Phosphorus Availability and Maize Performance in Response to P-Fertility Management, Mycorrhiza and Biostimulant in Ultisols of Owerri

The study assessed phosphorous availability and performance of maize to P-fertility management, mycorrhizal (AMF) inoculation and biostimulation in Ultisols of Owerri, Southeastern Nigeria. The experiment was conducted in the field as a Split-split plot experiment in randomized complete block design (RCBD). Treatments consisted of 2 levels P-management (LP and NLP), 2 levels of mycorrhizal inoculation (with and without AMF) and 2 levels of biostimulant (B and NB) with 3 replications, giving a total of 24 experimental units (plots). Prior to the experiment, soil samples (0-15 cm) were collected and analyzed in the laboratory to ascertain initial properties of the experimental soils as well as mycorrhizal populations. The farmland was prepared and mapped out and treatment applications cum sowing of maize seeds were performed accordingly. Plants were allowed to grow in the field for a period of 12 weeks. Maize growth parameters (plant height, stem girth, number of leaf and leaf area) were collected and recorded at 2, 4, 6, 8, 10 and 12 weeks after sowing (WAS) while yield data were taken at the 12th WAS. Data generated from soil and agronomic variables of maize were subjected to statistical analysis using the ANOVA and means were separated using the LSD test at 5% probability level. Results showed that the experimental soils belong to the loamy sand textural class and were prior to the experiment, extremely acidic (pH in water = 4.28) with low levels of available P (6.53 mg kg-1 ) and exchangeable base-forming cations. Application of lime-phosphate (LP) significantly (P < 0.05) increased soil pH (5.11) and available P levels (20.93 mg kg-1 ) as well as growth and yield parameters of maize. There were also positive effects of AMF inoculation and biostimulant on soil P availability and maize performance relative to the control units. Maize yield was significantly (P > 0.05) higher in plants under LP-treated soils (2.92 t ha-1 ) compared to those in NLP plots (1.50 t ha-1 ). Also yield of plants which received AMF-inoculation (2.94 t ha-1 ) significantly (P > 0.05) outweighed that of the un-inoculated plants (1.47 t ha-1 ) and same trend occurred with biostimulation (B = 2.42 t ha-1 ; NB = 1.99 t ha-1 ). Interaction of lime-phosphate and mycorrhizal inoculation (PM x I) recorded the greatest impact on soil P availability whereas interaction of all three treatment combinations (PM x I x B) had greater influence on maize performance. Significant positive correlations were observed between available P and each of soil pH (r = 0.834**), AMF population (r = 0.699**) and seed yield of maize (r = 0.626* ). Coapplication of lime, superphosphate fertilizer and mycorrhizal inoculant was recommended for increased P availability and maize performance in the Ultisols of Owerri, Southeren Nigeria.