Exam 2

Question 1

What are the 3 tools that can be used for diagnosing nutrient deficiencies and toxicities?

Answer 1

Foliar analysis, soil/substrate analysis, visual diagnosis

Question 2

Describe the procedure for collecting a foliar sample

Answer 2

The youngest fully expanded leaf, 20+ leaves (30 g dry weight)

Question 3

Why does position of the leaf matter when collecting a foliar sample?

Answer 3

There’s different nutritional zones on a plant

Question 4

What is a nutritional zone?

Answer 4

The top half of a plant would mean the nutrient problem is immobile, and the bottom would be a mobile element

Question 5

What information can be gathered from a soil/substrate sample analysis?

Answer 5

Real time and futuristic data

Question 6

What are the 5 integral set of information that need to be gathered to diagnose a proble?

Answer 6

crop history, water analysis, visual diagnosis, soil testing, foliar analysis

Question 7

How do you collect a soil sample and a substrate sample?

Answer 7

4-8” soil probe (removed top mulchy bits), dry soil in the sun, ship asap

Question 8

Soluble ions in irrigation water can be both good and bad for plants in production. For example, Na is a beneficial nutrient for many plants. However, when Na levels in irrigation water are too high, or out of proportion with other nutrients, Na levels can be a problem. What are the possible beneficial and harmful components in irrigation water?

Answer 8

Good-N,P,K,Mg,S,Fe,Mn,Cl,B,Zn,Mo,Cu, good amounts of salt, microbes
Bad-fluoride, too much salt, microbes

Question 9

Why does poor water quality have a greater impact on the nutrient uptake of plants growing in substrate than plants growing in soil?

Answer 9

Soil has a buffering capacity, where substrates do not, they can work around bad water for the most part

Question 10

If soil/substrate pH is too high, how will nutrient uptake by the plant be affected?

Answer 10

Certain nutrients just won’t be taken up

Question 11

If soil/substrate pH is too low, how will nutrient uptake by the plant be affected?

Answer 11

It may over absorb certain nutrients and cause a toxicity

Question 12

What is hardness? How does hardness affect plant nutrition?

Answer 12

The amount of Ca and Mg in water

Question 13

Describe salt stress associated with irrigation water with high soluble salts

Answer 13

It will cause nutrient antagonisms

Question 14

Define primary and secondary macronutrients

Answer 14

Primary are the most limiting to growth and secondary are not limiting to growth

Question 15

T/F: Liebig’s Law of the minimum states that the capacity for growth is limited by that is in least supply

Answer 15

True

Question 16

What are specific functions of the essential plant nutrients?

Answer 16

-N+S=integral elements of C compounds
-P=essential in energy acquisition and utilization in the genome
-Ca,B,Si=structurally associated with the cell wall
-Mg,Fe,Mn,Ca=serve to activate or control the activity of enzymes

Question 17

What are the non-specific functions of the essential plant nutrients?

Answer 17

-K,Na,NO3,Cl,SO4,Ca,Mg=counter ions to positive or negative charges
-K,Na,NO3,Cl=major cellular osmotica

Question 18

What are the major ionic forms that N can be taken up by plants?

Answer 18

NO3- and NH4+

Question 19

What are the minor ionic forms that N can be taken up by plants?

Answer 19

N fixation, urea, soluble organic compounds

Question 20

How do plants differ in their NH4:NO3 preference and uptake? As a rule, how does N rate play into a plant’s NH4:NO3 preference?

Answer 20

Preference is species specific, as a rule mix NH4+ and NO3-

Question 21

What are the sources of N in the soil? Explain the steps of mineralization, ammonification and nitrification. How does pH affect each of these?

Answer 21

-Ammonification=organic N>NH4
-Nitrification=NH4>NO3
-A lower pH will inhibit nitrification
-A higher pH favors nitrification

Question 22

What are the major ionic forms that P can be taken up by plants? Which form is the easiest for the plant to take up?

Answer 22

H2PO4- and HPO4(2-), labile P is easiest to take up

Question 23

How does low (less than 7.22) and high (greater than 7.22) pH affect the P form present in the soil?

Answer 23

Low pH gets its H2PO4 from Al and Fe compounds, high gets it from Ca compounds

Question 24

What are the sources of P in the soil? Describe the 3 pools of P in the soil (soil solution P, labile P, and non-labile P)

Answer 24

-Solution is available now, labile is available in mins/hours, non-labile is not available

Question 25

What ionic forms of K, Ca, and Mg are taken up by plants?

Answer 25

K+,Ca2+,Mg2+

Question 26

How can pH and the other ions in solution affect K, Ca, and Mg retention on the CEC and uptake? By the plant?

Answer 26

pH does not affect these, just how they compete with each other and other ions

Question 27

What ionic forms are S taken up by plants? Which of these is the primary form of S uptake?

Answer 27

SO2, SO4(2-)

Question 28

Does S in solution interact with pH or other nutrient ions

Question 29

Does S in solution interact with pH or other nutrient ions?

Answer 29

No

Question 30

How is P solubility affected by both pH and the other ions in solution?

Answer 30

Low pH=P links to Fe or Al becomes insoluble/unavailable
High pH= P links to Ca and becomes insoluble