Fertilizers

Question 1

What are the two categories of plant nutrients?

Answer 1

Macronutrients and micronutrients.

Question 2

What are macronutrients?

Answer 2

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.

Question 3

What are micronutrients?

Answer 3

Elements that plants need in small amounts, usually in the parts per million ranges, like Fe, B, Mn, Ni, Zn, Cu, Cl, and Mo.

Question 4

What is the difference between organic matter and soil organic matter?

Answer 4

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.

Question 5

What are advantages of organic matter in soil?

Answer 5

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.

Question 6

What is humus?

Answer 6

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.

Question 7

How can humus be added to soil?

Answer 7

By adding compost, plant or animal manures, or green manure.

Question 8

What types of vegetables do best in high N soils such as organic or muck soils?

Answer 8

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.

Question 9

What is a fertilizer?

Answer 9

A substance that contains one or more recognized plant nutrients and promotes plant growth.

Question 10

What is tested by a standard soil test?

Answer 10

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.

Question 11

Does a soil test include a nitrogen test?

Answer 11

No, because it is very difficult to estimate because of its dynamic nature and many different forms in the soil.

Question 12

What is the importance of pH?

Answer 12

It impacts both nutrient availability and nutrient-related toxicity.

Question 13

What are negative effects of acid soils?

Answer 13

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.

Question 14

What are negative effects of alkaline soils?

Answer 14

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.

Question 15

Is N availability affected by pH?

Answer 15

N availability is less sensitive to pH than other elements such as P.

Question 16

In what form is N applied as fertilizer?

Answer 16

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.

Question 17

What is the target pH for most vegetables?

Answer 17

The majority of vegetable crops have a target pH range of 6.2–6.8.

Question 18

What are the roles of the xylem and phloem in a plant?

Answer 18

Xylem carries water up to the leaves; Phloem moves sugar down to the roots and fruit.

Question 19

What are the two types of mineral nutrients taken up by a plant?

Answer 19

Mobile or immobile.

Question 20

How do deficiencies of mobile nutrients manifest themselves?

Answer 20

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.

Question 21

How do deficiencies in immobile nutrients manifest themselves?

Answer 21

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.

Question 22

What are symptoms of N deficiency?

Answer 22

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.

Question 23

What are symptoms of excessive N fertilization?

Answer 23

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).

Question 24

What is significance of C:N ratio?

Answer 24

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.

Question 25

What are symptoms of a P deficiency?

Answer 25

P-deficient plants generally appear stunted, with older leaves that turn purplish due to the accumulation of sugars, which favor anthocyanin synthesis In cases of severe deficiency leaf tips will brown and die. Plants suffering from P deficiency appear weak and maturity is delayed. Leaf expansion and leaf surface area may also be reduced, causing curled small leaves

Question 26

What are symptoms of Mg deficiency?

Answer 26

Mg is the central molecule in chlorophyll and is an important cofactor for the production of energy storing compound ATP. Symptoms of Mg deficiency include interveinal chlorosis and yellow or reddish-purple leaf margins with green midribs

Question 27

Where are B deficiencies most likely to occur?

Answer 27

In asparagus, most bulb crops, celery, beets, the brassicas and tomatoes where soils are low in B.

Question 28

What are symptoms of B deficiency

Answer 28

Chlorotic young leaves and death of the terminal bud. Leaves may also develop dark brown, irregular lesions that will progress to leaf necrosis in severe cases. Poor cell-wall development causes leaves and stems of B-deficient plants to become brittle and distorted and leaf tips tend to thicken and curl.

Question 29

What are symptoms of Fe deficiency?

Answer 29

Fe plays an important role in plant respiratory and photosynthetic reactions. Fe deficiency reduces chlorophyll production and is characterized by interveinal chlorosis with a sharp distinction between veins and chlorotic areas in young leaves since it is non-mobile. Fe deficiency is strongly associated with calcareous soils and high pH, anaerobic conditions, and excess of heavy metals in soil.

Question 30

Why is Ca an essential macronutrient?

Answer 30

Ca is needed in larger quantities because it is a component of plant cell walls and regulates cell wall construction.

Question 31

What are symptoms of Ca deficiency

Answer 31

Blossom-end rot of tomato, pepper, and watermelon (necrotic tissues on the end of the fruit with a “burned” appearance), tip burn of lettuce, black¬heart of celery, and death of the meristematic tissues in many plants.

Question 32

What is a complete analysis fertilizer?

Answer 32

A fertilizer that has an analysis containing all three of the nutrients N-P-K.

Question 33

What are common sources of organic fertilizer?

Answer 33

Composted manure, worm castings, blood meal, seaweed, guano, composted natural wastes, or naturally occurring mineral deposits.

Question 34

What is a “green manure”?

Answer 34

A cover crop which supplies organic matter, and, if the crop is a legume, N. The green manure biomass is incorporated by plowing or left on the surface as mulch to decompose and recycle mineral nutrients back into the soil. The decomposing plant tissue or “green manure” acts as a slow-release fertilizer. Legumes, like hairy vetch and clover, and small grains, such as barley, rye or millet, are examples of overwintering green-manure crops.

Question 35

What is soil priming?

Answer 35

The use of special cover crops that promote beneficial soil bacteria.

Question 36

What is meant by “precision” or “prescription” fertilization?

Answer 36

It is a test–apply–test method whereby no materials are applied unless soil or plant tissue analysis shows that the crop actually requires and would benefit from the input.

Question 37

What are common fertilizer application methods?

Answer 37

Broadcasting, row banding, top-dressing, side-dressing, liquid “starter” solutions, foliar application, and fertigation – the combined application of nutrients through irrigation water.

Question 38

What is row banding?

Answer 38

A common technique used with granular fertilizer where a thin band of fertilizer is placed a few inches to the side and below the seed or transplant. Row banding confines the fertilizer to the root zone so it is not wasted on areas inaccessible to plant roots. Row banding works well for crops at wide-row spacing and when only a single application of fertilizer is needed.

Question 39

What is side dressing?

Answer 39

Side-dressing applies nutrients to the soil after the crop is established. This technique places fertilizer either on top of or below the soil surface and to the side of the row. Side-dressing is beneficial for many vegetables, since it adds fertilizer when it is most needed by the crop.

Question 40

What is foliar feeding?

Answer 40

Application of liquid fertilizer formulations directly to the foliage rather than the root zone. Useful to supply micronutrients, which are only needed in very small quantities, but not the most efficient way to apply N, P, K, and other macronutrients, which are required in much higher quantities.

Question 41

When should a starter fertilizer be used?

Answer 41

Starter fertilizers are most beneficial when crops are planted into cold, wet soils in early spring or late fall, regardless of soil fertility. Starter fertilizer is important because it meets the demands of the seedling for readily available nutrients until the plant’s root system develops. Using a starter is especially important in conservation tillage systems and transplanted vegetable crops.

Question 42

What is fertigation?

Answer 42

When fertilizer is applied in the irrigation water. This is most commonly done through a drip irrigation system but fertilizers can be added though other types of irrigation as well.

Question 43

What are the advantages of fertigation?

Answer 43

It is one of the most efficient methods for feeding plants. Nutrients can be supplied directly to the root zone in precise quantities so there is very little waste. Nutrients are only provided as needed and can be altered throughout the season to meet the changing nutrient requirements of the crop.

Question 44

What is a possible explanation for a nutrient deficiency in a plant even where nutrient levels in the soil are adequate?

Answer 44

Cold soils, wet soils, root damage by disease or insects as well as other factors may prevent plants from taking up nutrients even though they are available in the soil.

Question 45

What is the purpose of plant tissue analysis?

Answer 45

It is an effective aid in evaluating the actual nutrient status of a crop and is an important part of prescription fertilization (test–apply–test).

Question 46

What is required to adequately feed soil microbes so that the soil remains healthy and alive?

Answer 46

For agricultural production on organic soils or mineral soils amended with animal manures, crop residues, and various organic waste materials, sufficient carbon sources and nutrients are available to adequately “feed” soil microbes so the soil remains “healthy” and alive with biological activity.