# Using 1,000 Kernel Weight for Calculating Seeding Rates and Harvest Losses

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Optimal (target) crop densities | Seed germination and mortality | Calculating seeding rate to achieve target plant density | Seed drill calibration | Shattering and combine losses

The 1,000 kernel (1,000 K) weight is a measure of seed size. It is the weight in grams of 1,000 seeds. Seed size and the 1,000 K weight can vary from one crop to another, between varieties of the same crop and even from year to year or from field to field of the same variety. Because of this variation in seed size, the number of seeds and, consequently, the number of plants in a pound or a bushel of seed is also highly variable.

By using the 1,000 K weight, a producer can account for seed size variations when calculating seeding rates, calibrating seed drills and estimating shattering and combine losses.

Optimal (Target) Crop Densities

Optimal plant densities for crops depend on the crop type, the intended end use for the crop, the region and the growing conditions. Cereals intended for silage, greenfeed or grazing often use higher target densities than grain crops. Similarly, cereals grown as cover crops with forages are seeded at lower plant densities than what is used normally for grain production.

Target plant densities are generally lower in areas of limited rainfall than in areas with plentiful growing season moisture. Higher plant densities can increase crop competitiveness with weeds or can advance maturity by a few days in short season zones. High plant populations, however, can slightly reduce seed size and affect the quality of some crops such as malt barley.

Figure 1. The crop yield and plant density relationship normally follows a pattern

After an initial rapid increase in yield with increasing plant density, there is a plateau of maximum yield over a broad range of plant densities. At very high densities, the yield then declines.

The yield plateau occurs because most crop plants are able to compensate for lower plant densities by increasing branches or tillers, heads or flowers and kernel size. An optimal plant density would be located in the initial part of the plateau, but the exact target would depend on the price of seed and risks.

The target plant densities listed in Tables 1 to 3 are based on trials over many years by different researchers.

Seed Germination and Mortality

To properly calculate the seeding rates needed to achieve target densities, germination tests and 1,000 K weights should be done on all seed lots. An estimate is also needed of seedling mortality to account for seed that germinates but fails to develop into viable plants.

There are many reasons for seedling mortality including disease, insects, excessive fertilizer in the seedrow, improper seeding depth, frost and drought. Unfortunately, seedling mortality can vary greatly from year to year, and field to field.

Mortality in cereals typically ranges from 5 to 20 per cent whereas canola mortality often ranges from 30 to 60 per cent. Since mortality depends on the combination of conditions and practices of individual farms, producers should keep records of emergence (and thus mortality) on their fields.

Calculating Seeding Rate to Achieve Target Plant Density

After a desired target density is chosen, use the actual 1,000 K weight and germination of the seedlot to calculate seeding rates using Equation 1 or 2 below or the seeding rate calculators on Alberta Agriculture’s website.

Steps:

• Choose a desired plant population range from Table 1, Table 2 or Table 3.
• Count out 1,000 seeds and weigh them (grams).
• Estimate a seedling survival rate, which is the germination percentage minus a small amount for seedling mortality (usually 5 to 20 per cent). A common range for estimated cereal seedling survival is 80 to 90 per cent, calculated by subtracting 5 to 10 per cent mortality from 90 to 95 per cent germination.
• Calculate seeding rate in lb/ac or kg/ha for upper and lower limits of target plant density range. The seed drill will then need to be calibrated to fall within this range.
Equation 1 seeding rate (lb/ac) = desired plant population/ft² x 1,000 K wt. (g) ÷ seedling survival rate (in decimal form such as 0.90) ÷ 10.4

Example:
Wheat seeding rate (low end target) =
16 plants/ft² x 35 g ÷ 0.90 ÷ 10.4 = 60 lb/acre

(high end target)= 30 x 35 ÷ 0.90 ÷ 10.4 = 112 lb/acre

Metric formula
Equation 2 seeding rate (kg/ha) =
desired plant population/m² x 1,000 K wt. (g) ÷ seedling survival rate (in decimal form) ÷ 100

Table 1. Cereal seeding rate
 Desired plant population per square meter per square foot (range) 1,000 kernel weight (grams) seeds per pound (average) Wheat Hard red 250 24 (16 - 30) 31 - 38 12,000 - 14,600 CPS 250 24 (18 - 30) 39 - 50 10,800 - 12,000 Durum 210 20 (16 - 24) 41 - 45 10,000 - 11,000 Extra strong 210 22 (20 - 24) 40 - 44 10,000 - 11,000 Soft white 210 20 (18 - 25) 34 - 36 12,600 - 14,200 Barley 2 row 210 22 (16 - 30) 40 - 50 9,000 -11,000 Barley 6 row 210 22 (16 - 30) 30 -45 10,000 -15,000 Oats 250 24 (16 - 30) 30 - 45 10,000 -15,000 Fall rye 250 24 (16 - 25) 30 - 35 13,000 - 15,000 Triticale Spring 310 30 (25 - 35) 42 - 48 9,500 - 10,800 Winter 250 24 (18 - 30) 43 - 46 9,900 - 10,600 Corn Sweet 5 0.5 380 1,200 Grain 6.1 0.6 380 1,200 Silage 7.6 0.7 380 1,200

Table 2. Oilseed seeding rate
 Desired plant population per square meter per square foot (range) 1,000 kernel weight (grams) seeds per pound Canola Polish 70 - 170 7 - 17 2 - 3 151,000 - 227,000 Argentine 40 - 60* 4 - 6* 2.5 - 4 OP 113,500 - 182,000 3 - 4.5 SYN 91,000 - 151,000 3.5 - 5.5 HYB 83,000 - 130,000 Flax 300 - 400 30 - 40 5 – 6.5 70,000 - 91,000
*Newer canola varieties and research have shown lower plant populations can still produce very acceptable yields. However, the "plant population" in this table does not take into account other possible risks to the plant population such as flea beetle depredations, timing of fungicides, swathing, maturity or green seed risk.

Table 3. Special crop seeding rate
 Desired plant population per square meter per square foot (range) 1,000 kernel weight (grams) seeds per pound Pea 75 7 (7 - 9) 125 -300 1,500 - 3,600 Bean 25 2.4 (2.2 - 2.6) 200 - 350 1,300 -2,300 Fababean 45 4.3 (4.0 -4.3) 350 - 425 1,000 - 1,300 Lentil 105 - 147 12 (10 - 14) 30 - 80 5,600 -15,000 Buckwheat 150 14 30 15,100 Safflower 30 - 60 3 - 6 36 12,600 Sunflower Confection 4.5 0.4 175 2,600 Oil 6 0.6 126 3,600

Forage grasses and legumes
In forages, the bulk seeding rate refers to the final weight of seed applied to the land. The bulk seeding rate should be based on a desired seeding density or the number of seeds placed in a meter of row or in a square meter. For good stand establishment, seeding densities should be based on pure live seed (PLS).

Tables 4 and 5 provide the PLS seeding densities for individual grass and legume species. Select from the lower PLS range for drier soil zones and the higher PLS range for higher moisture areas. For example, with meadow bromegrass, a seeding density of 40 PLS/meter of row is appropriate for the Brown soil zone while 70 PLS/meter of row would be suitable for the Black soil zone.

Seeding rates for 15, 23 and 30 cm rows are listed in Tables 4 and 5. These seeding rates are based on the average seeding density for each species listed in the tables. The final bulk seeding rate will reflect other factors such as seed quality and amendments such as seed coatings. The seeding system, broadcast or row seeding, may also influence the final quantity of seed required.

Example:
For pure stands, an initial bulk seeding rate can be obtained with the following formula:

Target PLS seeding rate ÷ per cent PLS (seed certificate) = bulk seed requirements

Meadow brome in 23 cm spacing = 13 kg/ha ÷ 75% PLS = 17.3 kg/ha

Table 4: Forage grass species seeding rate
 Seeding density for pure stands 1,000 kernel weight Seeds per pound Seeding rate PLS kg/ha row spacing in cm PLS/meter of row PLS/m2 (grams) (average) 15 23 30 Bromegrass Meadow 40 - 70 175 - 350 5.22 86,860 19 13 10 Smooth 40 - 70 175 - 350 3.17 142,855 12 8 6 Foxtail Creeping 150 - 200 600 - 900 0.58 785,930 7 4 3 Meadow 130 - 150 600 - 950 1.11 406,810 10 7 5 Fescue Creeping red 90 - 120 400 - 550 1.20 374,800 8 7 4 Meadow 70 - 100 300 - 450 1.97 230,000 11 7 6 Tall 70 - 100 300 - 450 2.20 205,685 12 8 6 Kentucky bluegrass 250 - 300 950 - 1300 0.20 2,176,628 4 3 2 Orchardgrass 180 - 200 700 - 900 1.06 427,127 13 9 7 Reed canarygrass 180 - 200 700 - 800 0.84 537,828 10 7 5 Timothy 150 - 225 650 - 1000 0.39 1,163,000 5 3 2 Wheatgrass Crested (diploid) 30 - 60 130 - 260 1.46 311,147 4 3 2 Crested (tretraploid) 30 - 60 130 - 260 5.15 194,087 7 5 4 Intermediate 30 - 60 130 - 260 5.66 80,066 17 11 9 Northern 30 - 60 130 - 260 3.12 144,975 9 6 5 Pubescent 40 - 60 175 - 260 5.66 80,066 17 11 9 Slender 30 - 60 130 - 260 3.35 134,977 10 7 5 Tall 40 - 60 175 - 260 6.02 75,307 20 13 10 Western 30 - 60 130 - 260 3.94 114,980 12 8 6 Hybrid grass Hybrid brome 40 - 70 175 - 350 4.99 90,821 18 12 9 Hybrid wheatgrass 30 - 60 130 - 260 3.84 117,980 12 8 6

Table 5. Forage legume species seeding rate
 Seeding density for pure stands 1,000kernel weight Seeds per pound Seeding rate PLS kg/ha row spacing in cm PLS/meter of row PLS/m2 (grams) (average) 15 23 30 Alfalfa 40 -120 175 - 550 2.00 226,760 11 7 5 Birdsfoot trefoil 100 -150 450 - 650 1.23 369,777 10 7 5 Cicer milkvetch 70 - 90 300 - 400 3.70 122,539 19 13 9 Clover Alsike 160 750 0.67 680,283 7 5 4 Red 110 -130 450 - 550 1.67 272,108 13 9 7 Sweet 80 - 120 350 - 550 1.75 258,516 12 8 6 White 160 750 0.58 775,867 6 4 3 Sainfoin 40 - 60 175 - 250 19.96 22,716 65 43 33
To convert PLS/meter to PLS/ft of row, divide by 3.28; to convert PLS/M2 to PLS/ft2 , divide by 10.80.

To evaluate seeding success, new seedings should be inspected in the year of seeding and the following spring to confirm stand density. Table 6 provides an estimate for forage seedling densities for first-year stands.

Table 6.
 Suggested seedling density (plants/m2 ) Soil zones Legumes Grass/legume(50:50) Grass Black 80 -100 80 -100 100 -160 Dark Brown 60 - 100 60 - 100 100 -160 Brown 30 - 50 20 - 40 20 - 40 Grey Wooded 40 - 50 30 - 40 40 - 50 Irrigation 150 - 250 150 - 200 200 - 300 To convert plants/m2 to plants/ft2, divide by 10.80
Source: Alberta Agriculture and Food forage staff, AFSC Crop Insurance

Further information on forage establishment can be obtained from the factsheet Perennial Forage Establishment in Alberta, Agdex 120/22-3. Assistance in developing forage seed mixtures can be obtained through the use of the Forage Seed Mixture Calculator found in the “calculators” section of Alberta Agriculture and Forestry website.

Seed Drill Calibration

Once the desired seeding rate is calculated, the next step is to calibrate the seed drill so that it drops the right amount of seed. The following formula tells you how many grams of seed should be collected from one drill run after driving a distance of 100 feet. To make this measurement easier, stake out the distance or count the number of turns of the front tractor tire makes over the required distance.

Formula:
Seed weight per 100 feet of row (grams) = seeding rate (pounds per acre) x row spacing (inches) ÷ 11.5

Metric formula:
Grams of seed per 100 m of row = seeding rate (kg/ha) x row spacing (cm) ÷ 10

Shattering and Combine Losses

The following tables can be used to calculate yield losses of five crops with a range of 1,000 K weights.

 Average number of seeds per square foot to equal a 1 bushel per acre loss (g) Wheat Oats Barley 1,000 K weight of crop (grams) 25 24 13.6 30 20 11.3 16 35 17.1 9.7 13.7 40 15 8.5 12 45 13.3 7.6 10.7 50 12
.
 Average number of seeds per square foot to equal a 1 bushel per acre loss (g) Canola (g) Peas 1,000 K weight of crop (grams) 2 261 1,000 K weight of crop (grams) 125 5 2.5 208 150 4.2 3 174 175 3.6 3.5 149 200 3.2 4 130 225 2.8 4.5 116 250 2.5 5 104 275 2.3

A range of seeding rate calculators can be accessed through the Alberta Agriculture and Forestry website. Look under “calculators” and then “seeding.”
• barley
• wheat
• oats
• triticale
• fall rye
• winter wheat
• winter triticale
• peas, pulses
• forages

Prepared by
Alberta Agriculture and Forestry

Source: Agdex 100/22-1. Revised May 2018.