Abstract: A degradable agricultural mulch film as disclosed herein includes a plurality of layers for the controlled release of plant nutrients. The first layer is formed from a water-soluble synthetic resin, a releasable form of nitrogen and a releasable form of a plant nutrient in addition to nitrogen. A second layer includes a water-soluble synthetic resin having an average molecular weight which is greater than the average molecular weight of the water-soluble synthetic resin in the first layer and a releasable form of nitrogen admixed therein. The second layer also includes a thin film of water-resistant polymer to retard the degradation rate of the second layer and to slow the release of nitrogen in the second layer. And in the preferred embodiment of the invention a second film of water-resistant polymer which is relatively thin with respect to the first film separates the first and second layers.

Abstract: An agricultural mulch film is prepared by mixing conventional plant nutrients with a water-soluble polymer such as polyvinyl alcohol. The mixture is cast in the liquid form and allowed to dry to form a thin film. The dried film is then coated with a thin layer of a water-resistant resin such as polyvinyl acetate to form a composite mulch film. The release of the nutrients contained in the mulch film is controlled by the addition to the water-soluble polymer mixture of either (1) a nitrification inhibitor along with urea, or (2) a water-soluble urea-formaldehyde condensation product. The release of the nutrients is also controlled somewhat by the water-resistant resin coating. Other additives may be added to the mulch film to produce a multi-purpose product.