Effect of Selected Forage Legumes on Soil Quality and Maize Yield in the Savanna
Abstract
A study on the effect of selected forage legume on soil quality and maize yield in the Guinea Savanna was conducted in Ahmadu Bello University Farm, Samaru, Zaria (longitudes 7o 301 and 7o 501 E and latitudes 11o 001 and 11o 101) Nigeria in the year 2008 to 2009.
The study involved planting two forage legumes; Centrosema Pascuorum (Cp) and Macrotyloma uniflorum (Mu) as the main plots.
A natural vegetation regrowth was used as control.
The treatments consisted of a factorial combination of Nitrogen rates (0, 40, 80 and 120 kg ha-1) and Phosphorus rates (0, 13.2 and 26.4 kg ha-1) imposed as sub-plots.
Data obtained were evaluated on a split-plot design for soil chemical [organic carbon, available phosphorus, total nitrogen, soil carbon fraction, CEC, soil ph, exchangeable bases (Ca, Mg, Na, K), and micronutrients (Zn, Mn, Fe) ] properties measured.
Crop phrenology (plant height, leaf number, maize stover yield, maize cob weight, and grain yield), soil physical (bulk density, hydraulic conductivity, particle size distribution, dry and wet aggregate stability, and total porosity).
properties were also measured and soil microbial biomass (carbon, nitrogen, phosphorus, and particulate organic matter) were also measured.
Results showed that pre-maize planting soil condition, Centrosema pascuorum planted (CPF) fallow significantly improved soil chemical properties {Available phosphorus (10.50 mg kg-1), total nitrogen (0.88 g Kg-1), ph (6.0), CEC (6.8 c /mol Kg-1), manganese (9.3 mg Kg-1), Iron (42.2 mg Kg-1 ), exchangeable calcium (2.80 c /mol Kg-1), exchangeable sodium (0.68 c /mol Kg-1) and mean weight diameter (1.37g) } compared to all other treatments.
This indicates that Centrosema pascuorum planted Fallow is a better soil amendment than natural vegetation regrowth which gave a lower improvement in soil chemical properties {Available phosphorus (8.75 mgkg-1), total nitrogen (0.53 g Kg-1), ph (5.9), CEC (5.0 c mol Kg-1 ), manganese (6.4 mg Kg-1), Iron (31.1 mg Kg-1), exchangeable calcium (2.40 c mol Kg-1), and exchangeable sodium (0.58 c mol Kg-1) }.
Macrotyloma uniflorum planted fallow (MPF) slightly improved soil chemical properties {Available phosphorus (5.25 mg kg-1), total nitrogen (0.35 g Kg-1), ph (6.0), CEC (6.6 c /mol Kg-1), manganese (7.9 mg Kg-1), Iron (31.1 mg Kg-1), exchangeable calcium (2.40 c /mol Kg– 1), and exchangeable sodium (0.48 c /mol Kg-1) }.
However, natural vegetation regrowth contributed higher organic carbon (6.1 g Kg-1), exchangeable potassium (0.17 c /mol Kg-1), and soil zinc (10.7 mg Kg-1) to the soil than CPF and MPF under one-year fallow management at pre-maize planting.
Phosphorus application significantly influences soil properties with 26.4 kg P ha-1 producing higher values among other rates, suggesting that 26.4 kg P ha-1 was optimal for maize production under the legume short fallow production.
This study, therefore, suggests the application of 80 Kg N ha-1 and 26.4 kg P ha-1 under the one-year Centrosema pascuorum planted fallow and one-year maize cultivation as being the most beneficial.
The practice will ensure sustainable maize production, reduced (less than 120 Kg N ha-1) the use of inorganic fertilizer for maize production, and improve soil quality.
Introduction
Maize (Zea may L.) Is a very important staple cereal produced both for cash returns and for food in the savanna agro-ecologies (Jagtap, 1995).
It has a high yield potential and occupies about 40% of the area under agricultural production in the savanna zones.
Enhanced maize production, therefore, has a strong potential for improving the livelihood of small-scale farmers in Nigeria.
However continuous cropping of maize, a major staple crop in Nigeria, has adversely affected soil quality, especially under monocropping systems in savanna ecologies.
Various attempts have been made to improve soil productivity through the application of inorganic fertilizers and intercropping cereals with legumes (Reijnties et al., 1992, Adepetu, 1997).
Studies have shown that continuous use of inorganic fertilizers alone is not helpful under intensive agriculture as it aggravates the problem of soil degradation (Marinari et al., 2000; Ayoola and Makinde, 2007).
In the Nigerian savanna, loss of organic matter consequently results in low soil biological activities (Pascual et al., 1997), increase soil acidity, soil nutrient imbalance, low water uptake, and ultimately low crop yield (Giller et al., 1998; Marinari et al., 2000 and Tarawali et al., 2001) has been observed.
Reduced cation exchange capacity, exchangeable cations, and upset in the cationic balance have also been reported (Agbenin and Goladi, 1997).
Soils of the West Africa Savanna dominated by kaolinite clays are inherently poor in fertility, fragile, and degrade rapidly under continuous intensive cropping and livestock production systems (Jones and Wild, 1975; Adeoye, 1984; Lombin, 1987; Lal, 1979; Odunze et al., 1992).
Upland soils in the Nigerian savannas are known to be sandy loam at the surface layer, have low water holding capacity, low organic matter level, and result in low soil microbial activity and cations exchange capacity (Pascual et al., 1997, Tarawali et al., 2001).
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