Poor sweet potato production despite very healthy vines and leaves

Asked September 9, 2019, 8:11 AM EDT

We planted Georgia Jets sweet potatoes this spring in beds heavily amended with composted manure and other forms of compost over the years. We have rotated crops in our beds, but sweet potatoes planted in this particular bed over the years have been really productive. This year we had very strong vines and leaves but very little production in terms of potatoes -- a tiny fraction of previous years. Could it be that the bed contained too much nitrogen? Is there another possible explanation? The potatoes we did harvest were long and thin for the most part, not thick as in the past. And in the past we would get 4-5 potatoes per plant, but not this year. Thank you very much.

District of Columbia County District of Columbia vegetables soil fertility abiotic issues

1 Response

Hi- some possible causes of reduced yield and reduced storage root size (without signs of insect or wildlife feeding) are close plant spacing, excess water, and/or excess nitrogen. It's also possible that roots would have enlarged with more time in the ground.

Sweet potato does not require a lot of nitrogen, only 0.10 pounds of N/100 sq. ft. of garden space. 100 lbs. of compost (2 1/2 bags of LeafGro) contains about 1 lb. of N. 10-15% of it is available to plants the first year, approximately providing the recommended amount of N. If you are adding compost and organic matter every year you could be overfertilizing with N and building up excessive levels of phosphorous which is a potential water pollutant when it runs off soil.