Nitrogen, phosphorus and potassium influence on infections by arbuscular mycorrhizal fungi in Dactylis Glomerata roots

The aim of this research was to compare effects of fertilization with various ratios of N, P and K (N:P:K) on arbuscular mycorrhizal fungi (AMF) infection in roots of Dactylis glomerata in Ca-carbonate (limed) and non-limed meadow plots at the Research Centre of Skriveri, Latvia University of Agriculture. Dactylis glomerata roots were excavated from variously fertilized plots, a minimum 3 root samples per plot and analysed for two consecutive years. Arbuscular mycorrhizal fungi infection rates were estimated according to accepted scoring tables used for determination of AMF colonization. In 2003 the non-limed plots showed the highest AMF infections treated with fertilizer N:P:K (3:1:3 ratio) 8.5%, and in control 5.7%. The lowest results were with N:P:K ratio1:3:3, 0.8% and N:P:K (1:3:1), 0.9%. In the limed plots the highest AMF infection were with N:P:K (3:1:3) 6%, and N:P:K (1:3:3) 5.3%, but the lowest was in the control, 1.5%. In 2004 the non-limed plots had the highest arbuscular mycorrhiza infection with the fertilizer N:P:K ratio 3:1:1, 7.8%, and N:P:K (3:1:3) 7.1%, but the lowest with N:P:K (1:3:1) 4.1%. In the limed meadows the greatest arbuscular mycorrhiza infection rate was at N:P:K (3:1:1) 9.6% and N:P:K (1:3:3), 7.5%, but the lowest result at N:P:K (1:3:1), 3.4%, and N:P:K ratio 3:3:3, 4%. In 2003 the fertilizer N:P:K ratio3:1:3 favoured arbuscular mycorrhiza infections in limed and non-limed plots, but in 2004 plots fertilized with N:P:K ratio 3:1:1. In 2004 AMF infections in Dactylis glomerata roots were greater than in 2003. We conclude that fertilization with N:P:K ratio 3:1:3 markedly increased the AMF infection rates in non-Ca-carbonate amended soils, but in the Ca-carbonate amended soils the results were variable due to the increased soil pH causing apparent non-specific phosphate precipitation/dissolution processes.