Effects of different photovoltaic shading levels on kiwifruit growth, yield and water productivity under “agrivoltaic” system in Southwest China

Agrivoltaic systems (AVS) are emerging mixed production systems where crops are cultivated below the photovoltaic (PV) panels. This study investigated the effects of different PV shading levels on kiwifruit growth, yield and water productivity (WPc), with three densities of 19.0% (T1), 30.4% (T2) and 38.0% (T3) of translucent PV panels installed on the South-oriented AVS roof. The AVS perimeter was left open with the full sun treatment outside the AVS as the control treatment (CKL). Results showed that the solar radiation in T1, T2 and T3 was reduced by 43.8 ± 0.6%, 50.5 ± 0.6% and 55.0 ± 0.5%, respectively, compared with CKL, whereas the air temperature was uniform and the relative humidity increased with increased PV shading. The leaf area index and leaf light use efficiency improved, while the leaf transpiration rate, photosynthetic rate and water use efficiency decreased with increased shading. The accumulated transpiration (T) was higher in CKL (419.9 ± 9.9 mm) than shading treatments (380.8 ± 26.7, 319.2 ± 15.1 and 308.8 ± 12.9 mm in T1, T2 and T3, respectively), and shading also reduced soil evaporation (E) (63.4 ± 1.0, 51.9 ± 3.1 and 47.4 ± 3.8 mm in T1, T2 and T3, respectively, compared to 79.4 ± 1.1 mm in CKL) and thus decreased the total evapotranspiration (ETc act=E + T) requirement. The kiwifruit volume and yield were slightly reduced (−7.3 to 5.5% and −6.5 to −2.6%) in T1 relative to CKL (101.4–106.8 cm3 and 17.6–18.9 t/ha), while the negative effects of shading on the volume and yield were significant (p < 0.05) in T2 and T3. The water productivity (WPc) was improved in T1 (8.2 ± 5.7%) and T2 (5.8 ± 1.9%) relative to CKL, however, it was significantly reduced in T3 (−9.8 ± 1.4%). It was concluded that 19% (T1) PV coverage was a suitable shading treatment management in the AVS, as kiwifruit growth and yield were less affected, and WPc was increased with reduced water consumption. The total potential profit can be largely promoted from electricity production, especially for dry rainfed and no electricity remote areas, where they can benefit from using produced electricity locally for irrigation.