Functional contribution of two perennial grasses to enhance pasture production and drought resistance under a leaf regrowth stage defoliation criterion

Abstract

Lolium perenne L. (Lp) is the main pasture species in New Zealand, but climate change increases the likelihood of drought during summer and consequently lowers its growth rates. Bromus valdivianus Phil. (Bv) tolerates better the summer soil water restriction, but its competitiveness in a diverse pasture relates to the defoliation management and soil moisture levels. The performance of both species in terms of production, persistence and feed quality across seasons under different defoliation regimens was evaluated when the species were mixed and in monoculture. The treatments were applied in a randomised complete block design with three blocks. Bromus valdivianus and Lp monocultures and the 50/50 mixture (Mx) were grazed at low and high defoliation frequencies (i.e. based on Bv and Lp optimal leaf regrowth stage [LS], respectively). Herbage mass production was 15% higher in the Mx, mainly due to an increase in production in spring and summer. In spring, there was complementarity growth between the species, while during summer/early autumn, the Mx production relayed in the higher participation of Bv. Root biomass at depth (31–70 cm) was 38% greater for Bv monoculture and the Mx compared with Lp monoculture, which demonstrated the contribution of Bv to a better production of the mixture during and following the dry periods. In addition, the maintenance of the Bv tiller population and the higher growth rate during dry periods demonstrated its better fitness to low soil water availabilities than Lp. Although herbage mass was not modified by the defoliation frequency, forage quality of Bv showed values at low defoliation frequency that could compromise animal production during spring. However, there was an increase in root biomass under low defoliation frequencies, which suggested that a flexible grazing management across seasons would increase the niche utilisation between species in the mixture. The defoliation frequency of the mixture could be based on Lp LS during spring and winter, and slowed down, following Bv criteria, during summer and autumn.

Impact of precipitation and grazing on recovery of plant vegetation in temperate grasslands

“…Because PR grasses are drought tolerant, have small leaf areas, and are drought resistant (Lucas et al, 2013), perennial grasses such as Salicaceae and Lithospermum and PRs, as well as ABs, increased under grazing (Figure 3). Consistent with other studies, our study demonstrated that the 5-year grazing prohibition effectively increased the species diversity and coverage (Figures 2 and 7) by protecting grassland vegetation and soil from destruction (García-Favre et al, 2023;Xia et al, 2022), which is conducive to efficient grassland management and utilization. Meanwhile, grazing inhibition increased perennial grasses such as L. chinensis, Stipa krylovii, and C. squarrosa (Figure 3).…”

Nitrogen Use Efficiency and Partitioning of Dairy Heifers Grazing Perennial Ryegrass (Lolium perenne L.) or Pasture Brome (Bromus valdivianus Phil.) Swards during Spring

“…There is scarce information on nutritional strategies to cope with climate change (adaptation) and in turn, reduce the N partitioning and excretion of pasture-based dairy heifers (mitigation of climate change). Furthermore, the current study evaluated growth performance and N partitioning of heifers grazing a traditional pasture species (Lp) and a promising native species, Bv, which tolerates the summer soil water restriction better than Lp, being an alternative as climate change increases the likelihood of drought during summer and consequently lowers its growth rates [37].…”

“…Previously, it has been shown that mixtures dominated by perennial ryegrass and pasture brome can have similar attributes to Lp pastures in terms of DM yield [54] and fermentation in the rumen [38,39]. More recently, García-Favre et al [37] observed a synergy when combining Lp and Bv by increasing DM yield by 15% compared with Lp, mainly due to an increase in production in spring and summer. In spring, there was a complementarity growth between both species, while during summer/early autumn, the production resulted in the higher participation of Bv as well as a greater root biomass at a depth of 31-70 cm.…”

Tall fescue tiller survival over summer in a subtropical environment: The role of the size and depth of root systems

“…Water stress has been shown to reduce tiller survival in tall fescue swards (Assuero et al., 2002; West et al., 1993), particularly in Mediterranean climates (Norton et al., 2016; Poirier et al., 2012). Tolerance to water stress associated with large root systems has been proposed as a relevant trait to explain vegetative pasture persistence (García‐Favre et al., 2022; Garwood & Sinclair, 1979; Langworthy et al., 2019; Nie et al., 2008). Deep and functional root systems may delay water stress by providing a continuous supply of water during droughts (Garwood & Sinclair, 1979; Ludlow et al., 1989; Volaire et al., 1998), and thus strengthen dehydration avoidance in summer‐dry environments (Norton et al., 2016).…”