Hydro-retention polyacrylamide gels amendment to potting media increase water availability

The aim of the paper is to clarify the advantages for the hard ornamental nursery stocks and for the environment derived from the addition of two commercial hydrophilic polyacrylamide gels to a peat/pumice (1:1 V/V) substrate. Also tomato crop was investigated. In both cases, the water absorption capacity of the two hydrophilic polyacrylamide gels was proportionally reduced with the presence of dissolved salts in the water. It was found that in the tested substrate an addition of 2 g L-1 of super-water-retention gel can increase the amount of retained water by about 130 g for each liter of substrate. However, only 40-50% of the higher amount of water retained by super-water retention was available for the crop. Under the operating conditions (drip irrigation with relatively saline water) the increase of water available for the crop (in the range 0-10 kPa) is only about 30 g for each gram of polymer added to the substrate. This higher substrate available water amount could increase the resistance of the plants to the absence of irrigation for 1-2 days. In conclusion, the addition of hydrophilic polyacrylamide gels to the substrate seems to have positive effects on plants, especially after the end of cultivation (selection and preparation of plants, packaging, storage, transport) and, probably, also during the early stages after transplanting in the customer's garden, where optimal irrigation could be not always guaranteed.