In South America, the Incas invented Terrace farming in 1150 CE. Terrace farming is when you make step-like platforms, where each section looks like a stair and is its own farm. They had to fill the terraces with something, so they used dirt, gravel, and sand. The terraces were so big that they covered over a million hectares. 

The Incan Empire had a severe drought for over a century. The Incas needed a way to farm while conserving water, so they developed terrace farming. Terrace farms can last over 6 months without being irrigated(supply water to). So if you have a drought, they’re the best possible mechanism. This means that the Incas could wait for over six months to irrigate the terrace. 

Terrace farming doesn't just conserve water, it also had other advantages. For example, it also increased plant density and shortened time for crops to ripen. The stone retaining walls next to the terrace warmed it up at night. It also increased the amount of food the Incas were producing, making it easier to feed the vast empire. The terraces prevented soil erosion and utilized crop rotation so that they preserved soil fertility and protected the crops from pests.