Gardens: Soil Preparation

Before I begin, let me say once again, I am in no way an expert on the subject, but I am willing to share my experience through my years of gardening. Based on the comment on my last article, this week  I will be focusing on soil preparation. I have found that success in gardening is highly dependent on how “good” your soil is. But what exactly determines “good soil”? There are three common types of soil we have here on the island of Saipan; humus, clay, and sandy. The best part is, you can work almost any soil to be more productive. If your property was ever back-filled, then you may find rebars, rocks and other debris depending on where the back-fill material came from. You may also be the lucky lottery winner and own a back yard with mostly rocks. That should not stop you from gardening though!

The best soil you could start with is humus soil. This is the typical dark brown to black colored soil that you may see at the farms when passing through Kagman’s main road. Humus soil consists of mostly broken down compost from leaves, tree branches, and any other organic material that has fully decomposed. Earthworms and a variety of micro organisms have gone through the process of consuming the raw material and literally pooping out the humus in the end. It is loaded with all the nutrients plants need, such as nitrogen, which drains well, yet retains moisture too. With a depth of 10 to 12 inches of humus soil, you won’t need to add any amendments in the beginning, you simply level your garden area and begin planting.

Clay soil on the other hand is basically the opposite. Most of the nutrients have been consumed by previous plants or weeds and you are left with a light brown to reddish dirt. This can be a problem being that it is low in nutrients, mostly non-acidic (which some plants prefer acidic soil) and it retains water for a long time. When water is unable to drain properly, the soil gets water logged and hence causes problems for the plant roots. The best way to counter this problem is to add amendments such as peat moss, perlite or vermiculite. Peat moss helps to prevent the clay from sticking together while perlite and vermiculite allow it drain better. How much to add? That is dependent on your situation. The formula I use is based on a 5 gallon bucket. Half bucket of clay soil, a fourth bucket peat moss, and a fourth bucket of equal parts coarse perlite and vermiculite. Mix well, and viola, ready to plant. Because the clay soil is mostly depleted of nutrients, you may want to use water soluble fertilizers such as miracle grow or seaweed extract on your first watering to help the seeds or transplants root faster. You could also use slow release fertilizers like Triple 16, Osmocote, or a combination of mineral additives like blood meal, bone meal, and azomite. These fertilizers can all be found at our local hardware stores. However, if you happen to have a compost pile at home, you may mix your compost and clay soil on a 1 to 1 ratio. Basically that’s half a bucket of clay soil to half a bucket of compost. This will save you money on having to use fertilizers to feed your plants along the way.

Sandy soil is actually not so bad. The biggest problem with sandy or loamy soil is that is does not retain water. Water simply flows right through and plants are barely able to absorb enough water. This problem can easily be addressed with peat moss and compost which both absorb water. This allows the soil to drain well, yet some of the moisture will be stored in the added organic matter. There is a part of my yard that was back-filled with beach sand from 40 years ago or so. Every year we would add a little compost and plant taro. The taros grow well because the soil is soft, but I have to water it regularly to ensure that they have the right amount of water. Now I know you may be thinking of adding clay soil to balance out the sand, however, once the sun bakes that newly watered planting area, it will slowly begin to harden into clumps of rocks all over the surface area.

If you are working directly into the soil, the very first time you decide to plant in that area, it would be best to turn over the soil at least three times. You can either use a tiller, or a garden pick to dig through and loosen the soil. If you don’t have a tiller, no worries, just a little back breaking work will do with a pick. Each time, try to dig as deep as 12 inches or so. The reason for this is that over time, nutrients that were once available on the surface of any soil are slowly washed down by rain. By turning over the soil and allowing the bottom part of it to be at the surface, you are essentially reversing the washout and letting whatever nutrients that remain become accessible to your plants. In addition, it helps to soften the soil and allow the roots to take better hold. If you are planting root crops, it would be best to add as much organic material like compost into the soil. This allows the soil to remain soft longer and provide a softer growing medium for your root crops to develop. 

What if you don’t have compost? Another quick solution is to add dried cut grass and leaves into your soil directly. It would work best if you leave this mix in the soil for a few weeks. Allow the cuttings and leaves to decompose somewhat before planting. Make sure you don’t allow weeds to grow during that waiting period. An awesome benefit to this method is that the rotting organic matter will attract earthworms. Earthworms not only help to breakdown the organic matter and leave behind fertilizer, but they also create burrows throughout your garden, allowing water and air to pass through the ground. As the organic materials begin to decompose, it will generate heat. Root crops like tapioca do not like that. The roots will be under-developed if exposed to such heat. On the other hand, radishes do not mind the added heat from below as long as they are able to tolerate it. 

For more information on soil preparation, you could always search Google or refer to one of my personal favorites, YouTube! Don’t take my word for it, listen to what other farmers or gardeners have to say and then do what works best for you. Healthy soil leads to healthy plants, which in turn leads to healthy eating. Happy gardening!