Past IEM Features tagged: gdd

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GDD Probabilities

20 Jun 2017 12:16 AM
The featured chart displays probabilities of reaching a given amount of growing degree days by a date shown on the y-axis after a planting date on the x-axis for Des Moines. The left hand plot presents the overall frequencies and the right hand plot shows the scenario based frequencies based on this year's data appended to by each previous year on record. The chart would indicate that we are in pretty good shape this year thanks to our reach stretch of very warm weather that helped to make up deficits incurred during May.

Voting:
Good: 6
Bad: 0
Abstain: 1

Tags:   gdd  

Daily GDD Climatology

11 Apr 2017 04:59 AM
The growing season is tantalizingly close and computed variables like growing degree days become important for tracking plant growth and development. The featured chart displays the combination of daily GDD totals for this year, the range between the 5th, 95th percentile and average of daily values based on period of record data. This year has seen a number of days with very warm temperatures and you can see these showing dots well above the 95th percentile. Of course, even with the warm weather, there is still plenty of time for freezing temperatures.

Voting:
Good: 8
Bad: 0

Tags:   gdd  

Tassel to Silking Period

14 Jul 2016 05:05 AM
One of the fun things to watch in Iowa during the summer is the corn rapidly develop! It only takes a few weeks for corn to tassel and then silk. The featured chart shows the period between growing degree day values 610 and 1000 for Ames based on a specified planting date. This period is roughly the time between corn tasseling and silking. The color of the bar represents the number of days it took to transverse this interval. Only very late planted corn in May has yet to reach 1000 GDUs.

Voting:
Good: 6
Bad: 0
Abstain: 1

Tags:   gdd  

GDD Periods

12 Aug 2015 05:44 AM
For farmers, this is about the time of the year when one worries about the progress of crop maturity and the hope that the crop reaches maturity prior to the first fall frost. The featured chart presents the period of days this summer in-between the growing degree day accumulation levels of 1135 and 1660, which are important levels for corn development. The thought is that having a longer period is a positive for corn yields. Of course, this period is going to vary depending on the planting date, which is why this analysis indicates that corn planted after 11 May has yet to reach 1660 units.

Voting:
Good: 18
Bad: 6
Abstain: 8

Tags:   gdd  

Loosing GDD Ground

10 Jul 2015 05:37 AM
After our recent stretch of cool summer days, it is a good time to check in on Growing Degree Day (GDD) totals since 1 May. The featured chart shows the increasing departure from average our recent cool weather has put us into. While warmer weather is in the forecast, it is difficult to make up ground as this is the warmest time of the year and so our expected GDD accumulation is already high.

Voting:
Good: 14
Bad: 5
Abstain: 9

Tags:   gdd  

Behind on GDDs

09 Jun 2015 05:41 AM
Warm weather has been difficult to come by so far this growing season and with often chilly overnight lows, the growing degree day accumulation is running behind average. The featured chart shows the accumulation for Ames since 1 May. The dashed line in the bottom chart shows the to date departure. Since mid May, we have been loosing ground. Today will be the warmest high temperatures we have seen this year, but rain and a bit cooler weather is in the forecast for the rest of the week.

Voting:
Good: 13
Bad: 6
Abstain: 5

Tags:   gdd  

Daily Growing Degree Days

07 May 2015 05:40 AM
The featured chart displays the daily climatology of growing degree days for Ames along with the actual values (dots) for this year. We have seen plenty of above average days this spring with each day so far this May above average. Our average daily accumulations this time of year are half of what we can expect during the warmest time of the year. Having warm over night low temperatures makes a big difference with the computation of this value.

Voting:
Good: 16
Bad: 15
Abstain: 5

Tags:   gdd  

Daily Degree Days

22 Aug 2014 05:39 AM
The big story this summer is the lack of heat leading to a deficit in growing degree day accumulation. The featured chart displays the daily accumulation this year (dots) and the long term climatology (red line and filled segments). The brown extent represents the majority of the long term data range. You can see a number of days this year on the low end of the daily distribution and only a handful of dots above average since the start of July. Heat has arrived this week in Iowa, but next week looks to be back below average for this time of year.

Voting:
Good: 19
Bad: 10
Abstain: 12

Tags:   gdd  

GDD Comparison

21 Aug 2014 05:43 AM
Growing Degree Day accumulation has been difficult this year thanks to the cool conditions that have persisted for most of the summer. The featured chart compares the summer to date accumulation since 1 May for this year, 2013, 2012 and 2009. This year has resembled 2009 quite closely and current deficits are below negative 200 units. There are warm temperatures in the current near term forecast, but it is starting to get late in the season as we are nearly to September 1 already!

Voting:
Good: 10
Bad: 6
Abstain: 5

Tags:   gdd  


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Slow Accumulation

11 Aug 2014 05:36 AM
Even having the Iowa State Fair currently in session could not provoke hot temperatures as our cool summer drags on. The featured chart compares the period between growing degree day accumulation value 1135 and 1660 (important for corn) by planting date for 2012 and 2014. It has taken seven to eight more days this year to accumulate the same number of GDDs vs 2012. For later planting dates, we have yet to even complete this accumulation (gray bars). Slow GDD accumulations during this highlighted period is considered good for corn yield production, but it comes at an expense of concerns of early frost and late/wet corn harvest moisture.

Voting:
Good: 15
Bad: 7
Abstain: 8

Tags:   gdd   corn  


Getting late for GDD catchup

20 Aug 2013 05:20 AM
More summer like conditions have finally returned to Iowa after a number of weeks of very cool weather. The cool weather has provided a substantial deficit of growing degree days. The featured chart shows the number of days of given weather it would take to catch us back up to average for GDD accumulation since 1 May. The green bars are for a scenario whereby we accumulate 120% GDDs of average each day and under such a scenario we only get back to average by the first of October! The red bars assume daily record GDD accumulations based on long term data and this unrealistic scenario only gets us back to average by the first week of September. This deficit is not a terrible thing as the crop growth situation in the state is very complex at the moment. The cool weather was a good thing given the lack of rain for most of the state as it mitigated water stress. While the weather turning warmer will help GDDs and crop maturity, the lack of moisture will mean water stress should dramatically increase. The further complication is that very little corn was planted by 1 May, with most of it emerging by mid to late May.

Voting:
Good: 86
Bad: 8

Tags:   gdd  

Daily GDDs

15 Aug 2013 05:43 AM
The featured chart shows the daily climatology of growing degree days along with the actual values for 2013. The past three weeks have been a struggle with most days only accumulating 10-20 units. Given the late planting dates for crops in the state, having cool weather this time of year is actually the better of two evils. Having hot weather and little precipitation would have imposed heat stress on the crop. Instead the cool and dry weather has allowed the crop to limp along as it matures. While the near term benefits of cool weather are good, an early fall frost is of now of concern more than ever.

Voting:
Good: 56
Bad: 11

Tags:   gdd  


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Reaching 2600 GDDs

08 Aug 2013 04:41 AM
Growing Degree Days are commonly used to track crop development. For "105 day" corn, about 2600 GDD units are necessary to reach maturity. The cool and wet spring combined with a early May snowfall made it difficult for corn to get into the ground on time in Iowa. Planting corn deep into May and June puts the crop at risk of not accumulating enough GDDs prior to the fall freeze. The featured chart attempts to provide probabilities of accumulating GDDs based on the combination of growing season begin (planting / crop emergence) and end (first freeze) date. The left hand plot shows the overall frequencies based on yearly data for Ames since 1893. The right hand plot combines what has already happened this year with scenarios based on all previous years for 7 August and on. For example, for a corn crop emerging on 15 May, about 20% of the years got to 2600 GDDs by 15 September prior to the first fall freeze. Given this year's condition, for a corn crop emerging on 15 May, there is near no chance that 2600 GDDs can be reached by 15 September and only about 50% of all years will get us to 2600 GDDs at all. One mitigation is that as planting dates get later, farmers will plant hybrids with shorter maturities (less GDD requirements). Although, this seed change is not always logistically possible. The chart would indicate that we need to make it through much of September without a freeze to give the longer maturities a chance.

Voting:
Good: 152
Bad: 11

Tags:   gdd   2013  


GDDs

23 May 2013 05:45 AM
Growing Degree Days (GDD) are a measure of heat units that have typically been associated with plant development. The equation to compute them is simple and only uses commonly available data variables of daily high and low temperature. The featured chart displays the daily distribution and average accumulation of GDDs for Ames. This year's values are the blue dots. This year has seen near zero GDDs up until near the start of April and a number of very cool days since then. The cool weather looks to continue until a warmup next week.

Voting:
Good: 57
Bad: 10

Tags:   gdd  


Rapid Development

27 Sep 2011 06:01 AM
The 2011 corn crop harvest is well underway in Iowa. One of the detrimental factors to this year's crop was a very hot stretch of weather in July during an important crop development stage. The featured chart looks at the number of days between two key stages in the corn development based on accumulated growing degree days from 1 May. Some suggest that longer the crop stays in this sweet spot for development, the more time the plant has to cycle water and nutrients leading to a better yield. The 19 days that it took this year tied the shortest period on record for Ames. Of course, there are caveats galore to this plot as corn could have been planted earlier or later than 1 May, also could have been a shorter or longer maturity variety, and crop physiology / genetics continue to improve.

Voting:
Good: 14
Bad: 4

Tags:   corn   gdd  


Guess the yield

23 Sep 2011 05:56 AM
The featured chart presents accumulated growing degree day (base 50) departures from 1 May to 1 Oct for each of the past 10 years for Ames. The number at the end of the line is the reported corn yield by the USDA for Story County (the county of Ames). The total season departure does not tell the entire story for the resulting corn yield. The black line is so far this year, wish to guess the yield based on this chart? :)

Voting:
Good: 25
Bad: 7

Tags:   gdd   yield