Like all living organisms, vegetables need nutrients for their proper growth and development. But where do they get their mineral nutrients from? The answer is soil. Okay, the next question is, how do nutrients go from the soil and into the vegetables?
The three processes responsible for nutrients from the soil reach the plant are diffusion, mass transport, and root interception. I know it seems to be complex to understand, but I promise it is not.
Diffusion
When the concentration of nutrients is higher in the soil than in the plant root, then the nutrients in the soil will move from a region of higher concentration (soil) to a region of lower concentration (vegetable). Potassium and phosphorus are examples of nutrients that get into the vegetables by diffusion.
Mass transport
Nutrients move to the roots via water. As plants transpire water, it draws water and nutrients from the soil up through the root system. Mass transport accounts for nutrient acquisition of mobile nutrients, such as nitrogen and sulfur.
Root interception
Vegetable roots grow through the soil to meet nutrients. As the root grows through the soil it generally only comes in contact with about 1% of soil volume. Good soil structure is essential in the process of root interception. Soil compaction can significantly limit root growth and interception with nutrients throughout the soil. Some important macro and micronutrients such as calcium, magnesium, iron, manganese, and zinc are absorbed by root interception.
Of course, some nutrients are absorbed in more than one way. For example, iron and zinc can be absorbed by three different methods. As you can see, there are a lot of variables that may impact how vegetable acquire their nutrients.
Moving within the plant
Once the nutrients get inside the plant, they can move upward to the leaves and developing vegetables. How? Like a human body, plants also have a vascular system. Rather than a bloodstream, they have xylem and phloem. The Xylem distributes water and dissolves nutrients upward to the plant, from the roots to the leaves. The phloem carries nutrients downward, from the leaves to the roots (photosynthesis). In simple words, the root is the mouth and xylem and phloem are the veins of a “plant body.”
Checking soil nutrients
Soils nutrient concentration is crucial for ensuring high nutrient content vegetables. If the soil has few nutrients, no matter how the plant tries, it will not be able to acquire the nutrients it needs for good yields and plant health.
That is why soil testing is important, and correct fertilization might be needed. Understanding how nutrients are absorbed is vital for a placement strategy. Phosphorus and potassium are nutrients with low mobility and are absorbed by diffusion, so it is important to place them near the plant. On the other hand, nitrogen can be spread over the plants since it is mobile in the soil. This is true whether you are applying organic or mineral fertilizer.
In agronomy, we pay attention to the nutrient 4R’s: right source, right rate, right time, and right place. This refers to choosing the right type of nutrient or fertilizer, applying at the right amount, when the plant can use it the most, and in the right location. By applying these principles to your home garden, you can increase your yields and create more nutritious produce for your next meal! — By Carlos Bonini Pires, Kansas State University
American Society of Agronomy, Soil Science Society of America, Crop Science Society of America: Collectively, these Societies represent more than 12,000 individual members around the world. Members are researchers and professionals in the areas of growing our world’s food supply while protecting our environment. Together we work toward solutions to advance scientific knowledge in the areas of agronomy, crop science, and soil science.
