Sweet Potato Problem - third year in a row - why??

2008 - While most of my yard is hard-packed red clay, there is one area that is very sandy. I thought this would be the best place to plant them. The first year I planted Beauregard and Vardeman. It was a drought year so I watered it about once a week when there was no rain. I got a wonderful crop, many large and medium tubers and a few small ones from both Beauregard and Vardeman.

2009 - I decided maybe I should plant the slips (Beauregard and Vardeman) in one of my newly-made lasagna beds, because of the drought the previous three years. I got quite a few medium-sized, a number of small tubers, and a number of orange "roots" that had thickened to about 1" in diameter and about 2-3 feet long. This was again a drought year, but I watered less often as this bed held moisture much longer than the sandy plot. I thought maybe the weird long roots were that the bed had gotten too much moisture and not drained well enough for sweet potatoes.

2010 - I planted the slips ( Beauregard and Vardeman) in the original sandy bed since I had gotten such good results from there the first time. This was not a drought year. Lots and lots of rain all spring and summer. If I watered at all it was very infrequent. Nothing!! There were no sweet potatoes at ALL, not even the long weird roots I had gotten in the other bed the year before, only ordinary plant-type roots.

2011 - This spring I planted again in the same sandy plot. This time I planted Beauregard, Vardeman, and Georgia Jets. This was also not a drought year except for August. We had lots and lots of rain except in August. I watered about once a week in August. Went out yesterday to dig them. I dug up about a 2x2 foot area and found about 8-10 very small potatoes, 1-3 inches and several long skinny orange-colored roots about 6-12" long.

I planted the first three years during the second half of April and this year I planted the first half of May. I dug them up each year in late September. I fertilized the plants after they'd been in the ground about a month when I planted in the sandy soil. I did not fertilize them when I planted in the lasagna bed.

Even with the increased rain the last two summers, I thought I should still have gotten a decent crop by September. The sandy soil is very fast draining, no standing water.

Anyone else have this kind of experience or have any idea what is going on here? Because I do have some small ones, will they develop into larger ones if I wait for another month before digging them? I know sweet potatoes are hot-weather plants, and the weather has already begun to cool off. My first frost date is October 15th, but we usually don't get frost until around the end of October. Still, since these are 80-90 days to maturity, why haven't they developed long ago? Do sweet potatoes not develop if there is too much rain?

What are you fertilizing with? Sweet potatoes need adequate potassium. They are very tolerant of both rain and drought. They also do not tolerate crowding. They need about 3-4 sqft per plant.

Covington on sand, stage 4 drought from April til now, no irrigation. Curtailed crop but a crop non-the-less

Fertilized with 10-10-10. I spaced them about 18" apart in rows about 2 feet apart. So my problem is that I may need to add potassium instead of regular fertilizer and space them farther apart?

That should work. I do use 5-10-15., 12-14 inch spacing on 4 ft centers. Not that different. I plant in April, dig last of september first of October. Possibly a soil disease like Fusarium or those pesky nematodes.

I bought the slips from a certified source on line. I used 10-10-10 because that's what the local Farmers Co-op sells here. Since it may be that the first year depleted the potassium and the fertilizer I used was either not strong enough in potassium or I did not use enough, I'll use more next year with a higher K number. Should I just get some straight potassium and use it? If so, what is it called - potassium (what)?

How can I check for nematodes and Fusarium? The leaves and vines look normal. I don't even see any bug holes in the leaves. The tiny potatoes I dug up look normal except for being way too small. I saw online a reference to "strings" but there was no description of this condition. Are these "strings" what I saw when I dug up the long, pink, thickened roots? The reference sounded as if a certain number of strings were to be expected and not abnormal.

I did have something chomping on the leave at the edge of the patch. Looked as if Bambi had stopped for dinner. Leaves were chomped off an inch above the stem.

If I leave them in the ground until the first frost is threatened, will they continue to grow?

Yes, But slowly. If you have good vines and Beauregard has lots of vine, the potatoes should form. One thing, sweet potatoes don't like to grow flat. I plant on a list about 4 inches higher than the surrounding ground. Usually the worst effect of planting flat is that they grow out along the vine rather than directly under the plant. Both fusarium and nematodes affect the vines. I really can't comprehend why you don't have sweet potatoes.

glendalekid - I set sweet potato slips around the beginning of May and wait until the first expected frost to dig them. It's getting cold enough here for us to pull them next week. We pulled about 300lbs last year.

I put the slips in hills about 24 inches apart.

I'll post here again when I've dug up a few of this year's crop. When I dug a few at the end of August, all I found were tiny things not much bigger than my thumb! We ate them anyway! LOL

I, too, grow Vardeman.

The vines are certainly long enough. I looked up nematodes and Fusarium online. I don't see anything on the vines or the potatoes that I dug that looks like the pics or descriptions of these problems.

I knew about planting them on a list, which I did every year except this year. Because I got absolutely no sweet potatoes, not even small ones, last year I figured why bother. The small ones this year are pretty much under the plants, though. Last year I wrote to the fellow I bought the slips from and asked him why I didn't have any at all. He doesn't know either.

I've read not to plant them several years in the same place, but I don't really have anywhere else to put them. The lasagna bed did not work well, but was better than the last two years back in the sandy plot. The only thing I can think of is that you are correct about the potassium, that it was depleted by the first year's crop, and I've not put enough back in the soil since then. I did use more fertilizer this year than last year. So, that might be the reason that I got small ones this year and none last year. I keep reading that sweet potatoes need little or nothing "extra" in the soil, so I've been leery of using too much. On the other hand, I've also read that potassium leeches out of the soil very quickly and easily.

glendalekid - try using organic fertilizers, here's a link that explains why

http://www.cleanairgardening.com/npkexplanation.html

(I've never purchased from this Company)

Farmerdill: Thank you very much for the help. I will get a fertilizer next year with a higher potassium number. Probably I should also increase the amount of fertilizer I am using as well. I'm always worried about using too much. Looks as if I need to get over that.

HoneybeeNC: Thank you for your suggestions. I will give some thought to organic fertilizer.

glendalekid - I pulled a sweet potato vine today and got several nice tubers.

When I planted the slips, I put a small handful of organic fertilizer in the hole, and mixed it in well. Once the slips established, and before they began to run, I sprinkled another small handful around each plant.

Other than watering them until they were established, they received no more care.

I have another row where I put in some slips from my own saved sweet potatoes. I didn't fertilize or water them all summer. I'm anxious to see how many tubers I get from them, but I'm going to wait until after the first frost before digging any.

I really know nothing about sweet potatoes other than how to eat them. I do live about 3 miles from the biggest sweet potato producer in the U.S. He never starts planting before the middle of May and it is usually the first of August before he gets through planting. You might do better to delay the planting date. He also plants on a high row. I assume to give the potatoes a good deep bed to put roots down in. He gives all of us in this area potatoes so we won't plant any. That's his way to keep down the potato beetle that ruins potatoes and you can get a whole area put under quarantine if you have them.

I never plant the same veg in the same plot the following year, this I was taught to prevent the spread of diseases and also because different veg require different types of soil / fertilisers and textures. Beans, Pea's and all that family require a good rich deep dug soil with plenty of manure added to the planting drills, Cabbages / sprouts etc, like their soil to be more compacted, some lime added to the soil and need there roots / soil around the planting hole firmed well to prevent them rocking about in colder weather, Carrots, Beetroot's etc like a stone free soil, where last years manure was added, never plant this family in newly manured or fed soil as this causes the roots to split they grow too fast and the manure encourages moisture to stay around the roots where it is taken up too quickly splitting the crops roots.
what I was taught and still do is split the garden into 3-4 veg beds whee I manure add feeds etc to 3 beds, plant the carrots etc in the manure free beds, the others are split into peas, beans etc, next the greens like cabbage etc, the other Potato and while they are underground awaiting to have the soil drawn up to peaks both sides pf the rows,about 6 inches will do, the next month draw up another inch or so, this is to prevent light getting onto the tubers as it turns them green and inedible, repeat again. Forgot to mention that I dig the potato bed in Autumn and leave the frost to help break down the larger clumps of soil, I also add manure with lots of straw in it spade and half deep and cover this as I dig the soil over, the winter frost breaks down the soil, once I have stopped pilling up the soil, I plant all my fast growing salad crops between the rows, things like lettuce and spring onions, radishes etc, all things that will help keep weeds away and will be pulled up before the potato is ready,
The following year I would rotate where the potato's are planted, like put them where the cabbages were and the carrots where the potato because the digging of the potato's will have cleaned the soil of any perennial weeds etc, it's just the way I learned to veg garden and it works for me, I never have a problem like cabbage root rot, potato blight etc, etc, and IF I had, then rotation would prevent it happening the following year. after the beds are emptied I throw as much animal manure I get my hands on, leave it on the top soil and come spring it is ready to dig in with the exception of where the carrots are to be sewn.
WeeNel.