According to the invention, the productivity of cultivated plants is controlled by a microbiological process. At least one telluric microorganism having a favorable rhizospheric effect on a plant is embedded in a polymer gel. Fragments of the gel are then inoculated into the rhizosphere of the plant. The invention also relates to a process for preparing the required fragments of polymer gel. Polymerization of the gel is carried out in the presence of a culture of the desired microorganism, and the polymer block is thereafter broken up prior to use.

The invention relates to a fertilizer rod composition comprising about 100 parts of a polyvinyl alcohol, about 0 to 20 parts of a plasticizer and about 10 to 350 parts of a fertilizer, a process for producing said rod and a product of said process.

Solid plant food formulations are disclosed which can be embedded in the soil adjacent but spaced from the plant roots for the release of primary plant nutrients and fertilizing components each time the plant is watered. The solid compositions contain fertilizer constituents, gel-forming materials and reactants therefore which, in the presence of water, combine to form a semi-permeable surface membrane or layer through which the plant nutrients migrate. Beneficial trace elements are also included. Sequestering agents are incorporated to enhance and insure the migration of the nutrients, particularly the trace elements, into the soil and preventing the formation of water-soluble products through metathetic reactions or reactions with the ingredients in the soil. The amount of nutrients released is proportionate to the volume of water applied. The formulations, in one embodiment, are in the form of a cylindrical, solid stick that can be readily segmented into shorter pieces for small potted plants or one or more such solid sticks can be used for larger pots and larger plants. A probe for forming an appropriate hole of the required diameter and depth is provided to facilitate placement of the stick in the soil to the proper depth and insuring that the requisite amount of nutrients is available and furnished for the plant at each watering.

An attrition resistant fertilizer spike composition, exhibiting a mechanical strength which allows the spike to be hammered unsupported into the soil without suffering damage, to provide an effective source of slow releasing plant nutrients to the soil. The composition comprises between 93 and 98 percent of particulate plant nutrient compounds containing one phosphate ion chemically combined with one divalent cation and one monovalent cation, including the compounds magnesium ammonium phosphate and magnesium potassium phosphate. The composition includes a coating of between 2 and 7 percent of thermoplastic adhesive with a softening temperature between 65 and 160.degree. C. on the particles. The coated particles are formed into an attrition and shatter resistant spike shape, suitable for hammering into the soil, by pressing into a die at a temperature higher than the softening temperature of the thermoplastic adhesive and then cooling to a temperature lower than the softening temperature. A method of preparing these improved spikes is provided. In the method the thermoplastic adhesive is applied as an aqueous dispersion or emulsion along with a die lubricant prior to pressing the coated particles into a spike exhibiting a high degree of physical integrity.

A free-flowing fertilizer comprising: i) from 25 to 99.5% by weight of a powdered water soluble nitrogen containing fertilizer. ii) from 0.05 to 1.5% by weight of a polyacrylamide liquid emulsion/dispersion. iii) from 0.1 to 3.0% by weight of a polyacrylamide powder whose particle size is primarily 50 to 100 mesh in size.