NDSU Crop and Pest Report

Plant Science


ISSUE 9  July 1, 2004

CANOLA TEMPERATURES AND SOIL MOISTURE

Heat injury to canola occasionally occurs on hot sunny days, with air temperatures in the range of 90-95 F and soil temperatures of 120 F. Heat injury is commonly associated with drought injury, but excessive heat will also injure or kill seedling plants even if moisture is plentiful.

When in the blooming stages, heat blasting and or flower abortion is a strong possibility also when under high temperatures in the 90’s and higher. This can vary from field to field and is very dependent on stage of flowering, soil moisture and humidity during the hot periods. Usually in this situation one would see no or limited pod growth and thus no seed set. It will usually be seen in sections of the main stem and branches as related to time of flowers pollinating and the heat stress. With good soil moisture under canola usually flower abortion will be minimized to some extent.

Both low and high temperatures can adversely affect development prior to and during flowering. Low, but non-freezing, temperatures just prior to flowering slow the rate of plant development. The start of flowering is delayed or, if begun, the rate of flower opening is slowed and the amount of pollen shed is reduced. High temperatures at flowering will hasten the plant's development, reducing the time from flowering to maturity. High temperatures during flowering shorten the time the flower is receptive to pollen, as well as the duration of pollen release and its viability. This can decrease the number of pods which develop and the number of seeds per pod, resulting in lower yields. It appears that Brassica rapa (Polish) is more susceptible to this type of damage than Brassica napus (Argentine). Very hot weather combined with drought may cause bud blasting wherein the flower clusters turn brown and die resulting in serious yield losses.

Once pods are formed, canola is more tolerant than at flowering to high temperatures. Cool night temperatures at this time also help the plant recover from extreme heat or dry weather.

However, during this stage, a combination of heat and extreme drought will severely affect the pod and seed development including formation of seeds, seed size and oil content. The seed oil content is highest when seeds mature under lower temperatures (50 to 70 F). High temperatures during seed maturation result in reduced oil content. High temperatures, drought and long days hasten maturity and in combination, can reduce yield through fewer pods, with fewer lighter seeds per pod.

 

CHECKING PLANT POPULATIONS - ROW CROPS

Use the table below to estimate plant population

  1. Count number of plants in the length of row equal to 1/1000 of an acre.
  2. Make several checks within a field and average the stand counts.
  3. Multiply the average by 1000 to get population per acre estimate.

Row width spacing

Row Length for 1/1000 acre

Row width spacing

Row Length for 1/1000 acre

7"

74' 8"

30"

17' 5"

14"

37' 4"

32"

16' 4"

20"

26' 2"

34"

15' 4"

22"

23' 9"

36"

14' 6"

24"

21' 9"

38"

13' 9"

28"

18' 8"

40"

13' 1"

Hint: Use a small diameter rope, cord or a tape measure for the correct distance.

Duane Berglund
NDSU Extension Agronomist
duane.berglund@ndsu.nodak.edu

 

HOW COOL IS COOL: CORN GROWING DEGREES FOR THE 2004 GROWING SEASON COMPARED

Anyone that knows anything about crop growth knows that it has been an unusually cool spring this year. The cool weather has been great from the cool season crops. The small grains that have not been hammered by frost, hail or drought appear to now have the potential for record breaking yields. Corn growth has been frustratingly slow, however. I thought it might be useful to do some analysis of corn growing degree days over the past few seasons in order to allow one to put this year’s early growing season in perspective.

Corn growth is directly related to the accumulation of corn growing degree days (GDDs). GDDs are far more useful in predicting the growth and development of a crop than are calendar days. GDDs for the many NDAWN sites in the state can easily be obtained from the internet at:

http://ndawn.ndsu.nodak.edu/corndd_form.html

The following table compares this year’s corn GDDs accumulations to date with those of the previous two seasons.

Corn GDD accumulations for selected locations in North Dakota for the period May 1 to June 28, 2002-2004.

Location

2002

2003

2004

Carrington

652

585

494

Fargo

761

724

555

Hettinger

661

531

581

Langdon

554

555

374

Minot

622

587

468

Oakes

782

680

595

Williston

646

598

490

The first two months of the 2004 season have indeed been significantly cooler than average. As can be noted from the above table, corn GGDs this season are averaging 100 to 200 behind the previous two seasons, depending on the location and year. This means that corn development is 1 to 2.5 leaves behind the development of the previous two years (it takes about 85 GDDs to produce a new leaf during early corn development). There is still a lot of season ahead of this current crop but if the remainder of the season is “average”, this cool spring weather will likely translate into corn that is 2 to 3 percent higher in moisture at harvest this fall. Hopefully, the warmer weather of the last few days will continue and the crop will catch up, but you should probably plan on having to deal with a bit more moisture at harvest this season than last.

Joel Ransom
NDSU Extension Agronomist - Cereal Crops
joel.ransom@ndsu.nodak.edu


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