Is good freesia cultivation possible without steaming the soil?

April 4, 2022

Growing freesias without gas seems to be possible, according to research in KAS2030, in which cultivation is already done almost without fossil fuels. But after each cultivation, the soil must be disinfected from possible diseases and pests. This is done by steaming, and that requires a lot of gas. The Business Unit Greenhouse Horticulture and Flower Bulbs of Wageningen University & Research (WUR) is investigating whether cultivation without steaming can be possible.

KAS2030 is a demonstration greenhouse at WUR in Bleiswijk. Here the challenges of fossil-free and emission-free cultivation are investigated. The research is carried out in four crops: strawberry, gerbera, freesia and potted Anthurium. The Freesia’s are grown in sand beds and four cultivations for freesia have been done so far. The sand beds have been steamed after each cultivation as common in practice. The most recent planting was on November 9, 2021. Four different varieties were planted: two that are sensitive to fusarium, and two that are less sensitive to that fungal disease.

Steaming effects

For this cultivation half of the sand beds were pre-steamed, the other half were not. The WUR wants to use this to investigate the effects of steaming. For example, steaming the soil is known to kill harmful fungi and bacteria. But there is a chance that good micro-organisms are also killed. In addition, growers indicate that steaming also stimulates growth in new plantings. It is not yet known what causes this. That’s why the researchers started this experiment to monitor if and which differences occur in the water content, nutrient status, growth inhibitory substances and microbiome of the steamed and unsteamed sand beds.

Alternative to steaming

The researchers also look at the effect of the moisture content of the sand at three different watering strategies during the cultivation: dry (-25%), normal and wet (+25%), and at the microbiome with and without steaming. They look for bacteria and fungi that make a plant more resistant to fusarium, and that are already present in the sand beds. Stimulating those organisms may offer an alternative to steaming the soil in the future.

Research into fossil-free cultivation is financed by the Kas als Energiebron program, the leading innovation program that stimulates energy conservation and the use of sustainable energy in greenhouse horticulture. Greenhouse horticulture in the Netherlands and the Ministry of Agriculture, Nature and Food Quality (LNV) are working together on this.