TECHNOLOGY FOCUS - POLYMERS - Preferred Material: The content loading of the incorporated second polymeric material is 0.0001-50 wt.% of the matrix material. The incorporated second polymeric material is covalently associated with or mechanically entrapped within the matrix material. The hydrophobic polymeric material is lipophilic or lipophobic. The hydrophobic polymeric matrix material and the incorporated hydrophilic second polymeric material form nanocomposite fibers. The hydrophobic polymeric matrix material is chosen from poly(lactic acid) (PLA), poly alpha hydroxy 1 acid, poly glycolic acid (PGA), poly(lactic acid) (PLA, PLLA, PDLA, or poly lactide), poly epsilon caprolactone (PCL), polybutylene succinate (PBSU), polyethylene succinate (PESU), polyesteramides (PEA) and polyhydroxybutylvalerate (PHBV), preferably PLA. The hydrophilic polymeric material is chosen from cellulose, starch, lignin, keratin, fibroin, polysaccharides, proteins, polyvinylalcohol and polyvinylacctate (PVA), preferably cellulose. The incorporated second polymeric material includes nanofibrils, nanocrystals, nanoparticles, droplets or phase-separated domains within the polymeric matrix material. The polymeric matrix material is PLA and is hydrophobic. The incorporated second polymeric material is cellulose and is hydrophilic. The cellulose forms nanofibrils and the polymeric material is in the form of a fiber. The water contact angle of the fiber, film or powder is 0-140 degrees . The polymeric material is a non-woven fabric and the water absorbance of the fabric is 0-30 times the fabric weight. The polymeric material has hydrolytic degradation rate that increases with increased proportion of the hydrophilic polymeric material. The degradation is enzymatic, microbial or photolytic. Preferred System: The release rate is controlled by varying the composition of hydrophilic polymeric material to hydrophobic polymeric material. Preferred Method: The substrate includes substrate for growing a plant. The desired location includes a substrate for growing a plant e.g. water body. The method involves regulating plant growth by promoting rate of growth, inhibiting rate of growth, inhibiting maturation, enhancing competition against weeds or stimulating germination. ACTIVITY - Acaricide; Avicide; Antibacterial; Fungicide; Insecticide; Molluscicide; Nematocide; Herbicide; Virucide; Fertilizer; Animal repellent. No biological data given.    MECHANISM OF ACTION - None given.    EXAMPLE - No suitable example given.