MILLET YIELD AS AFFECTED BY TRACTOR TRAFFIC IN A SANDY LOAM SOIL IN BORNO STATE, NIGERIA

The effect of traffic on the production of pearl millet (Pennisetum am ericanum (L.) Leeke) was investigated in a sandy loam soil (Typic Usti psamment) of Borno State, Nigeria. A randomized complete block design was used with treatments of 0, 5, 10, 15, and 20 passes of a tractor w ith 31.0 kPa contact pressure. The soil dry bulk. density, penetration resistance, and air permeability for each applied load were measured from the soil surface to a depth of 0.20 m and the yield from each tre atment was determined. Dry bulk density and penetration resistance inc reased with an increase in the number of tractor passes, while air per meability decreased with increases in the number of tractor passes. He ad weight increased with increases in the number of tractor passes up to 15 passes, and then decreased. Plant moisture content and stem diam eter increased with increases in the number of tractor passes. Statist ical models were used to predict head weight in terms of the number of tractor passes, contact pressure, air permeability, and soil paramete rs; with air permeability giving the best prediction. (C) 1997 Elsevie r Science B.V.