Although atmospheric nitrogen (N2) is almost 80% of our air, plants can not use nitrogen in the form N2. N2 is considered an inert gas because it is very stable, consisting of two nitrogen molecules are held together by a triple bond. Plants need ammonia, nitrogen, along with hydrogen (NH3), to amino acids, protein production, and other supplies. However, unable to break the link N2 without FixationLegumes help.Nitrogen and rye are known for their ability to "fix" nitrogen. Indeed, both have a symbiotic relationship with the various strains of Rhizobium bacteria. Rhizobium bacteria attaches to the roots of host plants and absorbs nitrogen and hydrogen (NH2) from the air in the ground, using some of the energy of the plant (carbohydrate) to switch to ammonia (NH3). The plant absorbs the NH3 and makes NH4 (ammonium nitrate). Ammonium nitrate is a fertilizer for the plant. Both bacteria and plants to benefit from trade off.If oxygen your plants legumes such as beans or peas, in the vicinity of nitrogen, members love the cabbage family like broccoli and kale, the family of cabbage and relatives of both legumes smile. repel and attract vermin help some plants release chemicals from their roots or leaves, called allelochemicals, which prevent pests. As an example, tomatoes repel Diamondback moth caterpillars, which like to use cabbage leaves food.Other plants attract insects that feed on pests that would otherwise damage nearby plants. As an example, beans, corn that attract insect pests like leaf eating beetles. Factor space and other plants that need partial shade, often grow better in the shade of a large plant or shrub. As an example, spider flower (Cleome) mean that lettuce prefers shade. Sometimes a row of hardy plants to protect vulnerable plants from the depths of wind damage.Root vary from plant to plant. Take advantage of this difference to grow vegetables in a given area. As an example, by planting shallow-rooted onions in the vicinity of deep carrots, which grows each vegetable in basil UnexplainedWhen garden.The planted near tomatoes, both grow very well. This is a positive relationship is not explained.Another similar relationship between the climbing beans, corn and squash. As the three grow together, everyone is happy, but we know no one knows exactly why.