Subterranean Clover Enhances Production of ‘Coastal’ Bermudagrass in the Revegetation of Lignite Mine Spoil
- Pamela A. Harris and
- David A. Zuberer
Lignite mine spoils in Texas are commonly revegetated with ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.]. Legumes bare been overseeded in bermudagrass in reclamation programs in Texas, but information regarding establishment and persistence in mine spoil is limited. Therefore, we conducted a field study to investigate the effects of fertilization and inoculation with Rhizobium spp. on subterranean clover (Trifolium subterraneum L.; subclover) establishment and production in mine spoil and to assess the effect of subclover on a subsequent crop of Coastal bermudagrass. Subclover seed was broadcast into a 6-mo-old bermudagrass sod in October 1986. Individual plots were fertilized with 57-25-47 kg ha−1 (N-P-K), 0-25-47 kg ha−1, or left unfertilized at the beginning of each clover season (Sept.–Oct.); however, all plots were fertilized with 57-25-47 kg ha−1 at the start of each grass season (April–May) to ensure grass growth. Although low numbers (0–l02 g−1) of native rhizobia were present in plots, inoculation with a commercial, multi-strain inoculant increased subclover forage production (100%) and total N and P yields of subelover early in the first season. Yields from inoculated and uninoculated plots were generally comparable later in the first season and in the second year. The overseeding of subclover into the bermudagrass sod increased grass production and total N and P yields later in the first year and in the second season. However, inoculation of subclover had little effect on subsequent grass production. We also demonstrated the apparent positive benefit of P fertilization on subclover and bermudagrass production. Clover forage production, as well as N and P yields, were enhanced with P fertilization. In addition, P fertilization was necessary to achieve the greatest benefit of clover enhancement of bermudagrass production. The effect of subclover on grass production was apparent by the end of the first grass season, and it became even morevident in the second year. The results showed that subclover was established and maintained for at least two seasons in a bermu* dagrass sod on reclaimed lignite spoil, and that the clover benefited the subsequent grass crop when fertilized with P and K, apparently by providing extra “fixed” N for grass production.
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