Can anyone please suggest what I need to add to my soil to help the development of the root crops I try to grow? I can grow radishes successfully but vegetables like parsnips, beets, turnips and carrots never seem to fully develop. The carrots grow a little but remain very small. However the green tops grow well which leads me to think I have too much nitrogen in the soil and maybe not enough phostrogen or potassium?
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Thanks for your comments. I created the raised bed last year and I bought in all the compost from Singh's farm but it is only about 8" deep. The soil underneath may be compacted (although I dug it first) but I thought you only needed a depth of about 6" of soil to grow in. If the roots can''t go down further will the vegetable not develop at all? They don't appear to be stunted just not developed.
It is drip irrigated.
Did you mix his compost 50/50?
50% native soil with 50% Singh compost? If not, that may be contributing to your problem.
Yes and no Ericka!
In my own yard I just used his compost neat as we were told it was alright to use for seeds and vegetables, although it was a very "chunky" mix. In my community garden bed we mixed it and I still had a similar problem. Other peoples root crops grew well and we all have the same depth beds.
Carol, just another point. Sometimes the variety of carrots, for instance, makes a difference. The shorter versions (think small and chunky) may do better in beds than the long varieties.
Carol, although 6-8 inch depth might work in other parts of the country it will not work here in the desert. The growable soil depth should be a minimum of 12 inches and preferably 18 for maximum performance of veggies, root crops etc. Obviously trees need more. If you can raise the bed height up and add more soil.
Many thanks for all your help. I will try raising the bed and make any new ones deeper.
Most gardeners know that plants acquire water and minerals through their root systems, and leave it at that. But the process is not quite that simple. The actively growing, tender root tips and almost microscopic root hairs close to the tip absorb most of the plant's moisture as they occupy new territory. As the root continues to extend, parts behind the tip cease to be effective because, as soil particles in direct contact with these tips and hairs dry out, the older roots thicken and develop a bark, while most of the absorbent hairs slough off. This rotation from being actively foraging tissue to becoming more passive conductive and supportive tissue is probably a survival adaptation, because the slow capillary movement of soil moisture fails to replace what the plant used as fast as the plant might like. The plant is far better off to aggressively seek new water in unoccupied soil than to wait for the soil its roots already occupy to be recharged.
A simple bit of old research magnificently illustrated the significance of this. A scientist named Dittmer observed in 1937 that a single potted ryegrass plant allocated only 1 cubic foot of soil to grow in made about 3 miles of new roots and root hairs every day. (Ryegrasses are known to make more roots than most plants.) I calculate that a cubic foot of silty soil offers about 30,000 square feet of surface area to plant roots. If 3 miles of microscopic root tips and hairs (roughly 16,000 lineal feet) draws water only from a few millimeters of surrounding soil, then that single rye plant should be able to continue ramifying into a cubic foot of silty soil and find enough water for quite a few days before wilting. These arithmetical estimates agree with my observations in the garden, and with my experiences raising transplants in pots."
Hi Carol,
I would agree with Brian on whether you have a sufficiently loose enough soil. Dense soil tends to impede the root growth. If the tops were nice and green and you have good radishes the soil consistency seems to be the issue (radishes don't need a lot of depth).
Do you have well cultivated soil?
I've read where caliche or a plowpan will prevent roots growing deeply. While it's hard to believe, the books say that carrot, beet and parsnip roots go down more than 2 feet. A good bed for them needs to be double dug and deeply fertilized. Drip fertilizer does well.
Read Gardening Without Irrigation: or without much, anyway by Steve Solomon
Here's a link where you can get a copy -
http://www.gutenberg.org/ebooks/search.html/?default_prefix=author_...