Response of Soybean and Maize Varieties to Different Soil Fertility Management Options in Southeastern Nigeria

ABSTRACT Promiscuous (naturally nodulating) IITA (International Institute of Tropical Agriculture) soybean (Glycine max (L) Merrill) varieties and elite varieties of maize (Zea mays L.) were evaluated in four experiments between 2007 and 2009, for their growth and yield responses to an area without history of soybean cultivation, some soil fertility management options and for soybean fertilizer replacement value (FRV) to companion and subsequent non-legume maize crop. These experiments were conducted at Abakaliki in the derived Savanna of Southeastern agro-ecological zone of Nigeria, located at latitude 060 19´ 407´´ N, longitude 080 07´ 831´´ E and an altitude of about 447m above sea level, with a mean annual rainfall of about 1700mm to 2060mm spread between April and October. The maximum mean daily temperature is between 270 C - 310 C with abundant sunshine and a high humidity all through the year. The soil is shallow with unconsolidated parent materials (shale residuum) within 1m of the soil surface, described as Eutric leptosol. The first experiment assessed twelve IITA promiscuous soybean varieties (TGx 1740-2F, TGx 1904-2F, TGx 1904-4F, TGx 1903-5F, TGx 1909-3F, TGx 1844-4E and the selected six varieties used in Experiment II), for their growth and yield performances in the derived savanna belt of Southeastern Nigeria. These varieties showed high adaptable potentials by exhibiting significant good growth and high yield components. Varieties like TGx1740-2F, TGx1485-1D, TGx1904-6F, TGx1908-8F, TGx1903-5F, TGx1844-18E, TGx1904-2F and TGx1903-7F produced seed grain of up to 6.0-7.5 tons/ha, seed weight between 29.1-33.5 g/plant, nodule number between 20.9-37.1 and a vigorous growth to a height of up to 30.8-69.3 cm with girth size of 1.2-1.5cm. These qualities observed were good evidence that soybean can be successfully cultivated in Abakalki climatic conditions and that with application of the management options implicated in this study, soybean can be a veritable resource among the resource-constrained smallholder farmers for food and for their soil fertility improvement without the costly external fertilizer inputs. In Experiment II, eight soil fertility management options (lime at 10 tons/ha, wood ash (WA) at 10 tons/ha, urea at 20 Kg/ha, poultry manure (PM) at 20 tons/ha, muriate of potash (MOP) at 30 Kg/ha, single super phosphate (SSP) at 40 Kg/ha, NPK (15:15:15) at 40 Kg/ha and a control) were evaluated for their effects on the growth and yield of six selected soybean varieties xi (TGx1876-4E, TGx1903-7F, TGx1485-1D, TGx1844-4E, TGx1904-6F and TGx1908-8F) from Experiment I. A soil test was carried out before planting (BP) and after harvesting (AH), which indicated that the area was acidic with pH values between 5.50 (BP in 2008) and 5.85 (AH in 2009), but with high available phosphorus (24.57 mg/kg AH in 2009) while other elements were low. Poultry manure was found highly significant (P