Root Response of Merion Kentucky Bluegrass Sods to Various Nitrogen Applications near the Time of Transplanting1

Abstract Regrowth of the root system of transplanted sod has become a major concern in turf production. Since nitrogen is used on most turf sod installations, the amount of nitrogen applied and the time of its application may have important effects on the regeneration of roots from sods. Re‐rooting of Merion Kentucky bluegrass sods given surface applications of N before transplanting, at the time of transplanting, and after transplanting to root observation containers in spring and summer was compared with that of sods given no N. Measurements included dry weights of roots grown from sods, rate of new root appearance, and color ratings. Applications of 98 and 293 kg/ha of N to the surface of Merion Kentucky bluegrass sod before transplanting and at the time of transplanting increased re‐rooting compared with sods given no N. Proper timing is important for the best use of N in root regrowth from sods. Applications of N dose to the time of transplanting were more beneficial to rerooting than applications at longer intervals before or after transplanting. N decreased the carbohydrate content of topgrowth of sods by 20 to 25% at 23 days after transplanting in the summer test compared with sods given no N. Increased root regrowth was associated with decreased carbohydrates of topgrowth of sods given N at 4 days before transplanting and at the time of transplanting, but this did not occur when N was applied 9 days after transplanting.