SSC 341 Soil Fertility Exam 4

Explain how nutrients applied on the soil surface at planting (directly over the seed row) can be considered a subsurface application.

With irrigation, nutrients dissolve and move down the soil profile, entering the root zone. since it is applied in a narrow band over the crop row, it isn't broadly over the soil surface.

True/False

Surface application of UAN before planting is called "topdressing"

False

True/False

Soil test interpretation is the largest source of error in the soil testing system.

False

True/False

FeSO4 application to a calcareous soil would likely not correct an Fe deficiency

True

True/False

Mn deficiency will likely occur in soil with pH 7 compared to pH 5

True

True/False

Sidedressing is a surface or subsurface band application after planting

True

True/False

Factors affecting Fe, Mn, Zn, and Cu availability in soils are similar

true

True/False

Mo availability decreases with increasing pH

False

True/False

Foliar application of macronutrients is as effective as soil applications

False

True/False

Application of 20 lbs of N + K directly with the seed may cause seedling damage

True

True/False

Mn toxicity will likely occur in soil with a pH of 4.2 compared to pH 6.2

True

True/False

Potential for B deficiency increases with increasing pH

True

True/False

Subsurface band applied P is recommended on soils testing low in plant available P

True

True/False

Crop response to P applications after planting are small compared to preplant P

True

Identify two benefits of crop rotation on soil productivity.

a. Rotating high residue crops reduces soil erosion.

b. Rotating crops with different nutrient requirements balances soil nutrient content.

Broadcast N applied in no-till (high C:N residues) is not as effective as subsurface N. Why?

Soil microbes will decompose the carbon through immobilization, and they will also use any nitrogen in the soil as energy for this process, tying it up so that crops cannot use it.

Briefly describe the function of riparian buffers to reduce P loading to surface waters.

Water slows down through the buffers, and phosphorus is immobile in the soil, sticking to the same soil particles, so as those particles are picked up by rainfall, they are trapped in the buffer, and the nutrients are then absorbed by the plants instead of leaching into open bodies of water.

Increase/Decrease/No Change

for recommended fertilizer N rate:

Decreasing realistic yield expectation or yield goal

Decrease

Increase/Decrease/No Change

for recommended fertilizer N rate:

previous legume crop (vs. previous grass)

Decrease

Increase/Decrease/No Change

for recommended fertilizer N rate:

Increasing soil test P from low to high

No Change

Increase/Decrease/No Change

for recommended fertilizer N rate:

minimizing water as a limiting factor to yield potential

Increase

Increase/Decrease/No Change

for recommended fertilizer N rate:

increasing profile N content

Decrease

Increase/Decrease/No Change

for recommended fertilizer N rate:

applying NH3 vs NH4NO3

No Change

Increase/Decrease/No Change

for recommended fertilizer N rate:

Increasing soil erosion rate

Decrease

Nutrient management plans always include 4 essential components, with the most important being applying the "right" rate. What are the other 3 components?

Right time, Right Placement, Right source

Identify the 6 general nutrient placement options

1. Broadcast 2. Banding 3. Dribble 4. Subsurface Injection (Knifing) 5. Sidedressing 6. Foliar

Increase/Decrease/No Change

Salt damage to germinating seedlings

40% clay compared to 4% clay content

Decrease

Increase/Decrease/No Change

Salt damage to germinating seedlings

30" row width compared to 15"

Increase

Increase/Decrease/No Change

Salt damage to germinating seedlings

Increasing fertilizer grade (5-10-5 vs 10-20-10 at the same lb N/a)

Decrease

Increase/Decrease/No Change

Salt damage to germinating seedlings

N + K sources compared to N + P sources

Increase

Increase/Decrease/No Change

Salt damage to germinating seedlings

Pop up instead of starter application

Increase

Increase/Decrease/No Change

Salt damage to germinating seedlings

40lb/a 10-10-10 compared to 20lb/a

No Change

Define soil test critical level and how is it interpreted in determining a nutrient recommendation.

It is the soil test value where above it Does Not require nutrient application, but below requires nutrient application. Labs will compare your soil sample value to its critical level and make recommendations to get it closer to that level.