Turf and Landscape - Slow Release Fertilizers: IBDU

This is the sixth in a series on slow release fertilizers for turf and landscapes. This post contains information on IBDU.

Isobutylidene Diurea (IBDU). Unlike the condensation of urea and formaldehyde, which forms a distribution of different UF polymer chain lengths, the reaction of urea with isobutyraldehyde forms a single oligomer. Although similar in chemical structure to methylene diurea (MDU), its physical properties are quite different.

Isobutylidene diurea (IBDU) is a non-hygroscopic white crystalline solid available in fine (0.5-1.0mm), coarse (.7-2.5mm) and chunk (2.0-3.0mm) particle sizes. The product contains a minimum of 30% N with 90% of the N in water-insoluble form. The typical commercialized product contains 31% N.

Nitrogen from IBDU becomes available to plants through hydrolysis. In the presence of water, the compound will hydrolyze to urea and isobutyraldehyde. The rate of hydrolysis is accelerated by low pH and high temperature. Unlike UF polymers that rely on soil microbialpopulations to make the N available, IBDU is primarily dependent on water as the critical element in N availability. Its low water solubility controls the transport of the product into the soil solution. Once in the soil solution, the rate of hydrolysis is affected by both soil pH and temperature. The rate of dissolution is affected by particle size and amount of water available. The powder form is mineralized much more rapidly than large particles under the same field conditions. Because the release is not microbe-dependent, N can become available at low temperatures; thus IBDU is one of the preferred products for cool-season application. This attribute and the dependency on moisture are the distinguishing characteristics of IBDU.

IBDU is used on turfgrasses, in commercial nurseries, and in landscaping, forestry, and speciality agriculture. Although some fine-size IBDU (31-0-0) is used for direct application to golf course greens, most of the turfgrass use is in the form of blended fertilizers, often in combination with other types of controlled release fertilizers.

Reprinted from Selected Fertilizers Used in Turfgrass Fertilization by J. B. Sartain and J. K. Kruse, University of Florida Extension.