QUESTION:
Imagine
you are an agronomist, using your soil resources knowledge, what information
can you get from leaf colour in a farm land.
Leaf color refers to a phenomenon that affect the
normally green leaves of many deciduous trees and shrubs by which they take on
during a few weeks in the autum season various shades of red, yellow, purple,
black, orange, pink, mangeta, blue and brown. (Davies, Kevin M. 2004)
Agronomist is a
specialized person who deals with soil resource and plants scientist (Robert G.
2000)
Plants make an amazing
variety of pigment molecules. There are three types of pigments present in the
leaves of plants and their retention or production determines the colors of
leaves before they fall. These are chlorophyll, carotenoids and anthocynanis which
make up color of leaf from plants
The
followings are the pigments molecules that make up leaf color;
1
chlorophyll(s)
it is a green pigment and responsible for the green
color of foliage and leaves and enabling plants to produce oxygen during
photosynthesis. Chlorosis is a
condition in which leaves produce insufficient chlorophyll, as it is
responsible for green color of leaves. Chlorotic leaves are pale, yellow or
yellow white, yellowing of leaf tissue due to a lack of chlorophyll. The causes
of chlorosis include; poor drainage, damaged roots, high alkalinity and
nutrient deficiencies in the plants. Nutrient deficiencies may occur due to
insufficient in the soil or the nutrients unavailable due to high soil Ph.
2.
Anthocyanins
It adds the color red
to plants, including red apple, cherries and strawberries.
3.
Carotenoids
These are very long
chain water repelling that are synthesized in plastids of plants cells. For example
sunflower, common carotenoids is produced in the chromoplants of ray flowers to
produce bright yellow colors. These pigments primary absorb in the blue
wavelength, allowing the longer wave to be scattered and producing yellow
color.
As
an agronomist, the following information can be obtained from leaf color in farm
land, as factors that influence leaf color appearance:-
Nitrogen
deficiency.
All plants require
sufficient supplies of macro nutrients for healthy growth and Nitrogen (N) is a
nutrient that is commonly limited supply. It’s deficiency in plants can occur
when organic matter with high carbon content, such as sawdust is added to soil organism
use any nitrogen to breakdown carbon sources, making nitrogen unavailable to
plants. This is known as robbing the soil of nitrogen.
Some symptoms of
nitrogen deficiency (absence or less supply);
1.
Chlorophyll content of plant leaves is
reduced which results in paleyellow color, older leaves turn completely yellow.
2.
Flowering, fruits, protein and starch
contents are reduced reduction in protein results in stunted growth and
document lateral buds.
Measures
Fertilizers such as
Amonium, phosphate, calcium, ammonium, nitrate, and urea can be supplied. Also
can be prevented in short term by using grass mowing as a mulch or foliar
feeding with manures and sowing green manures crops such as grazing rye to
cover soil over the winter will help to prevent nitrogen leaching.
Iron
(fe) deficiency
Is a plant disorder
also known Lime induced chlorosis. A deficiency in the soil is rare but iron
can be unavailable for absorption if soil pH is not between about 5 and 6.5 A
common problems is excessive alkalinity of the soil (the pH is above 6.5) also
iron deficiency can develop if the soil is too water logged elements such as
Ca, Zinc, Manganese, Phosphorus or copper can tie up iron if they are present
in high amounts. Iron is needed to produce chlorophyll, hence its deficiency
cause chlorosis (Schuster. J, 2010)
Symptoms;
Leaves turn yellow or
brown in the margins between the veins which may remain green when young leaves
may appear to be bleached fruit would be of poor quality and quantity.
Treating.
Iron deficiency can be
avoided by choosing appropriate soil for the growing conditions for example
avoid growing acid loving plants on lime soils. In by adding well – rotted
manure or compost. If iron deficit chloris is suspect then check pH of the
soils with an appropriate instrument. Take a soil sample at surface and at depth.
If pH is over 7 then consider soil remediation that will lower the pH toward
the 6.5 – 7 range. Remendiation includes adding compost, manures or organic
matter and applying ammonium solphate as nitrogen fertilizer (acidifying
fertilizer due to decomposition of ammonium to nitrate in soil.
Zinc
deficiency
It occurs when plant
growth is limited because the plant cannot take up sufficient quantities of
essential micro nutrient from its growing medium. It is one of the most
widespread micronutrient deficiencies in crops and pastures worldwide and
causes large losses in crop production and crop quality (Alloway B. J 2008)
Deficiency symptoms
Chlorosis; yellowing of
leaves; young leaves are the most affected , example Maize leaves.
Brozing of leaves;
chlorotic areas may turn bronze colored.
Treatment
Therefore, Zinc
sulphate or Zinc oxide can be applied to soils to correct Zinc deficiency,
because severe Zinc deficiency in the maize plants in farm land it turns its
leaves into yellowish color.
Sulfur
(S) deficiency
Sulfur is mobile in plants, rarely immobile in soil,
organic sulfur is converted into available sulfate sulfur by soil bacteria.Also
it is easly leachable and it is
necessary to maintain dark green colour, stimulate seed production, promote roots
and general plant growth. Its deficiency, it occurs is mostly likely on sandy,
low organic matter soils. (Weir, R. 1995)
Symptoms
General; yellowing of
the wholeplant, starting with the younger leaves, plants may be light green or
may be stunted and exihibit delayed maturing. Deficiencies most likely on sandy
soils, lower in organic matter. Crops such as corn has stripping of the upper
leaves notably on young plants.
Turf; general yellowing
of leaves, broadleaf: are entirely pale yellow green in both young and old
plants shorts are stunted.
Phosphorus
It is very mobile in
plants: relatively immobile in soil does not lead, it is stored in seed and
fruits. It is most available to plants between a pH 6 and 7.5 (unavailable in
very acid and alkaline soils). Phosphorus is to stimulate early roots formation
and growth hasten crop maturity, stimulating flowering and seed production.
Deficiency symptoms
General; red or purplish
color (anthocyanin) in leaves especially undersides, roots growth poor, lower stems may be purplish, plants may
exhibit stunting and delayed maturity and loss of leaves..
Crops such as corn have
purplish taint, legumes bluish green and stunted, Tomato has yellowing of
leaves, appearance of purpling on underside of leaf, delayed maturity.
Potassium
(K)
K(potash k2o) is highly mobile in plants
and generally immobile in soil tends to leach. Potassium promote vigor and
disease resistance, helps development of root system, improve plant quality as
well as increase protein production (Pandey, S 2009)
Deficiency symptoms
General: bronzing and
during a leaf margin, some spotting between veins chlorotic with brown spots
throughout leaf. Broad plants: leaves exhibit marginal and interveinal
chlorosis (yellowing) older leaves are affected first leaves may crickle and
roll.
Magnesium
(mg)
Magnesium is mobile in plants, mobile in acidic
soils and fairy immobile above pH 6.5 leaches from soil. Magnesium is necessary
for formation of sugars, proteins and regulate the uptake of other nutrients, example
phosphorus is a component chlorophyll. (Pandey,
S 2009)
Deficiency Symptoms
General: mottled
yellowing between veins of older leaves white veins remain green, yellow areas
may turn brown and die. Yellowing may occur on older leaves which may turn
reddish purple due to low phosphorus metabolish. Deficiencies most likely on
leached sandy, soils and where high levels of Nitrogen (N) and Potassium (k)
have been applied. Broadleaf: leaves are thin, brittle and drop early, redding
of older leaves shoot growth is not reduced until deficiency is severe.
REFERENCES:
Alloway, B. J (200), Zinc in Soil and Crop Nutrition.
Brussels International Zinc
Association and international
fertilizer industry association.
Pandey, S. N, Sinha, B.
K (2009), “Mineral Nutrition” Plant
Physiology: New Delhi,
Schuster , J (2010), Focus on Plant Problems Chlorosis;
university of Illinois Press
VIkas Publishing House Pvt, Ltd.
Weir, R. G, Cresswell,
G. C (1995), Plant Nutrients disorders,
Melbourne: Inkata Press.
Hakuna maoni:
Chapisha Maoni