Many Kansas wheat fields that have already been planted might end up with poor stands due to the prolonged wet and cool period observed in the first few weeks of October. These cool and damp conditions can influence seed viability and have delayed emergence in many fields. Unfortunately, there is not much that can be done at this time. Right now, the best thing we can do is wait to see what proportion of the plants emerge, and critically evaluate whether the plant population is sufficient to meet our yield goals. Below, we outline some steps to assess the need for replanting in the near future.
Figure 1. Slow and scattered wheat emergence in a field planted October 2, 2018 near Belleville, Republic Co., Kansas. Photo taken October 18, 2018 by Andrew Esser, K-State Research and Extension.
In many cases, the emergence is “spotty” with lower areas in the field presenting worst stand establishment (Fig. 2). These low-lying areas are typically not as well drained as other areas in the field. These areas can become saturated quickly resulting in a low oxygen soil environment that suppresses seed germination and seedling growth. In other fields, the upper portions of the soil were hardened by heavy rains. This “soil crusting” can prevent the coleoptile from breaking through the soil surface. If the coleoptile has not been able to break through to the soil surface within 7-10 days, the health of the young plants will decline rapidly. At that point, the producer will need to consider replanting.
Figure 2. Poor wheat emergence in lower portions of a wheat field in Saline County, Kansas. Higher areas, as seen in the back of the photo, tend to have good emergence and stand establishment. Photo taken mid-October 2017 by Tom Maxwell, Extension Agent for the Central Kansas District.
Factors to consider when making replant decisions in wheat include: stand uniformity, actual stand compared to the target stand, replanting date, weed control, and insurance cutoff date.
Recent K-State research indicates that approximately 900,000 emerged plants per acre are needed for most varieties to maximize yields under normal fertility conditions in Kansas. Thus, if producers are not aware of their target plants per row foot, the above threshold might be a good goal for central Kansas producers.
Table 1. Target plants per row foot (80% emergence) based on seeding rate, seed size, and row spacing.
Seeding rate |
Seed size |
Row spacing (inches) |
||||
6 |
7.5 |
8 |
10 |
12 |
||
lb/ac |
seeds/lb |
Target plants per row foot (80% emergence) |
||||
45 |
12,000 |
5 |
6 |
7 |
8 |
10 |
14,000 |
6 |
7 |
8 |
10 |
12 |
|
16,000 |
7 |
8 |
9 |
11 |
13 |
|
18,000 |
7 |
9 |
10 |
12 |
15 |
|
60 |
12,000 |
7 |
8 |
9 |
11 |
13 |
14,000 |
8 |
10 |
10 |
13 |
15 |
|
16,000 |
9 |
11 |
12 |
15 |
18 |
|
18,000 |
10 |
12 |
13 |
17 |
20 |
|
75 |
12,000 |
8 |
10 |
11 |
14 |
17 |
14,000 |
10 |
12 |
13 |
16 |
19 |
|
16,000 |
11 |
14 |
15 |
18 |
22 |
|
18,000 |
12 |
15 |
17 |
21 |
25 |
|
90 |
12,000 |
10 |
12 |
13 |
17 |
20 |
14,000 |
12 |
14 |
15 |
19 |
23 |
|
16,000 |
13 |
17 |
18 |
22 |
26 |
|
18,000 |
15 |
19 |
20 |
25 |
30 |
|
120 |
12,000 |
13 |
17 |
18 |
22 |
26 |
14,000 |
15 |
19 |
21 |
26 |
31 |
|
16,000 |
18 |
22 |
24 |
29 |
35 |
|
18,000 |
20 |
25 |
26 |
33 |
40 |
Figure 3. USDA 2018 crop year final planting date for wheat. Crops planted before the dates above can be insured with no reduction in coverage or adjustment to premium. The final planting date for wheat is generally 15 days after the dates above, at a reduction in coverage of 1% per day during the period between initial and final plant date.
Romulo Lollato, Wheat and Forages Specialist
lollato@ksu.edu
Erick DeWolf, Extension wheat pathologist
dewolf1@ksu.edu
Tags: wheat replanting