msu-ceco/aec_v1 · Datasets at Hugging Face

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There remains considerable unexplained scatter in this graph that does not appear to be related very well to differences in evaporative demand between the years.
For example, there was very little effect on relative kernels/area in 2002, although it had a moderately high evaporative demand.
The relationship of relative kernels/area to a critical level of available soil water can have some merit as a signal for determining the need for irrigation because available soil water can both be measured in real-time and the value can be projected a few days into the future.
The ratio of calculated well-watered crop ETc to the sum of irrigation and precipitation for July 1 through 15 was also related to the relative kernels/area.
The relative kernels/area tended to decrease when this water deficit ratio was less than 70 to 80%.
Attempts were also made in varying the timeframe of the ratio.
It appears that some of the remaining scatter in this graph is related to timing of irrigation and precipitation near the actual point of silking.
For example, the isolated point from 2002 near the vertical axis may be related to a significant precipitation event that occurred near silking, but later than July 15.
Further analysis should be conducted to allow the window to actually vary around the individual silking dates of each year.
This might be done by computing windows based on the number of thermal units required for silking.
This relationship might also be a good signal in determining the need for irrigation because it can be determined in near real-time using the accumulated ratio to that point in time.
Figure 4.
Relative kernels/area as affected by the July 1 through 15 water deficit in an early-season corn water stress study, KSU-NWREC, Colby, Kansas, 1999-2007.
Further analysis should focus on attempts to combine multiple factors with a focus on developing irrigation signals that can be used in near real-time to make early season irrigation decisions.
Recommendations for managing pre-anthesis corn water stress
Producers should use a good method of day-to-day irrigation scheduling during the pre-anthesis period.
To a large extent the information being used to make day-to-day irrigation scheduling decisions during the pre-anthesis period can also be used as in making the macromanagement decision about when to start the irrigation season.
This is because even though the corn has considerable innate ability to tolerate early season water stress, most irrigation systems in the Central Great Plains do not have the capacity or practical capability to replenish severely depleted soil water reserves as the season progresses to periods of greater irrigation needs.
However, there is some flexibility in timing of irrigation events within the vegetative growth period.
In years of lower evaporative demand, corn grown on this soil type in this region can extract greater amounts of soil water without detriment.
Timeliness of irrigation and/or precipitation near anthesis appears to be important in establishing an adequate number of kernels/area.
The strong linear 1:1 relationship that existed between the relative corn yield and the relative number of kernels/area indicates that optimizing kernels/area is a key in optimizing grain yields.
Producers growing corn on deep silt loam soils in the Central Great Plains should attempt to maintain a water deficit ratio during July of approximately 0.7 to 0.8 and not allow the available soil water within a 4-ft soil profile to decrease below 70%, particularly in years of greater evaporative demand.
Results for Post-Anthesis Water Stress Studies
Tabular data analysis for post-anthesis water stress studies
Results from 16 years of studies indicate that anthesis for corn in Northwest Kansas varies from July 12 to July 24 with an average date of July 19.
Physiological maturity ranged from September 14 through October 10 with an average date of September 27.
The average length of the post-anthesis period was approximately 70 days.
Using the corn grain yield results from the study and the individual treatment irrigation termination dates responsible for those yields, Table 3 was created to indicate the problems with using inflexible dates for determining the irrigation season termination date.
Additionally, the corn grain yield results and the treatment irrigation dates were used to estimate the date when a specified percentage of maximum grain yield would occur.
Because there was not an unlimited number of irrigation treatment dates there are years when the date required for a specified percentage of maximum grain
yield was the same as the date for the next higher percentage.
The average estimated termination date to achieve 80, 90 and 100% of maximum corn grain yield was August 2, 13, and 28, respectively, but the earliest dates were July 17, July 17 and August 12, respectively, while the latest dates were September 14, 21, and 21, respectively.
Irrigators that use average or fixed dates to terminate the corn irrigation season are not realistically considering the irrigation needs of the corn that may be greater or smaller in a particular year, and thus, often will neither optimize corn production, nor minimize water pumping costs.
Table 3.
Anthesis and physiological maturity dates and estimated irrigation season termination dates* to achieve specified percentage of maximum corn grain yield from studies examining post-anthesis corn water stress, KSU Northwest Research-Extension Center, Colby, Kansas, 1993-2008.
Note: This table was created to show the fallacy of using a specific date to terminate the irrigation season.
Note: Because there was not an unlimited number of irrigation treatment dates, there are years when the date required for a specified percentage of maximum grain yield was the same as the date for the next higher percentage.
Year Date of Date of Irrigation Season Termination Date For
Anthesis Maturity 80% Max Yield 90% Max Yield MaxYield
1993 20-Jul 30-Sep 5-Aug 5-Aug 15-Aug
1994 20-Jul 15-Sep 5-Aug 15-Aug 15-Aug
1995 20-Jul 29-Sep 5-Aug 13-Aug 18-Aug
1996 20-Jul 3-Oct 17-Jul 17-Jul 29-Aug
1997 23-Jul 1-Oct 23-Jul 23-Jul 27-Aug
1998 20-Jul 28-Sep 20-Jul 20-Jul 24-Aug
1999 23-Jul 6-Oct 24-Jul 13-Aug 20-Sep
2000 12-Jul 20-Sep 14-Sep 20-Sep 20-Sep
2001 16-Jul 29-Sep 30-Jul 22-Sep 22-Sep
2002 22-Jul 30-Sep 4-Aug 30-Aug 7-Sep
2003 22-Jul 23-Sep 3-Aug 3-Aug 18-Aug
2004 19-Jul 28-Sep 8-Aug 21-Aug 27-Aug
2005 20-Jul 28-Sep 2-Aug 9-Aug 29-Aug
2006 17-Jul 25-Sep 30-Jul 13-Aug 13-Aug
2007 18-Jul 19-Sep 14-Aug 21-Aug 28-Aug
2008 24-Jul 10-Oct 31-Jul 6-Aug 27-Aug
Average 19-Jul 27-Sep 2-Aug 13-Aug 28-Aug
Standard Dev.
3 days 6 days 13 days 19 days 13 days
Earliest 12-Jul 14-Sep 17-Jul 17-Jul 12-Aug
Latest 24-Jul 10-Oct 14-Sep 21-Sep 21-Sep
* Estimated dates are based on the individual irrigation treatment dates from each of
the different studies when the specified percentage of yield was exceeded.
Maximum corn yields during the 16-year period in the various studies averaged 258 bu/acre with a range of 154 to 298 bu/acre.
Extremely poor growing conditions greatly reduced yields in 1993 and hail suppressed yield in 1995.
The post-anthesis water use that occurred for the irrigation treatment that maximized yield averaged 16.9 inches with a range of 14.9 to 20.2 inches.
Assuming that yield formation for the corn crop started at anthesis, the average post-anthesis water productivity was 15 bu/inch and the range of water productivity over the years was 8 to 20 bu/inch.
Table 4.
Maximum corn yields and post-anthesis water use data from studies examining post-anthesis corn water stress, KSU Northwest ResearchExtension Center, Colby, Kansas, 1993-2008.
Maximum PAWU MY PAWU MY
Year Yield PAWUMY* PAWUMY during last during last 15
30 days days
1993 154 19.23 0.287 0.288 0.178
1994 246 15.52 0.277 0.218 0.178
1995 170 18.23 0.285 0.201 0.174
1996 280 15.38 0.220 0.161 0.137
1997 245 16.13 0.230 0.162 0.150
1998 262 16.55 0.236 0.155 0.136
1999 272 18.49 0.247 0.134 0.081
2000 259 20.24 0.289 0.276 0.302
2001 268 19.44 0.259 0.161 0.160
2002 284 16.63 0.238 0.139 0.017
2003 269 15.12 0.240 0.089 0.105
2004 283 16.25 0.229 0.181 0.164
2005 295 16.31 0.233 0.088 0.036
2006 268 16.48 0.235 0.098 0.101
2007 273 16.25 0.258 0.104 0.106
2008 298 14.85 0.190 0.115 0.091
Average 258 16.94 0.247 0.161 0.132
Standard Dev.
40 1.65 0.027 0.061 0.066
Minimum 154 14.85 0.190 0.088 0.017
Maximum 298 20.24 0.289 0.288 0.302
PAWUMY is the post-anthesis water use occurring for the irrigation treatment that
achieved maximum corn grain yield within the specified year.
PAWUMY averaged 0.247 inches/day during the approximately 70-day period between anthesis and physiological maturity and remained at 65 and 53% of that value during the last 30 and 15 days of the season, respectively.
This emphasizes that although crop water use is tapering
off during the latter part of the season, due to maturing crop canopies and also due to lower reference evapotranspiration , therefore, it must be considered an important factor in late season crop management.
Producers should also be aware that irrigation systems with marginal or insufficient capacity may have allowed considerable soil water depletion during the preanthesis period.
Graphical data analysis for post-anthesis water stress studies

There remains considerable unexplained scatter in this graph that does not appear to be related very well to differences in evaporative demand between the years.

For example, there was very little effect on relative kernels/area in 2002, although it had a moderately high evaporative demand.

The relationship of relative kernels/area to a critical level of available soil water can have some merit as a signal for determining the need for irrigation because available soil water can both be measured in real-time and the value can be projected a few days into the future.

The ratio of calculated well-watered crop ETc to the sum of irrigation and precipitation for July 1 through 15 was also related to the relative kernels/area.

The relative kernels/area tended to decrease when this water deficit ratio was less than 70 to 80%.

Attempts were also made in varying the timeframe of the ratio.

It appears that some of the remaining scatter in this graph is related to timing of irrigation and precipitation near the actual point of silking.

For example, the isolated point from 2002 near the vertical axis may be related to a significant precipitation event that occurred near silking, but later than July 15.

Further analysis should be conducted to allow the window to actually vary around the individual silking dates of each year.

This might be done by computing windows based on the number of thermal units required for silking.

This relationship might also be a good signal in determining the need for irrigation because it can be determined in near real-time using the accumulated ratio to that point in time.

Figure 4.

Relative kernels/area as affected by the July 1 through 15 water deficit in an early-season corn water stress study, KSU-NWREC, Colby, Kansas, 1999-2007.

Further analysis should focus on attempts to combine multiple factors with a focus on developing irrigation signals that can be used in near real-time to make early season irrigation decisions.

Recommendations for managing pre-anthesis corn water stress

Producers should use a good method of day-to-day irrigation scheduling during the pre-anthesis period.

To a large extent the information being used to make day-to-day irrigation scheduling decisions during the pre-anthesis period can also be used as in making the macromanagement decision about when to start the irrigation season.

This is because even though the corn has considerable innate ability to tolerate early season water stress, most irrigation systems in the Central Great Plains do not have the capacity or practical capability to replenish severely depleted soil water reserves as the season progresses to periods of greater irrigation needs.

However, there is some flexibility in timing of irrigation events within the vegetative growth period.

In years of lower evaporative demand, corn grown on this soil type in this region can extract greater amounts of soil water without detriment.

Timeliness of irrigation and/or precipitation near anthesis appears to be important in establishing an adequate number of kernels/area.

The strong linear 1:1 relationship that existed between the relative corn yield and the relative number of kernels/area indicates that optimizing kernels/area is a key in optimizing grain yields.

Producers growing corn on deep silt loam soils in the Central Great Plains should attempt to maintain a water deficit ratio during July of approximately 0.7 to 0.8 and not allow the available soil water within a 4-ft soil profile to decrease below 70%, particularly in years of greater evaporative demand.

Results for Post-Anthesis Water Stress Studies

Tabular data analysis for post-anthesis water stress studies

Results from 16 years of studies indicate that anthesis for corn in Northwest Kansas varies from July 12 to July 24 with an average date of July 19.

Physiological maturity ranged from September 14 through October 10 with an average date of September 27.

The average length of the post-anthesis period was approximately 70 days.

Using the corn grain yield results from the study and the individual treatment irrigation termination dates responsible for those yields, Table 3 was created to indicate the problems with using inflexible dates for determining the irrigation season termination date.

Additionally, the corn grain yield results and the treatment irrigation dates were used to estimate the date when a specified percentage of maximum grain yield would occur.

Because there was not an unlimited number of irrigation treatment dates there are years when the date required for a specified percentage of maximum grain

yield was the same as the date for the next higher percentage.

The average estimated termination date to achieve 80, 90 and 100% of maximum corn grain yield was August 2, 13, and 28, respectively, but the earliest dates were July 17, July 17 and August 12, respectively, while the latest dates were September 14, 21, and 21, respectively.

Irrigators that use average or fixed dates to terminate the corn irrigation season are not realistically considering the irrigation needs of the corn that may be greater or smaller in a particular year, and thus, often will neither optimize corn production, nor minimize water pumping costs.

Table 3.

Anthesis and physiological maturity dates and estimated irrigation season termination dates* to achieve specified percentage of maximum corn grain yield from studies examining post-anthesis corn water stress, KSU Northwest Research-Extension Center, Colby, Kansas, 1993-2008.

Note: This table was created to show the fallacy of using a specific date to terminate the irrigation season.

Note: Because there was not an unlimited number of irrigation treatment dates, there are years when the date required for a specified percentage of maximum grain yield was the same as the date for the next higher percentage.

Year Date of Date of Irrigation Season Termination Date For

Anthesis Maturity 80% Max Yield 90% Max Yield MaxYield

1993 20-Jul 30-Sep 5-Aug 5-Aug 15-Aug

1994 20-Jul 15-Sep 5-Aug 15-Aug 15-Aug

1995 20-Jul 29-Sep 5-Aug 13-Aug 18-Aug

1996 20-Jul 3-Oct 17-Jul 17-Jul 29-Aug

1997 23-Jul 1-Oct 23-Jul 23-Jul 27-Aug

1998 20-Jul 28-Sep 20-Jul 20-Jul 24-Aug

1999 23-Jul 6-Oct 24-Jul 13-Aug 20-Sep

2000 12-Jul 20-Sep 14-Sep 20-Sep 20-Sep

2001 16-Jul 29-Sep 30-Jul 22-Sep 22-Sep

2002 22-Jul 30-Sep 4-Aug 30-Aug 7-Sep

2003 22-Jul 23-Sep 3-Aug 3-Aug 18-Aug

2004 19-Jul 28-Sep 8-Aug 21-Aug 27-Aug

2005 20-Jul 28-Sep 2-Aug 9-Aug 29-Aug

2006 17-Jul 25-Sep 30-Jul 13-Aug 13-Aug

2007 18-Jul 19-Sep 14-Aug 21-Aug 28-Aug

2008 24-Jul 10-Oct 31-Jul 6-Aug 27-Aug

Average 19-Jul 27-Sep 2-Aug 13-Aug 28-Aug

Standard Dev.

3 days 6 days 13 days 19 days 13 days

Earliest 12-Jul 14-Sep 17-Jul 17-Jul 12-Aug

Latest 24-Jul 10-Oct 14-Sep 21-Sep 21-Sep

* Estimated dates are based on the individual irrigation treatment dates from each of

the different studies when the specified percentage of yield was exceeded.

Maximum corn yields during the 16-year period in the various studies averaged 258 bu/acre with a range of 154 to 298 bu/acre.

Extremely poor growing conditions greatly reduced yields in 1993 and hail suppressed yield in 1995.

The post-anthesis water use that occurred for the irrigation treatment that maximized yield averaged 16.9 inches with a range of 14.9 to 20.2 inches.

Assuming that yield formation for the corn crop started at anthesis, the average post-anthesis water productivity was 15 bu/inch and the range of water productivity over the years was 8 to 20 bu/inch.

Table 4.

Maximum corn yields and post-anthesis water use data from studies examining post-anthesis corn water stress, KSU Northwest ResearchExtension Center, Colby, Kansas, 1993-2008.

Maximum PAWU MY PAWU MY

Year Yield PAWUMY* PAWUMY during last during last 15

30 days days

1993 154 19.23 0.287 0.288 0.178

1994 246 15.52 0.277 0.218 0.178

1995 170 18.23 0.285 0.201 0.174

1996 280 15.38 0.220 0.161 0.137

1997 245 16.13 0.230 0.162 0.150

1998 262 16.55 0.236 0.155 0.136

1999 272 18.49 0.247 0.134 0.081

2000 259 20.24 0.289 0.276 0.302

2001 268 19.44 0.259 0.161 0.160

2002 284 16.63 0.238 0.139 0.017

2003 269 15.12 0.240 0.089 0.105

2004 283 16.25 0.229 0.181 0.164

2005 295 16.31 0.233 0.088 0.036

2006 268 16.48 0.235 0.098 0.101

2007 273 16.25 0.258 0.104 0.106

2008 298 14.85 0.190 0.115 0.091

Average 258 16.94 0.247 0.161 0.132

Standard Dev.

40 1.65 0.027 0.061 0.066

Minimum 154 14.85 0.190 0.088 0.017

Maximum 298 20.24 0.289 0.288 0.302

PAWUMY is the post-anthesis water use occurring for the irrigation treatment that

achieved maximum corn grain yield within the specified year.

PAWUMY averaged 0.247 inches/day during the approximately 70-day period between anthesis and physiological maturity and remained at 65 and 53% of that value during the last 30 and 15 days of the season, respectively.

This emphasizes that although crop water use is tapering

off during the latter part of the season, due to maturing crop canopies and also due to lower reference evapotranspiration , therefore, it must be considered an important factor in late season crop management.

Producers should also be aware that irrigation systems with marginal or insufficient capacity may have allowed considerable soil water depletion during the preanthesis period.

Graphical data analysis for post-anthesis water stress studies