In article , Serendipity
writes

Many moons ago, as a young man, someone told me that
the secret of firm sprouts was firm soil. I always followed the
advice and was reasonably satisfied - on occasion even
delighted - with the quality.
Excellent advice, and it applies to all brassicas where firm hearting is
required. The soil should be cultivated first, then firmed in the seed
bed before planting out. The same applies to onions.
Also, when the ground was cleared
of the crop, I used a spade to good effect, and limed the soil.

We're fortunate enough to be over limestone, so we don't need to lime,
but any vegetable area should be well limed to keep the soil and the
plants healthy. It helps to prevent brassica club root to some extent.

Despite being considered an eccentricity, it also works to
chat to your crops , even- occasionally - to threaten them.
Agreed! I don't actually speak to plants, but they respond to thought
transference if they are given a chance to. I don't threaten them
either, but Joan and I have noticed that if we talk about an
unsatisfactory plant in its presence, it will often respond in the way
we wish it to. There's no scientific or logical explanation for this
effect but it has happened in our garden too often for co-incidence.
--
Alan & Joan Gould, North Lincs.