A question in a recent kitchen gardening program has had me thinking about nutrients and vegetables again. Vegetables are so much more nutrient-intensive than perennials, shrubs, trees, or any 'landscape' plants, it's hard to realize sometimes how much they appreciate excellent, fertile soil to grow in.
The person who asked the question wondered why her vegetables just seemed average, in their compost-enriched raised beds (but with no added fertilizer). Her soil test was 'fine' for vegetables, according to our state Ag Services Lab.
But another participant had just told us about her two Early Girl tomato plants last season that produced so many tomatoes that she was giving them away to her friends, neighbors, people at her church, etc. But she was fertilizing her plants.
Hmm. Most of my vegetable plants are a lot more in the average category - nice and productive, but nothing overwhelming. But I don't fertilize much either, after adding compost at each rotation or bed preparation. It's hard (as a plant ecologist) to get my head around nutrient and water hungry vegetables.
I think the key is that if you look at the advice for sustainable gardening using compost and green manures, it takes a LOT more than you'd ever think to keep soil nutrients high. 4-5 inches of compost is often recommended for additions to each year's bed -- that's a lot of compost!
And actually, now that I think about it, the Ag Services Lab recommendations are probably assuming that you'll add fertilizer (whether inorganic or organic) to your vegetables over the growing season.