We have been working a lot on building soil fertility lately. We live in a very arid region, right on the Mexico border in the mountains of Southern California. Water is a serious issue here. We are in an extreme drought with the very real possibility that it could carry on for many years to come. We never have as much as we would like and are forced to learn about ways to conserve water for agriculture. Our soil is sandy and poor, lacking in organic matter and having difficulty holding onto either water or nutrients for long. We have almost 3/4 of an acre in cinder block raised beds with soil we have built from composted horse manure, alfalfa and dirt from our property. Everything is on drip irrigation and timers. As we expand the farm we are working on building up the soil on other parts of our property. we have studied a lot of farms in arid regions of Australia that have been dealing with years of extreme drought and various other farms around the world using organic growing and permaculture techniques. We continue learning about just how much good soil and mulch can reduce the need for watering.