Optimizing the growth and production of sorghum by intercropping with peanuts under effective photoprotection

This peanut-sorghum intercropping study examined the effects of peanut habit of posture (one erect and one semi-erect accession) on dwarf sorghum growth and yield over two years under field conditions. In northern China, the dwarf sorghum (Sorghum bicolor [L.] Moench) is an important and widely planted industrial crop for ethanol fermentation. Substantial efforts are in progress to reduce the negative environmental impacts arising from sorghum monocultures and other conventional farming practices. Intercropping, especially with nitrogen-fixing legumes, was identified as one of the effective and sustainable agricultural practices for maintaining productivity while minimizing ecological impacts. In this study, the intercropping of a dwarf sorghum cultivar with peanuts (two accessions) increased the sorghum yield over two crop cycles. Relative to peanuts planted in monocultures, the intercropping process with sorghum generally reduced peanuts' yield. Specifically, intercropping lowered the total dry matter, yield, and leaf net photosynthetic rates (Pn) in both peanut accessions. Conversely, in the semi-erect peanut-sorghum system, the total seed yield of the peanut-sorghum system increased by 19.5% in 2021 and 21.2% in 2022, resulting in a land equivalent ratio (LER > 1), whereas the erect peanut-sorghum system failed to deliver better outcomes (LER < 1). Interestingly, the semi-erect habit mitigated intercropping-induced yield losses in peanuts while conferring a significant yield advantage to sorghum compared to the erect system. From the photosynthesis perspective, the intercropped peanut plants had lower quantum yields of photosystems I (PSI) and II (PSII) than the monocultured peanuts; and this inhibition was less pronounced in the semi-erect peanuts. Additionally, the cyclic electron flow (CEF), proton gradient (triangle pH), and non-photochemical quenching were higher in intercropped peanuts than in monocultured peanuts. The increased foliar CEF and Delta pH plausibly helped the semi-erect type peanut to alleviate photoinhibition and growth reduction in the peanut-sorghum intercropping system. These enhanced photoprotective mechanisms (increased CEF and Delta pH) facilitated photosynthetic acclimation in the semi-erect peanuts, highlighting the value of habit-specific selection for optimizing sorghum-peanut intercropping.