Impact of Fallowing on the Emergence of Weed Species, Soil Nutrient Dynamics and Yield of Maize (Zea mays L.)

Fallowed uplands dominated by Chromolaena odorata, Hyptis suaveolens, Tithonia diversifolia, Imperata cylindrica and other grasses were selected and their effects on the emergence of associated weed species, the nutrient status of the soil and subsequent maize yield were examined. A survey was conducted to estimate the floristic composition in each field in 2017 and 2018. Five fallowed fields and one arable field were used during the 2018 and 2019 seasons. The trial was laid on each field in a Randomized Complete Block Design with 3 replicates. Zero tillage was adopted for the fallow land while the arable field was ploughed, harrowed, and ridged. Weed, soil, and grain yield data were collected and subjected to analysis of variance at P=0.05. The results showed that weed composition and emergence pattern differed marginally among the five fallowed fields. Tridax procumbens, Brachiaria lata and Cyperus rotundus were the most associated weed species. Soils under T. diversifolia and C. odorata were rich in organic carbon and total porosity and low in bulk density with an average return biomass to the soil amounting to 23.18 - 27.18g/m². The continuously managed arable field showed maize grain yield of 2.72 t/ha compared with fallowed fields dominated by T. diversifolia (2.64 t/ha) and C. odorata (2.38 t/ha). Tithonia diversifolia and C. odorata contributed positively to reducing weed emergence and improving soil nutrients. Small-holder farmers can re-incorporate the tested weed species into the cropping system to reduce herbicide usage and improve maize grain yield in the Nigerian southern Guinea savannah.