Fertiliser disaster

Help!


I am a novice gardener who has dived in at the deep end with the aid of a few books. In attempting to crete a seed bed for vegetables I used a Growmore fertiliser. After a long day I misread the quantities and have applied 10 times the recommended dosage! Having conscientiously hoed it in I realised the mistake.

What can I do?? Will vast amounts of water leach it out? Should I add new topsoil (or will this just add to the excess mineral content? Will any vegtables be safe to eat even then?

Rich

 

Rich,

Firstly you can't take it back out as you've realised, but neither can you water it out either.

Plant's main requirement is for Nitrogen (N), Phosphorus (P) and Potassium (K) fertilisers. Whether they come from organic or inorganic sources plants always take them in the same form from either - something not always appreciated in the 'organic' or 'conventional' debate.

While Nitrogen fertiliser (Nitrate or Ammonium types mainly) are soluble and will move reasonably rapidly under watering, Potassium fertilisers are 10 times less soluble and Phosphorus is 1000 times less soluble - you could empty a swimmming pool on it before the Phosphorus moved appreciably!

So, you are left with a 'high fertility' problem.

In the first instance it would be worth 'double digging' the ground to two spade depths to mix the fertilser with more soil and dilute it this way.

Secondly, adding chopped straw at the bottom of the digging (but mixed thoroughly with the soil) will remove alot of the Nitrogen and Potassium because soil bacteria will need it to help breakdown the nutritionally poor straw.

Thirdly, plant 'greedy' vegetable crops like potatoes or sweetcorn. These have a pretty high NPK requirement anyway.

Yes, the vegetables will be safe to eat. If the plants grow healthily, then they will be fine to eat.

Fertiliser is not poisonous in itself, but in the wrong place - rivers & streams - can cause inappropriate growth of algae etc. which can remove oxygen from water and kill fish. Obviously, this applies equally to organic manures and conventional fertilisers.