Appendix: Harvest Loss Calculations

As the price of cotton rises, the value of “fine-tuning” picker operation and adjustment can easily exceed $1,000 per day. Estimating stalk and ground losses of seed cotton after the picker has passed can help determine what additional adjustments should be made. Two methods of estimating losses are (1) gleaning and weighing replicated plots (greatest accuracy) and (2) counting seed.

Seed Count Method of Estimating Picker Loss

  1. Measure and mark several 10-foot sections of representative rows within the field to be harvested.
  2. Count the open bolls on every plant within each 10-foot section of row.
  3. Glean any seed cotton from the ground that fell from the sample row. Count and record the number of seeds in this cotton (preharvest loss).
  4. Randomly select 20 open bolls, cut the stems, and save the bolls from at least five random but representative plants within the 10-foot section. Bolls should be representative selections, considering fruiting positions and relative yield contribution.
  5. Count the number of locks in each of the 20 bolls and then record and determine an average number of locks per boll. If boll rot is significant, estimate the percentage of locks that are hard locks.
  6. Pull one lock of seed cotton from each boll, and count the number of seeds within the locks to estimate an average number of seeds per lock.
  7. Calculate the base seed count for yield by multiplying the number of bolls per 10-foot sample by the average number of locks per boll and then by the average number of seeds per lock.
  8. Harvest the field and again select several 10-foot row sections to glean for composite postharvest, stalk, and ground loss. Maintain a separate count of stalk loss. If you determined hard locks in step 5, count the hard locks still on the stalk and those on the ground (loss due to hard lock).
  9. Count all the seed contained in the cotton gleaned from the post-harvest, stalk, and ground loss samples; record and determine a total seed count.
  10. Divide the number of seeds in each gleaned portion by the total base seed count (step 6) and multiply this number by 100 to obtain the percent loss in each category.
  11. To estimate yield, divide the number of bolls counted per 10-foot section in step 2 by 120 bolls (equals approximately 1 bale per acre). However, this is a very preliminary estimate, which is sensitive to variety and weather.

These are estimates for yield and losses. Boll position on the plant affects boll size, yield from that boll, and picking efficiency. Smaller bolls from the top of the plant may not pick as well as big, open, fluffy bolls from the middle of the plant. Lower bolls, exposed to more weathering, may have locks that have dropped and lost before picking. Improve your estimate precision by increasing the number of sections, length of row, or number of bolls used for the base seed count and the loss sample.

Weight Method of Estimating Loss:
(More applicable to researchers)

  1. From the “Row Length Table” on page 36, for the appropriate row spacing determine or calculate the equivalent row length to represent 1/1,000 acre or 1/100 acre to be gleaned (43,560 square feet per acre; 1/1,000 acre = 43.56 square feet). For a field with a uniform 38-inch row spacing: 43.56 square feet/38-inch row/12 inches per foot = 13.75 feet of row to equal 1/1,000 acre.
  2. Harvest the field with the picker keeping accurate records of lint per acre.
  3. Locate six representative plots within the field to be sampled. Glean the seed cotton from the row length determined in step 1, separating cotton gleaned from the stalks and from the ground in different containers. If preharvest losses are significant, keep weathered seed cotton distinct from ground losses while gleaning. Glean from all rows to be harvested with different row units on the picker. However, gleaning in middles where the tires have been generally results in a lowered amount of ground losses because the tires bury some locks.
  4. Note appearance and condition of the stalks and losses. Noting this may help explain what seem to be irregularities in loss calculations later.
  5. Remove the gleaned seed cotton from the field containers and spread it on a table to dry at standard room temperature (72°F) and humidity for 24-48 hours.
  6. Clean large sticks and burs from the gleaned seed cotton by hand. If a seed cotton fractionation device is available, establish a standard “run time” and clean each of the samples to remove leaves and dirt during the standard run time.
  7. Weigh the seed cotton in grams. Convert grams to pounds (454 grams = 1 pound) and multiply by 1,000 (or 100 if using 1/100-acre plots) to obtain the seed cotton loss per acre. Estimate the turnout (ratio of lint to seed cotton harvested from ginning or assume 38% of the total weight is lint). If a small sample gin is available, the loss samples can be combined and ginned to estimate turnout for the samples. Use this ratio only for the sample turnout, since it may not be representative of the picked seed cotton sent to the gin.
  8. Divide the lint yield per acre by the gin turnout (converted to a decimal) to obtain the seed cotton yield per acre. Add this to the losses in pounds per acre for a total seed cotton yield per acre. Divide the harvested seed cotton by the total seed cotton yield for harvester efficiency. Divide the losses by the total seed cotton yield for picker losses. Multiply these by 100 to obtain the percent loss within each category. Add the losses for a total loss per acre.

Note: 1 gram from 1/1,000 acre is equivalent to 2.2 pounds of seed cotton per acre; 1 gram from 1/100 acre is equivalent to 0.22 pound per acre. Therefore, it is extremely important to glean and clean the samples very carefully. Increasing the number of rows or the multiple lengths of 1/1,000 acre or choosing the 1/100-acre row length in a sample increases the precision of the measurements, if you can justify the increased cost (i.e., time and labor for sample gleaning and preparation). Weather loss is a function of conditions before harvest and is largely an unavoidable loss with the exception of a more timely harvest. Stalk and ground loss from the picker indicate the composite of the picker’s mechanical condition and adjustment and the operator’s proficiency.

Row Length Table:

Row length in feet required to glean for 1/1,000 and 1/100 acre to represent each row unit.

Effective Row SpacingRow Spacing (inches)Row Length (feet) to Glean for:
Row Unit Coverage (inches)Regularly Spaced Row Patterns1/1,000 acre1/100 acre
30
15
17.4
174.2
30
30
17.4
174.2
36
36
14.5
145.2
38
38
13.8
137.6
 
40
13.1
130.7
40
Alternating Skip-Row Patterns
 
 
45
15 with one row skipped for every two planted
11.6
116.2
60
15 with two rows skipped for every two planted
8.7
87.1
45
30 with one row skipped for every two planted
11.6
116.2
54
36 with one row skipped for every two planted
9.7
96.8
72
36 with two rows skipped for every two planted
7.3
72.6
57
38 with one row skipped for every two planted
9.2
91.7
76
38 with two rows skipped for every two planted
6.9
68.8
60
40 with one row skipped for every two planted
8.7
87.1
80
40 with two rows skipped for every two planted
6.5
65.3
50
40 with a 60-inch skip for every two rows planted
10.5
104.5
 

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