How to design cost-effective soil profiles in plastic greenhouses?

Plastic-greenhouse soils, spanning approximately 4.8 million hectares worldwide, are predominantly cultivated by smallholder farmers for horticultural production. These soils contribute greatly to the production of vegetables, herbs, and fruits, and thus to a healthy diet and high farmers' income. Nevertheless, the current challenge is a comprehensive understanding and design of cost-effective profiles for plastic-greenhouse soils of low to medium technology. Here, we devised a novel conceptual framework of a plastic-greenhouse soil profile, considering the environmental limitations imposed by the plastic covering. The profile comprises four distinct layers: a mulch layer to reduce evaporation, a root-carbon layer to facilitate nutrient, CO₂ and heat generation, a soil-carbon mix layer for effective soil buffering, and a water conservation layer to store water and nutrients. Two typical examples of this concept were summarized, the sand mulching profile in Almería, Spain and the sunken profile in Shouguang, China. This soil profile design is affordable and cost-effective for smallholder farmers to produce horticulture product sustainably, therefore, it is worth being applied worldwide. Future studies should adopt the current concept but modify it based on the local soil profile and available resources. More importantly, controlling organic input and thus microbial functions are required to facilitate either plant or soil health.