Preliminary studies of soil erosion in a valley bottom in Ibadan under some tillage practices.

摘要

The effects of soil type and tillage interaction on nutrient loss in surface runoff and eroded soil, soil physico-chemical properties and maize growth and yield was assessed at a valley bottom in the University of Ibadan, Ibadan extends from Latitude 7 degrees 241 N to Longitude 3 degrees 54 E. Field experiments were carried out for four months on 5% slope as a 2x3 factorial in a randomized complete block design involving two soil types (Apomu and Osun series) as factors, each at three levels of tillage practices; stubble mulch tillage (ST), Traditional tillage (TT), and Zero tillage (ZT). Each tillage method occupied 22x5 m size erosion plot, which was replicated three times on each soil type. Pre-and post study soil samples were analysed for physical and chemical properties. The plots were sown to maize at 90 cm between and 30 cm within rows spacing under which runoff and soil loss from each plot were determined using soil and water collecting devices at the end of each plot. Results showed that soil bulk density at 0-30 cm soil depths was lower in ZT than ST and TT by 0.06 and 0.17 g/cm3 and 0.09 and 0.14 g/cm3 on Apomu and Osun series, respectively, after cropping cycle. Zero tillage was higher in moisture content than ST and TT on both Apomu and Osun series by (10.83; 11.67)% and (4.05; 8.77)%, respectively. The interaction between soil type and tillage had no significant effect on soil physical properties while it had effect on some soil nutrients: org. C, Ca, Mg, K and Zn. Although soil nutrients declined in all plots after cropping cycle but lowest declines were in ZT plot on both Apomu and Osun Series: Soil loss was higher in ST and TT than ZT by (56.27, 79.46)%, (30.36, 56.52)% on Apomu and Osun series, respectively. Corresponding runoff were (36.50; 52.38)% and (22.58; 26.52)% respectively for the Apomu and Osun series. Maize height, stem girth and leaf area index were in the following order: TT>ST>ZT on Apomu and Osun series with significant interaction (P<0.05). Maize grain yield was higher on TT than ST and ZT by (14.98; 11.56)% and (5.62; 15.08)% on Apomu and Osun series, respectively. Eroded soils and runoff water obtained from ST and TT plots were consistently richer in nutrient contents than ZT plots on both soil types. ZT could be a better option for soil and water conservation on Apomu and Osun series, which dominate the valley bottoms in Ibadan.