Growth of corn roots and associated arbuscular mycorrhizae are affected by long-term tillage and phosphorus fertilization

Abstract

Phosphorus deficiency is a major constraint for corn (Zea mays L.) production. Cropping practices, such as tillage, modify corn P absorption, but the underlying mechanism must be assessed. A study was conducted at a long-term (18-yr) experimental site in Quebec, Canada, to evaluate the effects of tillage and P fertilization on arbuscular mycorrhizal (AM) fungi, soil properties, root attributes, corn growth, and corn P concentration. Soil (0-10 cm) and plant samples were collected at the 8 to 10 leaf stage from plots under moldboard plow (MP) and no till (NT) fertilized with 0, 17.5, or 35 kg P ha-1. Tillage increased soil bulk density, vesicular colonization, shoot and root biomass, root surface area, average diameter, volume, total root length density, and the percentage of medium-sized roots; it decreased total soil C and N concentrations, specific root length, percentage of fine roots, and arbuscular and total AM fungal colonization. Phosphorus fertilization reduced total AM fungal colonization, enhanced soil Mehlich-3 P level, total root length density, and the percentage of fine roots. Corn shoot and root P concentrations, reduced by tillage, were positively correlated with the percentage of fine roots and arbuscular colonization, but negatively correlated with vesicular colonization and the percentage of medium-sized roots. Overall, P fertilization reduced total AM fungal colonization and increased root length density, and tillage decreased arbuscular development in roots and fine root growth in soil resulting in the low corn P concentration. © 2012 by the American Society of Agronomy.