How Previous Year's Soybean Herbicides Can Affect Planting of Corn, Sweet Corn, and Popcorn This Year

April 7, 2020

Amit Jhala - Extension Weed Management Specialist

2019 was challenging year for Nebraska agriculture. Several areas in south-central and central Nebraska encountered severe rain last year in June/July. Rainfall reported ranged from 3 inches to 10+ inches overnight. Therefore, corn and soybean planting was very late last year or replanted in several fields. Corn-soybean is the most common cropping system in eastern Nebraska. While corn growers are getting ready for planting in 2020, it is important to pay attention to the planting interval of corn to herbicides applied the previous year in soybean.

Certain soybean herbicides have relatively longer planting intervals for corn, especially if they are applied post-emergence in soybean (Table 1). This is particularly important because soybean planting was late last year in much of Nebraska due to early season flood and continuous rains. This caused pre-emergence and post-emergence herbicides to be applied later in the season than they might normally be, making it important that you pay attention to the planting interval (Table 1).

Table 1. Planting interval (in months) of field corn, seed corn, popcorn, and sweet corn after soybean herbicides applied.
Soybean Herbicide	Field Corn	Seed Corn	Popcorn	Sweet Corn
	Planting interval (months)
Flexstar/Rhythm/Rumble	10	10	10	10
Flexstar GT	10	10	10	10
Warrant Ultra	10	10	12	12
Pursuit	8.5	8.5	18	18
Raptor	8.5	8.5	8.5	8.5
Reflex	10	10	10	4
Rowel	1	1^a	4 to 18^b	3 to18^b
Valor	1	12	12	4
Rowel FX/Valor XLT	10	10	10	18
Marvel	10	10	10	10
Enlite	9	9	9	9 to 18^c
Envive	10	10	10	18
Trivence	10	10	10	18
Torment	10	10	40	18
Sonic	10	10	10	18
FirstRate	9	9	9^d	18

^a With application of Rowel at 3 oz/A rate and at least one inch of rainfall/irrigation. Check the label if Rowel is applied more than 3 oz/A.

^b Planting interval changes depending on rate of Rowel applied and tillage practice, check the label.

^c Planting interval changes depending on processing sweet corn variety or other sweet corn variety. Check the label of this herbicide.

^d Verify with seed company (supplier) the safety of herbicide on inbred lines or hybrids.

For example, herbicides with fomesafen (Flexstar/Flexstar GT/Marvel/Reflex/Rumble) have 10 months of planting interval for most corn types. When herbicide tank-mixture is applied, consider the longest planting interval mentioned for any tank-mix partner.

Popcorn and sweet corn are more sensitive to herbicides compared to field corn; therefore, certain herbicides have a longer planting interval for popcorn/sweet corn. For example, Pursuit has a planting interval of 8.5 months for field corn and seed corn, but 18 months for popcorn and sweet corn.