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Digestate as alternative substrate for soil-less lettuce farming

The consumption of ready-to-eat salad has been growing over the last 20 years in the European market. The annual growth rate is at 4%. That's why this food category is renowned as one of the most profitable horticultural segments.

As a result of a growing trend, the lettuce and chicory are farmed over a 1.2 million hectares surface globally. The global production is of 27 million tons, almost.

Italy occupies the fourth place in the world, with 38.542 hectares farmed with lettuce and chicory (31.7% in the north, 10% in the Centre, and 58,3% in the South) for a total production of 8.1 million tons. Additionally, greenhouse production is important as well, for a total surface of 4.549 hectares (37.3% in the North, 31.9% in the Centre and 30.8 in the South).

Leafy produce is considered to be one of the most exposed to microbiological risks. The ready-to-eat lettuce is often connected to food poisoning. The Escherichia Coli O157: H7 has been often associated with lettuce.

Researchers from Modena University and Reggio Emilia University – in collaboration with the Foggia’s CRA – evaluated the digestate as an alternative and sustainable substrate for farming and as a nutritive solution in the hydroponic farming of lettuce. In three different experiments, nine hydroponic combinations of substrate and fertilization (agriperlite + standard solution, agri-perlite + liquid digestate, solid digestate + standard solution, solid digestate + liquid digestate, soil + standard solution, peat + standard solution, peat + liquid digestate, digested pelleted + standard solution and digested pelleted + liquid digestate) were tested and compared for the cultivation of baby leaf lettuce.

During crop cycles, the yield and other agronomic and microbiological parameters have been studied. In all the experiments, the combination of agri-perlite + liquid digestate, solid digestate + standard solution and pelleted digestate + standard solution improved the plant growth by influencing roots (+ 32%), buds (+ 40%), total dry weight (+ 29%) and SPAD parameters (+ 17%).

As the results illustrate, the digestate represents a nutritive sustainable solution and an alternative for the soilless baby leaf lettuce farming.

Source: Domenico Ronga, Leonardo Setti, Chiara Salvarani, Riccardo De Leo, Elisa Bedin, Andrea Pulvirenti, Justyna Milc, Nicola Pecchioni, Enrico Francia, 'Effects of solid and liquid digestate for hydroponic baby leaf lettuce (Lactuca sativa L.) cultivation', 2019, Scientia Horticulturae, Vol. 244, pag. 172-181. 


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