Effects of pH on interactions between rice and pea grown under hydroponic condition

Interactions between plant species from different families have been extensively studied and practiced globally, particularly in agroecosystems. However, the effects of pH environments on plant growth regulation remains an area that warrants further investigations. To explore the effects of pH on plant interactions and growth, a hydroponic microcosm experiment was conducted with two crop species: rice (Oryza sativa L.) and pea (Pisum sativum L.). These two crop species were grown by mono- and intercropped under three pH conditions of acid (pH = 3.0), neutral (pH = 6.0), and alkaline (pH = 9.0) and were harvested at the tillering, flowering, and fruiting stages of pea, respectively. Results revealed that rice grew better in acid and neutral conditions than in alkaline environments. In alkaline environments, intercropping restrained the growth of both crops at tillering stage but promoted growth at flowering and fruiting stages. The alkaline environments largely decreased the P (phosphorus) and Fe (iron) content in the nutrient solution promoting rice to allocate more carbon (C) towards root development. A strong correlation was observed between dissolved organic carbon (DOC) levels and plant C investment in roots. In the intercropping regime, the DOC concentration was significantly higher in the alkaline than neutral environment during the flowering stage. These findings indicate that under pH stress, rice invested more C belowground and released more root exudate C to support its growth, in contrast to pea. While interactions between rice and pea did not consistently result in positive growth effects, they did exhibit a competitive effect. This study provides valuable insights into how interspecies interactions can regulate plant growth under pH stress conditions.