Why Do Plants Need the Elements Nitrogen and Magnesium?

Nitrogen's Role

• Nitrogen is the nutrient required in the largest amounts. It is also among the most commonly deficient of the essential elements. Plants use nitrogen for a variety of functions, including growth, increasing leaf size, synthesizing proteins and manufacturing chlorophyll. Symptoms of nitrogen deficiency include stunted growth, yellowing of the foliage and leaf drop. Leafy plants such as grass, lettuces, tobacco and many vegetables require a great deal of nitrogen to produce bigger, healthier leaves.

Magnesium's Role

• While not a primary nutrient, magnesium still plays a pivotal role in plant life and development. As a part of chlorophyll molecules, magnesium is vital in producing chlorophyll for photosynthesis. This nutrient also carries phosphates, sugars and starches through the plant sugars and helps the plant produce oils and fats. Deficiency symptoms include leaves with dark green veins and yellowing or whitish areas between the veins. Sandy soils are more prone to magnesium deficiency, because they are subject to leaching. Foraging crops are among those most susceptible to magnesium deficiency, which can lead to health issues in cows and other ruminant animals.

Sources of Magnesium and Nitrogen

• Many fertilizers contain a great deal of nitrogen. Every package of fertilizer has a three-digit number known as the N-P-K ratio, which lists the percentage of nitrogen, phosphorus and potassium, respectively. Too much nitrogen can burn the roots; organic sources of nitrogen release more slowly and are also less likely to burn the plants' roots. Compost and many manures are examples of organic nitrogen sources. Magnesium fertilizers are a little harder to find but still line the shelves of many nurseries and garden centers. Apply dolomitic lime or a specialty magnesium fertilizer to increase the soil's magnesium content when needed based on soil tests. Dolomitic lime is particularly useful when the soil is slightly acidic.

Testing

• Performing a soil test is the most effective method of learning whether or not your soil is deficient in nitrogen, magnesium or any of the other essential nutrients. A soil test will also reveal your soil's pH, another factor that can greatly alter plants' abilities to take up nutrients. Neutral soil pH is 7.0, any pH below this is acidic and anything more than this is considered alkaline. Magnesium deficiency, for example, is more likely in acidic soils or in soils where calcitic lime has been applied. Soil tests are available at many garden centers, nurseries and online retailers. Many university extension offices also offer soil tests.