We also have annual calendars to tell us when specific plants should be planted and also to predict what the year should be like, the one we use today is called l The farmer's almanac. Many backyard farmers use space saving techniques that Native Americans used called Three Sisters, they grew corn and stakes or climbing beans together, they also planted squash planted around to cover the ground. This works well because the corn provides a solid place for the beans to climb and the beans produce nitrogen for other plants and the squash shades the soil helping to reduce the amount of weeds and grass that grows. A growing form of agriculture, known as hydroponics and aquaponics, was used by the Chinese. They grew rice in the flooded fields during the hot season. The Aztecs also used it, they built rafts that floated in the water with earth with crops on top. The soil would stay moist and as the plants grew, the roots would hang in the water. Today we use ponds, tanks or artificial fish tanks, which produce nitrates, excellent as fertilizer for plants. This system also provides all the water a plant needs, while providing a rich supply of oxygen