In Nigeria significant efforts are being made to improve and conserve the soil. In the time past the soil resource base was sustained through long fallows of 10-15 years. Due to population pressure and other conflicting interests on land, fallow period is now between 6 and 12 months. This natural fallow has proved ineffective for the sustenance of soil productivity. The present study compared the soil productivity improvement attribute of three fallow management systems - two leguminous cover crops (Mucuna pruriens var. utilis and Pueraria phaseoloides) seeded in June 2012 and natural fallow dominated by guinea grass (Panicum maximum).  Mucuna provided about 68 % soil cover and suppressed weeds by 12 % for the first six months. But at 12 months after seeding (MAS), average Mucuna cover was 33.92 % and weed increased to 37.65 %. Also, Mucuna provided about 48 % leaf litter from 6 to 10 MAS. Pueraria at 6 MAS provided about 69 % soil cover and reduced weeds to 10 %, Pueraria maintained adequate soil cover at 78 % and suppressed weeds effectively by 8 % during the one year fallow. The average root numbers at anthesis for Mucuna and Pueraria were 15 and 21 per plant respectively, compared to the control which recorded 203 root numbers. However, there were no significant differences in soil physicochemical properties before and after the one year fallow. Mucuna treatments significantly provided soil cover until six months, while Pueraria provided soil cover for 12 months and reduced weeds compared to Mucuna and the control. Therefore, both cover crops could be sown to replace the natural fallow. Mucuna fallow appears to be an effective system for 6 month fallow while Pueraria could provide cover and effectively suppress weeds for 12 months.

Key words: crop yield; Cover crops; Soil; Short fallow; Conservation.