NITROGEN STRATEGY: SPOON-FEED OR NOT

Recent research at North Carolina State University suggests that, in the long run, turf response to spoon-feeding and fertigation is not much better than intermittent nitrogen (N) application. The idea behind spoon-feeding and fertigation is to offer turf a continual supply of N with small, frequent applications. The intent is to avoid a flush of growth that is associated with less frequent, heavier applications of soluble nitrogen. Although this makes sense, researchers wanted to determine the practical significance and whether this strategy offers any long-term benefit to turf in comparison to intermittent application. Researchers conducted a greenhouse study to compare perennial ryegrass (Lolium perenne L.) turf response to constant feeding under solution culture versus soluble nitrogen application on a less frequent, intermittent schedule (8, 16 and 32 days). Perennial ryegrass was grown in solution culture and fertilized daily with KNO3 at rates equivalent to a range of from 0.01 to 0.25 pound N/1,000 square feet per day (daily N), or less frequent applications every 8, 16 or 32 days to supply 1 pound N/1,000 square feet per month (intermittent N). Leaf growth rate and NO3 — N content were relatively stable under daily N. Researchers noticed that increased growth and tissue N content coincided with timing of intermittent N applications. Nitrogen uptake was rapid and complete over an 8- to 36-hour period for all but the highest rate of daily N, and practically all absorbed N was allocated to new leaf growth. Shoot biomass increased, whereas root biomass and length decreased with increasing daily N rate. The researchers concluded 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.

Source: Crop Science 43:631-638 (2003), “Daily vs. Periodic Nitrogen Addition Affects Growth and Tissue Nitrogen in Perennial Ryegrass Turf,” D.C. Bowman.

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