Vol. 15—1961 - NorthEastern Weed Science Society

91.
Chemical Weed Control in Onions Grown on Mineral Soils
Charles J. Noll 1
In the 1959 onion weeding experiment only one chemical, CIPC,
out of 7 chemicals in the test offered promise for the weeding of this
crop. In last years experiment there was found to be an increase in
onion yield and an increase in weed control as the rate of CIPC
application increased from 4 to 6 to 8 1bs. per acre applied the day
after seeding. The possibility that time' of pre-emergence application
might be important as well as rate of a.pp1ication was taken into
consideration in planning work in 1960.
Procedure
The variety Sweet Spanish was seeded May 2, 1960. The
pre-emergence treatments were applied from 2 to 10 days after seeding.
The emergence treatment with KOCNwas made 19 days after seeding and
the post-emergence treatments with Atratone 30 days after seeding.
The soil at planting time was dry and no rain fell until the 6th day
after seeding. Sufficient rain was received from the 6th day after
seeding through the next few days to germinate the onions and weeds.
Individual plots were 28 feet long and 2 feet wide. Treatments were
randomized in each of 8 blocks.
The chemicals were applied with a small sprayer over the row for
a width of 12 inches. Cultivation contro11~d: the weeds between the
rows. The growing season was cooler than average and rainfall below
normal. An estimate of weed control was made June 30 on a basis of
1 to 10, 1 being most desirable and 10 being least desirable. Onions
were harvested September 28.
Results
The results are presented in Table 1. All chemicals gave highly
significant increase in weed control as compared to the untreated check.
All chemicals, except Dactha1 had increasing weed control as the rates
of application increased. Dacthal had equal weed control at 6, "9, and
12 Lbs , per acre. Weed control was genera1J.y from fair to poor. The
time of application of CIPC had little effect on the weed control
rating, although in general the later applications resulted in poorer
weed control.
1 Associate Professor of 01ericu1ture, Dept. of Horticulture, College
of Agriculture and Experiment Station, Pennsylvania State University,
University Park, Penna.