Radishes and Onions With No Bulb

Question from Sally:
My radishes and onions have really nice green leaves and don’t bulb my radishes where like the size of my little finger. What could be the problem?

My soil in my raised beds test great but they tested having like NO nitrogen. I put aged chicken manure in the beds 2 or 3 times a year and rabbit manure when I plant and to side dress and it still tests very little nitrogen. What could cause that… the amount of rain the winter?

Answer from Pat:
When radishes make leaves but no bulb that usually means that they are growing in too much shade or that they got too much nitrogen and not enough phosphorus and potassium.

When onions are all green with no bulb, it may just be that it’s not the month yet for that particular variety to begin growing a bulb. Nonetheless, all root crops need bone meal or another source of phosphorus and potassium also to be in the soil at planting time.

Among organic sources of phosphorus and potassium are banana peels and also fossilized seabird guano, which comes in a bag. Banana peels are a source of both potassium and phosphorus. You can cut them up and put them into an empty mayonnaise jar, fill it with water and let sit for a week to ferment and pour the whole thing onto the ground. This gives a quicker result than burying the peels.

If your soil tested low in nitrogen last year, this could be the result of too much unrotted carbonaceous material (i.e.: dry woody stuff, such as sawdust, straw, dry plant stems, or dry leaves) in the ground and not enough nitrogen to correct the imbalance. Carbonaceous materials could have come from dry bedding (sawdust or straw) mixed in with manure and not enough animal urine in the manure to compensate. Carbonaceous materials in soil sometimes result from mulch getting mixed into beds accidentally. An application of blood meal can provide the necessary nitrogen to straighten out the imbalance. I have also mentioned human urine diluted with water as a solution, but it’s alkaline so one needs a lot of rain to wash away the salts. Nonetheless it’s used by some families as the only fertilizer they ever use for raising vegetables since it also has ample phosphorus and potassium and is clean. (We might as well be frank about these things!)

Rabbit manure is very mild. It does not have a high nitrogen content. Chicken manure should have ample nitrogen, phosphorus, and potassium in it, but if bedding was included that could explain the low nitrogen. Also if you were aging manure in the rain, much of the nitrogenous goodness could have washed into the ground. Phosphorus, however, is slower acting.

Organic sources of potassium include greensand and SulPoMag, which comes in a bag or box and goes a long way.

Nitrogen subtracted from soil by carbonaceous materials is not gone forever. Once the woody stuff has absorbed all the nitrogen it needs in order to rot, then it will give that nitrogen back to the soil. Maybe that’s what happened this year.

I suggest that next time you plant radishes or any root crop you put bone meal into the ground prior to planting and go easy on nitrogen. Perhaps you could correct the problem by mixing up a batch of 0-10-10 according to package directions and pouring it around the plants to see if they will then make a bulb.