Simulating the Photosynthetic and Annual-Yield Enhancement of a Row-Planted Greenhouse Tomato Canopy Through Diffuse Covering, CO₂ Enrichment, and High-Wire Techniques

Abstract

In greenhouse horticulture, the potential impacts of different technical interventions on the net canopy photosynthetic rate (Ac) and annual crop yields (FWyear) are often unclear. This study evaluated the impact of three modern greenhouse techniques—diffuse greenhouse coverings, CO2 enrichment, and high-wire cultivation—on Ac using a canopy photosynthesis model that represents a vegetable canopy as rows of cuboid blocks. The model-estimated Ac was consistent with the chamber-measured Ac of a tomato canopy (mean absolute error ≤ 2.3 μmol m−2ground s−1 and the coefficient of determination ≥ 0.91), indicating the validity of the constructed model. Scenario analysis, which assumes typical tomato cultivation in a Japanese greenhouse and uses literature values for carbon-partitioning parameters, indicated that (1) changing greenhouse coverings from clear to diffuse can increase FWyear by 6% (+2.7 kg m−2), (2) doubling the CO2 concentration from 400 μmol mol−1 to 800 μmol mol−1 can increase FWyear by 30% (+12.6 kg m−2), and (3) doubling the canopy height from 1.8 m to 3.6 m can increase FWyear by 12% (+5.4 kg m−2). Combining all these techniques could achieve an FWyear of 59 kg m−2 in Japan. Although there are uncertainties in the model parameters, these provisional estimates offer useful information for stakeholders considering investments in these techniques.

Keywords

• canopy height
• carbon balance
• CO₂ enrichment
• diffuse greenhouse coverings
• high-wire cultivation