Organic soil amendment provides many benefits to sandy soil. Adding organic matter to sandy soil improves its condition and structure. It also allows for better temperature control, and it increases aeration. Adding this component also increases the soils capacity to retain water and nutrients. Furthermore, organic matter supports organisms living in the soil that break down it's composition into usable forms. By not having to use manufactured chemicals it provides an inexpensive energy source, and recycles organic waste at the same time. Organic materials can buffer chemical imbalances in the soil, as well as, change the ph and salt content.
There are 2 different forms of organic manure. One type is animal and bird manure. This type of manure should be obtained from vegetation eating animals. This type of manures can be mixed with green manures or used independent of them. Used alone, animal manure has a higher carbon to nitrogen ratio. To change this ratio, it should be mixed with green manure or compost. Other animal products that can be used in the garden are blood meal and fish meal. Green manure comes from yielding a fast growing one season crop. By cutting it down and tilling the plants back down into the dirt where it can decay, you have created plant manure. Other green manures comes from your typical compost pile composed of a mix of woody plants, whole plants, and yard waste. Do not use pinewood or pine needles with your compost unless you are prepared to wait a long time for them to break down. These are better served as mulch.
Cover crops are also used for organic soil amendment to sandy soil. These are the fast growing crops that are later tilled up into the soil. Legumes work especially well for this because of their nitrogen content. Some ideal legumes to use are beans, alfalfa, and clover. Use cereal grains such as rye grasses and oats as good sources for cover crops. Do not let these plants get full grown before tilling them up because their nitrogen content will be lower. After tilling those up allow them time to decay to become beneficial.
When using animal and plant based manures always mix them together using a 1:1 ratio, and allow them to sit for a few weeks. Using them separately can cause the roots to burn on new plants. You need enough material to spread an inch thick layer per square feet and till it six inches deep down into the soil.
Another tip when trying to amend your soil is to have a landscaper apply a 1 inch layer of clay soil to the sandy soil. You should till this into the ground at least 3 to 4 inches. These two forms of dirt can offset each other. You will still want to add some organic soil amendments to the mix in order to achieve the right texture and structure, because if the clay soil is not add correctly, you could end up with very hard clumps of dirt with little or no nutritional value.