Starting a Garden

The Simple Secret to Improving Soil Fertility: Using ‎Nitrogen-Fixing Plants! ‎

The Simple Secret to Improving Your Soil's Fertility‎

I want to let you in on a little secret – farmers have been enriching their soil for generations in a ‎completely natural way without the use of harmful pesticides! The process is using ‘green manure’ – i.e. growing nitrogen-fixing plants that are cut down and then fed into the soil! And we’re going to show you how ‎you can use this same method to improve your soil’s health! ‎

Why nitrogen is so important for healthy vegetables

Closeup of Alfalfa Green Manure

Nitrogen is one of the essential elements for plant growth (along with potassium and ‎phosphorus).  It’s part of the green chlorophyll molecule (required for photosynthesis) and is one ‎of the main components of the plant cell.  It enhances leafy growth, aids formation of healthy ‎flower buds, and helps fruits form.  It also functions as a catalyst for other minerals.  Now since ‎it’s so essential, you can easily have a situation where plants deplete all the nitrogen available in ‎their soil.  Nitrogen also naturally leeches away from soil with the twin effects of the sun and ‎water. ‎

And here’s the irony:  while nitrogen is the most abundant uncombined element on the planet, ‎consisting about 78% of the atmosphere, plants can’t take it in from the air!  Atmospheric nitrogen ‎must be converted, via a series of processes, to nitrates, which can be absorbed by plant roots. ‎

The problem: Using synthetic nitrogen fertilizers

So where does a regular gardener find nitrates?  She turns to fertilisers.  Ever heard of NPK ‎fertilisers?  That’s just a fancy way of saying “nitrogen, phosphorus, potassium” fertilisers.  But ‎the thing is, the majority of these fertilisers are synthetic.  They are harmful in more ways than ‎one:‎

😔 They harm the environment during their manufacture

😔 Using these fertilisers make it easy to overload the nitrogen content in your soil.  This harms ‎your garden and your local environment

😔 They can cause an imbalance in your soil ecosystem

😔 An excess of nitrogen can over-stimulate green growth, which means your plants put on ‎leafy growth at the expense of flowers and fruits

😔 Overuse of these fertilisers leads to nutrient leaching, destroying local rivers, waterways and ‎marine environments

But we’re not regular gardeners, are we, you and I?  We’re organic gardeners.  So here’s our ‎solution for improving soil health with regards to naturally adding nitrogen to the soil, while also ‎adding organic matter, preventing erosion and improving overall soil health. ‎

But we’re not regular gardeners, are we, you and I? We’re organic gardeners. ‎

The solution: Growing organic nitrogen-fixing crops

Certain soil microbes ‘fix’ nitrogen from the atmosphere into the soil. As a result, nitrogen is ‎converted into a delicious form that your vegetable plants can now soak up! ‎

Fabaceae – or plants of the leguminous family – work in symbiosis with nitrogen-fixing rhizobium ‎bacteria which are present in tiny nodules in the roots of the plant. Together with the legume ‎plant, they convert nitrogen from the air into nitrogen that is available in the soil. When these ‎nitrogen-fixing plants die, decomposing microbes in soil break down the plant material and pass ‎nitrogen into the soil system.‎

So what are these magical plants that help maintain a natural soil balance?  Here are just a few:‎

😊 Alfalfa

😊 Fava Beans, Green Beans, French Beans, Runner Beans‎

😊 Garden Peas, Field Peas, Pigeon Peas

😊 Soybeans

😊 Peanuts

😊 Lupins ‎

😊 White Clover, Red Clover

How you can improve your soil by growing nitrogen-fixing plants

Field of alfalfa - after growing for around 6 weeks
Field of alfalfa - after growing for around 6 weeks
The alfalfa on the left has been chopped and lightly tilled into the soil after 8 weeks
Black polyethylene tarp for solarizing soil in the Middle East
Black tarp to cover the chopped alfalfa to allow it to decompose for 3 weeks

To improve your soil, plant one of the above nitrogen-fixers; alfalfa is what we use as it is the ‎most easily available. Note that alfalfa does not do well in the heat of the summer, especially in ‎the Gulf. ‎

Plant the alfalfa by broadcasting your seeds. Use between 6-8 grams of alfalfa per square meter ‎of soil. After broadcasting, use a rake to mix the soil a bit with the alfalfa to ensure there is seed ‎to soil contact. If your soil is of poor quality, add compost when planting as well. Next, water ‎regularly – once a day. After about 7-8 weeks, when the alfalfa has grown 20-30cm tall, cut it ‎down to the level of the soil and immediately cover with mulch (either nylon/straw) for 3 weeks to ‎give the alfalfa the time to decompose. (You can also choose to wait until half of the alfalfa has ‎flowered; at this point the nitrogen content in the plant is at its peak). The decomposition process ‎will both release nitrogen into the soil and add biomass (organic nutrient matter) to the soil. ‎Remove the nylon/mulch and plant your vegetable crops in this fertile, nitrogen-rich soil. ‎

Other ways to improve soil health

As we’ve explained in The Gardening Secrets Blueprint, using cover crops, adding compost, crop ‎rotations all improve soil health.‎

Don’t forget to include nitrogen-fixers into your garden rotation plan to increase its soil’s nitrogen ‎content.  Your plants will thank you!‎

Comments (3)

  1. Jefna
    October 29, 2020 Reply

    WhICH is the best option of crop cover suitable for UAE CLIMATE ??

    • Nasser
      October 29, 2020 Reply

      Alfalfa (‘barseem hijazi’ in Arabic) works well in the UAE as does does cowpea (‘loobiya’); but I wouldn’t grow it during the hottest months i.e. July and August. Will you be trying it, Jefna?!

  2. Yellow plants making you blue? Avoid plant nutrient deficiency of the 7 Micronutrients your ‎vegetables need to grow - SoWeGrow
    March 18, 2021 Reply

    […] Practice “green manuring” – grow a crop of leguminous plants followed by cutting and incorporating them into the […]

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