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Field response of groundnut (Arachis hypogea L.) cultivars to mycorrhizal inoculation and phosphorus fertilizer in the transitional agro-ecological zone of South West Nigeria
A field experiment was conducted in Abeokuta, South Western Nigeria, to evaluate the growth and yield response of three groundnut cultivars to inoculation with mycorrhizal fungus (Glomus mosseae) and phosphorus (P) fertilization in 2003 and 2004 planting seasons. The design was split-split plot in randomized complete block design (RCBD) in a 3x2x2 factorial combination of groundnut cultivars (RMP91, RRB and RMP12), phosphorus (54kgha-1 and 0Kgha-1) and mycorrhizal inoculation (inoculated and uninoculated). Observations were made on canopy spread, leaf area, dry matter yield and grain yield. Mycorrhizal root infections, leaf P uptake and available P in the rhizosphere were also determined. Result shows that inoculation of groundnut cultivars with G. mosseae significantly enhanced grain yield in the 2003 planting season (54 % in RMP91 to 66% in RMP12) whereas the enhancement was lower and only significant in RRB (21%) in the 2004 planting season. Phosphorus fertilization enhanced grain yield by a range of 22% (RMP91) and 40% (RMP12) in the 2003 planting season while it was a range of between 20% (RMP91) and 16% (RRP) in the 2004 planting season. Mycorrhizal root infection was as high as 64.1% relative to control (10.6%) in 2003 season. Inoculation with G. mosseae increased leaf P uptake by 30% within the two planting seasons. Phosphorus application increased the level of P in the leaf (average 32%}in the two years and rhizosphere soil P (average 1400%) only in the 2004 planting season. Percentage root colonisation ranged between 60 and 67% in all the inoculated plots in the two years. There was a marked increase in the root infection rate in the uninoculated plots (averaged 180%) in the 2004 planting season. In the 2004 planting season, available rhizosphere soil P averaged 2.06 mg/kg in the inoculated plots when compared to 2.6mg/kg in P fertilized and 2.69mg/kg in the P+M plots. All the treatments increased canopy spread (average 25%), leaf area (average 14%) and root dry weight (17%) over the control in the 2003 planting season, while in 2004 planting season, increase was recorded in canopy spread (average 22%), leaf area (average 40%) and shoot dry weight (average 35%) over the control. Inoculation of groundnut cultivars with the mycorrhizal fungus improved their performance in the field and compared favorably with the groundnuts fertilized with 54kg ha-1 of SSP fertilizer.
Keywords: Groundnut cultivars; Arbuscular mycorrhizal inoculation; Leaf phosphorus uptake; grain yield; transitional agro-ecological zone
Moor Journal of Agricultural Research Vol. 6 (1&2) 2005 pp. 60-69