What's Baffling Me: The Taste of My Shamba's Sukuma vs. Kanairo's

Nime-notice a curious difference between the taste ya sukuma wiki (pictured) from my shamba na za huku Kanairo. The sukuma from my shamba ukuwa na uniquely pleasant taste, and as a mkulima, I'm left wondering what could be causing such a noticeable difference. Could it be the soil type? The overuse of foliar sprays, pesticides, and herbicides? Or maybe it's the seed type?