Fertilizers Flashcards
(46 cards)
What are the two categories of plant nutrients?
Macronutrients and micronutrients.
What are macronutrients?
Mineral elements needed in relatively large amounts, expressed as a percentage of the plant’s dry weight and including C, H, O, P, N, S, Ca, K, and Mg.
What are micronutrients?
Elements that plants need in small amounts, usually in the parts per million ranges, like Fe, B, Mn, Ni, Zn, Cu, Cl, and Mo.
What is the difference between organic matter and soil organic matter?
Organic matter comes from decomposed plants and animals in the environment such as decomposing manure, animals, plants, and other living organisms and their remains.
When organic matter decays to the point where it is no longer recognizable it is called soil organic matter which comprises all of the organic matter in the soil exclusive of the material that has not yet decayed.
What are advantages of organic matter in soil?
It improves vegetable production by improving fertility by slowly releasing mineral nutrients to the crop, increases water retention, improves soil structure. In medium and light sandy soils, and organic matter helps to hold moisture and nutrients.
What is humus?
Organic matter broken down into stable humic substances that resist further decomposition. Humus holds water and nutrients that plants can use for growth and improves soil structure.
How can humus be added to soil?
By adding compost, plant or animal manures, or green manure.
What types of vegetables do best in high N soils such as organic or muck soils?
Many salad and root vegetables, such as radish, potato, beets, carrot, celery, spinach, lettuce, etc., that do not go through a reproductive phase and have a high N requirement.
What is a fertilizer?
A substance that contains one or more recognized plant nutrients and promotes plant growth.
What is tested by a standard soil test?
Soil pH, P, K, Ca, Mg, Zn, Mn, Cu, Fe, B, and estimated cation exchange capacity plus a fertilizer and lime recommendation tailored to the crop to be grown and soil type. Optionally soluble salts and organic matter.
Does a soil test include a nitrogen test?
No, because it is very difficult to estimate because of its dynamic nature and many different forms in the soil.
What is the importance of pH?
It impacts both nutrient availability and nutrient-related toxicity.
What are negative effects of acid soils?
Al, H, and/or Mn toxicity, as well as deficiencies of Ca and Mg. Al is not a nutrient but causes damage to plants by interfering with Ca uptake. Mn increases as pH drops, much like Al, so Mn toxicity symptoms are most common at pH 5.6. Classic symptoms of Mn toxicity are crinkling or cupping of leaves.
What are negative effects of alkaline soils?
In moderately alkaline (pH greater than 7.0) soils, Mo and macronutrient (except P) availability is increased, but P, Fe, Mn, Zn, Cu, and Co levels are greatly reduced and may limit plant growth.
Is N availability affected by pH?
N availability is less sensitive to pH than other elements such as P.
In what form is N applied as fertilizer?
Nitrogen may be applied in fertilizer as ammonium (NH4) or nitrate (NO3) and dissolved N is most available in soil in a range of pH 6–8.
What is the target pH for most vegetables?
The majority of vegetable crops have a target pH range of 6.2–6.8.
What are the roles of the xylem and phloem in a plant?
Xylem carries water up to the leaves; Phloem moves sugar down to the roots and fruit.
What are the two types of mineral nutrients taken up by a plant?
Mobile or immobile.
How do deficiencies of mobile nutrients manifest themselves?
Because mobile nutrients move inside plants to where they are most needed, a plant can reallocate mobile nutrients from its older leaves to younger ones. So when nutrients are mobile, nutrient deficiencies first appear on older leaves. N, P, K, Mg, Mo, and Cl are considered mobile nutrients.
How do deficiencies in immobile nutrients manifest themselves?
When immobile nutrients are lacking, the younger leaves show symptoms before older ones because the nutrients are fixed in the tissue and cannot move to where they are most needed.
What are symptoms of N deficiency?
General chlorosis of lower leaves (light green to yellow), stunted and slow growth, and necrosis of older leaves in severe cases. Nitrogen-deficient plants will mature early and crop quality and yield are reduced depending on the severity of the deficiency.
What are symptoms of excessive N fertilization?
Plants developing a deep green color with stimulated vegetative growth, often with delayed maturity. With vegetable crops that are harvested for reproductive tissues, such as broccoli, tomato, pepper, squash, pumpkin or melon, N also stimulates vegetative growth at the expense of reproductive growth. In these crops, excessive N fertilization early in the season may delay or even inhibit flower production and fruit set and reduce early market yields. Since N stimulates vegetative growth, excess N results in tall plants with weak stems and contributes to lodging (plants falling over).
What is significance of C:N ratio?
N status is often discussed in terms of C:N of the plant tissue. The optimum nutrient status for some crops changes during the growing season. After fruit set or flower initiation, the C-to-N ratio should ideally fall to stimulate growth of the developing fruit.
