The uptake and maintenance of mineral nutrients such as N in the rooting zone is a beneficial contribution of perennial grasses, including tall fescue, to nutrient cycling. More emphasis has been placed recently on the importance of C sequestration to reduce atmospheric CO2 levels associated with global warming. The large amount of biomass produced by grassland species makes perennial grasses an ideal crop for capturing and holding CO2. Even when grasses are harvested for forage or biomass production, the remaining root and crown tissues comprise as much as 84% of the total plant biomass (Frank et al., 2004). Their studies with switchgrass indicated that even though C loss through soil respiration accounted for 44% of the total C in plant biomass, a significant amount of C was still sequestered by the grass.
Tall fescue may have some added benefits in C sequestration. Recent studies (Franzluebbers et al., 1999) showed that soil organic C and total N were increased by 13% under tall fescue with a high endophyte infection level compared to soils under tall fescue with a low endophyte infection level (Fig. 28-2). Neotyphodium coenophialum is known to confer biotic and abiotic stress tolerances (see Chapter 4) to tall fescue, enabling the grass to persist and maintain productivity in stressful environments (Joost, 1994). At least some of the biotic stress tolerance (see Chapter 8, Chapter 9, and Chapter 10) found in E+ tall fescue has been attributed to ergot alkaloids produced by Neotyphodium (Latch, 1997) (see Chapter 13). Further study has shown that endophyte infection did reduce the breakdown of C and N in the soil by reducing soil microbial activity. It is possible that this reduction in microbial activity was caused by an accumulation of ergot alkaloids in the soil under Neotyphodium-infected tall fescue (Franzluebbers and Hill, 2005). Therefore, endophyte infection in tall fescue may result in an increase in C sequestration through inhibition of soil organic matter breakdown by microbes.
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Fig. 28-2. Soil organic C and total N under tall fescue as affected by E+ level (* and *** indicate significant differences at P ≤ 0.05 and P ≤ 0.001, respectively) (from Franzluebbers et al., 1999).
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