Sentence:  If you look down at the Punjab from an aircraft, you will see here and there below you, splotching the green fields like mold on the wall of an old house, patches of gray decay, rising patternless and ominous across the landscape. This is <WSD>salination</WSD>, a rotting of the land caused by a rise in the level of the underground water table, which forces the salts of the earth to the surface and gradually turns fields back to desert. 
Meaning of the word marked with <WSD> tags:  The increase of salt content in soil.