Alteration of fertility and ovarian cysts can also occur in females. They are viewed as symbols of womanhood, fertility, birth and wealth. It is also a method used by couples using donor sperm in a fertility centre. Other important factors include fertility and salinity. There is evidence that TNT adversely affects male fertility. Cows were connected with fertility and motherhood. Livestock manure helps maintain the fertility of grazing lands. Parvati is the Hindu goddess of love, beauty, purity, fertility and devotion. In spite of poor fertility, however, agriculture is intensive. She is the goddess of divinity, feminity, fertility, beauty and love. Today, the U.S. is recognized as having both low fertility and mortality rates. These are grown mainly for their protein, vegetable oil and ability to uphold soil fertility. Females can often breed until age 40, followed by a rapid decrease in fertility. This leads to a reduction in soil fertility and productivity. Enki was god of freshwater, male fertility, and knowledge.