I don't know about that either, I made a new garden last year using the lasagna method, had 6.5ph, everything I planted, except the onions, did good. I'm amending the soil where I'm putting the onions next year with rabbit manure and compost, and letting it sit over the winter. Don't know what I'm doing wrong. I split some onion bulbs with a friend this year, and his onions are as big as softballs, he just plants his and keeps the weeds out. I do that and they don't grow. go figure.