Soil quality and eggplant (Solanum melongena L.) productivity in response to different mulching strategies under conservation tillage in organic greenhouse production

Roua Amami^1*Khaled Ibrahimi¹TARCHOUN NEJI¹Saadaoui Wassim¹Nour ElHouda Boughattas¹Hiba Ghazouani¹Farooq Sher²Davey Jones³Paul James Milham⁴

• ¹High Agronomic Institute of Chott Mariem, Sousse, Tunisia
• ²School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom
• ³School of Natural Sciences, College of Environmental Sciences and Engineering, Bangor University, Bangor, United Kingdom
• ⁴Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia

Mulching plays a key role in modern sustainable agriculture, offering a versatile way to improve soil quality, conserve resources and optimize crop performance. The aim of this study was to evaluate the effects of different organic mulch materials on soil parameters, mineral nutrient content, and the growth and yield of eggplant (Solanum melongena L.) in an unheated greenhouse organic farming system. Four types of mulch were compared: black (BM) and white (WM) polyethylene plastic film mulch, straw mulch (SM) or compost (CM). No mulch (bare soil) was used as a control (CK). The experiment was designed as a randomized block design with three replications. The white plastic mulch significantly increased soil pH relative to the control. The control treatment (CK) resulted in the highest soil electrical conductivity, while the soil covered with black polyethylene had the highest soil temperature and soil water content during all measurement dates. Relative to CK, the compost mulch gave the largest increase in soil organic matter (SOM, +0.32 g kg-1), available soil phosphorus (P, +41 mg kg-1), available soil potassium (K, +302 mg kg-1) and total nitrogen (N, + 5.33 mg kg-1). Straw mulching promoted the greatest abundance of bacteria, mesophilic fungi and thermophilic fungi. The Soil Quality Index (SQI) ranged from 0.34 to 0.58, with the highest values seen under the BM treatment and the lowest in the no mulch control (CK). For plant related parameters, the plastic film mulch treatments consistently outperformed the other treatments. The results showed significant effects of plastic mulch, especially black plastic (BM), on plant growth, flowering and production parameters (i.e. higher leaf number, longer stems, higher fruit set) resulting in 29.5 t ha-1 greater yield than the other treatments. These results suggest that plastic mulch is economically viable option for improving eggplant production, soil quality and climate resilience in semi-arid regions. These findings are based on a short-term greenhouse study with only one soil type and therefore require validation via long-term field trials across diverse agricultural systems.