Why did southern plantation owners need slaves for labor

mainly cotton

Explanation:

cotton had many thorns, so no one wanted to do the work. when slaves came along, it was an advantage. they used it for other puposes too, like gathering other  crops, or planting them, or tending to them, butit was cotton that was the main thing.

adopted the practice of proskynesis, a persian court custom that involved bowing down and kissing the hand of others, depending on their rank.