Date of Award
Master of Science
Slow and controlled release fertilizers have often been used to prevent N loss through leaching. Recently, new slow release fertilizers have been developed and their potential use in corn production is an alternative to increase N efficiency. An incubation study was performed to measure and compare the release rates from two urea-formaldehyde (UF) liquid resins and conventional urea. Four different representative soils from corn production areas of Iowa were collected. The soils were classified as: Harps (Typic Calciaquoll), Nicollet (Aquic Hapludoll), Okoboji (Cumulic Hapluquoll) and Sac (Oxyaquic Hapludoll). Soil samples (10 g) were amended with solutions containing rates of N equivalent to 0, 50, 100, 150 and 200 kg N ha⁻¹ of urea and the UF materials and incubated at 20 ⁰C for 0, 7, 15, 30, 45 and 60 days. At the end of the respective incubation periods each sample was analyzed for nitrate-N (NO₃-N) and ammonium-N (NH₄-N). The results obtain showed that UF fertilizers might not meet the N requirements for corn production in Iowa due to the low percentage N recoveries (60 - 80% N) observed. The soils had different release rates mainly affected by pH and organic matter content. A two year trial was conducted to asses the effect of a polymer-coated urea (ESN) fertilizer upon corn biomass and grain N uptake and yield when applied in the fall or spring. Nitrogen fertilizer rates used for urea and ESN treatments were 0, 34, 67, 101, 135, 168 and 200 kg N/ha. The results obtained showed that corn biomass was not affected by the use of ESN or urea in particular. Biomass weight and N uptake tended to respond to N rates in some treatments. Grain yield always increased with N rate. However the effect of ESN and urea application varied from one year to the next and among locations.
González, Marianela, "Effect of slow release nitrogen fertilizers on corn production in Iowa" (2005). Retrospective Theses and Dissertations. 18776.