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to find its nutrient and pH levels. Knowing the pH level of your soil is important because different plants thrive under different pH levels. It's also helpful for you to know the nutrient levels so you know what you need to add to the soil to help the tomato plants thrive. Use a commercial testing kit to collect and test a sample of the soil where you plan to plant your tomatoes.  Tomatoes grow best in slightly acidic soil, with the optimum pH level being between 6.2 and 6.8. Soil that falls below 6.0 is too acidic for tomato plants to thrive. An even balance of nitrogen, phosphorus, and potassium is necessary for your tomato plants to produce lots of healthy fruit. Too much of 1 nutrient can affect the health of your tomato plants. If the pH of your soil is below 6.2, mix in crushed eggshells at a ratio of 1 pound (0.45 kg) for every 100 square feet (9.3 m2). For soil that has a pH above 6.8, you need to make it more acidic. Mix together equal parts water and cold coffee in a water can and apply it to the soil.  For example, if you have a tomato garden that is about 20 square feet (1.9 m2), then mix in about .2 pounds (0.091 kg) of eggshells. Turn the soil over and mix it up after you apply the eggshells or coffee mixture. Retest the soil to see if the pH level is between 6.2 and 6.8 before you plant your tomato plants. Your soil needs to have an even ratio of nitrogen, potassium, and phosphorus for your tomato plants. If you have a low amount of nitrogen, add in a natural source, then retest the soil to make sure the levels are even. Combine the nitrogen source with the top layer of soil and compost by mixing it together with a shovel.  Natural sources of nitrogen include alfalfa meal, blood meal, feather meal, and fish meal. You can also add artificial nitrogen fertilizers like ammonium nitrate or ammonium sulfate. Bone meal is a great organic source of phosphorus that you can add to your soil raise the levels of that nutrient. Mix in the bone meal with the soil then retest it to make sure the levels are even with the nitrogen and potassium levels.  Artificial phosphorus fertilizers include rock phosphate and superphosphate. You can find bone meal and phosphorus fertilizers at garden supply stores, nurseries, and online. If you need to elevate your potassium levels so they're even with the levels of nitrogen and phosphorus in the soil, add some wood ash or granite dust and mix it in with the top layer of soil. After you combine it with the soil, retest it to make sure the levels are even.  You can use potassium sulfate or rock sand as artificial fertilizers that will raise the potassium content of your soil. Find wood ash, granite dust, or artificial potassium fertilizers at local nurseries, home improvement stores, or online. No matter what fertilizers or nutrients you plan to add to your soil to prepare it for tomato plants, you need to add them to the top layer of the soil that you tilled for your garden. Mix in the compost or nutrients well with the soil so the roots of the tomato plants can start to absorb them as soon as you plant them. Turn the dirt over with your shovel to help combine the nutrients, compost, and soil. If your soil is lacking in nutrients, you can add a continuous-release fertilizer that will provide the nutrients your tomato plants need. Artificial fertilizers are less natural and organic, but they quickly raise the nutrient content of your soil. Mix in the fertilizer with the top layer of soil and compost.  Choose a fertilizer that has an even ratio of potassium, phosphorus, and nitrogen for your tomato plants. You can find fertilizers at garden supply stores, plant nurseries, or online. Popular continuous-release fertilizers include Miracle-Gro, Tomato-tone, and Fox Farm Tiger Bloom. Add the artificial fertilizer according to the directions on the packaging. Different fertilizers have different concentrations and application methods. The compost will add a small but continuous amount of nutrients and will help the soil hold water and keep the roots from drying out. Cover the top of the soil with a 1 inch (2.5 cm) layer of compost, then mix it into the soil.  Compost will also help any fertilizer that you add stay in the soil until it's needed by your tomato plants. You can find compost at garden supply stores, nurseries, or online.
Test the soil Adjust the pH with eggshells or coffee so it's between 6.2 and 6.8. Mix in a natural source of nitrogen into the soil if needed. Raise the phosphorus content by adding bone meal to the soil. Increase the levels of potassium with wood ash or granite dust. Place any nutrients you add into the top 6 inches (15 cm) of soil. Mix in an artificial fertilizer for an easy way to increase the nutrient content. Add compost to help the soil retain moisture and nutrients.