The fate of 15N fertilizer and nitrate leaching losses in perennial wheat (Thinopyrum intermedium) versus annual wheat (Triticum aestivum)

Abstract:

Perennial and annual grain differ in ways that may affect their nitrogen (N) fertilizer use efficiency, total N losses, and water use. Larger root systems in perennial crops, less disturbance of the soil, and the year-round cover that perennial crops provide may reduce erosion, nitrate leaching, and overall N losses compared to annual crops. We set out to quantify nitrate leaching, N mineralization, and the fate of ¹⁵N-labeled fertilizer in both annual (Triticum aestivum) and perennial (Thinopyrum intermedium) wheat crops over two growing seasons at a long-term agricultural research site in southern Sweden.

Our preliminary findings are that nitrate concentrations in soil water collected from tension lysimeters were approximately one order of magnitude higher in annual wheat compared to perennial wheat in year one in the beginning of the winter when the soil gets wet enough for leaching to occur. Soil moisture was generally lower in the perennial wheat plots compared to annual wheat plots. Fertilizer recovery within the plant biomass was higher in annual wheat than perennial wheat in year one (2019), and we will collect samples from the 2020 harvest to track the fate of fertilizer into year two to be able to infer total ecosystem N recovery versus N loss. Perennial grain crops may reduce many of the negative environmental consequences of annual crops, but more research is needed to test and quantify potential differences between these cropping systems.