Effects of ginger-citrus intercropping on ginger growth, photosynthesis traits and yield

Intercropping is a traditional cultivation system wherein two or more plant genotypes are grown together for a certain period. Intercropping not only facilitates full use of the available land space, but also contributes to optimizing the light environment and improving yields. In this study, we conducted a field experiment to examine the effects of different cropping patterns of ginger on the growth, photosynthesis and yield of ginger under hot summer conditions in 2021 and 2022, based on the following three treatments: unshaded ginger monoculture (CK), shaded ginger monoculture (CK1), and intercropping of ginger and citrus (CI). To determine the effects of intercropping with citrus, the ginger plant growth characteristics, leaf burn, photosynthetic key enzymes, photosynthetic pigments, chlorophyll fluorescence parameters, osmoregulatory substances, antioxidant enzyme activity, and yield under different cropping patterns were investigated. The results revealed that compared with CK treatment, the CI treatment was associated with a significant reduction in canopy light intensity and plant leaf burn index by 55.40%−55.80% and 61.14%−70.20%, respectively (P<0.05), whereas there were significant increases in the activities of key photosynthetic enzymes, photosynthetic pigment, net photosynthetic rate, and maximum photochemical efficiency of 22.34%−50.55%, 14.36%−50.00%, 51.04%−70.64%, and 5.56%−7.79%, respectively (P<0.05). Furthermore, the CI treatment contributed to the highest ginger yield (63.00−66.08 t·hm⁻²), which represented a significant increase of 23.28%−23.77% (P<0.05) when compared with that obtained under the CK treatment. Moreover, we detected no significant differences between the CK1 and CI treatments with respect to light intensity, leaf burn index, net photosynthetic rate, or yield. However, compared with the CK1 treatment, the CI treatment significantly enhanced the activities of key photosynthetic enzymes, photosynthetic pigment contents, and maximum photochemical efficiency by 26.88%, 7.74%, and 2.47%, respectively (P<0.05). In conclusion, intercropping with citrus can reduce light intensity at the ginger canopy during the hot season, reduce the degree of leaf burn, improve photosynthetic performance, and increase ginger yield. Among the three assessed planting patterns, ginger-citrus intercropping was identified as the most effective system, which contributed to achieving the highest crop yield, provided beneficial environmental conditions for ginger growth, and highlighted the production advantages of ginger under the citrus canopy.