Figures (2)  Tables (3)

    • Figure 1. 

      Profile of plastic-greenhouse soils as (a) conceptual framework and two examples for horticulture production as sand mulching profile charactered by sand mulch in (b) Almería, Spain modified based a previous study[25], and as sunken profile charactered by digging to obtain subsoils of clay in (c) Shouguang county, China.

    • Figure 2. 

      Plastic-greenhouse soil profile that motivates carbon and nutrient cycling, and heat production, and saves nutrient and water for that can counteract the environmental constraints of high atmospheric humidity, high water and nutrient loss, low atmospheric CO2, low soil temperature, soil compaction, and soil degradation. Some of the symbols were adopted from IAN/UMCES Symbol and Image Libraries.

    • ConstraintsReasons for the constraintsRemediation from soil perspectiveRef.
      Low atmospheric [CO2]Partly sealed environment by plastic covers limits CO2 diffusion from atmosphere to greenhousesApplication of organic or inorganic amendments to soils, accelerating their quick decomposition[47,48]
      High atmospheric humidityPlastics limit the diffusion of evaporated water, strengthened by frequent irrigationOrganic or plastic mulch, and drip irrigation to allow low evaporation[37,49]
      Low soil temperatureOff-season horticulture production, frequently in winter periodDecreased soil-specific heat capacity, and heat production and preservation[22,50]
      Nutrient lossHeavy chemical and organic fertilizer input and frequent irrigation, facilitating leaching of $ {\text{NO}^-_3} $, and production of NOX and NH3Limiting leaching or gaseous N loss by water conservation soil interlayer or less irrigation[5,51]
      Soil compactionExtensive mobility of machine and humanIncreasing organic fertilizer input, and frequent ploughing[52,53]
      Soil pollution, acidification, and salinizationHeavy chemical input and residue leftoverAddition of organic fertilizer, and decreasing the origin of residual toxins[26,54]

      Table 1. 

      The constraints for plastic-greenhouse horticulture production, corresponding reasons and remediation measures from soil perspective.

    • Soil profilePrimary functionPractices
      Soil mulch layerEvaporation inhibitionRice husk mulching
      Root-carbon layerRoot and microbe activationManure or compost application
      Soil-carbon mix layerIncrease soil resilienceBiochar or peat input
      Water conservation layerWater and nutrient preservationDeep placement of
      clay soils

      Table 2. 

      The profiles of plastic-greenhouse soil, their primary function and the practices to establish the cost-effective soil layer.

    • ItemsSunken profileSoilless culture
      Total costs379,500657,000
      Seedlings45,00048,000
      Water and fertilizers108,000165,000
      Workforce180,000285,000
      Substrate090,000
      Others46,500117,000
      Income634,500877,500
      Tomato yield (t·ha−1)211.5292.5
      Net profits255,000220,500
      The price of tomato was CNY3,000 t−1. The others include machine and land rent, fertigation energy consumption, and pesticide. The data were based on a survey of the local smallholder farmers.

      Table 3. 

      The comparison of the costs of tomato production in plastic greenhouses between sunken profile and soilless culture (CNY ha−1) in the Shouguang county, Northern China in 2022.