ISSUE 10  July 16, 2009

HAIL AND CROP INJURY

During the last weekend in June there were a number of strong storm systems that moved through the state. Heavy rainfall pounded northeastern North Dakota and hail was reported in a number of areas. The hail hit some of my trial plots and damaged soybean and corn plants. Most crops will recover to produce a crop if weather conditions are favorable. Injured plants need about one week to show whether they will recover or not. Small dormant buds, present on the plant, must begin to grow and replace the lost and damaged tissue before it will become clear if the injured plants will recover and to what extent.


Soybean plants four days after hail damage.

If the hail damage is 100 percent, you might decide to fallow the field for the rest of the season or replant to another crop (cover or hay crop) but it is too late in the season to replant the same main crop. Limited crop choices include millet for seed and Sudan grass for pasture or hay if seeded by mid-July, but reduced yields must be expected. The producer should take into consideration the availability soil moisture, the loss of surface moisture in preparing a seedbed after hail injury to the earlier crop, whether the reseeded crop will germinate quickly, and the expected financial return on the reseeded crop. If there was too much moisture it is a good idea to plant a crop to use some of the excess moisture in preparation for next year’s crop.

If the crop has hail damage it should still be kept free of weeds to allow plants to recover successfully. Because of the opening of the canopy, weeds will benefit from the available sunlight and start to compete with the main crop.

Soybean

Soybeans will recover from hail damage if the plants are not cut off below the first node (where the cotyledons were attached). The cotyledonary node has two cotyledons (seed leaves), which are directly opposite each other at the bottom of the main stem. The unifoliate node has two unifoliolate (single oval shaped leaves) directly opposite each other. All nodes above the unifoliolate node have trifoliate leaves (three leaflets make up one leaf). If the dominant growing point is damaged, (for instance by hail or deer feeding) the dormant growing points, located in the axil of the leaf and the stem, will be stimulated to grow.

If 50 percent of the leaf area is removed due to hail before the plant begins to flower, the yield loss is only limited. However stand reduction and weed competition are critical issues in the eventual yield potential. If hail damage occurred at the eight leaf stage (V8) of growth and if the terminal bud is not damaged, plants can still recover but maturity may be delayed.

Sunflower

If the established stand of sunflower after seeding was good and an early season hail reduced the stand, the yield will not be reduced unless the stand reduction exceeds 50%. This is because the remaining sunflower plants are able to producer larger heads and compensate for the reduction in plant numbers. However, if the terminal bud or head of the sunflower is injured by hail, the plant tends to produce a few smaller heads from buds in the leaf axils and stems. These heads do not contribute much to crop yield. Maturity of sunflower is delayed after significant hail injury.

It is amazing how much leaf tissue can be removed from the sunflower plant in the vegetative stage before there is a significant yield reduction. The growth stage at which the damage to leaf tissue occurs determines the effect on yield reduction. Table 1 indicates that the most sensitive growth stages are R3-R5.

Table 1. Approximate percent yield reduction from plants with 25, 50, 75 or
100 percent total leaf area destroyed at several stages of sunflower plant development.

Growth Stage

Percent leaf area destroyed

25

50

75

100

-Approximate percent yield loss -

V3

1

3

5

15

V5

2

4

7

21

V11

3

5

9

24

V12-Vn

4

6

15

35

R1

5

7

20

47

R3

10

24

51

99

R5.2-5.9

5

16

43

90

R7

1

10

17

22

R9

0

0

0

0


Viewing R3 from the top. Source: NDSU Ext. Bulletin 25.


Sunflower at approximately R5.7. (Hans Kandel)

Hans Kandel
NDSU Extension Agronomist, Broadleaf crops
hans.kandel@ndsu.edu

 

CORN GROWTH IN 2009 LOOKS A LOT LIKE 2008!

Corn growth is starting to accelerate. Fields planted before the end of May are starting to form a complete canopy and most fields have a nice dark green color. The rate of corn growth at this stage can best be described as amazing. Having said that, the unseasonably cool temperatures of the past week, coupled with the relatively mild temperatures forecast for the next 10 days is worrisome when we think of where we want corn to be this fall. Typically by the 15th of July we accumulate half of all the corn growing degree days (GDDs) we get during a normal season. So with half of the season behind us, where are we this year relative to normal? A quick review of corn GDDs across the state indicates that we are 100 GDDs behind normal (plus or minus 30 GDDs depending on the location in the state, with northern regions being further behind than southern regions). Since we typically accumulate about 20 GDDs (fewer in the north) a day in mid-July, this suggests that we are about five calendar days behind normal. You should note, however, that these are July calendar days, since GDD accumulation in July occurs at twice the rate of those in May and September.

How does this season compare to last season? Assuming a May 1st planting date, we are about 20 to 30 GDDs ahead of last year at this time (see accompanying graphs for Carrington and Prosper). Unfortunately, most corn was planted at least two weeks later this year than last, thereby negating any benefit of these extra GDDs. This suggests that this year is turning out to be a lot like last year with regards to corn development. Though a great deal can happen during the rest of the season, we definitely need some heat units if we are going to avoid the protracted harvest and high drying costs that typified last year.

   

Joel Ransom
Extension Agronomist for Cereal Crops
Joel.ransom@ndsu.edu


NDSU Crop and Pest Report Home buttonTop of Page buttonTable of Contents buttonPrevious buttonNext button