Granular Fertilizer Formulations Affect Nutrient Uptake in Perennial Ryegrass Turf

Phosphorus (P) is an essential element for plant establishment and growth, but its uptake might be impacted by the formulation of fertilizer used.  A greenhouse study was conducted during 2011 and 2012 in Riverside, CA ,to test nutrient uptake between homogenous pellet and blended formulations of 16N–6P–8K derived from ammonium sulfate, monoammoinium phosphate, and muriate of potash, respectively. Perennial ryegrass (Lolium perenne L.) ‘Grandslam’ was established in pots containing sand and irrigated with deionized water. Two wks after seeding, turf received 24.5 kg·ha^-1 of N from potassium nitrate (13N-0P-37K).  At 4 weeks after seeding, the turf received 98 kg·ha^-1 of N from either the pellet or blended formulations. An untreated control was also included to determine nutrient uptake contributed from KNO­₃ only.  Turf (shoots and roots) in pots was harvested weekly thereafter for 3 weeks, washed free of sand, dried, weighed, and analyzed for tissue nutrient content. Overall, tissue dry weight was not affected by fertilizer formulation.  In the first experiment, turf fertilized with the pellet formulation contained higher P and K compared to the blend and the control at one week after application. When the experiment was repeated, significantly higher P was detected in turf fertilized with the pellet formulation at all three harvest dates. Potassium uptake was consistent with the first experiment. Our results suggest that uptake of P and, to a lesser extent, K in turf is increased by use of an homogenous pellet formulation compared to a blended form of the same fertilizer.