Introduction
Data collection is very important in determining the agronomic characteristics of rice varieties.
Significant figure
Standard of significant figure of observation is that figure of data between smallest and biggest is between 30 and 300.
For example: the tallest plant height is 160.5 cm and the shortest plant height is 50.5 cm. If we measure plant height by mm, 1605 – 505 =1100. So it is ok for us to measure by cm (16050 =110). 110 is between 30 and 300.
It is not needed to show many numbers’ place after the decimal point for mean of data collected (hundredth’s place, thousandth’s place, ten thousandth’s place, and more than those are not needed for showing means of rice agronomic data)
Important: Select the samples for data collection
Do not select the hills next to missing hills for the samples. The hills next to missing hills usually grow better than normal hills (more number of tillers and grains, higher plant height).
3.1. Plant height
Height is measured by holding your meter stick from the soil surface to the tip of the tallest plant
Measuring
Step 1: Grab gently all plants in the hill with single hand.
Right way of grabbing Wrong way of grabbing
Step 2: Carefully raised the plants up to determine the tallest plant in the hill.
Step 3: Place your meter stick right on the soil surface close to the hill and take measurement of the tallest plant in the hill.
Step 4: Record the reading on a plant height data sheet.
Note: Before going to the field, write the number on your meter stick as shown in photo below to save a time to read and record in the field.
3.2. The number of tillers
Counting the number of tillers will help in understanding the timecourse change of the number of tillers, the time of the maximum tiller number stage, and so on. To get accurate and more precise data, it is advisable to count the number of tillers weekly if you need collect the data of timecourse change of the number of tillers.
Step 1: Hold the hill on which tillers are to be counted
Step 2: Count the total number of tillers in the hill
Step 3: Record the total number of tillers in each hill in your data sheet
3.3. Leaf age development
This is can be determined the number of leaves produced by the rice variety from each principal culm from the first leaf to the flag leaf. If we want to know the time of the panicle differentiation stage and the speed of leaf development, it is advisable to observe the leaf age weekly.
Step 1: Marking on the leaves.
Mark on the 3^{rd} leaf of the healthiest plant within the hill with a permanent marker.
Timing of the marking on the 3^{rd} leaf is around 10 to 14 days after seeding
Remember to replace the mark leaves before they drop. It is advisable to make every 3 leaves like 6^{th} leaf, 9^{th} leaf, 12^{th} leaf, and so on to avoid wrong reading.
Do not mark the tip of the leaf to avoid missing the marked leaf by insect cut or dryingup. It is advisable to mark partially near the base of the leaf.
Do not mark the entire leaf but partially (1 to 2 cm is enough) on the leaf near the base.
Step 2: Reading the leaf age (please refer the figure below)
Count the number of the developed leaves in the main culm so far (The last marked leaf helps to count quickly).
Divide the developed leaf just before the last leaf into imaginative 8 portions.
Read the length of last growing leaf against the divided leaf (developed leaf): imaginatively determine at which portion it fall within divided portions of the developed leaf
Example (Leaf age 8.4): Leaf No.8 is divided into 8 portions. One portion is as a 0.1 leaf age. If the last leaf developing, which is leaf No.9, is growing around half way of the leaf No. 8, the leaf age is 8.4.
Note: In case the emerging leaf is growing longer than the developed leap, you read 8.9 or 9.0 depending on the length of an imaginative portion of the developed leaf.
Example: how to determine the leaf age of rice plants(in case leaf age is 4.5)
3.4. Heading Date Observation
The heading date is one of the most important agronomic characteristics. Heading date is that the percentage of the headed culms reached to the 50 % of the total number of fertile tillers. Heading is when panicles start emerging from the sheath. The date when 10 % of the plants in a plot show heading is called the “first heading date”, while the date when heading takes place in 50% of the plants is called the “heading date”. This heading date is regarded as the heading time of each plot. The date when more than 90% of the plants in a lot have ears is called the “full heading date”. The heading period is the period from the first heading date to the full heading date. This period is shorter when the number of ears per plant is smaller, and longer when the number is greater. It is usually longer under low temperature conditions than the under high temperature ones (partly modified the sentence in p.341 Vol.1 Science of the Rice Plant).
There are two methods of heading date observations. It is advisable to use the method 1 for field trial with many varieties to save your time.
Method 1: Determining heading date by general overview estimation
Step 1: Stand over the plot in which heading is to be observed.
Step 2: Carefully look around for any panicles emerging in the plot.
Step 3: Record the date when you observed the first panicle in the plot as an initial heading date.
Step 4: Survey and estimate the total number of fertile tillers in the plot from booting, flag leaf, and so on.
Step 5: Estimate percentage of heading (the number of emerged panicle/ the total number of fertile tillers).
Step 6: Determine if the heading percentage reaches to 10%, 50%, and 90% in your estimation.
Step 7: Record the date when the heading percentage reaches to 10%, 50%, and 90% in your estimation.
Step 8: Calculate the number of days from sowing date to each heading percentage.
Step 9: Calculate the duration between the “first heading date” and the “full heading date”
Note: Data sheet should be arranged as same as the field layout to collect data efficiently in the field, to avoid mistaking the data collection, and to save your time. Do not make the sheet according to the material number.
Method 2: Determining Heading Date based on selected samples
Step 1: Select 5 to 10 average growing hills within the plot for heading date observation.
Step 2: Count and record the number of panicles headed in the selected hills every day until the end of heading.
Step 3: Calculate the number of heading against the total number of panicles for each observed day and convert them to percentage.
Step 4: Find the date exceeding the heading percents of 10%, 50%, and, 90% as shown below.
Step 5: Determine each heading date (10%, 50%, and 90%).
Step 6: Calculate the number of days from sowing date to each heading percentage.
Step 7: Calculate the duration between the “first heading date” and the “full heading date”
3.5. Colum length, panicle length, and the number of panicles
The data on the culm length, panicle length, and the number of panicles are usually collected before harvesting.
(1) Culm length
Measure the culm length of the tallest plant in the hill from soil surface to the neck node (panicle base node).
Step 1: Grab gently all plants in the hill with single hand.
Step 2: Carefully raised the hand up to determine the tallest plant in the hill.
Step 3: Place your meter stick right on the soil surface close to the hill and take measurement of the culm length (from soil surface to neck node (panicle base node)) in the tallest plant in the hill
Step 4: Read and record by the 0.5 cm.
(2) Panicle Length
Measure the panicle length of the tallest plant in the hill from the neck node (panicle base node) to the end of the panicle.
Step 1: After finishing measurement of culm length, measure the panicle length above the same culm.
Step 2: Stretch out the panicle on the meter stick.
Step 3: Measure and record by 0.2 cm.
(3) The number of panicles
Count and record the number of panicles except panicles shorter than the half of culm length and late emerging heads.
3.6 Yield and yield component
Most of us are interested in the yield of variety. The yield is composed of the number of hills per area (1 m^{2} is usually used for it), the number of panicles per hill, the number of spikelet per panicle, the percentage of ripened kernels, and a kernel weight (1000 kernels weight is usually used for it).
The number of hills is determined at planting (at seeding). The value of the other components depends on various environmental conditions during growth. The tillers which develop in an early growing stage of a plant usually grow vigorously, produce panicles at the tip of the stem and finally contribute to the yield as productive tillers. The number of panicles in a yield component depends largely on the number of tillers (p.222. Vol. 1. Science of the Rice Plant). The number of spikelets per panicle and the percentage of ripened kernels are closely related with cultivation environment at the panicle formation stage and meiotic stage, respectively.
For yield analysis between varieties we usually use yield per unit area in the plot (hereafter it is called “the netted yield”). It is advisable to use the results of yield components as a diagnosis and/or analysis tools of the results of yield and your cultivation in the field. We can improve the cultivation method and field management in the next season based on the results of yield component analysis.
(1) Yield data collection
We harvest a sample per unit area (netted yield) and for yield component analysis separately in a plot. In case of variety trial, we use entire area of the plot for the yield analysis except for two border rows from each side because a plot size is relatively small such as 3 x 3m, 4 x 4m, 4 x 5m etc.
Growth and yield of rice plant in border area are usually better than ones growing inside of the plot because they can receive more sun shine and nutrient.
Step 1: Discard two border rows from each side of the plot.
Step 2: Prior to harvest the netted area in a plot, harvest samples for yield component analysis in the plot.
 Select the 20 hills in each plot for data collection.
 Measure the culm length, panicle length, and count the number of panicles per hill of the 20 hills.
 Calculate the mean of the number of panicles per hill of the 20 hills.
 Determine 12 hills with average panicle hills and/or the nearest average hills.
 Harvest the 12 hills, and put them apart for yield component analysis (a).
Step 3: Harvest the netted area to survey the netted yield and put them in a harvesting bag with name tag of the plot number and treatment.
Step 4: Dry them gradually in the airy shade.
Step 5: Thresh and winnow them, and obtain filled kernels
Step 6: Weigh the samples and record the weight.
Step 7: Measure immediately their moisture content 3 times after weighing, and record them
Step 8: Compute the weight adjusted to the 14% of the moisture content using the formula shown below = (b)
Step 9: Wait for results of weight for ripe kernels of the 12 hills in the yield component data. Compute the weight of it adjusted to the 14% of moisture content resulted from (c) in the Step 6 and (f) in the Step 10 for yield component data collection shown below.
Step 10: Add the kernels weight for yield component analysis (result of the Step 9) to the kernels weight for netted yield (result of the Step 8 shown above).
(2) Yield component data collection
Step 1: Dry 12 hills harvested in step 2 of the yield data collection = (a), gradually in the airy shade
Step 2: Thresh the samples after drying
Step 3: Prepare water in the bucket (sevententh of water against the depth of the bucket)
Step 4: Put the all grains threshed in Step 2 into the water and separate ripened kernels from infertile grains (floating grains)
Step 5: Dry gradually them again in the airy shade
Step 6: Weigh the total ripened kernel weight after drying = (c)
Step 7: Count the number of floating grains (infertile grains) = (d)
Step 8: Weigh out 2 grams of filled kernels for 3 samples from (c).
Step 9: Count the number of grains in each 2gsample of filled kernels = (e)
Step 10: Measure the moisture contents of each 2gsample of filled kernels and compute the mean of them = (f)
Step 10: Compute the mean of the number of 2gsample of filled kernels from (e) = (g)
Step 11: Compute the total number of filled kernels in the sample from the results of (c) and (g) = (h)
Step 12: Determine the total number of the grains in the sample from the results of (d) and (h) = (i)
Step 13: Determine the number of spikelets per panicle using results from (i)/ the number of panicles
Step 14: Determine the percentage of the ripened kernels using results from (h) and (i)
Step 15: Determine the 1000 grains weight from (e) and (f)
Step 16: Determine the yield from each component of the yield.
Note: If you want to check the number of spikelets every panicle and/or the status of the spikelets in a panicle, count the number of spikelets on the panicle before threshing.
Note: Moisture contents of filled kernels should be measured immediately after weighing the kernel weight and measure 3 times continuously at the same time. Do not take time intervals between measurements of the replicate to avoid changing the moisture contents of kernels.
Example:
Information: Calculation of the yield component:
NOTE: Consider the relationship between the yield components and growth stage
 the number of hills per unit area
 the number of panicles per hill,
 the number of spikelets per panicle,
 the percentage of ripened kernels,
 a kernel weight (1000 kernels weight).
Below are illustrative pictures of various steps in obtaining grain samples.
1. Threshing

2. Separating ripe grains from infertile grains
3. Drying the grains after separation
4. Counting the grains
5. Measuring moisture content of grains
Note: Flesh water can be used for separation instead of salt water.
Note: Be careful not to that the grains are not blown away by the wind when they are dried after the separation.