Cultivation of carrots

Project responsible: David Hansson, Department of Biosystems and Technology, SLU. 
Coworker: Sven-Erik Svensson, Department of Biosystems and Technology, SLU. 

The project aims to decrease the hand weeding requirement in row-sown organic crops through encouraging as many weed seeds as possible to germinate and emerge before the crop and killing these off by flaming immediately before emergence of the crop. This weed control strategy differs from methods where flaming is not included, and where the aim is to give the crop a competitive advantage over weeds through rapid emergence. The experiments in the project will be carried out in controlled environment (greenhouse and climate chamber) and in practical field plots in organic carrots.

The project will comprise controlled, practical experiments that examine and evaluate the weed control effect of delaying the time of emergence of carrots in a system where false seedbed, delayed sowing and flaming are combined to decrease the hand weeding requirement (Fig. 1).

In the trials we aim to create a situation where the carrots emerge somewhat later than normal, but growing with full vigour. This will increase the opportunities for effective weed control through flaming immediately before crop emergence without compromising crop growth and yield.

In previous trials in organic carrot crops in which flaming before crop emergence was delayed by three days, the amount of weeds present at the time of hand weeding was reduced by half. Another trial in organic carrots showed that every day of delay in flaming before emergence of the crop increased the weed control effect at the time of hand weeding by 10%. This in turn decreased the hand weeding requirement by 10-15 hours/ha.

The starting hypothesis is that similarly to delayed sowing, delayed time of emergence of the cultivated crop allows more weed seeds to germinate and emerge before the crop. This means that a greater number of weeds can be removed just before crop emergence, e.g. through flaming, thereby decreasing the weed pressure at the time of hand weeding. The time of emergence can be delayed through increasing the sowing depth, using slow germinating cultivars, various seed treatments, etc.