Farmer's Weekly (South Africa)
Hot Asparagus
47 years ago In this article, Farmer’s Weekly explains the benefit of using plastic tunnels to grow asparagus.
Under the warmth of plastic tunnels it is possible to bring asparagus to maturity a month earlier than normal, reports the American Vegetable Grower.
The first known project of using plastic tunnels for asparagus is being undertaken by the University of California and a farming organisation. It was stated that an extra R500 [about R32 000 today] to R700 [R45 000] per 0,4ha can be realised before the main season starts.
Installing the plastic costs about R350 [R22 000] per 0,4ha and it took three men an hour to erect each 61m tunnel. There were 24 tunnels of 61m per 0,4ha.
The experimenters feel the fast growth of asparagus is almost entirely due to air and ground temperatures under the plastic.
During 15°C to 21°C weather, temperatures under the plastic will reach 43°C to 46°C in the afternoon.
The ground temperature will be 4°C to
5°C higher at a 125mm depth than the soil outside at the same depth at night.
In the first experiment, plastic tunnels were used on 0,6ha, sheltering 36 double rows of asparagus. The covering remained over the plants for 15 to 20 days and was then removed.
The period of the extra warmth seemed to break dormancy and get the plants off to a fast start. Even after the plastic was removed, the plants grew faster.
More extensive trials are planned for the forthcoming season, and the experimenters are hoping to mechanise the application of the plastic.