Soil Preparation

Having the best soil condition you can get improves your chances significantly of having the biggest pumpkin you can.

While lots of people think there is a secret to growing giant pumpkins it comes down to basic gardening principles of providing the plant what it needs.

The soil is probably hands down the most important factor in growing a giant pumpkin.  No matter what seed is grown, the location or any other factor, without good soil your pumpkin plant cannot reach its full potential.

To get a better understanding of how important soil is and how it works on a microscopic level I highly recommend reading the book Teaming with Microbes.

It has both the scientific background on how soil works and the impact it has, as well as a practical second half on how to improve your soil.

The Different Levels of Soil Prep

Firstly you want to look at your soil, does it look dark and rich or pale and clay filled? Does it smell earthy, have a lot of insect and bug activity within it?

Have other plants been grown nearby in this soil successfully? Finding a good place to grow is your first step in having great results.

You’ll be wanting to test the soil pH level to find out what the acidity is, and amending when necessary. pH testing is simple can be done yourself at home and is inexpensive.

For giant pumpkins, a pH of 6.5 – 7 is recommended.

Getting soils tests done is what every serious grower should be doing. Finding out the exact makeup of your soil allows you to amend it and get it to the right levels.

There is a cost involved and both getting the test done and using products to amend the soil, having a plan on how many tests you are going to get is a good idea.

pH Level Explained and How To Amend It

The pH level of the soil is a measure of how acidic or alkaline the soil is.  This is important as it directly affects the nutrient availability to the plant. pH tests are included as part of a soil test done by a laboratory, but they can also be done at home yourself using a pH test kit.

I cover how you can do your own pH soil test at home in this video. pH is measured on a scale ranging from 0 – 14, 7 is neutral pH, numbers less than 7 indicates acidity, numbers above 7 indicates alkalinity.

Different plants prefer different pH levels, having the correct level for whatever you are growing allows the plants to uptake all available nutrients in the most efficient manner.

But what happens if your pH level is wrong?  You are going to need to correct it.

  • There are usually two products that can be used to lower the pH level of your soil, Aluminum Sulphate and Sulphur.
  • Both of these products can be obtained from most garden centres.
  • Aluminium Sulphate is a faster acting product with results noticeable instantly as the aluminium produces acidity in the soil as it dissolves.
  • Sulphur, on the other hand, is a much slower method to reduce the pH level and can take some months to achieve the desired result.
  • Both options should be worked into the soil after application for best results and make sure to follow recommended application rates on the packaging as these can be easily over applied.
  • Low pH can be a common problem in a lot of areas and the most common way of bringing the pH level up is to apply lime.
  • Lime can come in chip form or finer.  The finer the product the faster it will work.
  • Paying attention to the application rate is important.  To be most effective lime needs the contact with the soil, this provides the moisture lime needs to work properly.  Dry soil will make the lime have very little effect on the pH level.
  • A cheaper alternative to using lime is wood ash, this method will take longer and should be applied well before the season start.

Soil Testing – How it is Done

Soil sample are taken following the guidelines provided by the lab doing the soil test.

A certain amount of soil will need to be provided and from different points from across your patch.

The soil samples taken from your patch are given to the lab.  There are many different tests they can run.  A good start is:

  • A Basic Soil Profile
  • Available Nitrogen
  • Trace Nutrients

The next step in soil testing is interpreting the results.  This is where talking to experienced growers will help.

They will be able to provide you with advice on what products to use and how much to bring your soil up to optimum levels.

My Soil Testing Journey

One year I was growing in a large enough area to get a soil test done, I documented it over 3 blog posts.

Organic Matter

Having high organic matter in your pumpkin patch gives your a soil a rich structure with many organisms working for you and your pumpkin.

What makes up organic matter?

This term of organic matter covers a wide variety of living or dead and animal material, which ranges from kitchen waste, shredded leaves to well rotted compost and manure.

The benefits of having organic matter in your patch is:

  • Help supply nutrients for plants by providing surfaces where nutrients can be held in reserve in the soil.
  • Help with better drainage by loosening the soil structure.
  • Can help store water within the soil
  • Helps increase the air flow in the soil
  • Increases the activity and numbers of soil microorganisms
  • Encourages earthworms

Having around 10% organic matter in your patch is a good starting point, your soil test will be able to tell you how much you have started with.

Animal manure can and is used, but caution has to be given as too much can upset the balance of microorganisms within your patch.

Cow and horse manure are the two best options for manure in your patch, but only if it is well rotted and aged. There is no point in adding manure if you can’t do it early enough so it breaks down.

Keep in mind that animal manure that is not heat treated will contain grass and seeds which can lead to more weeds than expected during the season.

Getting your pumpkin patches soil into the best possible condition will pay off big time later on.

It might seem overwhelming to first time growers, but doing what you can to improve the soil is something everybody should be doing no matter their skill level or budget.

Cover Crops

Cover crops bring a lot of advantages to your pumpkin patch, especially if timed well during the season.  Benefits of a cover crop are:

  • It can be a great green manure that can be dug back into the soil
  • Great as a nitrogen fixing plant, storing nitrogen from the air into nodules on the roots
  • A natural way to provide weed protection
  • Can help stop the effects of soil erosion caused by wind, rain and the sun.
  • Water retention can be improved in soils with hard soil pans
  • Can control soil borne fungi and nematode problems within the soil

For all the different types of cover crops you can use, growth times and sowing rates head over and read this in depth post.

The No Dig Principle

In a lot of organic gardening literature the no dig way of gardening is outed as being one of the best things you can do.

While this might sound a bit crazy the idea behind it is once organic material has been added and possibly dug in, leaving the soil as untouched as possible allows for all the microorganisms to do their work.

Any digging or tilling as it is sometimes called can ruin the relationship of the soil structure, and could do more harm than good.  It is an interesting concept which can be part of your giant pumpkin patch.

Soil Temp

Having your soil temp correct at time of transplanting your plant out into the patch is important, it helps prevent as much shock as possible for the plant, and also allows all the soil organisms to work in harmony to create an ideal soil structure for your seedling.  A temperature of around 18 degrees Celsius is ideal.

To achieve this ideal soil temperature can be tricky.  Factoring in when the last frosts of the season should be part of your planning for your patch.  Really cold areas of the world use soil heating cables and heating lamps within a temporary structure.  While the heating cables and lamps probably won’t be needed for most parts of NZ, a temporary structure is a must.

More information on these temporary structures can be found in the transplanting section of the How-To pages.

There is always more to learn with soil

As you can see there is a lot of information out there around soil, and this is just a very small selection to help get you thinking.  If there is one area in giant pumpkin growing that helps people gain an edge and break records it has to be soil.

Getting the soil right will help you grow bigger pumpkins.

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