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  • Author or Editor: Kuan Qin x
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Soil organic matter degradation and water limitation caused by intense farming activities are some of the major threats affecting agricultural production. Accordingly, the concepts of sustainable agricultural systems with optimized irrigation and improved soil quality can be adapted to address these issues. During this 2-year field study, two management factors—humic substances (HS) as organic inputs (HS vs. control) and deficit irrigation as the irrigation method (50% vs. 100% based on evapotranspiration)—were evaluated based on triploid watermelon (Citrullus lanatus cv. Fascination) yield and soil property changes. HS application increased watermelon early yield by 38.6% and total yield by 11.8% compared with the control; the early yield mainly increased under deficit irrigation. Compared with full irrigation, deficit irrigation increased water use efficiency (WUE) without significantly affecting total yield. In addition, HS application significantly increased the soil organic carbon (SOC) content, which was found to be positively correlated with crop WUE. These results indicate that soil organic inputs with HS and deficit irrigation are valuable strategies to establish sustainable systems for watermelon production, which will not only increase yield and WUE but also significantly improve soil quality and save irrigation water.

Open Access

Rockwool and peatmoss are commonly used substrates in the greenhouse industry due to their quality, stable pH, exceptional water retention properties and air porosity that is important for plant root development. Although rockwool is commonly used in deep water culture (DWC) hydroponic systems as the base support, there is a lack of studies comparing different types of substrates that could be used in DWC systems, especially considering the increasing market value and awareness of sustainable production in controlled environment agriculture. We identified 13 commercial substrate mixes with different compositions and conducted a series of studies in a DWC system in a greenhouse for three seasons to evaluate their effects on arugula ‘Slow Bolt’ (Eruca sativa L.) and lettuce ‘Summer Crisp’ (Lactuca sativa L.) growth, yield, and quality. The substrates tested significantly influenced the growth, yield, and quality of both arugula and lettuce. The average leaf fresh weight per plant could range from 44 to 190 g for arugula and 89 to 265 g for lettuce. The peat-based products outperformed the coir and other inorganic substrates (phenolic foam, rockwool). The substrate with 75% peat + 25% fine coir produced the greatest plant height, width, and biomass for arugula and lettuce over three growing seasons. Examining arugula and lettuce growth, the fall season produced plants with higher water and nutrient use efficiency, while plants grown during the winter had lower resource use efficiency. Further research is needed to engineer hydroponic substrates suitable for various seasons of leafy green production that results in comparable yield and quality.

Open Access