Daily vs. Periodic Nitrogen Addition Affects Growth and Tissue Nitrogen in Perennial Ryegrass Turf
2003
Bowman, D. C.
Nitrogen is typically supplied to turfgrasses either in large episodic pulses of readily available fertilizer N, or in relatively small, constant fluxes from mineralization, slow release fertilizers, or fertigation. There is little information on the comparative physiology and productivity resulting from each strategy. A greenhouse study was conducted to determine turfgrass productivity and N partitioning as a function of daily (near-constant) vs. intermittent N supply. Perennial ryegrass (Lolium perenne L.) was grown in solution culture and fertilized daily with KNO₃ at rates ranging from 0.56 to 11.1 kg N ha⁻¹ d⁻¹ (daily N), or in pulses delivered every 8, 16, or 32 d to supply 50 kg N ha⁻¹ mo⁻¹ (intermittent N). Leaf growth rate, reduced N, and NO₃–N content were relatively stable under daily N, with steady state values for each parameter strongly affected by N rate. Intermittent N caused fluctuations in growth and tissue N coincident with application. Nitrogen absorption was rapid and complete for all but the highest rate of daily N. Nitrogen supplied intermittently was absorbed quantitatively across a period of 8 to 36 h. Allocation to new leaf growth accounted for 88 to 119% of the absorbed N. Shoot biomass increased, whereas root biomass and length decreased with increasing daily N rate. The results indicate that while daily N supply produces relatively constant growth and stable tissue N pools, there is little benefit to long-term productivity and N use efficiency when compared with intermittent supply of N.
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