We can use slaked lime (calcium hydroxide) which is a base which neautralises the excessive acidity in the soil which can kill plants  so after neautralisation it mix's 
with acid and form's salt and water
In order to increase the fertility of the soil,before cultivation farmers plough the field this method airation of the soil will increase.if the acidity of the soilis more they add alkalies like calcium neutralise it.its better to use oraganic manure like decaying or dead leaves and cowdung toincrease the fertility of the soil.if chemical fertilisers are used.number of bio organisms willdecrease.Bio fertilisers will provide high yield eventhough ittakes more time