soil fertility and essential nutrients Flashcards
what is the definition of soil fertility
the ability of the soil to supply essential nutrients to support plant growth and reproduction
what is the criteria of plant nutrient essentiality
1) element is necessary for the plant to complete the vegetative or reproductive stage of its life cycle
2) deficiencies of the element are specific to that element; the element is not replaceable by another
3) element is directly involved in growth or metabolism
where do elements come from
most essential elements are derived from the mineral and organic fractions of the soil
exceptions are C,H,O which are supplied as CO2 and H2O
what are macronutrients
elements required in relatively large quantities—make up the bulk of structural and protoplasmic tissue
what are micronutrients and what do they help with
elements required in small amounts— for enzymatic, oxidation, reduction, and other reactions
how are macronutrients measured
in percent dry weight
how are micronutrients measured
parts per million dry weight
why are macronutrients and micronutrients equally important to plant growth
nutrients are assimilated and become components of cell constituents in defined proportions.
ex. think of it as building a house without nails. they are small but you can’t build a house without them you cant
what is Liebig’s Law of the minimum
crop yield is proportional to the amount of the most limiting growth factor (e.g., nutrients) and that additions of resources to alleviate the limiting growth factor will increase yield until the point that some other growth factor is needed in greater quantity than the soil or environment can provide
what forms do plants take up nitrogen
NO3-, NH4+
what are the functions of nitrogen in plants
combines with carbohydrates to form amino acids and proteins involved in enzymatic processes; components of DNA and RNA
what forms do plants take up phosphorus
PO4^3-, H2PO4-, HPO42-
what is the function of phosphorous in plants
energy transfer-constituent of ATP
how do plants take up potassium
K+
what is the function of potassium in plants
activates cellular enzymes; regulates osmotic potentials
how do plants take up sulfur
SO4-2
what if the function of sulfur in plants
an essential component of some amino acids; important for the synthesis of oils, especially in oil crops like canola
what are the ways roots take up nutrients from the soil
diffusion, mass flow, root interception
how does diffusion work for root nutrient uptake and what nutrients get taken up this way
dominant for K & P, concentration gradient drives diffusion
how does mass flow work for root nutrient uptake and what nutrients get taken up this way
dominant for Ca & Mg and anions like NO3-, mass movement of nutrients with water driven by transportation
haw does root interception work for nutrient uptake and what nutrients get taken up this way
a very small contribution to overall uptake. as the root grows the root moves toward the nutrients and intercepts the nutrients in the soil
what are symptoms of N deficiency in plants
yellowing of the leaves and stems–older leaves yellow first.
stunted growth
less tillering in cereals
what are some symptoms of P deficiency
stunted growth, limited root development
purplish coloration of stems and leaves
what are some symptoms of K deficiencies
dull green leaves
yellowing leaves (you can distinguish the difference between N because it will be yellowing on the edges although a test can be done to determine)
if you do suspect a deficiency whats the best way to confirm
identifying by doing a chemical analysis of plant tissue is especially helpful for micronutrient diffecencies.
nutrient deficiencies can be hard to diagnose. what can deficiencies be confused with
diseases, herbicide damage, heat?cold damage, drought damage, insect damage
