Intercropping legumes and intermediate wheatgrass increases forage yield, nutritive value, and profitability without reducing grain yields

Abstract

IntroductionKernza intermediate wheatgrass (IWG) is a perennial grain and forage crop. Intercropping IWG with legumes may increase the forage yields and nutritive value but may compromise Kernza grain yields. The interaction between IWG and legumes depends on planting season, row spacing, and legume species. Our aim was to evaluate the effects of those management practices on Kernza grain yield, summer and fall forage yield and nutritive value, weed biomass and, the profitability of the cropping system in Wisconsin, USA.MethodsIn the spring and fall of 2017, we planted eight cropping systems at 38 and 57 cm of row spacing: four IWG monocultures [control without N fertilization or weed removal (IWG), hand weed removal (hand weeded), IWG fertilized with urea at rates of 45 or 90 kg ha−1], and four IWG-legume intercrops (IWG with alfalfa, Berseem clover, Kura clover, or red clover).Results and discussionMost of the intercropping systems were similar to IWG monoculture in grain (ranging from 652 to 1,160 kg ha−1) and forage yield (ranging from 2,740 to 5,190 kg ha−1) and improved the forage quality. However, for spring planted IWG, intercropped with red clover or alfalfa, the grain and forage yields were lower than the IWG monoculture (~80 and 450 kg ha−1, respectively). The best performing intercrops in the first year were Kura clover in the spring planting (652 kg Kernza grain ha−1, 4,920 kg IWG forage ha−1 and 825 kg legume forage ha−1) and red clover in the fall planting (857 kg Kernza grain ha−1, 3,800 kg IWG forage ha−1, and 450 kg legume forage ha−1). In the second year, grain yield decreased 84% on average. Overall, the profitability of the IWG legume intercropping was high, encouraging the adoption of dual-purpose perennial crops.

Forage harvest management impacts “Kernza” intermediate wheatgrass productivity across North America

“…Avoiding the decline in IWG grain yield in subsequent harvest years remains a major challenge for this perennial crop. Previous research has explored fertilization, row spacing, intercropping, strategic soil disturbance, and postharvest management practices to maintain grain yields but the results are highly variable (Han et al, 2013;Bergquist et al, 2022;Law et al, 2020;Pinto et al, 2021Pinto et al, , 2022Crews et al, 2022).…”

“…For example, in Minnesota, Hunter et al (2020b) reported forage mass of 1.0-2.4 Mg ha −1 in the spring, then 1.1-2.8 Mg ha −1 in the fall. Pinto et al (2022) reported ∼1.0 Mg ha −1 of fall forage in Wisconsin. Another Wisconsin study reported spring and fall forage mass approximately equal (1.4 Mg ha −1 ) with the spring relative forage quality values 50% greater than the fall (Favre et al, 2019).…”

“…Managing IWG as a dual‐use crop (grain and forage) could address challenges associated with grain production (Favre et al., 2019; Hunter et al., 2020b). These two sources of income may relieve the economic disparity between perennial grain and annual cereal systems (Bell et al., 2008; Law et al., 2022; Pinto et al., 2022; Watt, 1989). Harvesting summer forage, that is, immediately after grain harvest, represents the most opportune time to capture and use forage mass in a perennial grain system.…”

“…Pinto et al. (2022) reported ∼1.0 Mg ha −1 of fall forage in Wisconsin. Another Wisconsin study reported spring and fall forage mass approximately equal (1.4 Mg ha −1 ) with the spring relative forage quality values 50% greater than the fall (Favre et al., 2019).…”

“…Another Wisconsin study reported spring and fall forage mass approximately equal (1.4 Mg ha −1 ) with the spring relative forage quality values 50% greater than the fall (Favre et al., 2019). Both spring and fall forage have suitable nutritive value for lactating beef cows, dairy cows, and growing heifers (Favre et al., 2019; Pinto et al., 2022).…”