Pre-plant and pre-emergent herbicide options are used extensively by experienced chickpea growers. A spring glyphosate application, either pre-seed or pre-emergent, is recommended. This provides early season weed control and may provide control of weeds for which no in-crop control is available.
Sulfentrazone (Authority®), can be applied either pre-plant incorporated or surface applied pre-emergent. On most acres, it is mixed with glyphosate in a pre-seed or pre-emergent application. If applied post-seeding prior to emergence, apply within three days of seeding to prevent crop injury when emerging. Authority® works through root uptake in the soil, meaning precipitation must follow application for proper activation and good weed control. Ten to 20 mm of precipitation within 10 to 14 days is needed for optimum efficacy. If weeds start to grow prior to activation, the result will be poor weed control.
Authority® (sulfentrazone) absorption by plant roots increases as soil pH decreases. At soil pH of 6.5 or less, which can occur even in localized areas of the root zone, greater sulfentrazone uptake can occur and explain unpredictable patterns of injury to crops.
Herbicide testing indicates that chickpea is especially sensitive to many post-emergent herbicides registered for the control of broadleaf weeds in lentil or pea. SENCOR (metribuzin) herbicide is registered for suppression of some broadleaf weed seedlings in chickpea. Application should take place at the 1 to 3 above-ground node stage (maximum crop height 6 cm) with best results when the weeds are small. Application past this crop stage can lead to significant crop injury.
Clethodim-based (SELECT/CENTURION), Post Ultra and Quizalofop-based (Assure II/Yuma GL) herbicides are registered for control of annual grassy weeds in chickpea. Application should take place at the 1 to 6 leaf stage of the grassy weeds. Consult the product label or the Saskatchewan Agriculture and Food publication, Guide to Crop Protection, for more information on the use of herbicides.
If weeds are present, control them early. Chickpea is not a competitive crop, especially when weed competition can severely reduce yield. If weeds have emerged, apply herbicides at early crop stages. This will improve weed control, reduce competition from the weeds, and usually reduces herbicide injury.
Non-herbicide options may be considered as well. Tillage can have a beneficial effect for control of some weeds, while having the opposite effect on others. For example:
Herbicide-resistant weeds: herbicide choice should take into account herbicide rotation to slow the development of resistant weeds. Resistant weeds are troublesome in chickpea simply because it is a less competitive crop and there are limited herbicide options. A few examples of herbicide resistant weeds that are particularly troublesome for chickpea growers include Group 2 resistant kochia, wild mustard, and cleavers, as well as Group 1 and Group 2 resistant wild oat. Rotating herbicide groups away from Group 1 and 2 products, especially in rotational years where pea is not grown, can help prevent or manage resistant weeds. BASF recommends that Group 2 products be applied no more than twice in a four year period, and never twice in the same year. Research indicates that alternating between two modes of action for wild oat control will double the number of years for resistance build-up, and alternating with a third mode of action will increase the time of resistance build-up to four times as long as for a single mode of action for wild oat control.
Use integrated control methods through the rotation, such as higher seeding rates, promoting quick crop emergence, and using herbicides only when economic thresholds are reached. Preventing kochia from setting viable seed for one or two years greatly reduces kochia populations in a field because the seed is short lived in the soil.
Minimizing crop injury to herbicides: during periods of crop stress the ability of the chickpea crop to tolerate herbicide application may be reduced. Crop injury can be reduced by waiting approximately four days after the crop stress occurs before applying herbicide, by maintaining water volumes at label recommendations, and by applying the product during the evening.
Chickpea can be damaged easily by some herbicides registered for other crops. Sprayer tanks should be thoroughly cleaned before applying any crop protection product to lentil and care taken not to drift herbicides from other fields onto chickpea fields.
Alternatives to chemical weed control: non-herbicide options may be considered as well and include tillage and higher seeding rates. Tillage may be a tool to reduce kochia populations. Burial of kochia seed to at least one cm or deeper can result in reduced germination or death of the germinated seed prior to emergence. Spring tillage, even minor, significantly increases the burial and resulting germination of false cleavers and catchweed bedstraw. Farmers should consider limiting spring tillage as part of an integrated weed management program for cleavers.
Post-emergent harrowing of chickpea is not recommended. It can spread disease and cause severe mechanical crop injury.
Higher seeding rates can increase crop competitiveness against weeds and reduce maturity. However, increase crop canopy can lead to higher disease issues.