Like people, plants need a variety of minerals for healthy growth. Plants can absorb some minerals directly from the soil, but they rely on soil organisms to deliver other minerals in a form that they can use.
A healthy soil is a living system, known as the soil food web. As roots grow and die, they open up pores in the soil and provide food for insects and microbes. Roots, worms, and microbes work together to aggregate soil into a porous “crumb structure” that facilitates nutrient exchange and the movement of air and water. Fungi and bacteria break down dead plant and animal tissue, mobilizing the nutrients it contains. And fungi intertwine with root systems, supplying the roots with nitrogen and minerals in exchange for sugars exuded by each growing rootlet.
Because plants are interdependent with soil organisms, there are two ways to provide them with supplemental nutrients:
We can feed the plant directly. When we add elements like silicon, __, and __ to the soil, plants can absorb them directly and put them to use. Silicon, for example, helps reinforce the structure of leaves; __ helps the plant do __, and __ is essential to the plant’s __.
We can also feed the plant by feeding the soil. Certain minerals help support the organisms that support the plant; others can only be absorbed by the plant once a soil organism has converted it to a form the plant can use. __ is applied in the form of __; in the soil, __ convert it to __ and transport it to the roots. __ helps the growth of __, and __.
Another way to feed the soil is to add leaf mulch, compost, or the clippings created by a mulching mower. As these materials decay, they nourish the soil food web and travel through it to the plant’s roots. The nutrients in these materials are less vulnerable than applied fertilizers to being washed away in the rain, and make a good complement to the minerals that need to be applied directly.
As with mowing and watering, timing and quantity are important. For example, if __ is applied too late in the season, it can spur the plant to put on new growth at exactly the time it ought to be going dormant. And any nutrient applied in excess will be washed away by the rain, leading to harm downstream. Nitrogen can boost plant growth, for example, but if it percolates into the soil it can pollute the aquifer below, and if it flows into a river, lake, or harbor it can harm fish and wildlife. For these reasons, it is important to apply nutrients with great care.