RESIDUAL EFFECT OF MAIZE-LEGUME SYSTEM FALLOW AND NPK FERTILIZERS ON MAIZE PERFORMANCE AND WEED GROWTH
Field experiment was conducted at the Faculty of Agriculture Teaching and Research University of Port-Harcourt between May to September 2018, to evaluate the residual effect of maize-legume system fallow and NPK fertilizers on maize performance and weed growth. The experiment was a 3 x 3 factorial scheme consisting of 3 levels of NPK-15-15-15 (0 Kg NPK/ha, 15 Kg NPK/ha and 30 Kg NPK/ha) and (3) levels of legume system fallow (Natural fallow (Fallow, Mucuna pruriens (MP) and Lablab purpureus (LP) fallows, making up of 9 treatment combinations which were laid out in a randomized complete block design (RCBD) replicated three times. Results showed that there were no significant (P > 0.05) residual interaction effects of fallow species and NPK fertilizer on weed growth, maize yield and yield components. Although there were no significant interaction effect between legumes system and NPK fertilizer but all the legume fallow with or without NPK had higher whole plant yield (Biological yield) and grain than the NF with NPK at 30 kg NPK/ha. Both legumes without NPK (0 Kg NPK/ha) had grain yield advantages of 87 % (MP) and 28 % (LP) respectively over NF without NPK; and about 53 % (MP) and 4 % (LP) grain yield advantages over NF + 30 Kg NPK/ha. Mucuna pruriens (MP), Lablab purpureus (LP) plots showed better growth and yield when compared to plots with Natural fallows (NF). Legume systems at 6 and 12 WAP significantly (P< 0.05) suppressed weed growth when compared to NF. Highest weed densities of 58 weeds/m2 and 132 weeds/m2 w were recorded respectively at 6 and 12 WAP, in plots with NF, while the lowest weed densities of 21 weeds/m2 and 39 weeds/m2 were recorded in plots with LP fallow at 6 and 12 WAP respectively. There were no significant differences among the legume systems on weed dry weight throughout the sampling time except at 12WAP, with LP (88 g/m2) and MP (116 g/m2) having the lower weed dry weight compared to the NF. . Among the legume systems at 12WAP, NF fallow plots had the highest weed dry weight but at par with MP plots while plots grown with LP had the lowest weed dry weight but at par with MP. This implies that Mucuna pruriens fallow and Lablab purpureus suppressed weed growth better than the natural fallow and it is more beneficial than NF in terms of soil fertility enhancement. Farmers can be encouraged to adopt leguminous fallow as way of suppressing weeds and enhancing subsequent crop performance. It also reduces the cost weeding on farm and cost of fertilization as well as encourages production and land utilization.