Plant Environment - Soil, Water, Nutritions

Question 1

Soil horizons

5 layers

Answer 1

Organic (o)
Surface (A)
Subsoil (B) 
Substratum (C)
Bedrock (R)

Question 2

Law of minimum

Answer 2

Growth is limited by the nutrient in the lowest supply

Often referred to as leibigs barrel or law

Question 3

Essential plant nutrients

Macro
Secondary
Micro

Answer 3

N, P, K are macro
S, Ca, Mg are secondary
Zn, B, Cu, Mo are all micro

Question 4

Micro

Answer 4

Help the plant have the ability to handle seasonal changes
Influence in grain quality
Critical in plant germination and root development

Question 5

Macro

Answer 5

Becomes deficient first

Needed in large amount

Question 6

Factors influencing soil fertility

Answer 6

• Nutrients export in harvested crops products
• Leaching, erosion and loss to atmosphere
• Nutrients being ‘locked up’ in soil clays (eg P& K)
• Organic Matter (OM) decomposition – first immobilises nutrients, then releases them
• pH
• nutrients going into seeds – taking nutrients off farm
• nutrients go from leaves to seeds
• at milky doe stage turn green manure crop into soil
• leaching – water runs straight through soil into water table. To fix this add clay, organic matter to improve soil structure as this slows down leaching.
• pH locks up nutrients. Also burns leaf tips and destroys root hairs

Question 7

Managing soil acidity

Answer 7

Add lime
Add dolomite through incorporating or broad spreading
Reduce nitrogen and sulphur based fertilisers
Grow legumes eg) clover
Crop and pasture rotations and also using grazing

Question 8

Managing alkaline soils

Answer 8

pH of above 7
Apply nitrogen, sulphur and nitroso based fertilisers
Adding clay to the soil which is high in sodium
Increase organic matter

Question 9

Water availability

Field capacity

Answer 9

Amount of water held in soil after gravitational flow (drainage) has stopped.

How much it can hold naturally

Question 10

Water availability

Wilting point

Answer 10

Remaining soil water is held too tightly for a plant to extract. Therefore plants start to wilt.

Reduces water

Question 11

Water availability

Plant available water capacity

Answer 11

Difference between field capacity and wilting point

Question 12

Management response to water availability

Answer 12

• Apply surface mulches – reduce evaporation
• Wetting agents – increase water infiltration
• Increase OM – improve structure and water holding capacity
• Plant deep rooted varieties – access deeper moisture
• Furrow sowing – bottom of furrow harvests water
• Variety of plant
• Crop selection
• Row spacing, plant spacing