Effects of agronomic management practices on soil microbial communities in a maize cropping system

Conventional and organic agriculture are mainstream soil agronomic management practices used by farmers in Kenya to improve crop production and soil fertility. However, long-term use of these soil management systems can have deleterious or positive effects on soil microbiota. Soil microorganisms, especially arbuscular mycorrhizal fungi colonize about eighty percent of plants promoting absorption of essential nutrients such as phosphorous (P) and nitrogen (N), and protection of plants against biotic and abiotic stresses. A 5-year field experiment was conducted at Kirege, Tharaka-Nithi County in Kenya to determine the response of soil mycorrhizal infection potential, growth of maize, uptake of N, and soil bacterial diversity to tillage, mulch and inorganic fertilizers. The study involved two tillage systems (conventional and minimum tillage), mulching (with and without) and mineral fertilizers (0 and 120 kg N/ha) set up in randomized complete block design and the test crop used was maize (Zea mays L.). Number of infective AMF propagules in the soil were highest at V4, intermediate at V6 and lowest at harvest stage. At maize juvenile stage, tillage, mulch and fertilization significantly (p < 0.0001) affected maize shoot dry matter and uptake of N. Shannon’s Wiener Index (H) showed that the bacteria isolates from different treatments were genetically diverse with a genetic diversity estimate ranging from H= 0.11 to H= 0.32. Therefore, there is need for proper integration when using organic inputs such as mulch, inorganic fertilizers as well as minimum and conventional tillage so as to enhance crop growth and protection of beneficial soil microorganisms.