Utilization of Urea or Polymer-Coated Urea in Florida Slash Pinestraw Production

Abstract

Abstract Controlled-release fertilizers may improve productivity and mitigate environmental hazards in Southern pine plantations intensively managed for pinestraw harvesting. We examined the effects of pinestraw removal and fertilization with conventional and polymer-coated urea (PCU) on foliar, needlefall, and pinestraw nutrients and yields in a North Florida slash pine (Pinus elliottii Engelm.) plantation. Raking treatments (raked or nonraked) were applied annually in February 2014–2017. Fertilization treatments (PCU at 0, 28, 56, 140, or urea at 56 kg N ha−1 year−1) were applied annually in June 2014–2016. Four years of pinestraw removal did not affect needlefall mass or foliar and needlefall nutrient concentrations. The positive fertilization rate effect on pinestraw yield, needlefall mass, foliar, needlefall, and pinestraw total Kjeldahl nitrogen (TKN) and K concentrations, and on foliar and needlefall Ca concentrations increased in magnitude with subsequent applications. TKN, total P, and K concentrations were lower in needlefall and pinestraw relative to foliage by 65%–90%, whereas Ca concentrations were higher by 120%–180%. Three PCU applications at 140 N ha−1 year−1 increased three-year cumulative pinestraw yield over the control by 19% and TKN, K, Ca, and Mg removals by 49%, 86%, 24%, and 32%, respectively. Responses to PCU did not differ from urea.