Plant salt stress is a condition where excessive salts in soil solution cause inhibition of plant growth or plant death. On a world scale, no toxic substance restricts plant growth more than does salt. Salt stress presents an increasing threat to plant agriculture. Among the various sources of soil salinity, irrigation combined with poor drainage is the most serious, because it represents losse...

Earthworms mix soil layers and incorporate organic matter into the soil. This mixing allows the dispersion of the organic matter through the soil and makes the nutrients held in it available to plants and improves the fertility of the soil. Earthworms when present improve the soil physical, chemical and biological properties and acts as soil conditioner. They do so by fragmentation, aeration, b...

expansive soils can be found in many parts of the world particularly in arid and semi-arid regions. these soilspose a significant hazard to civil engineering structures due to its high swelling and shrinkage potential. this paperpresents the results of an experimental program developed to investigate the effect of cyclic drying and wetting on theswelling potential of expansive soils with variou...