These are often split into 2 lines per row with rows 12 to 18 inches apart on top of beds that are on 30 to 44 inch centers. This is equivalent to about 150,000 plants per acre. Cultivation is usually not necessary with excellent chemical control, but when there are problems, the grower may cultivate as many as three to four times. Growers usually prefer to not have to irrigate until the onion plant has emerged from the soil. Then the fields are irrigated regularly until the plant has matured, typically around mid-August.
Soil conditioning is typically necessary.
Onion plants are shallow-rooted and plant growth is good when nitrogen is carefully applied with irrigation water. It is important that excellent plant development is achieved before bulbing starts. After bulbing begins, high temperatures and low humidity continuing through the harvest process are important. Through the entire growing process, adequate soil moisture must remain constant. Back to Top of Page Diseases and Pests Growers must closely monitor onion plants for pests and diseases.