The Effects of Soil pH on Setaria viridis and Abutilon theophrasti Seedling Growth and Tissue Nutrients

Weeds vary in their response to soil pH in how they become established, grow and thrive. Knowledge of how a weed species responds to soil pH could help in evaluating their competitive ability against crops under different soil conditions and provide valuable insights into their biology and adaptation in agroecosystems. Studies were conducted to determine the effect of three soil pHs (4.3, 5.3, 6.9) on the seedling growth of Setaria viridis and Abutilon theophrasti in terms of seedling shoot biomass accumulation and tissue nutrient content. The effect of several postemergence-applied herbicides (bentazon, cyanazine and 2,4-D) on established seedlings of those species was also investigated. Untreated Setaria viridis, as well as untreated and treated (bentazon, cyanazine and 2,4-D) Abutilon theophrasti, seedlings accumulated less biomass as the soil pH decreased from neutral to acidic reaction. In both species this reduction in growth was associated with interference of uptake and incorporation of calcium, magnesium and phosphorus, as well as toxicity caused by excessive amounts of aluminum, manganese and zinc in seedling tissue. These nutrient imbalances also led to enhanced injury of Abutilon theophrasti with bentazon, cyanazine and 2,4-D.