Preparation and properties of chitosan-coated NPK compound
fertilizer with controlled-release and water-retention
, Mingzhu Liu
Department of Chemistry and State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, PR China
College of Chemical Engineering, Northwest Minorities University, Lanzhou 730030, PR China
Received 22 April 2007; received in revised form 5 August 2007; accepted 8 August 2007
Available online 6 September 2007
To improve the utilization of fertilizer and water resource at the same time, a new type chitosan-coated nitrogen, phosphorus and
potassium compound fertilizer with controlled-release and water-retention (CFCW) was prepared, which possessed the three-layer struc-
ture. Its core was water-soluble nitrogen, phosphorus and potassium (NPK) fertilizer granular, the inner coating was chitosan (CTS), and
the outer coating was poly(acrylic acid-co-acrylamide) (P(AA-co-AM)) superabsorbent polymer. Atomic absorption spectrophotometer
and element analysis results showed that the product contained 7.98% potassium (shown by K
O), 8.14% phosphorus (shown by P
and 8.06% nitrogen. The synthesis conditions of inversion suspension polymerization were studied systematically. The water absorbency
of the product was 70 times its own weight if it was allowed to swell in tap water at room temperature for 90 min. The nutrients slow
release behaviors of the CFCW in soil and water-retention capacity of the soil with CFCW were investigated. A possible slow release
mechanism was proposed and the release rate factor K and the release exponent n of nutrients in CFCW was calculated. This product
with good controlled-release and water-retention capacity, being degradable in soil and environment-friendly, could be especially useful
in agricultural and horticultural applications.
Ó 2008 Published by Elsevier Ltd.
Keywords: Chitosan; P(AA-co-AM) superabsorbent; Controlled-release; Water-retention; NPK compound fertilizer
The growth of plants and their quality are mainly a
function of the quantity of fertilizer and water. So it is very
important to improve the utilization of water resources and
fertilizer nutrients. However, about 40–70% of nitrogen,
80–90% of phosphorus, and 50–70% of potassium of the
applied normal fertilizers is lost to the environment and
cannot be absorbed by plants, which causes not only large
economic and resource losses but also very serious environ-
mental pollution. Recently, the use of slow release fertiliz-
ers is a new trend to save fertilizer consumption and to
minimize environmental pollution (Akelah, 1996; Jar-
osiewicz & Tomaszewska, 2003).
Slow release fertilizers are made to release their nutrient
contents gradually and to coincide with the nutrient
requirement of a plant. These fertilizers can be physically
prepared by coating granules of conventional fertilizers
with various materials that reduce their dissolution rate.
The release and dissolution rates of water-soluble fertilizers
depend on the coating materials. At present, coating mate-
rial’s degradability is an important focus of the research in
this ﬁeld because of the renewed attention towards environ-
mental protection issues (Ge et al., 2002; Shavit, Reiss, &
Chitosan is a highly deacetylated derivative of chitin,
one of the most abundant natural and biodegradable poly-
mers. It has been widely applied in the biomedical, pharma-
ceutical, and agricultural ﬁelds. In many of these
applications chitosan is extremely attractive due to its bio-
degradability, biocompatibility, and nontoxicity (Huacai,
Wan, & Dengke, 2006). Therefore, the soluble fertilizer
0144-8617/$ - see front matter Ó 2008 Published by Elsevier Ltd.
Corresponding author. Tel.: +86 931 8912387; fax: +86 931 8912582.
E-mail address: firstname.lastname@example.org (M. Liu).
Available online at www.sciencedirect.com
Carbohydrate Polymers 72 (2008) 240–247