Damage to crops and fields harms the agricultural sector. The South developed an agricultural economy dependent on commodity crops. Urban agriculture in Accra centres on the growth of vegetables, several crops and poultry. Horticulture crops include plants used for other crops (e.g. fruit trees). Soybeans accounted for half of all genetically modified crops planted in 2014. Control of crops and livestock leads to food surpluses. Farms also grew small quantities of potatoes, other root crops, and legumes. Growers eliminate milkweed that previously grew between the rows of food crops. Plant domestication begins with cultivation of Neolithic founder crops. The women were in charge of planting, weeding, and harvesting the crops. Atrazine is a herbicide used to control weeds that grow among crops. Transportation is fundamental to the distribution of crops and livestock. In a technique known as companion planting the three crops are planted close together. Olives are one of the most extensively cultivated fruit crops in the world. World trade in wheat is greater than for all other crops combined.