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.
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.
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.
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!
Answered by Carlos Bonini Pires, Kansas State University
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How do microbes influence nutrient availability?
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Categories: Home gardens, Nutrition, Sustainability
Two quick reactions to this simplified explanation. Last week, at a Soil Health Symposium held at Rutgers University, Dr. Jim White presented some amazing work being done in his lab showing how plants, or specifically plant roots and root hairs, have symbiotic relationships with bacteria and other microorganisms that actually gather and harvest some nutrients (N in particular) from the soil into the roots (and not the well known nitrogen-fixing bacteria inhabiting nodules on roots of legumes). As we increase our understanding of the microbiome, we’re finding even with plant nutrients getting into plants, that the process may be much more complex than described by simple diffusion and mass transport.
Secondly, plant nutrients from the soil do not necessarily equate to plant nutrients we consume, so the first paragraph under ‘checking soil nutrients’ is a little misleading, oversimplifying the relationship between soil nutrient content and ‘high nutrient content vegetables’. The illustration above that paragraph implies soybeans growing in both high and low levels of soil nutrients will only differ in the nutrient contents of the plants, but in real life, that much difference in soil nutrients would lead to much smaller plants and lower, if any, production of edible pods. Plants growing in optimum levels of plant nutrients will grow well and produce desirably nutritious edible plant parts (assuming other growth factors such as light and water are not limiting), while a plant growing in substrate with one or more plant nutrients (there’s an issue of balance too) below optimum may create the same desirable levels of nutrients in the edible portions, but will likely produce less (fruit, leaves, etc) or create inedible/undesirable products. For example, blossom end rot due to low Ca in soil, or poor movement of Ca within the plant, on tomatoes, and other vegetables (lettuce internal tip burn), will lead to discarding all or part of those affected plant parts, while other fruit/leaves on the same plant will have the same desirable nutrient content as plants growing uninhibited by low soil nutrient levels.
Hi Rick – thank you for your thoughtful response. Our blog audience is the general public, so we unpack as much as we can into shorter blogs. SVF
Iam learning so much on this written information thanks alot….
You can not leave out the role that microorganisms play in nutrient cycling.
Hi Laura, we try to keep our blogs brief, but we did add the following link at the bottom of the blog – because we dedicated an entire blog on our sister site Soils Matter to this very topic!! https://soilsmatter.wordpress.com/2018/06/01/how-do-soil-microbes-influence-nutrient-availability/ Thank you for your comment SVF