You will need
  • - fertilizers that contain nitrogen
  • - drugs to combat the onion fly
  • - salt
Often the yellowing of onion due to lack of nitrogen in the soil where it is grown. This happens if the soil is dry, or Vice versa, in the case of frequent rains, when nitrogen goes deep into the soil. If the reason, you need to make nitrogenous fertilizers such as ammonium nitrate, ammonium sulphate. And, you can pour the onion extract of manure or urea.
Insect-pest of onion fly can be the reason that yellow onion. The larvae of this fly are found inside the follicles and liquefy it. To detect this attack easily. You just need to cut the onion in half, if the larvae have, they can be seen immediately. In order to avoid the emergence of onion flies often need to change the place of planting onions, planting it next to the carrots, onions fertilize saline. To deter onion fly, if the scatter between the patches or tobacco cigarette dust. You can also buy the drugs to fight a fly.
Yellow onion is often due to improper watering. Pour it is impossible, as the plant begins to rot, but dry it is also not recommended. The best option irrigation of onions is watering abundant, but infrequent.