Cranberry Photosynthesis and Nutrients
Standards
• 6-8th grade: SCI.PS3.D.m, SCI.LS2.C.m, SCI.LS1.C.m
• 9-12th grade: SCI.ETS1.A.h, SCI.PS3.D.h, SCI.LS2.C.h
Cranberries are perennial plants and have the same basic needs of other plants: sunlight, water, and nutrients from the air and soil. These essentials are used in photosynthesis, keeping the plant hydrated, and aiding in other essential processes.
How does the plant obtain and use the sunlight, water and nutrients?
Water is taken up from the roots and transported through the plant by the xylem. Xylem is the tissue in vascular plants with the basic function of transporting water and some nutrients from the roots to the stems and leaves.
The leaves of the plant contain stomata and chlorophyll. The stomata are small openings on the underside of the leaves that are used in gas exchange such as carbon dioxide absorption and oxygen release. Chlorophyll is the substance that gives plants their green color and absorbs the Sun’s energy.
The Sun’s energy together with carbon dioxide and water are used in Photosynthesis. Photosynthesis is the process that uses energy from the sun, together with carbon dioxide and water, to make sugar and release oxygen.
Once the sugars are produced, they need to be translocated or moved to other parts of the plant. Phloem moves sugar that the plant has produced by photosynthesis to where it is need for processes such as growing or storage.
Use the cranberry learning lessons plant to discuss photosynthesis as it relates to a specific plant/crop.
For older or advanced students take it a step further and discuss why farmers have to fertilize.
If cranberries and other plants can produce their own sugar/food why do growers have to fertilize them?
Fertilizer provides plants with all sorts of nutrients they need to grow strong and healthy. Plants look for nutrients in the soil to use in photosynthesis and other plant functions. If the nutrients are not there the plant may become weak. A weak plant is susceptible to insects, weeds, diseases, and may not yield a crop.
Cranberry growers and other farmers have nutrient management plans which includes soil and tissue testing. Soil and plant tissues are collected and analyzed at a laboratory for nutrient content and availability. With the laboratory analysis farmers know how many nutrients need to be added to the soil.
The pH of the soil is also a major component to all plants. What is pH? pH is the measure of the amount of H+ ions in the soil solution. It is measured on a scale that ranges from 1 (VERY acid) to 14 (Very alkaline). A low pH soil (acid) has greater amounts of H+ ion compared to OH– whereas a high pH soil has the opposite with high amounts of OH– and lower amounts of H+. The pH level of the soil determines what nutrients are readily available for the plant to use.
Why does it matter? The soil pH directly affects how fertilizers and nutrients released from organic matter will react in the soil. Each nutrient has a pH range in which it is most available for plants to take up, therefore, as the pH of a soil changes, the availability of nutrients changes. The ideal pH for cranberries is 4.5-5.5, which is quite acidic compared to other crops. If the soil is higher than 5.5, the availability of nutrients dramatically changes. Calcium, magnesium and potassium become much more available and can become ‘toxic’ by creating nutrient imbalances in the soil.
If cranberry soil analysis indicates a pH over 5.5 growers may need to add fertilizer to lower the soil pH. A common technique is to add elemental sulfur to lower the soil pH. If the soil pH is too high certain nutrients become available and unavailable disrupting the cation exchange.
Take the opportunity to explain to your students the importance of using science (laboratory analysis) to make management decisions on farms. Dive into the different careers that are needed to help farmers in this process. Examples: Horticulturist, Ag Scientists, Crop Consultants, Soil and Tissue technicians, Lab Technicians, Soil Scientists, Fertilizer Suppliers, Truck Drivers, Crop Physiologist, and the list goes on.
