Steps To Proper pH and Soil Nutrients For Your Garden

In order to promote good plant growth, both macro and micro-nutrients are required, as well as the right soil pH. And, while it is important that your plants receive sufficient amounts of these nutrients, over-application of them can be as detrimental as a deficiency. Over-application of plant nutrients may not only impair plant growth, but may also contaminate groundwater by leaching through the soil or pollute surface waters by washing away.

Plants require twenty nutrients in order to thrive. Of these, nitrogen, phosphorus, and potassium are required in relatively large amounts and along with calcium, sulfur, and magnesium are referred to as macro-nutrients. The remaining nutrients are required in trace amounts and are referred to as micro-nutrients. These include such elements as copper, zinc, iron, and boron.

In addition to sufficient nutrients, your plants also benefit from soil with the proper pH levels. Testing your soil for both pH levels and nutrients is important to provide your plants with a balance of nutrients while avoiding over-application.

A pH of 7 is considered neutral, below 7 acidic and above 7 is alkaline. Since pH greatly influences plant nutrients, adjusting the pH alone, will often fix a nutrient problem. At a high pH, several of the micro-nutrients become less bio-available for plants. Iron deficiency is a common problem even at a neutral pH for such plants as rhododendrons and blueberries.

At very low pH, some micro-nutrients may be too available, resulting in plant toxicity. Phosphorus and potassium are tested for regularly by commercial testing labs and while there are soil tests for nitrogen, these are less reliable because nitrogen is present in several forms and the forms can change rapidly, so most university labs do not routinely test for nitrogen.

Once you have the results of the soil test, you can add nutrients or soil additives such as lime, as needed. If you need to raise the pH, use lime. Lime is most effective when it is mixed into the soil, therefore it is best done before planting. If you need to lower the pH significantly, you can use aluminum sulfate.

Commercial fertilizers are typically applied as a dry granular material or mixed with water and watered onto the garden. If using granular materials, avoid spilling on sidewalks and driveways. These materials are water-soluble and can cause pollution problems if washed into storm sewers. Granular fertilizers are a type of salt and if applied too heavily on plants, they can burn the plants. If using a liquid fertilizer, apply directly to or around the base of the plant.

For the most efficient use, fertilizer should only be applied when the plants have a need for the nutrients. Therefore, fertilizing dormant plants or plants growing slowly due to cool temperatures, is unnecessary.