ISSUE 5   June 11, 2009

EVALUATING THE CROP

Most of the crops are now planted, and the focus of production has shifted to in-season crop management. One of the important aspects of farming right now is crop scouting, the regular inspection of the fields during the growing season. Scouting is the key to successful crop management. Just after emergence it is important to find out if there are any issues with the plant establishment. Weeds, pests and diseases can all influence the outcome of the cropping season and producers need to personally inspect fields, or use hired scouts, to diagnose the potential crop problems. Early season scouting will provide information to make the right management decisions before problems become too serious to mange. Early detection of pests and diseases will assist in the determination if a pesticide treatment is needed and when the best timing of the application might be.

Record the insect, weed, or disease infestations on a map when inspecting the field. Notes should be taken about the infestation type and how severe the problem is. As pests are not always randomly distributed throughout a field it is essential to scout different areas of the field and not only those areas in the field which are easily accessible. One of the first decisions will have to do with replanting. If the crop did not germinate properly and stands are erratic or very low, replanting of sunflowers, soybean and dry bean may still be considered. Producers trying to make decisions on replanting need to consider that by replanting the yield potential of the crop will be lower than planting at the optimal time.

Producers need to accurately evaluate the stand in each field. In solid seeded fields, take several counts (each a few square feet) at various places in the field to determine the average established plants per square foot. For example if 170,000 soybean seeds per acre were planted this would equal to 3.9 seeds per square foot (divide the number of seeds by 43,560; which is the number of square feet per acre). If the count indicates 2 established plants per square foot the population is (2 x 43,560) = 87,120 plants per acre. Although plants can compensate by producing more seeds per plant and/or increased seed size, there will be a reduced yield potential with below optimum plant stands.

The other way to calculate stand for row crops is to count the number of plants in the length of row equal to 1/1000 of an acre and multiply the counted plants by 1,000 to get the population per acre. It is suggested to make several counts and average them. Sometimes only parts of the field have a low stand while other areas have a sufficient number of established plants.

Table 1. Length of row equal to 1/1000 of an acre

Width of the row
in inch
Row length for 1/1000 acre Width of the row
in inch
Row length for 1/1000 acre

7

74' 8"

28

18' 8"

14

37' 4"

30

17' 5"

20

26' 2"

32

16' 4"

24

21' 9"

34

15' 4"

Knowing the number of established plants may help to diagnose if there was a planting difficulty and what percent of the seed developed into established plants. Although one cannot change the stand, except for replanting, the information is important for next yearís planting decisions.

In some cases the producer may consider replanting. Besides the possibility of higher yield potential due to better stand, the producer needs to estimate the cost of replanting and estimate the chance that a replanted crop will properly establish and produce a higher net financial return than the field with the poor stand. Producers sometimes also evaluate the social cost of having a poor looking field. Land lords may not rent the land to the producer if they think the producer is neglecting the field.

Cost associated with not replanting

  • Percent yield reduction due to the poor stand.
  • Potential increase in herbicide cost as reduced stands tend to have more weeds.
  • Increased harvest cost due to uneven maturing of the crop.
  • Cost associated with replanting

  • Labor, equipment cost, and fuel to destroy the present crop.
  • Labor, equipment cost, and fuel to prepare a new seedbed and seeding.
  • Seed cost to replant.
  • Changed variety because of late planting (likely a lower genetic yield potential).
  • Delayed planting (seeding after the optimum time) provides the crop with a shorter growing season and yield potential is lower.
  • If a pre-plant incorporated herbicide was used, the tillage and replanting may reduce its effectiveness.
  • Increased chance of frost of the end of the season resulting in higher drying cost and or poor quality product.
  • Often the economics of replanting are not very good so producers need to carefully weigh the pros and cons of their replanting decision. For information about replanting or late planting crops see http://www.ag.ndsu.edu/pubs/plantsci/crops/a934.pdf

    Hans Kandel
    Extension Agronomist - Broadleaf Crops
    hans.kandel@ndsu.edu

     

    COOL SPRING WEATHER IS GOOD NEWS FOR SMALL GRAINS, BUT WORRISOME FOR CORN

    This spring has turned out to be one of the coldest springs in many years. Like much of the recent economic downturn, global warming seems to have missed North Dakota! The cooler temperatures are good news for the small grain crops, including and especially those that were planted later than is considered optimal. Cool weather favors more tillering and the development of larger spikes in wheat and barley. Potential spike size and potential tiller numbers are "fixed" in the plant before the 5-6 leaf stage, so the current cold weather should add a few bushels of yield potential to these cool season crops. In fact our current weather is nearly ideal for small grain development. Protecting and maintaining this higher yield potential will be the challenge in the weeks ahead. Hot and dry weather during flowering, scab and foliar diseases are worries as we look to the rest of the growing season.

    For corn, on the other hand, cool spring weather is worrisome. Cool weather does not necessarily reduce yield potential in corn. What concerns us is that corn development is delayed. Since we need every growing degree day (GDD) we can get to mature and dry our corn in ND, delayed development means that the corn crop may be immature, have low test weight and most assuredly have more moisture at harvest than is desired. We only have to look to last year to remember the impact of a cool growing season on corn. In this article my intent is to compare the corn growing degree day accumulations this spring with those of other years since 2000 and for the same years determine if there is a relationship between GDD accumulations in the spring and GDD accumulations for the entire corn growing season (May 1 through October 1).

    This year corn GDDs, assuming a May 1st planting date, range from 207 in Landon to 327 in Fargo and are lagging behind normal by 86 to 169 GDD (Table 1). When considering normal GDDs from May 1st to October 1st, this deficit represents about 5% of the total growing seasonís GDD. This spring is coolest (largest negative departure from normal) of any year for the period analyzed (since 2000).

    Table 2. Corn GDD accumulations for May 1 to June 9, 2009, departures from normal for this period and total GDDs May 1st to October 1st, for selected locations in ND.

     

    GDDs May 1 to June 8

    Departures from normal GDDs, May 1 to June 8

    Normal GDDs
    May 1 to
    October 1

    Carrington

    280

    -169

    2281

    Dickinson

    298

    -86

    2183

    Fargo

    327

    -103

    2348

    Langdon

    207

    -130

    1770

    Minot

    291

    -92

    2007

    Weather is hard to predict, but often follows trends. This spring I have been asking myself, does this cool spring weather mean that we will end up with a short season, or might we catch up in GDDs as the season progresses? To answer this question, I analyzed the departures from normal of GDD accumulations for the spring and for the entire season since 2000 to see if there might be any obvious trends (Table 2). I averaged data for the five locations included in Table 1 to give a more statewide picture. The first thing to note from these data is that eight of the last ten springs have been cooler than normal (had negative departures from normal); six of those negative departures were greater than -60 GDDs. Only two (2004 and 2008) of the past nine years, however, have been cooler than normal seasons. Unfortunately, those two seasons started with the coldest springs of the years analyzed with the exception of this year. Before we despair, there have been a couple of years, 2002 and 2006 where the year started out cool but ended up warmer than normal. Moreover, the fact that only two of the last nine seasons have been cooler than normal should also give us some hope. This analysis suggests to me that there is a fairly high probability that this season will be cooler than normal. It does not close the door, however, on things improving later in the summer and we end up with a reasonable season for corn. Letís hope for the latter.

    Table 3. Departures from normal GDD accumulations for early in the season and the full season for the years 2000-2009.

     

    Departures from normal GDD accumulations for the period -

    Year

    May 1-June 9

    May 1 Ė Oct 1

    2000

    -8

    15

    2001

    15

    108

    2002

    -70

    87

    2003

    -76

    37

    2004

    -98

    -350

    2005

    -66

    18

    2006

    51

    200

    2007

    -8

    151

    2008

    -92

    -87

    2009

    -116

    ???

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


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