Checking Population and Scouting Weeds

Erin Eagen

Now that planting is done or wrapping up, it is time to get out and start walking fields. Here are some things you should be looking for and what we are seeing. Start checking your stand in corn and soybeans, though some soybeans are still emerging. To check the population for corn measure out 17 feet 5 inches then count the plants. So for example, if there are 32 plants within the 17’5”, it would be the equivalent of having 32000 plants per acre this is if you plant 30” corn. In the chart below, you will find the measurements you need to take a stand count if you are planting different row widths in corn.

Row Width (inches)

Row Length equal to 1/1000th of an   acre

15

34 feet 10 inches

20

26 feet 2 inches

30

17 feet 5 inches

36

14 feet 6 inches

38

13 feet 9inches

For soybeans I have found that the best way to check populations is to use a 34inch hula-hoop while correlates to certain populations per acre. It is possible to use different sizes of hoop as the below chart indicates.

Hoop Inside Diameter

Area of Hoop

Factor to multiply number   of plants within hoop to equal:

(in)

(ft2)

Plants per Acre

Plants per Hectarce

20

2.18

19977

49342

21

2.40

18119

44755

22

2.64

16510

40779

23

2.88

15105

37310

24

3.14

13873

34265

25

3.41

12785

31579

26

3.69

11820

29197

27

3.97

10961

27074

28

4.27

10192

25175

29

4.58

9501

23468

30

4.91

8878

21930

31

5.24

8315

20538

32

5.58

7803

19274

33

5.94

7338

18124

34

6.30

6912

17073

35

6.68

6523

16112

36

7.07

6166

15229

37

7.46

5837

14417

38

7.87

5534

13668

39

8.29

5254

12976

40

8.72

4994

12336

Some may ask, why check population after it is planted? Walking the field gives a good indication about skips and doubles and overall performance of a planter and what may need to be adjusted for the next year. While out walking fields we are also checking for weed pressure. As of late we are seeing a wide spectrum of weeds including lambsquarters, ragweed and redroot pigweed. In certain pockets we are seeing above normal populations of ragweed. Now with the rain not only will there be a decent amount of growth in your crops but also in the weeds present. It is essential to have your field scouted or scout them yourself. Now is the optimal time to spray to control the different weed pressures. Make sure you know what weeds you are trying to control when choosing herbicides. If you need suggestions on how to most effectively control certain weed do not hesitate to contact your Veritas Agronomist.

lambsquarter  lambsquarter

ragweed ragweed

redroot pigweed redroot pigweed