First time poster here from Texas. My garden has been thriving with the addition of some county compost this season, but in the last week I have run into a problem.
A portion of my garden has potatoes that are turning yellow at the bottom and now my tomato plants are doing the same. I don't believe it is a watering issue, but am starting to think it could be a disease because it seems to be sweeping across the garden.
I have attached a few photos. Anyone have any thoughts as to what this could be?
If you added more than 20 percent compost, it might be a compost issue. Tomatoes are heavy feeders and need a lot of nitrogen and the compost may still be cooking. If the lower leaves are yellowing more than the young leaves, it needs more nitrogen.
Compost adds organic matter that feeds the soil web carbon, but they also use nitrogen. Compost that is aerobically made will also be alkaline which makes nitrogen less available and with competition from microbes and the nitrogen lost through volatization and denitrifying bacteria you could end up with a nitrogen deficit.
Young growing plants have the greatest need for the essential nutrients and the plants will translocate nutrients from the older to the younger leaves when it cannot get enough. So the deficit usually appears on the lower leaves first. You need to make sure along with the compost you add enough fertilizer to cover the deficit.
Being organic is all about balance. It is more complex than you think. If you add an akaline compost you need to add something acidic to keep the soil from getting too alkaline, If you add more carbon, you need to add more nitrogen to balance things out. If you add 20% or less compost can usually be accommodated. More than that, I usually have to add more acid or fertilizer to counteract it and sometimes adjust the watering.
Yup, there are various causes of yellowing, but most likely is nitrogen deficiency. Compost is wonderful stuff, but it is not fertilizer. The nutrients in compost are not available until it is more broken down, so it is slow release.
I hope I'm wrong but it looks like blight to me. I would trim off all the yellowing and also trim all leaves that touch the ground. Throw them in a garbage bag and put it in the trash. Water the soil not to splash water or soil on the plants will also help to avoid this problem.
I'm not quite convinced, but if buddy gardener ever comes back, there's a test. If he fertilizes and the problem goes away, it was N deficiency. If the problem progresses/ gets worse after that, it was probably blight.
Did you mulch with wood, bark, sawdust or some other carbon? I don't see any soil. It looks like mulch. Mulch will suck all the nitrogen from the soil and plants too then they turn yellow and die. There is a name for this condition I don't remember what it is called.
Last edited by Gary350 on Wed Apr 13, 2016 4:43 pm, edited 1 time in total.
Wondered if maybe the plants just might not be getting enough direct sunlight? Looks like a high fence on one side, maybe more things around casting heavy shade?
