Intermediate Wheatgrass Grain and Forage Yield Responses to Nitrogen Fertilization

Abstract

Perennial crops have fewer environmental impacts compared to annual crops, but there are no perennial grains available to replace the annual grains that occupy a majority of U.S. cropland. Here we report grain and biomass yields from an improved breeding population of intermediate wheatgrass (IWG) [Th inopyrum intermedium (Host) Buckworth & Dewey], a perennial grass being domesticated to serve as the fi rst widely grown perennial grain crop. Our objective was to measure grain and biomass yields of this improved grain-type IWG (TLI-C2), a forage variety of IWG (cultivar Rush), and switchgrass (Panicum virgatum L.) in response to N fertilization rates ranging from 0 to 200 kg N ha -1 . TLI-C2 grain yields responded quadratically to increasing N rates in all but one environment, but yields declined at high N rates due to lodging. TLI-C2 grain yields were highest during the fi rst year of fertilization, yielding 961 and 893 kg ha -1 when fertilized at agronomically optimum nitrogen rates (AONRs) of 61 and 96 kg N ha -1 for stands seeded in fall of 2011 and spring of 2012, respectively. Grain yields declined with stand age. When fertilized with AONRs for grain, biomass yields of TLI-C2 harvested aft er grain ranged from 9.2 to 12.3 Mg ha -1 and had similar forage and bioenergy quality characteristics compared to Rush, which demonstrates the potential to manage TLI-C2 as a dual-use cropping system for both grain and forage.

Has Selection for Grain Yield Altered Intermediate Wheatgrass?

“…As previously reported [1], 2013 had the highest mean seed yield and the highest individual seed yields and SYA (Table 1). Field trials had yield decreasing as the stand aged [20]; however, this was not the general result on our space plants, with some plants retaining relatively high productivity.…”

“…Plant long-term yielding potential may be decreasing with age, or agronomic management deficiencies may be implicated here [39]. A rapid decrease in seed yield with stand age was reported in Minnesota with intermediate wheatgrass [20]. Seed yields of lines selected for seed production in Saskatchewan in the 1960s, showed comparative or sometimes higher three-year seed yields when compared to those reported recently [20].…”

How Does Nitrogen and Perenniality Influence Belowground Biomass and Nitrogen Use Efficiency in Small Grain Cereals?

“…Soil C sequestration and reduced NO 3 leaching are two of the most promising ecosystem services that can be achieved within perennial grain cropping systems (Culman et al, 2013). For example, perennial root systems have been shown to capture large amounts of N, which can lead to reduced NO 3 leaching (Syswerda et al, 2012;Jungers et al, 2017), and soil C accumulation is largely driven by the production and decay of fine roots ( Jackson et al, 1997). For example, perennial root systems have been shown to capture large amounts of N, which can lead to reduced NO 3 leaching (Syswerda et al, 2012;Jungers et al, 2017), and soil C accumulation is largely driven by the production and decay of fine roots ( Jackson et al, 1997).…”

“…However, these ecosystem services are primarily driven by root production. For example, perennial root systems have been shown to capture large amounts of N, which can lead to reduced NO 3 leaching (Syswerda et al, 2012;Jungers et al, 2017), and soil C accumulation is largely driven by the production and decay of fine roots ( Jackson et al, 1997). Given that practitioners will need to apply N fertilizer in order for perennial grains to reach their full yield potential, it will be crucial to know how N additions influence above-and belowground biomass allocation and fertilizer N use efficiency (NUE) in perennial grain crops.…”

Perennial Grain Legume Domestication Phase I: Criteria for Candidate Species Selection

“…Thus, perennials tend to be more competitive and longer-lived but at the expense of reproductive output [80]. By moving perennials to more favorable agricultural environments and applying selection pressure for increased seed yield, we expect to elevate the yield potential of perennial domesticates by increasing their harvest index as has been done in annual grains and more recently in the perennial grain, Kernza ® [81]. Even so, perennials with high overall fecundity are especially desirable candidates.…”