Plant Nutrition and Soil Fertility

Vocabulary flashcards covering plant essential nutrients, mobility, deficiency symptoms, soil reservoirs, availability, and nutrient loss pathways based on the lecture.

Liebig's Law of the Minimum

The principle stating that organism growth is controlled not by the total amount of resources available, but by the scarcest resource or limiting factor, meaning yield is proportional to the amount of the most limiting nutrient.

Criteria of Essentiality

Three guidelines established in the late 1930s to determine whether a nutrient is essential: 1) the plant cannot complete its life cycle without it, 2) no other element can substitute for its specific function, and 3) the element must be directly involved in plant metabolism.

Macronutrients

Essential plant nutrients required in large quantities

what nutrients are classified as macronutrients ?

carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, sulfur, and magnesium.

Micronutrients

Essential plant nutrients required in minute quantities

what nutrients are classified as micronutrients ?

iron, manganese, boron, zinc, copper, molybdenum, chlorine, and nickel.

Mobile Nutrients

Nutrients that can move freely through the vascular system and be remobilized from older leaves to sinks via the phloem, causing deficiency symptoms to appear first in older leaves.

what nutrients are mobile nutrients ?

Nitrogen, phosphorus, potassium, and magnesium

Immobile Nutrients

Nutrients that become permanently locked into older structures and cannot relocate, causing deficiency symptoms to appear first in young leaves and new growth.

what nutrients are immobile ?

Calcium, iron, and boron

Middle Lamella

An intercellular layer formed with calcium that functions to cement adjacent plant cell walls together.

Blossom End Rot

A physiological disorder commonly seen in tomatoes caused by calcium deficiency, resulting from the breakdown of cell walls that are no longer cemented together.

Anthocyanins

Purple plant pigments produced as a stress response, triggered during phosphorus deficiency when energy-dependent sugar transport fails and sugars accumulate in leaf tissues.

Fallow Syndrome

A condition resulting from leaving a field fallow for an extended period, which reduces populations of obligate symbiotic mycorrhizal fungi and leads to reduced nutrient acquisition in subsequent crops.

Plant-Available Nitrogen

The chemical forms of nitrogen that plant roots can absorb from soil solution, primarily nitrate and ammonium.

Soil Sulfur Mineralization

The biological conversion of organic sulfur into plant-available sulfate by soil microbes, necessary because approximately 95% of total soil sulfur is tied up in organic matter, humus, and crop residues.

Pre-Sidedress Nitrate Test (PSNT)

A diagnostic soil test that evaluates nitrate levels in the top $30\,\text{cm}$ of soil at the V3 to V4 growth stages in corn to predict potential deficiencies and nitrogen needs.

Tissue Testing

A diagnostic practice of testing plant tissue directly to assess nutrient status, recommended when evaluating nutrients like nitrogen that are in constant flux or in sandy soils with poor nutrient retention.

Nutrient Use Efficiency (NUE)

A measure of how effectively added nutrients are converted into crop yield, specifically calculated as the ratio of nutrient outputs to inputs within an agricultural system.

The 4 Rs

A nutrient stewardship framework designed to optimize nutrient use efficiency by applying fertilizer at the right source, right rate, right time, and right place.

Leaching

The process by which water, during heavy rainfall or irrigation, percolates through soil, transporting dissolved nutrients and contaminants from the surface into the subsurface or surface water bodies, potentially leading to groundwater pollution and eutrophication.

Volatilization

The pathway of nitrogen loss that occurs when surface ammonium transforms into ammonia gas and evaporates into the atmosphere, accelerated by warm weather and surface application of urea.

Urease

An enzyme present in high concentrations within plant residues that accelerates the hydrolysis of urea into ammonium and carbon dioxide.

Runoff

The movement of water and nutrients across the soil surface, primarily responsible for the loss of phosphorus

Denitrification

The microbial conversion of nitrate into volatile nitrogen gases occurring in saturated soils under low-oxygen conditions.

Facultative Anaerobes

Organisms that normally prefer aerobic respiration with oxygen but can switch to anaerobic respiration—such as utilizing nitrate instead of oxygen—when oxygen concentrations are low.