Towards improvement of peat substrates for greenhouse tomato

Growing media used for greenhouse tomato have long time been based on coarse blond peat (H₂-H₃ on the von Post scale) mixed with perlite and vermiculite, with excellent performances but at a relatively high cost. Recent research conducted over 4 years have focused on using brown peat (H₄-H₅-H₆), pure and in mixes with waste material, to achieve yield comparable to rockwool at a lower cost. Trials have shown that pure brown peat, despite adequate sieving to improve its drainage and gas diffusivity, has often achieved yield up to 25% lower than rockwool. Adding 60-70% spruce sawdust or coarse bark to 30-40% peat has been necessary to achieve yield comparable to rockwool. For pure brown peat, aeration had to be improved by modifying container geometry to give yield comparable to rockwool. Therefore, these studies conclude that brown peat can be used, provided its aeration is improved by adding spruce sawdust or coarse bark or by modifying the container geometry, to replace rockwool at a lower cost in greenhouse tomato.