Abstract:
The effects of some cropping systems on soil properties at two depths were investigated using physico-chemical and microbial properties. Soil samples were collected under four cropping systems at three locations. The lad use systems were (i) cocoa, (ii) citrus, (iii) oil palm plantation and (iv) fallow namely; Obaretin (Edo State), Ayetoro (Ondo State) and CRIN (Ibadan, Oyo State). The two depths were 0-15 and 15-30 cm. Soil core samples collected were used to determine some selected physical soil characteristics including bulk density, porosity and moisture content. Soil particle size analysis, dispersion ratio and infiltration rate were also determined. Soil chemical properties determined included pH, Organic carbon (O.C), Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Sodium (Na), and Magnesium (Mg). Microbial biomass determination based on fumigation – incubation method was also performed in the laboratory to assess the microbial activity in soils under different land use systems. The greenhouse work involved assessing the fertility status of the soils collected under the four cropping systems at the three locations making twelve (12) samples. Soils collected were air-dried and sieved using 2-mm sieve. Each sample was put into 4 litre pot with holes at the base. There were four pots per land use system given sixteen (16) pots, which were replicated three times using Randomized Complete Block Design (RCBD) given forty eight (48) pots altogether for each location. Maize (Zea mays) was used in assessing nutrient uptake (growth parameters determined included plant height, and girth (cm), leaf length and breadth (cm), leaf area (cm2) and number of leaves. Data were collected at 3, 6, 9 and 12 weeks after planting to study the influence of the previous land use on the crop productivity. Results obtained were subjected to ANOVA using SPSS 19.0, and mean separation was done using Duncan’s Multiple Range Test. The results from the study show that the fallow land have the highest exchangeable basic cations that were significantly difference at (P < 0.05) from other land use systems due to microbial activities on the quantity of plant residue and organic compound released by the root and shoot system. The finding revealed that cropping system causes significant changes in soil properties affecting soil fertility and productivity.
