Untitled Quiz

Soil Fertility

• Improving agricultural production leads to increased soil nutrient removal, decreasing soil fertility.
• Efficient nutrient management is critical for sustainable crop production.
• Soil degradation affects agricultural productivity, including physical, chemical, and biological processes.
• Onsite degradation includes erosion, crusting, compaction, and fertility depletion.
• Offsite degradation includes sediment deposition, water contamination, and atmospheric emissions.
• Soil fertility is the ability of soil to hold plant nutrients.

What is Soil Fertility?

• Soil fertility refers to soil's ability to hold and make plant nutrients available for growth.
• Two types of soil fertility exist: native fertility and managed fertility.
• Native fertility is the natural capacity of soil to hold and supply nutrients due to parent material and organic matter content.
• Managed fertility refers to added plant nutrients and amendments.

Plant Nutrients

• Essential for plant growth.
• 16 essential nutrients, three categories:
  • Macronutrients: Primary and intermediate nutrients are required in greater quantities. (N, P, K, S, Mg, Ca).
  • Intermediate nutrients: Sulfur, magnesium, and calcium.
  • Micronutrients: Required in smaller quantities. These include elements like iron, zinc, manganese, etc.
• Deficiency of any nutrient can limit crop yield (Law of the Minimum).

Essential Nutrient Forms in Soil

• Minerals.
• Inorganic cations and anions bound in soil colloids.
• Nutrient complexes.
• Soluble or soil solution ions.
• Organic matter.

Movement of Nutrients to Plant Roots

• Three methods:
  • Root interception: Physical contact between roots and nutrients. Increased root surface area = increased interception.
  • Mass flow: Nutrients transported to roots with water movement.
  • Diffusion : Nutrients move from higher to lower concentrations.

Nutrient Uptake into Plant Cells

• Plant cells have barriers that regulate nutrient and water movement.
• Passive transport: No energy required, movement with concentration gradient.
• Active transport: Energy required, movement against concentration gradient.
• Certain nutrients are mobile in plants and can relocate to new growth.
  • Mobile nutrients: Nitrogen, phosphorus, potassium, magnesium.
  • Immobile nutrients: Calcium, sulfur, boron, copper, iron, etc.

Beneficial Nutrients

• Elements that stimulate the growth of certain plants, but not all.
  • Silicon, sodium, selenium.
• Not required for plant growth

Soil Nutrient Cycles

• Nitrogen, phosphorus, and sulfur cycles are vital.
• Nutrient losses through runoff, erosion, leaching, and crop removal are important.

Soil Nutrient Cycles - Nitrogen

• Nitrogen is transformed by biological processes and microorganisms.
• Transformed from atmospheric nitrogen and incorporated into organic matter.
• Plant available nitrogen is critical for growth.

Soil Nutrient Cycles - Phosphorus

• Biological and geochemical processes involve phosphorus cycling.
• Organic phosphorus compounds are hydrolyzed by phosphatase enzymes, from plant roots and microorganisms.
• Weathering and dissolution of primary minerals can release phosphorus.

Soil Nutrient Cycles - Sulfur

• Sulfur can originate from weathering of parent material, atmospheric deposition, and organic matter.
• Sulfur oxidation reactions occur most rapidly in warmer soils.

Soil Testing and Sampling

• Soil testing determines current nutrient levels.
• Proper sampling is crucial to getting good results from soil tests.
• Multiple samples from different areas of the field should be collected.
• Sampling depth varies based on the crop.

Plant Analysis

• Plant analysis is a method to check for nutrient deficiencies, in conjunction with soil testing.
• Plant tissues, like leaves and petioles, are sampled at specific growth stages.
• Plant deficiencies may not be immediately visible and could be a late-season problem.

Soil Fertility Management

• Managing soil fertility is important, and the 4R principles (right source, right rate, right time, and right place) should be followed
• The Law of the Minimum: Crop yields are limited by the most deficient nutrient
• Critical nutrient levels: Nutrient levels needed to support sufficient plant growth. Deficiency range, critical range, and sufficiency range.

Importance of Measuring Residual Soil Nitrate

• Measuring residual soil nitrate helps determine how efficiently nitrogen is managed.
• This is important for adjusting nitrogen fertilizer for the next season.