Root Growth Responses of Maize (Zea mays L.) and Soybean (Glycine max L.) to Soil Compaction and Fertilization in a Ferric Acrisol

Mechanical impedance to root growth is one of the most important factors determining root elongation and proliferation within a soil profile. Two pot experiments were conducted at the Department of Horticulture, KNUST, Kumasi, Ghana, to determine the impact of subsurface compaction and different fertilizer amendments on the root growth of maize (Zea mays L.) and soybean (Glycine max L.). The experiments were arranged in a factorial Completely Randomized Design (CRD) with three replications. Maize and soybean varieties, “Obaatanpa” and “Anidaso” were sown in 72 plastic buckets (36 for each crop) of 12 L volume filled with a Ferric Acrisol. The treatments were different levels of compaction, using bulk density as proxy – 1.3, 1.5 and 1.7 Mg m-3, and fertilizer amendments of 100% poultry manure (15 g/pot), 100% NPK fertilizer (2.89 g/pot) and 50% each of poultry manure (7.5 g/pot) and NPK fertilizer (1.45 g/pot). The highest root growth occurred in the uncompacted soil and along the periphery of the soil core. The applied soil amendments significantly increased the root penetration ratio (RPR) of both crops in relation to the control. The shoot biomass of both crops decreased with increasing soil bulk density. All the applied soil amendments significantly increased the shoot biomass of maize and soybean over the control. The magnitude of response of the crops to the soil amendments was greater in soybean than in maize.