Phosphorus retention in United States Golf Association greens

Golf courses built to the U.S. Golf Association (USGA) specification requir e a minimum of 60% coarse and medium sand particles which may retain phosph orus (P) poorly leading to turfgrass P deficiencies and negative environmen tal impacts. Two glasshouse studies to determine the influence of sand type (clay coated vs, uncoated), amendment sources (peat and iron humate [FeHu] , the latter an agricultural amendment that contains iron and organic mater ial), and P fertilizer materials (monopotassium phosphate [MKP], 0-20-20 fe rtilizer as N-P2O5-K2O, and concentrated superphosphate [CSP]) on the reten tion of P were conducted during the summer and fall of 1998. Lysimeters con structed to simulate USGA golf green profiles were established with FloraDw arf(TM) bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt -Davy] and leached biweekly for 12 wk to evaluate uptake, retention and lea ching of P. Tissue, soil and leachate were analyzed for P content. Treatmen t effects were measured during an established and a grow-in (period of esta blishment after rhizomes and stolens are planted until grass is mature) tur fgrass study to quantify differences in the movement of P. More P leached d uring the grow-in study than in the established study. Coated sand retained more Mehlich I extractable P,which resulted in more P uptake, less P leach ing, and an improved cover rating than the uncoated sand. Tissue P concentr ations were reduced by the presence of FeHu, but not to levels considered a s being deficient. Iron humate reduced leachate P. Experimental units recei ving CSP leached the least P, whereas no difference in the quantity of P le ached from MKP and 0-20-20 was observed. Use of coated sand improved P rete ntion in a USGA golf green profile and should be used in construction, if a vailable. Amend a USGA green soil profile with FeHu (25 g kg(-1) by weight) to reduce P leaching while maintaining adequate plant uptake of P.