How can I improve the soil in a new allotment, which is covered in wild grass?

Question

I am in the process of getting hold of a standard style UK allotment, 10 poles or about 10x25m (2722.5 sq. ft., .052 acres) The plot will be covered mostly in wild tall grasses, and is likely to have been that way at least 6 months to a year.

The plot is the Bucks area, which is South Central England and the climate is temperate.

Will wild grasses have an impact (positive or negative) on the quality of the soil and it's minerals/nitrogen? By the time I've cleared out areas ready for planting it will be autumn. I'm thinking perhaps the best thing would be to plant a cover crop, like clover, over the majority of the plot and turn it over ready for planting in earnest in spring.

Would this make sense, or is the soil as good as it's going to get (using natural nitrogen fixing methods) right now?

Any thoughts? My aim is to fertilize the soil naturally using cover crops, compost and liquid feed (hopefully from a wormery). I will be growing squashes, root veggies and salad greens for the most part. Nothing too difficult, just simple vegetables that I would actually eat.

Answer 1

Wild grasses will add to the soil while decomposing, so the effect will be beneficial. The minerals in the soil will not be negatively impacted, because the grass absorbed the minerals they add back to the soil from the soil in the first place.

Also good to note: Decomposing organic matter produces humic acid, which breaks minerals from rocks into forms available to plants. I've found that mineral mixes will go twice as far with the same effect when spread with compost, for this reason. Soils with a high rate of decomposition will be much better in available mineral content. That is another plus for green manuring.

The nitrogen impact on the soil will vary with the condition of the grass going into the soil. Green grass will have a carbon/nitrogen ratio of 12-25/1, which is high in nitrogen and will add to the soil. If the grass is dry, the ratio will be around 50/1, which is slightly lower than the ideal decomposition ratio (30/1). Dry grass may pull some nitrogen out of the spoil for a short time while decomposing, but will release it back slowly once decomposition is complete.

Some grass will have a allelopathic effect on germinating seedlings, acting as a pre-emergent. For this reason, wait 2-3 weeks before sowing a cover crop. Row crops are a good idea, and will build your soil faster than you might think.

On 'is the soil as good as it's going to get (using natural nitrogen fixing methods) right now?'. There are very few cases where soil is that close to ideal. The more you can give your soil, the better.

What I have done in a very similar case to yours is:

• Green manure on the off season.
• Throw a layer of compost on each spring.
• Dig a trench for row crops, and a hole for hill crops, and fill with 1/3rd soil and 2/3rd's compost, well blended.
• Water the vermicompost tea as available.

This worked very well.