Responses of a Perennial Grass-Legume Mixture to Applied Nitrogen and Differing Soil Textures
- G. Y. Kanyama-Phiri,
- C. A. Raguse and
- K. L. Taggard
Sustained productivity in multiple-species, perennial grass-legume pastures depends in part on achieving and maintaining an appropriate species (SP) balance. Nitrogen levels for the grass component and consistent opportunity for rooting and nodulation of new legume stolons are important. Using an outdoor pot experiment, this study investigated perennial regrowth responses of orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), ladino clover (Trifolium repens L.) and strawberry clover (T.fragiferum L.) to differing soil textures (ST) obtained by addition of sand and peatmoss, together with N in split applications of 60 kg ha−1 to provide rates of 60,120, and 180 kg ha−1. Of particular interest were maintenance of a favorable (e.g., 1:1) grass-legume balance and identification of the effects of alteration in ST on legume root and nodule development (RND). The four SP were established as split plots of transplanted propagules on whole plots of N and ST treatments in a completely random design. At 30-d intervals dry matter (DM) was sampled for each species. Legume stolons were observed for leaf appearance rate (LAR) and were subsampled once during the 120-d experiment to determine RND. Differences in soil texture had no significant influence (P < 0.05) on DM yields or on legume LAR or RND, but significant (P < 0.001) effects on DM were observed for N and SP and for N × SP interactions. Increasing N significantly (P < 0.05) reduced LAR and RND. Percent N recovery was highest (72%) at 60 kg ha−1 N but legume dominance was avoided only at 180 kg ha−1 N, (N recovery = 12%). Successive split applications of N are useful in managing grass-legume balance and DM yield in closely-grazed perennial pastures, but at N levels effective in achieving these objectives a low recovery of applied N is likely.
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