Delayed onset of rains has also tended to shorten the growing season overall by about a month. These changes will delay planting as early planting becomes increasingly risky. The shortening of the growing season will affect the kinds of crops that can be grown profitably. Throughout Nigeria, there were fewer wet days per season, but the intensities of rainfall were greater. The fewer wet days underscore the need to conserve water and soil moisture, while greater rainfall intensities mean greater erosion hazards.
Intense rainstorms cause soil erosion and the runoff water carries away nutrients with the topsoil.
Research to relieve the impacts of these changes would include development of technologies to conserve soil moisture, increase soil organic matter, and reduce soil erosion. Also required is research to increase crop diversity in terms of both species and maturity periods to enable farmers to select crops to fit rainfall regimes. Some of the results of IITA's past research are pertinent to solving the problems posed by changes in rainfall. These include minimum tillage, the use of mulches, and the practice of tied ridges to reduce soil erosion and conserve soil moisture. Among the advantages of alley farming systems is erosion control.