The best soil fertilizer may be thought of as the product or combination of products that enables desired plants to flourish. No single fertilizer is always best; rather, it may be dependent upon factors including the type of existing soil in an area and the species of plants that will be grown. Choosing the best soil fertilizer involves some analysis of the existing soil as well as identifying the needs of the plants to be grown in that soil. To make an informed decision, it is important to know what the soil is lacking and what factors or soil specifications the plants need to thrive.
When the condition and deficiencies of the soil have been identified and the soil requirements of the desired plants determined, suitable soil fertilizer products can be selected to correct or amend any deficiencies that may exist. Important factors to consider before purchasing fertilizer include pH, drainage rate, and humus content of the soil. Some plants prefer a low or slightly acidic pH, while others prefer an alkaline or neutral pH. Similarly, some plants need a rich soil that stays slightly moist, while dry or sandy soils are ideal for other species. Interestingly, some plants actually prefer "poor" or non-amended soils; in these cases, adding fertilizer to the soil can actually harm the plant.
Soil is a combination of many things, both living and non-living. The non-living components of soil include sand, silt, and clay. Living components such as microbes like bacteria and fungi, as well as the decaying remains of plants and animals, also exist in soil. Humus is the term for this decomposed plant and animal waste, sometimes called organic matter. Humus is the natural source of many of the nutrients in soil, so it can be considered nature’s fertilizer.
Soil may be amended by adding either synthetic fertilizers or natural, organic fertilizers. There are mixed opinions and even conflicting scientific data as to whether or not organic fertilizers are as effective as synthetic fertilizers. Many times, cost is the deciding factor when choosing between natural or synthetic fertilizer. Produce that is grown using organic or natural fertilizers is often reported to be healthier, though that too has been disputed.
Mixed fertilizers may contain nitrogen, phosphorous, and potash. These types are generally considered all purpose fertilizers, and are readily available at home improvement stores in a variety of sizes. Specialty fertilizers used for specific plants such as roses or tomatoes are also quite common. These types are reported to include a mix of the nutrients appropriate for that particular plant. Such specialty mixes are simple to use and directions for use are often printed on the package.
Choosing the best soil fertilizer can be more of a personal decision that goes beyond the soil or plant needs. Some individuals may determine that knowing where and how a company makes a fertilizer is more important than how its effectiveness. Others may wish to avoid purchasing a product that is reported to harm the environment, while some gardeners may decide that a fertilizer that promotes optimum performance is the best choice regardless of ingredients.