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Developmental characteristics of grass varieties in relation to herbage production: 4. Effect of nitrogen on the length and longevity of leaf blades in primary growth of Lolium perenne, Dactylis glomerata and Phleum pratense

Summary The effects of nitrogen treatment on blade length and longevity were studied in primary growth of early and late varieties of perennial ryegrass, timothy and cocksfoot. Reproductive and vegetative tillers were examined in cocksfoot, but in perennial ryegrass and timothy the study was restricted to reproductive tillers, which accounted for a large proportion of the primary growth in these species. Results obtained by a technique which involved repeated recording of tillers were corroborated by those obtained by destructive sampling of tillers. With respect to the blade length of culm leaves, responses to nitrogen shown by S. 23 ryegrass and S. 48 timothy were greater than those of the early-heading varieties S. 24 ryegrass and S. 352 timothy. However, blade longevity was appreciably reduced by nitrogen in the late varieties whereas the early varieties showed a much lower response. Implications of these results in relation to the accumulation of senescing material in primary growth are discussed. The pattern of leaf expansion in vegetative tillers of cocksfoot is discussed in relation to regrowth.