Soil health with local recirculation and local amendments ensuring organic cucumber cultivation in Norway

Summary

Abstract:
The new European organic regulation claims that cultivation must occur directly in soil in greenhouses. Cultivation practices in accordance with organic principles require the use of sustainable growing media and the addition of compost for soil improvement, preferably local resources. Soil improvement aims to achieve good soil health, including biological soil activity, nutrient availability, and favourable physical properties. However, only a few studies have been conducted on biological soil health in greenhouses. Biological soil activity was monitored in a greenhouse cucumber experiment on organic soil enriched with biochar and supplemented with local 1) compost, 2) solid digestate from biogas production, or 3) imported peat. The effects of silage mulching were also tested. Biological activity was measured in the soil using different indicators, while plant growth was monitored above soil. Results indicated that the mixture with compost contained more organic matter than other mixtures. Biological activity in the compost mixture was lower and started later than in the other mixtures. Silage mulch increased biological activity in all mixtures. Respiration rates and fungi content classified all three mixtures as stable growing media. At the start of the experiment, nitrogen content and pH levels in all three mixtures were similar. The peat mixture required the most mineral amendments, phosphorous content was highest in solid digestate and lowest in peat. Plant nutrient turnover to the plants was appropriate, although a lack of micronutrients was observed. Yields performed well. Our results show that biological activity in compost starts later in compost compared to the other mixtures. Anyhow compost is considered a key component of soil health. Fungi:bacteria balance was similar and comparable to measurements in Norwegian organically managed soil. Indicators were useful at farm level; they could be diversified further. Local compost and digestate performed as good as peat.