Here an explanation, although not namely referred to the cotton.
Absolute Growth Rate (AGR), if referred to the size of a plant, represents the increase in its mass per unit of time: AGR = g day-1.
If referred to the number of organs it is a change in the number, usually an increase, per unit of time. In individual plants it is used to describe the growth as an increase in the number of roots, leaves, flowers (e.i. cotton) or other discrete organs.
AGR is the simplest index to measure plant growth rate. However, it has limitations due to the fact that it can be used only to compare growth of vey similar plants (es. with the same age or initial size).
Relative Growth Rate (RGR) takes into account the original difference in size of plants, which may have a significant influence on the increase in dry mass, and also the different performances due to the ageing of plants.
RGR = mg g-1 day-1 (g is the existing mass of the plant)
RGR is formed by two components: the leaf area ratio (LAR), which is the amount of leaf area per unit total plant mass, and the net assimilation rate (NAR), which is the rate of increase in plant mass per unit leaf, then it can be expressed as:
RGR = LAR * NAR
Crop Growth Rate (CGR) is referred to a whole crop, so you need to consider the area of the ground where crop is present.
CGR = g (crop) m-2 d-1
It can be calculated as
CGR = NAR * LAI
Where LAI stands for Leaf Area Index
The more optimal plant population density is, with a closed canopy, the greater photosynthesis and conversion of photosynthetic products to yield is.
I hope I have given you a help
All the best
Crop growth rate, Absolute growth rate and Relative growth rate?
crop growth rate: it is measured as mass increase in crop biomass per unit ground area per unit time. Equation for that is, CGR= W2-W1 / t1-t2
Absolute growth rate. Simply it is measured as total increase in plant weight over given period of time. Equation for that is, (W2-W1) / (t1-t2)
where as, W1 and W2 are plant weight at corresponding time t1 and t2,
Relative growth rate: it is measured as rate at which dry matter accumulated in plant that is related to a total dry weight at given period of time or measured as mean of relative growth rate b/w two points. Equation for that is, RGR=(InW2-InW1) / (t2-t1)
where as,
In=natural logarithm
t1=time one (in day)
t1=time two (in day)
W1=dry weight of plant in grams at one time
W2=dry weight of plant in grams at two time
Dear, these different ways in which plant growth is measured around the world, however they not sufficient and proper. Modern agriculture is changing in every one minute, there for a researcher should not hesitate to use own thinking and ideas for plant growth measurement. if you have an other great technology/own thinking to measure growth of plant more best compare to CGR, RGR, AGR, LAI, ULR. You must use.
A little work i am sharing with you, find attachment.
Article Invent of SAU-Growth Meter for the Production of Wheat Crop ...
Nice thinking by Shah Jahan Leghari. We should not be bound to use old thoughts and technologies, if anyone has new technology, he should share and don't care about the world.
Absolute growth rates: These are simple rates of change involving only one plant variate and time, examples being the whole plant's rate of dry weight increase, or the rate of increase in number of roots per plant. Most commonly applied to total dry weight or total leaf area per plant.
Instantaneously, G = dW/dt. The mean value over the interval t1 to t2 is
given by
G ̅=(W2-W1)⁄(t2-t1)
Relative growth rates: These are more complex rates of change, but still involve only one plant variate and time, an example being the whole plant's rate of dry weight increase per unit of dry weight. This allows more equitable comparisons than an absolute growth rate. Normally, RGR deals with total dry weight, but other measures of size may be used. In the fi.nancial world, RGR is analogous to the rate of compound interest earned on capital. Negative RGRs are relative decay rates.
Instantaneously, R = (1/W)(dW/dt). The mean value over the interval t1 to t2 is given by
R ̅ = (loge W2-loge W1)/(t2-t1).
Crop Growth rate:
An index of the productive efficiency of land area in producing plant biomass. An index of agricultural productivity due to D. A. Watson. Applicable only to plants growing together in closed crops stands or in natural communities.
Instantaneously (1/P)(dW/dt). Because P (unit land area) is not a plant growth variable, the usual formula for mean values of compounded growth rates does
not apply. Mean values are given by the simpler formula
C ̅ = (1/P)x(W2-W1)/(t2-t1).
Source: Basic growth analysis by Roderick Hunt
ABSOLUTE GROWTH RATE IN SIZE (AGR)
Underlying concept: The simplest index of plant growth; a rate of change in size, an increment in size per unit time. Most commonly applied to total dry weight or total leaf area per plant.
Symbol and definition G, the rate of increase of total dry weight per plant, W.
Dimensions and units MT-\ e.g. gday-1.
Formulae Instantaneously, G = d Wjdt. The mean value over the interval h to t2 is given by
G= (W2-W1)/(T2-T1).
Methods of calculation:
Instantaneously derived from functions fitted to W versus t; if W = fw(t), then G = fw'(t). Mean values are obtained from the separate destructive estimates W1 and W2 made at times hand t2 respectively.
CGR, AGR, RGR,RWC, and Chlorophyll content measuring procedures
Crop growth rate (g m-2 day-1)
Crop Growth Rate is referred to a whole crop, so you need to consider the area of the ground where crop is present.
Crop growth rate: it is measured as mass increase in crop biomass per unit ground area per unit time.
Equation for that is, CGR= W2-W1 / t1-t2
Instantaneously (1/P or GA) (dW/dt). Because P (unit land area or Ground area) is not a plant growth variable, the usual formula for mean values of compounded growth rates does Not apply. Mean values are given by the simpler formula
C ̅ = (1/P) x (W2-W1) / (t2-t1).
UNIT CGR = g (crop) m-2 d-1
It can be calculated as
CGR = NAR * LAI
Where LAI stands for Leaf Area Index
PROCEDURE
One meter long row will be selected in each subplot, harvested, sun dried and weighted. Data will be recorded at three growth stages i-e in case of maize crop (pre tasseling, tasseling and physiological maturity) of crop. CGR will be measured by the following formula:
CGR = W2 – W1/ T2 – T1 x 1/GA (g m-2 day-1)
W1 = Weight at T1 of the period
W2 = Weight at T2 of the Period
T1 = Time in date at the start of the period
T2 = Time in the date at the end of the period
GA = Ground area
Absolute growth rate (AGR)
If referred to the number of organs it is a change in the number, usually an increase, per unit of time. In individual plants it is used to describe the growth as an increase in the number of roots, leaves, flowers or other discrete organs.
AGR is the simplest index to measure plant growth rate. However, it has limitations due to the fact that it can be used only to compare growth of vey similar plants (es. with the same age or initial size).
Absolute Growth Rate (AGR), if referred to the size of a plant, represents the increase in its mass per unit of time: AGR = g day-1.
Absolute growth rate. Simply it is measured as total increase in plant weight over given period of time. Equation for that is, (W2-W1) / (t1-t2)
Whereas, W1 and W2 are plant weight at corresponding time t1 and t2,
Absolute Growth Rate (AGR), if referred to the size of a plant, represents the increase in its mass per unit of time: AGR = g day-1.
These are simple rates of change involving only one plant variate and time, examples being the whole plant's rate of dry weight increase, or the rate of increase in number of roots per plant. Most commonly applied to total dry weight or total leaf area per plant.
Instantaneously, G = dW/dt. The mean value over the interval t1 to t2 is
Given by
G ̅= (W2-W1) ⁄ (t2-t1)
Procedure:
One meter long row from the border rows in the each subplot will be cut and then it will be dried at 70 0C for 72 hours to calculate their dry weight at (1) pre tasseling (2) tasseling (3) physiological maturity (in case of maize cop). The following formula will be used for the absolute growth rate.
AGR = W2-WI / T2-T1
W1 = Weight at T1 of the period
W2 = Weight at T2 of the period
T1 = Time and date of the period
T2 = Time and date at the end of the period
Relative Growth Rate: (RGR) takes into account the original difference in size of plants, which may have a significant influence on the increase in dry mass, and also the different performances due to the ageing of plants.
RGR = mg g-1 day-1 (g is the existing mass of the plant)
RGR is formed by two components: the leaf area ratio (LAR), which is the amount of leaf area per unit total plant mass, and the net assimilation rate (NAR), which is the rate of increase in plant mass per unit leaf, then it can be expressed as:
RGR = LAR * NAR
RGR = mg g-1 day-1 (g is the existing mass of the plant)
RGR = LAR * NAR
CGR = NAR * LAI
Relative growth rate:
it is measured as rate at which dry matter accumulated in plant that is related to a total dry weight at given period of time or measured as mean of relative growth rate b/w two points. Equation for that is, RGR=(InW2-InW1) / (t2-t1)
where as,
In=natural logarithm
t1=time one (in day)
t1=time two (in day)
W1=dry weight of plant in grams at one time
W2=dry weight of plant in grams at two time
Dear, these different ways in which plant growth is measured around the world, however they not sufficient and proper. Modern agriculture is changing in every one minute, there for a researcher should not hesitate to use own thinking and ideas for plant growth measurement. if you have another great technology/own thinking to measure growth of plant more best compare to CGR, RGR, AGR, LAI, ULR.
Relative growth rates: These are more complex rates of change, but still involve only one plant variate and time, an example being the whole plant's rate of dry weight increase per unit of dry weight. This allows more equitable comparisons than an absolute growth rate. Normally, RGR deals with total dry weight, but other measures of size may be used. In the fi.nancial world, RGR is analogous to the rate of compound interest earned on capital. Negative RGRs are relative decay rates.
Instantaneously, R = (1/W) (dW/dt). The mean value over the interval t1 to t2 is given by
R ̅ = (loge W2-loge W1)/ (t2-t1).
Chlorophyll Content
For measuring the chlorophyll content in the leaves, SPAD meter by Atleaf Company was used.
Relative water contents (%)
Fully expanded leaf from top will be taken from each treatment. Fresh weight (0.5 g) of each sample will be taken. Leaves should be dipped in the water for 14 h, wiped with tissue paper to record the turgid weight. Leaves then be dried at 70oC to get dry weight. Relative water contents (RWC) will be calculated by using the following formula of Barr and Weatherley (1962):
Fresh weight – Dry weight
Relative water contents = --------------------------------- x 100
Turgid weight – Dry weight
Dry matter partitioning
Dry matter partitioning is determined by harvesting randomly 1 meter area at pre tasseling and physiological maturity (in case of maize crop) from the each plot. Harvest material alienated into leaves, stem, cob, tassel and grain. Then materials will be oven dried at 70 C° for 24 hrs and their weight will be noted and converted into m-2.
Alessandro Romano Nice explanation. So can we conclude that AGR and Growth Index are same.
While Growth rate and CGR are same.
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