Modeling Controlled Nutrient Release from Polymer Coated Fertilizers:  Diffusion Release from Single Granules

Abstract

A comprehensive model describing the complex and "non-Fickian" (mathematically nonlinear) nature of the release from single granules of membrane coated, controlled release fertilizers (CRFs) is proposed consisting of three stages: i. a lag period during which water penetrates the coating of the granule dissolving part of the solid fertilizer in it ii. a period of linear release during which water penetration into and release out occur concomitantly while the total volume of the granules remains practically constant; and iii. a period of "decaying release", starting as the concentration inside the granule starts to decrease. A mathematical model was developed based on vapor and nutrient diffusion equations. The model predicts the release stages in terms of measurable geometrical and chemophysical parameters such as the following: the product of granule radius and coating thickness, water and solute permeability, saturation concentration of the fertilizer, and its density. The model successfully predicts the complex and "sigmoidal" pattern of release that is essential for matching plant temporal demand to ensure high agronomic and environmental effectiveness. It also lends itself to more complex statistical formulations which account for the large variability within large populations of coated CRFs and can serve for further improving CRF production and performance.

Nitrogen Release Dynamic of Different Coated Urea under Puddle Lowland Rice Cultivation

“…These finding are in close conformity with those of Gandeza et al, (1991) and Zvomuya et al, (2003). Dissolution of nutrient in coating depends on coating thickness, size of urea particles and permeability of water into the coating (Shaviv et al, 2003). Nitrogen release from fertilizers generally influenced by weather elements specially temperature and soil moisture content.…”

“…Moisture is another factor that affects the rate, pattern and duration of release of nitrogen from coated urea (Fujinuma et al, 2009;Shaviv, 2005) (Table 1). However, since the trail was conducted under irrigated condition, the effect of moisture remained neutral for all the treatments.…”

“…Temperature and moisture are two climatic factors that affect the rate, pattern and duration of release of nitrogen from coated urea (Fujinuma et al, 2009;Shaviv, 2005).…”

“…Urea applied at sowing/ planting when need of nitrogen is less ensuing wastage of nutrient or fertilizer and in the succeeding growth stages when its requirement increases, plant suffer with nutrient stress. Controlled release fertilizer (CRF) is designed manure that releases active fertilizing nutrients in a controlled manner and delayed it in synchrony with the sequential needs of plants for nutrients (Shaviv, 2005). The widespread agriculturally important slow or controlled release fertilizers are coated urea such as sulphur coated urea (SCU), Neem coated urea (NCU), polymer coated urea, nitrification inhibitors and urease inhibitor.…”

Photodegradation of Polymer Materials Used for Film Coatings of Controlled‐Release Fertilizers

“…The release duration of the controlled-release fertilizer is defined as the time at which 80 % of the nutrients has been released. Shaviv et al [30] proposed a prediction model with the assumption that the volume of the polymer-coated fertilizer particles do not change. Using this model, the release duration of a 30 μm thick film is longer than 70 days when the film permeability coefficient is 5 10 -15 m 2 s -1 for a urea particle diameter of 3.0 mm.…”