Greenhouse Cultivation of Cucumber (Cucumis sativus L.) in Standard Soilless Media Amended with Biochar and Compost

Abstract

Peat is one of the most commonly used substrates in soilless cultivation. However, peat mining produces a negative carbon footprint, which raises the need for alternative sustainable substrate media. To address this, we studied the impact of peat replacement with a combination of various biochars and cotton burr compost on the growth and yield of cucumber (Cucumis sativus L.), and nutrient concentration of media, plant leaf, and fruit in greenhouse conditions. Two experiments were conducted from Nov 2020 through Jan 2021 (Trial 1) and from Feb to Apr 2021 (Trial 2). The treatments were control (peat, vermiculite, and perlite at 2:1:1) and in the control peat was either fully replaced (hardwood biochar+compost, softwood biochar+compost, and hemp biochar+compost) or partially replaced up to 50% (v/v) (hardwood biochar+compost, softwood biochar+compost, and hemp biochar+compost). The control media was more acidic with lowest electrical conductivity than the other treatments. The leaf chlorophyll content and the photosynthetic assimilation rate varied among the treatments in both trials. The final dry shoot biomass was lowest in peat-dominated control treatment suggesting biochar-compost in the substrate media contributed in increased dry biomass of the cucumber plant. The total number of fruits per plant and total yield per plant was significantly increased in all the treatments with the highest in hardwood biochar+compost, compared with the control. The nutrient concentration of media, leaf, and fruit indicates that biochar-compost enhances the nutritional status of the media, which supplies essential nutrients to the plant leaf and fruit while growing in different substrate compositions. Our results suggest that the replacement of peat with full or partial proportions of biochar-compost can produce similar and, in some cases, even better growth, yield, and physiology in potted cucumber than in the unamended control treatment.