proportion of dry matter and nitrogen (N) allocated within the different above- and belowground plant parts during an entire growing season. This first characterization of the N uptake across plant tissues could represent a preliminary step to improve Th. intermedium through crop breeding or field management. In this study, we used two experimental field with similar soil types located in the experimental farm of ULiège – Gembloux Agro-Bio Tech, Belgium, during the cropping year of 2022 representing the first and the third cropping year of the fields. Th. intermedium seeds originated from the fifth cycle of selection of the Land Institute (Kansas, USA). Biomass of the different plant parts (i.e., leaves, stems, spikes, stem bases, rhizomes, and roots) were sampled at specific phenological stages and their N concentrations were measured. The total aboveground biomass increased until grain maturity and ranged from 13 to 18t of DM ha-1. Within the aboveground biomass, stem bases represented an important proportion accounting from 30 to 54% during the reproductive phase. The belowground biomass sampled until 15cm deep increased until the flowering or the grain maturity and ranged from 4 to 5t of DM ha-1 at grain maturity. Rhizomes only represented 4 to 21% of this belowground biomass and were initiated at the flowering during the establishment year. Root biomass of Th. intermedium in third year halved between the flowering and the autumn vegetative stage. Concerning N allocations, N amount within stems and leaves decreased at the end of the growing season, that wasn’t transferred within spikes. An exception was observed for plants in the establishment year with a weak increase (i.e., 10 kg of N ha-1) of the spikes’ N amount from the flowering to the grain maturity. The N amount within stem bases and rhizomes slightly increased from the flowering to the autumn vegetative stage. Roots’ N amount stayed constant for plants in the establishment year and decreased from the flowering to the autumn vegetative stage for plants in the third year. This led to a loss of N within the whole plant of 56 kg of N ha-1, that was not observed during the establishment year. The first year represented a phase of field establishment of the crop, where the N and dry matter allocations during the growing season increased within perennial and reproductive organs. By contrast, for a crop in the third production year, we observed a decrease of root biomass accompanied by a decrease of the whole plant N at the end of the growing season, indicating no efficient nutrient recycling through translocation to perennial organs. The release of N-rich root exudates or root tissue turnover could lead to an influx of organic N in the soil, that was suggested by Dobbratz et al. (2023) for Th. intermedium from the grain maturity to the autumn regrowth.
Dobbratz, M., Jungers, J.M., & Gutknecht, J.L.M. (2023). Seasonal Plant Nitrogen Use and Soil N pools in Intermediate Wheatgrass (Thinopyrum intermedium). Agriculture, 13(2), 468. https://doi.org/10.3390/agriculture13020468
Fagnant, L., Duchene, O., Celette, F., & Dumont, B. (2024). Maintaining grain yield of Th. intermedium across stand age through constant spike fertility and spike density: Understanding its response to various agronomic managements. European Journal of Agronomy, 152, 127038. https://doi.org/10.1016/j.eja.2023.127038
Förster, A., David, C., Dumont, B., Dimitrova Mårtensson, L.M., Rasche, F., & Emmerling, C. (2023). Earthworm populations and diversity under annual and perennial wheat in a North to South gradient in Western Europe. European Journal of Soil Biology, 119. https://doi.org/10.1016/j.ejsobi.2023.103561
Jungers, J.M., DeHaan, L.H., Mulla, D.J., Sheaffer, C.C., & Wyse, D.L. (2019). Reduced nitrate leaching in a perennial grain crop compared to maize in the Upper Midwest, USA. Agriculture, Ecosystems & Environment, 272, 63–73. https://doi.org/10.1016/J.AGEE.2018.11.007
