For Ange, planting crops was his greatest joy, but it hinged on the climate. Now it's nearly the harvest season, which wasn't suitable for planting crops unless he was willing to consume his Soul Flame.
However, Ange didn't like using Soul Flame for farming. He used the Instant Death Halo primarily for comparison, not for merely accelerating growth, unless he was running out of food.
Only when he was alleviating famine in the Resting Abyss did Ange blaze a trail of cultivation. It also happened in the Light Sea Plane when Anthony needed food desperately, and also this time.
Most of the time he activated the Instant Death Halo was for selecting rice varieties and crossbreeding cereals. It was also used during the selection and hybrid grafting of crops.
If there wasn't a particular need, Ange preferred to let the crops grow naturally.
