ISSUE 11   July 22, 2010

CANOPY CLOSURE IN SOYBEAN 

Some soybean growers use 30 inch row spacing for soybean. Soybean yield research at NDSU, however, showed that reducing 30 inch row spacing to narrower intermediate row spacing on average increased yield potential. The yield potential depends on the growing season and other environmental conditions. Advantages for narrow row soybean include earlier crop canopy closure to help control weeds and potentially an increased yield. More light interception is considered the main factor explaining the higher yield potential in narrow- as compared to wide-row spacing in soybean in ND.

Last year, in the 2009 season, we estimated the percent canopy cover in some of our replicated soybean experiments. Looking down on the canopy we visually evaluated the percentage of land area covered by green plant tissue. A cover of 98% indicates that there was only two percent area of the soil visibly observed. The lower canopy cover numbers indicate that more sunlight reached the soil surface and was not used in photosynthesis. In this warmer year (2010), the crop has been more advanced and covered the soil quicker. Canopy closure data for 2010 was collected at Prosper on July 15 and at Carrington on July 20, and compared with similar data during the first week of August in 2009.   

Based on the data presented in Table 1, we concluded that both in 2009 and 2010, at the observed locations, the 14 inch row spacing had higher canopy closure percentages than the areas with 28 row spacing. In 2009, the yields of the 14 inch row spacing were numerically higher than the 28 inch row spacing, however the yields were not significantly different from each other at the P<0.05 level.

Table 1. Average percent canopy closure in soybean and Natto soybean with 14 and 28 inch row spacing, measured the first week of August 2009 and mid July 2010.

     

Carrington

     

----14 inch----

----28 inch----

     

Closure

Yield

Closure

Yield

     

(%)

(bu/a)

(%)

(bu/a)

2009 Soybean

981

53.7

70

53.4

2009 Natto soybean

93

38.4

67

37.8

2010 Soybean

97

-

75

-

 

Prosper

2009 Soybean

96

53.8

71

53.7

2009 Natto soybean

74

38.9

65

34.2

2010 Soybean

89

-

63

-

1 Each number in Table 1 is an average of about 32 experimental units.


Photo 1.
Soybean on 14 inch row spacing
at Prosper N.D., July 15
th 2010.


Photo 2.
Soybean on 28 inch row spacing
at Prosper ND, July 15
th 2010.

Hans Kandel
Extension Agronomist Broadleaf Crops
Hans.Kandel@ndsu.edu

 

LODGING AND GREEN SNAP IN CORN

Corn has grown rapidly these past few weeks, and in many areas of the state corn will soon be tasseling.  During this stage of development corn can be susceptible to root lodging and green snap.  Not surprisingly, the high winds this past week, coupled in many cases with heavy rain did caused a fair amount of root lodging (see picture).

 

Causes of root lodging

Root lodging occurs when roots are not able to anchor the plant against the force of the wind.  Plant growth stage, rooting depth, root feeding by rootworms, wind velocity, soil moisture content at the time of heavy winds, and corn hybrid are factors that influence root lodging.  Root lodging is most common during the mid-vegetative stage of development before brace roots have formed.  Brace roots provide a valuable function in anchoring and supporting the plant and do not fully develop until after silking.

Moist soil at the time of high winds increases the likelihood of root lodging as roots on the windward side of the plant are more easily pull from moist soil than those in dry or compacted soil.  Differences in soil moisture may have been one reason that lodging was localized this year.  Rootworm feeding can dramatically reduce root mass and increase the potential for lodging.  Check fields with lodging for rootworm damage.  Corn rootworm is currently not a widespread pest of corn in North Dakota, but it can be a localized problem and may be a causal factor in lodging in some fields.  Hybrids can vary significantly in their resistance to lodging.  If lodging appears to be hybrid-specific, select hybrids with better resistance to lodging in future years

Yield losses caused by lodging

Estimates in losses in yield caused by lodging vary from a low of 3% to a high of 40%.  The plant stage at the time of lodging and the environment after lodging are important factors in the yield loss equation.  Plants that have lodged usually erect themselves within a few days.  Often stems from lodged plants will goose neck as they erect themselves, making harvest more difficult.  A reduction in the number of ears per plant is the yield component most affected by lodging in the mid- to late-vegetative stage.  Much of the lodged corn this year has made a remarkable recovery.  Fields where plants have righted themselves already will probably not suffer much yield loss.

Green Snap in Corn

Green snap is the term used to describe the breaking of rapidly growing stalks of corn.  Corn is most susceptible to green snap during the 5 to 8 leaf and the 12-leaf to tasseling stages.  During these stages, if conditions are conducive to rapid growth (i.e. water and nutrients are not limiting and temperatures are high), cell division and elongation occurs so rapidly that there is no time for the cell wall to fully harden.  Factors such as the timing and velocity of the wind, the rate of growth of the corn plant and the hybrid that is grown are factors associated with the incidence of green snap.  High levels of nitrogen during vegetative development can increase the likelihood of this problem as can the use of growth regulator type herbicides such as 2, 4-D, dicamba, and clopyralid. 

Reports on how much yield loss is caused by green snap vary considerably.  Green snap at or near the soil surface can cause complete yield loss.  If green snap occurs above where the dominant ear would normally develop, however, losses will be moderate and will depend on how widespread the damage is in the field.  I did not see any fields where green snap was widespread this past week.  The most effective way of managing green snap, since the environment is difficult to control, is by growing a hybrid with known resistance.

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


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