Soil management practices affect arbuscular mycorrhizal fungi propagules, root colonization and growth of rainfed maize

Agronomic management practices influence beneficial soil biota, especially arbuscular mycorrhizal fungi (AMF). AMF colonizes about eighty percent of land plants, promoting absorption of essential nutrients and crop growth. Here, a 5-year field experiment was carried out in Central Kenyan Highlands to determine the effect of tillage, mulching and inorganic fertilizers on the number of infective AMF propagules in the soil, mycorrhizal root colonization of maize and uptake of P and N from the soil. The study involved conventional and minimum tillage systems, mulching using dried maize stovers and inorganic fertilizers (120 kg N/ha). The experiment was set up in randomized complete block design and replicated thrice. The number of infective AMF propagules decreased in the following order; V4 stage (p < 0.0001), V6 stage (p < 0.0001), maize harvest (p = 0.0076) and before maize planting (p = 0.0061). Minimum tillage + mulch + no NP fertilizer (ZRO) treatment recorded the highest number of infective AMF propagules with an average of 90 propagules g(-1) of soil whereas conventional tillage + mulch + NP fertilizer (CRF) and conventional tillage + no mulch + NP fertilizer (CWF) treatments recorded the lowest number of AMF propagules with an average of 1.33 propagules g(-1) of soil. Besides, AMF colonization of maize roots at V4, V6 and harvest stages was significantly affected by tillage (p < 0.0001), mulch (p = 0.0001) and fertilizer (p < 0.0001). Results at juvenile stage showed a strong positive correlation between AMF colonization and shoot P (r = 0.933, p < 0.0001) and N (r = 0.928, p < 0.0001). These findings demonstrate a strong effect of agronomic management practices on soil AMF propagules which subsequently affected root colonization and uptake of essential nutrients such as P and N.