Corn Production in the Texas High Plains:

Transcription

1 2014 Corn Production in the Texas High Plains: Gains in Productivity and Water Use Efficiency Prepared for Texas Corn Producers Board By Steve Amosson Shyam Nair Bridget Guerrero Thomas Marek DeDe Jones

2 Table of Contents Content Page No. Executive Summary 4 Introduction 5 Methodology 6 Description of Data 7 Baseline 9 Analysis of Scenarios 10 Comparison among Scenarios 20 Sources of Yield and Efficiency Improvements 21 Limitations 26 Summary 26 Acknowledgements 28 References 29 Appendix A 36 1

3 Table No. Title List of Tables Page No. 1 Descriptive statistics of the EPIC demonstration trials data 7 2 Descriptive statistics of the demonstration trials data 8 3 Descriptive statistics of the MC4TD demonstration trials data 9 4 Descriptive statistics of the baseline data (AgriPartners data from 1998 to 2002). 9 5 Year-wise, project-wise, and overall data on water use, production, and water use efficiency (Scenario I). 6 Year-wise, project-wise, and overall data on water use, production, and water use efficiency (Scenario II) Data on water use, production, and water use efficiency for normal (2010 and 2013) and warm (2011 and 2012) years along with the baseline (Scenario III). 19 2

4 List of Figures Fig. No. Title Page No. 1 The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water applied for data from the baseline (Scenario I) The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water for different years from the baseline (Scenario I). The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water applied for data from the baseline (Scenario II) The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water for different years from the baseline (Scenario II). The average of the daily maximum temperature (Tmax) for each month from May to September for 2010, 2011, 2012, 2013, and for the baseline (average of ). The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch total water for normal (2010 and 2013) years from the baseline (Scenario III). Comparison of the improvements in corn yield and water use efficiency estimates from the three scenarios

5 EXECUTIVE SUMMARY The high water demand and the susceptibility to water stress of corn have created an impression of corn being inefficient in water use. However, this high water use is usually more than compensated by increased yields. Moreover, genetic improvements and modern management practices have led to considerable yield and efficiency improvements in corn during the past decade. The objective of this study was to determine the benchmark water use by crop for the Texas Panhandle region from traditional crop production practices and evaluate the improvements over time due to improved technologies. Since insufficient field-scale data on irrigation and crop response of other crops in the region are not available, this analysis focused on quantifying the yield and efficiency gains of corn in the region. The AgriPartners demonstration from 1998 to 2002 served as the baseline for this analysis. The Efficient Profitable Irrigation in Corn (EPIC), the demonstration, and the More Crop for the Drop (MC4TD) demonstration provided recent data ( ). Corn yield (bushels per acre) per acre-inch of irrigation and yield per acre-inch of total water (irrigation + rain + soil profile contribution) were the two measures of water use efficiency used to analyze the efficiency improvements. Although 7.5% of fields were furrow irrigated in the baseline period, all fields were center pivot irrigated during Since the center pivot is more efficient than furrow, a direct comparison can bias the estimates. However, the adoption of center pivot irrigation increased significantly in the region in the last decade and its impact on efficiency gains should be considered. Moreover, 2011 and 2012 were unusually warm years, which may have influenced the yield and water use efficiency. Considering these factors, this study analyzed three different scenarios. In Scenario I, the data from only the center pivot irrigated fields are considered for the baseline enabling a pivot to pivot comparison. In Scenario II, the average of center-pivot and furrow irrigated data weighted by their respective adoption percentage is used as the baseline. The recent dataset was also readjusted as an average weighted by the adoption percentages in Since there were no furrow irrigated fields in the recent dataset, the furrow irrigation data from the baseline period was used for recent data after accounting for possible yield and efficiency gains. It is assumed that 75% of the improvement in yield and efficiency realized in the center pivot irrigated fields from the baseline to was attained by the furrow irrigated fields. The Scenario III is similar to Scenario II, but uses data only from 2010 and 2013 because of the significantly warmer weather encountered during 2011 and A significant reduction in water use and improvement in water use efficiency in the region were indicated in the results of all three scenarios analyzed. Results from scenarios I and II suggested % increase in irrigation water use efficiency and % increase in total water use efficiency. Scenario III can be considered as the most reliable estimate as it accounts for both the increased adoption of center pivot irrigation and the effects of differences in weather conditions. Estimates from Scenario III indicate that from to 2010 and 2013 the irrigation amounts decreased by 16.1%, total water applied decreased by 7.6%, corn yield per acre increased by 10.4%, corn yield per inch of irrigation increased by 27.7%, and corn yield per inch of total water applied increased by 18.6% in the region. Past research attributes about 60% of the historical yield increase in corn to genetic improvement and about 20% to increase in plant population. Irrigation scheduling and conservation tillage practices can reduce corn irrigation by 3 and 2 acre-inches per acre, respectively. The increased adoption of center pivot irrigation system in the Panhandle region from 2000 to 2013 is estimated to reduce the irrigation demand for corn in the region by approximately 3%. 4

6 INTRODUCTION The major irrigated crops in the Texas High Plains are corn, cotton, grain sorghum, and wheat. Corn is the primary user of irrigation in the Texas High Plains. In the Northern High Plains of Texas, 41% of the total irrigation water applied is used for corn production (Colaizzi et al., 2008). Corn has the highest seasonal evaporative demand among these crops with seasonal ET ranging from 29.5 to 35.5 inches depending on the prevailing weather conditions (Howell et al., 1996). This high evaporative demand and high water use have made the impression among the general public and policy makers that corn is not an efficient user of irrigation water. However, the high water requirement of corn is more than compensated by its increased productivity relative to other crops. Corn is physiologically more efficient in resource use compared to cotton and soybean. This difference in physiological efficiency makes corn potentially more efficient in the use of water, nitrogen, and CO 2 than crops like cotton, wheat, and soybean. (Brown, 1978; Held et al., 1990; Jones, 1983; McGinn and King, 1990; Pearcy and Ehleringer, 1984). For example, while soybean spends 704 water molecules to fix one molecule of CO 2, corn can do it by spending only 388 water molecules (Huang et al., 2006). The general concern over the high water use by corn also stems from the fact that it is more susceptible to water stress compared to most of the other field crops, particularly during the critical growth stages. However, field studies have demonstrated that techniques like controlled deficit irrigation can be used in corn to reduce the irrigation water application without significant yield reduction (Kang et al., 2000). While most of the corn produced in South and Central parts of Texas is dryland, almost all of the corn acreage in the Texas High Plains is irrigated. Considering the diminishing water availability from the Ogallala aquifer, the adoption of technological advances that lead to higher water use efficiency is essential for corn production to remain economically viable in the region. The Texas High Plains has experienced considerable changes in irrigated corn production during the last decade, which has led to significant improvements in corn yield and water use efficiency. Irrigated corn yields increased approximately 2.3 bushels/acre/year from 1980 to 2010 in the Northern High Plains (NASS, 2014). In the meantime, the declining water availability from the Ogallala aquifer, which is the principal water source for the region, has resulted in substantial decrease in water available for irrigation in several areas of the region. This suggests that the yield increase was also accompanied by improvement in water use efficiency enabling the producers to obtain higher yield with lower irrigation amounts. The major factors that led to the improvement in yield and water use efficiency were genetic improvements, better irrigation scheduling, adoption of conservation tillage practices, and adoption of more efficient irrigation equipment. However, the extent of improvement in yield and water use efficiency and the role of these important factors on these gains have not been well documented. The objective of this study is to determine the benchmark water use by crop for the region from traditional crop production practices and evaluate any improvements over time due to improved technologies. The original plan was to assess the improvements in yield and water use efficiency of the four major irrigated crops in the region (corn, cotton, wheat, and grain sorghum) and compare the efficiency gains of these crops. However, because of limitations on availability of field-scale data for cotton, sorghum, and wheat, this study focused on evaluating the yield and efficiency gains for corn in the region due to improved technologies. 5

7 The water use, yield, and water use efficiency data from the AgriPartners demonstration trials (Texas AgriLife Extension, 2011) from 1998 to 2002 was used as the baseline. This baseline data was compared with data from different recent demonstrations trials in the region during 2010 to 2013 to evaluate possible yield and efficiency improvements. Initially, the baseline was going to be compared to the most recent five year period ( ), however, the data for 2009 was not available from any of the demonstration projects and so the four year period ( ) was used in the analysis. METHODOLOGY Different measures of water use, productivity, and water use efficiency were used to quantify the improvements in the High Plains corn production over the last decade. The amount of irrigation and the amount of total water applied, both measured in acre-inches per acre were used to quantify water use. The total water applied is the sum of the amount of irrigation, seasonal rainfall, and soil profile contribution. Soil profile contribution is the difference between the soil moisture content in the beginning and at the end of the season. Corn yield expressed in bushels per acre was used as a measure of productivity. Since water use efficiency considers both the water use and crop productivity, it provides the most important comparison between the performance of conventional and modern practices. Corn yield per acre-inch of irrigation and corn yield per acre-inch of total water applied were the two measures of water use efficiency used in this study. The yield response of corn depends on the total amount of water received by the crop rather than the amount of irrigation applied. Hence yield per acre-inch of total water applied serves as a good measure of water use efficiency. However, rainfall, which is an important component of the total water, cannot be controlled by the producers. The amount and distribution of rainfall is stochastic whereas the producer can allocate irrigation to coincide with the crop needs. The producer also can usually adjust the irrigation based on the rainfall events. The production per unit of irrigation is also important from a water conservation point of view. Therefore, both the yield per acre-inch of irrigation and yield per acre-inch of total water were used in the analysis and considered equally significant measures of efficiency. The reduction in water use and gains in productivity and water use efficiency is estimated by comparing the measures of water use, productivity, and water use efficiency of the baseline period to the recent time period. The data for from the AgriPartners demonstration was used as the baseline based on the recommendation of the project advisory committee. The original plan was to compare data from this 5 year baseline period to 5 years of recent dataset from 2009 to However, field scale demonstration data was not available during 2009 in the region. Therefore, the data from the 4 year period (2010 to 2013) was used as the recent dataset. Three different demonstration projects provided the data on corn yield and water use efficiency for the recent years (2010 to 2013). The demonstration projects that provided recent data were Efficient Profitable Irrigation in Corn (EPIC) demonstration conducted by Texas AgriLife Extension and funded by the North Plains Groundwater Conservation District (Kenny et al., 2012; Kenny et al., 2013; Bragg et al., 2014), demonstration project of the North Plains Groundwater Conservation District (NPGCD, 2010; 2011; 2012; 2013), and More Crop for the Drop (MC4TD) demonstration project of the Panhandle Groundwater conservation district (PGCD, 2011; 2012). 6

8 DESCRIPTION OF DATA Detailed description of the data from the recent demonstration trials used in this analysis is provided in this section. Description of the baseline data is provided along with baseline analysis in the section titled baseline. The Efficient Profitable Irrigation in Corn (EPIC) demonstration provided water use, yield, and water use efficiency data for 2011, 2012, and EPIC is a field demonstration trial with two side-by-side plots designated as Legacy and EPIC. The Legacy plot served as control, where standard practices of the specific producer were followed. The EPIC plot was managed with the objectives of maintaining or improving yield compared to Legacy while reducing irrigation amount by one to four inches. All fields were center pivot irrigated during all years of the EPIC demonstration project. The descriptive statistics of the EPIC data are provided in Table 1. Table 1. Descriptive statistics of the EPIC demonstration trials data. Year No. of observations All Data 26 Water (inches) Production (Bushels) Statistic Total Per inch Per inch Irrigation Per acre Water irrigation total water Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation There were considerable differences in irrigation, total water applied, corn yield, and water use efficiency among different years during the EPIC demonstration trial (Table 1). The corn yield and water use efficiency was higher in 2013 compared to 2011 and The EPIC demonstration treatments had 6.63% less irrigation water applied and 5.36% less total water applied, but produced 10.44% more yield compared to the control ( Legacy ). The demonstration project conducted by the North Plains Groundwater Conservation District (NPGCD, 2010; 2011; 2012; 2013) provided data for 2010, 2011, 2012, and The demonstration project seeks to produce 200 bushels of corn with application of 12 inch irrigation through scientific irrigation scheduling. It also had control plots, where the specific producer s practices were followed. Other than the control and demonstration plots, several producers were also involved in small plot experiments to evaluate competing hybrids and different plant densities. Thus the project provided comparatively larger dataset. However, high temperature and drought during 2011 and 2012 forced some producers to 7

9 withhold irrigation in the demonstration plot to make water available to the larger control plots. Therefore, low yielding plots were not considered in the analysis. All fields were center pivot irrigated during all years of the demonstration project. The descriptive statistics of the data are provided in Table 2. Table 2. Descriptive statistics of the demonstration trials data. Year No. of observations All Data 123 Water (inches) Production (Bushels) Statistic Total Per inch Per inch Irrigation Per acre Water irrigation total water Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Significant differences in irrigation water applied, total water applied, corn yield, and water use efficiency among different years during the demonstration project can be observed from the data presented in Table 2. It is interesting to note that the average yield is relatively lower for 2011 and 2012, which may be a direct effect of the unusually high air temperature experienced during those two cropping seasons. The corn yield was the highest in 2013, where the average yield was 205 bu./acre and was the lowest in 2012, where the average yield was only 174 bu./acre. More Crop for the Drop (MC4TD) demonstration project of the Panhandle Groundwater Conservation District (PGCD, 2011; 2012) provided data on water use, corn yield, and water use efficiency for 2011 and The descriptive statistics of the MC4TD data are provided in Table 3. MC4TD project is a field scale crop production demonstration with producers using advanced soil monitoring, irrigation system tracking, and onsite data management to reduce corn and cotton irrigation (PGCD, 2014). All fields were center pivot irrigated during all years of the MC4TD demonstration project. The descriptive statistics of the MC4TD demonstration data indicate considerably lower corn yield and water use efficiency for the MC4TD demonstration project compared to other demonstration projects. The corn yield and water use efficiency is considerably lower in 2011 compared to 2012 for the MC4TD demonstration (Table 3). This demonstration project also had only a small number of observations. 8

10 Table 3. Descriptive statistics of the MC4TD demonstration trials data. Year No. of observations All Data 5 Water (inches) Production (Bushels) Statistic Total Per acre-inch Per acre-inch Irrigation Per acre Water irrigation total water Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation BASELINE The AgriPartners demonstration project (AgriLife Extension, 2011) provided water use, productivity, and water use efficiency data for corn from 1998 to The AgriPartners program was a demonstration project, where Texas A&M AgriLife Extension partnered with commodity groups, water districts, and producers to demonstrate and disseminate improved technologies and practices. The project provided data on irrigation practice, irrigation amount, rainfall and soil profile contribution to the consumptive use, crop productivity, yield per inch of irrigation, and yield per inch of total water (irrigation + rainfall +soil profile contribution). The five year average of the AgriPartners data from 1998 to 2002 was used as the baseline. The demonstration project during 1998 to 2002 had both center pivot and furrow irrigated fields. The descriptive statistics of the AgriPartners data during the baseline years is presented in Table 4. The statistics are provided separately for furrow and center pivot irrigated fields and for the overall data. Table 4. Descriptive statistics of the baseline data (AgriPartners data from 1998 to 2002). Irrigation method Center Pivot No. of observations 87 Furrow 7 All data 94 Water (inches) Production (Bushels) Statistic Total Per inch Per inch Irrigation Per acre Water irrigation total water Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation Average Minimum Maximum Standard Deviation

11 The baseline data ( ) had a total of 94 observations. Out of this 94 observations, 84 (92.55%) were from center pivot irrigated fields and 7 (7.45%) were from furrow irrigated fields. A total of 33 observations in the baseline data were from 1998 of which 28 (84.85%) of the observations were from center pivot irrigated fields and 5 (15.15%) were from furrow irrigated fields. Sixteen observations were from 1999, of which 14 (87.50) fields were center pivot irrigated and 2 (12.50%) were furrow irrigated. All observation in the years 2000, 2001, and 2002 were from center pivot irrigated fields. There were 17, 11, and 17 observations during 2000, 2001, and 2002, respectively. Considerable differences in water use, yield, and water use efficiency between center pivot and furrow irrigated fields can be observed from the data provided in Table 4. The average irrigation amount was acre-inches per acre in the center pivot irrigated fields and acre-inches per acre in the furrow irrigated fields. The average irrigation was acre-inches per acre over all observations. Similarly, the amount of total water applied was also higher in the furrow irrigated fields compared to the center pivot irrigated fields. The average yield was only bushels per acre in the furrow irrigated fields whereas the average corn yield was bushels per acre in the center pivot irrigated fields. There were considerable differences in the water use efficiency between the center pivot and furrow irrigated fields. The average irrigation water use efficiency was 6.53 and 9.31 bushels per acre per acre-inch of irrigation for furrow and center pivot irrigated fields, respectively. The average efficiency of total water use was 6.53 bushels per acre per acre-inch of total water applied for furrow irrigated fields while it was 9.31 bushels per acre per acre-inch of total water applied for center pivot irrigated fields. This shows that the corn yield per acre-inch of irrigation is 42.57% higher in center pivot irrigated fields compared to furrow irrigated fields. Similarly the yield per acre-inch of total water applied was 34.12% higher in center pivot irrigated fields compared to furrow irrigated fields. The large differences in water use, yield, and water use efficiency among center pivot and furrow irrigated fields indicate that the irrigation equipment used in the field can have significant impact on the water use, yield, and water use efficiency. All observations in the recent dataset are from the center pivot irrigated fields and this creates difficulty in having meaningful comparison between the baseline and recent data. Moreover, year to year differences in weather conditions will have significant impact on the yield and water use efficiency of corn. Therefore, controlling the effect of weather is also essential for arriving at reliable estimates of yield and efficiency gains. Considering these multiple confounding factors, the potential yield and efficiency gains were estimated under three different scenarios as described below. ANALYSIS OF SCENARIOS As per the recommendations of the advisory committee, the average of the AgriPartners data for 1998 to 2002 is used as the baseline for this analysis. However, about 7.5% of the fields were furrow irrigated (the rest of the fields were center pivot irrigated) during the baseline years, whereas all fields were center pivot irrigated in all of the recent demonstration trials. Hence comparing the average baseline data with the average of recent data may provide a biased estimate. Hence the first scenario (Scenario I) is a very conservative scenario, where the data from only the center pivot irrigated fields is considered for the baseline and it is compared with center pivot irrigated fields during enabling a pivot to pivot comparison. 10

12 Scenario I The first scenario uses the average of data only from the center pivot irrigated fields in the AgriPartners demonstration trials from as the baseline. This baseline is compared with the average of EPIC, , and MC4TD data to estimate improvements in yield and efficiency from the baseline period ( ) to due to technological improvements. Absolute and percentage gains in yield and water use efficiency are reported. Because there were significant differences in yield and water use efficiency among different years, annual comparisons were also made. Since the recent datasets are comprised of center pivot irrigated fields only, this scenario provides a straight forward pivot to pivot comparison. The baseline and recent data in Scenario I are provided in Table 5. Results are also analyzed by year and by project to identify differences among various years and projects. Table 5. The data on water use, production, and water use efficiency of corn (Scenario I). The data is presented by year and by project also. Project / Year Number of observations Water (acre-inches) Total Irrigation Water* Production (Bushels per acre) Yield/ inch Yield/ inch Yield irrigation total water EPIC MC4TD BASELINE** *The total water is the sum of irrigation, rainfall, and soil profile contribution. **The baseline in this analysis uses data only from the center pivot irrigated fields of the AgriPartners demonstration project from During the baseline period acre-inch of irrigation water (30.23 acre-inches of total water) was applied to produce bushels per acre of corn when the data from only center pivot irrigated fields are considered. This translates to 9.31 bushels of corn production per inch of irrigation and 6.25 bushels per inch of total water applied (Table 5). However, in the recent demonstrations, bushels per acre of corn was produced with only acre-inches of irrigation water (27.92 acre-inches of total water). This resulted in higher water use efficiency during the recent years with the production of bushels of corn per inch of irrigation and 6.98 bushels per inch of total water applied. There were significant differences in irrigation amounts, corn production, and water use efficiency among different years and different demonstration project. The yield per inch of irrigation was the highest in 2010 with bushels of corn production per inch of irrigation, whereas it was lowest in 2011 with only 8.36 bushels of corn produced per inch of irrigation. Among the different demonstration projects, EPIC recorded the highest yield ( bushels per acre) while MC4TD registered the lowest yield ( bushels per acre). The demonstration project had the highest water use efficiency with bushels of corn production per inch of irrigation and 7.21 bushels per inch of total water (Table 5). 11

13 Percentage change from the Baseline (%) The percentage change from the baseline serves as a good indicator that also allows comparison among the scenarios. The percentage changes in water use, yield, and water use efficiency relative to the baseline for the recent ( ) data is presented in Figure Irrigation (inch) Total Water (inch) Yield (bu/acre) Yield / inch irrigation Yield / inch total water -6-9 Figure 1. The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water applied for data from the baseline (Scenario I). The amount of irrigation was 7% lower and the amount of total water applied was 7.6% lower during compared to the baseline (Figure 1). Even with this lower amount of water, the corn yield increased by 3.7%. This suggests improvements in water use efficiency, which is evident from the 8.3% increase in yield per inch of irrigation and 11.6% increase in the yield per inch of total water applied. Therefore, corn producers in the regions are using lesser water and are using the available water more efficiently. As discussed earlier, there are significant differences in water use, corn yield, and water use efficiency among different years and among different demonstration trials. One reason for such significant differences among the demonstration trials is the differences in weather conditions because the trials were conducted during different years. The EPIC demonstrations were conducted in 2011, 2012, and The demonstration project was conducted during 2010, 2011, 2012, and MC4TD demonstration project was conducted during 2011 and The year to year differences in the amount and distribution of rainfall, air temperature, and solar irradiance can have significant impact on corn productivity and water use efficiency. Because the yield and water use efficiency depends on many climatic, soil, and agronomic factors, it is important to have annual and by project analyze of the data. To understand the year to year differences in corn yield, water use, and water use efficiency, the data was analyzed annually and the results are presented in Figure 2. 12

14 Percentage change from the baseline (%) Irrigation (inch) Total Water (inch) Yield (bu/acre) Yield / inch irrigation Yield / inch total water Figure 2. The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water for different years from the baseline (Scenario I). It can be observed from Figure 2 that years 2010 and 2013 were excellent in terms of water use efficiency and both also recorded higher yields than the baseline. Irrigation was 47.4% lower than the baseline in 2010 and in spite of that the yield increased by 0.76% leading to a staggering 75.8% increase in the yield per inch of irrigation. In 2013, the yield went up by 12.8% although irrigation and total water applied decreased by 8.1 and 7.3% respectively. This resulted in increase in yield per inch of irrigation by 15.4% and yield per inch total water by 20.5%. On the other hand, the yield was lower than the baseline in 2011 and The yield per inch irrigation decreased by 10.3% in 2011 whereas it decreased by 4.0% in There were differences in gains in yield and water use efficiency among different demonstration projects also. The analysis by project, which shows percentage change in irrigation, yield, and water use efficiency for each demonstration project from the baseline, is provided in Appendix A (Figure A-1). However, this analysis (Scenario I) compares only center pivot irrigated fields, thus may have underestimated the yield and efficiency gains. One possible source of underestimation is the gains in yield and water use efficiency from changes in irrigation equipment. This gain can be significant considering the increased transition from low efficiency furrow irrigation system to the high efficiency center pivot irrigation system in the region in the last decade. The effect of increased adoption of the more efficient irrigation equipment on the corn water use, yield, and water use efficiency is considered in the Scenario II. 13

15 Scenario II The second scenario uses the average of the data from center pivot and furrow irrigated fields in the AgriPartners demonstration project from weighted by their respective adoption percentages in the Texas Panhandle region in the year 2000 as the baseline. The recent dataset also is readjusted as an average weighted by the respective adoption percentages in Since the recent dataset did not have any furrow irrigated fields, the data from the furrow irrigated fields in the AgriPartners demonstration project from is used to estimate yield and water use efficiency for furrow irrigated fields in To account for the yield and efficiency improvements from genetic improvements and advances in irrigation scheduling in the past decade in the furrow irrigated fields, it is assumed that 75% of the improvements in yield and water use efficiency realized in the center pivot irrigated fields (estimated in Scenario I) will be attained by the furrow irrigated fields. This improvement is added to the data for the furrow irrigated fields in the baseline period to estimate the water use, yield and water use efficiency of furrow irrigated fields in This estimated data for furrow irrigated fields is then used along with the demonstration data for center pivot irrigated fields to find the average of center pivot and furrow irrigated fields as an average weighted by the adoption percentage of center pivot and furrow irrigated system in the region in This analysis used the average of both the center pivot and furrow data weighted by their respective adoption percentage in the Texas Panhandle region in the year 2000 to estimate the baseline. Since only a small percentage of the acreage is irrigated by sub surface drip system (less than 1.5%), it was ignored in this analysis. The adoption percentage of center pivot irrigation system in the Panhandle region of Texas was approximately 81% in 2000 (Texas Water Development Board, 2001). Therefore, the baseline data was calculated as the average of center pivot and furrow data weighted by 0.81 and 0.19, respectively. The demonstrations did not have any data from the furrow irrigated fields. Therefore, the data from the furrow irrigated fields during the baseline period is used to estimate the water use, yield, and water use efficiency of furrow irrigated fields in Since the furrow irrigated data is from , it was necessary to account for the enhancement in yield and water use efficiency for the furrow irrigated fields from to A major portion of the improvements in yield and water use efficiency in corn is from genetic improvement and better irrigation scheduling. Both of these factors can enhance the yield and water use efficiency of corn in both the center pivot and furrow irrigated fields in the same way. This analysis assumes that 75% of the yield improvement achieved in the center pivot irrigated fields from the baseline to is achieved by the furrow irrigated fields also. The data from furrow irrigated fields during the baseline period is modified to account for this yield and efficiency enhancements. To do the modification, the irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water of the furrow irrigated fields during is estimated by applying the percentage increase in these measure (from the baseline to estimated in Scenario I) to the data from furrow irrigated fields during the baseline period ( ). Then the average of these modified data (furrow) and data (center pivot) weighted by the percentage of adoption of furrow and center pivot during 2013 in Texas Panhandle was calculated. This new dataset was then used to perform analysis in Scenario II. 14

16 No regional data is available on adoption of different irrigation systems in the Texas Panhandle in The adoption percentage of center pivot irrigation system in the region in 2013 was estimated by comparing the historic adoption rates in the region with the adoption rates in the state of Texas. Historic data on adoption of sprinkler irrigation system in the Panhandle region of Texas is available from the survey of irrigation in Texas for 1958, 1964, 1969, 1974, 1979, 1984, 1989, 1994, and 2000 (Texas Water Development Board, 2001). The adoption percentage of center pivot irrigation system in Texas is available for 1998, 2003, and 2008 from the Farm and Ranch Irrigation Survey of the respective years (USDA, 1998; 2003; 2008). The adoption percentage of center pivot irrigation system in the Texas Panhandle region for 1998 was estimated applying a cubic fit regression analysis to the regional data from This analysis showed that about 75% of the irrigated acreage in the Panhandle region was center pivot irrigated in The state level data showed that the adoption percentage of sprinkler irrigation in Texas is increasing at a decreasing rate. The adoption percentage increased by about 25% for a five year period when the beginning level of adoption was about 75%, but the increase for the five year period was only 20% when the beginning level of adoption was about 80%. Therefore it was assumed that there was a 25% increase from the adoption rate of 75% in 1998 for the first five years, 20% for the next five years, and 15% for the next five years. From these calculations the adoption percentage of the center pivot irrigation system in the Texas Panhandle was estimated to be approximately 87% in Hence, the demonstration data (center pivot) from is averaged with the estimated furrow data (after adjusting for yield and efficiency gains) weighted by 0.87 and 0.13, respectively, to get the modified data for The data used for analysis in Scenario II is provided in Table 6. Results are also delineated by year and by project to identify differences among different years and projects. Table 6. The data on water use, production, and water use efficiency of corn (Scenario II). The data is presented by year and by project also. Project / Year Number of observations Water (acre-inches) Total Irrigation Water* 15 Production (Bushels per acre) Yield/ inch Yield irrigation Yield/ inch total water EPIC*** *** MC4TD*** *** *** *** *** *** BASELINE** *The total water is the sum of irrigation, rainfall, and soil profile contribution. **The baseline in this analysis the weighted average of the data from center pivots and furrow irrigated fields from the AgriPartners data from weighted by the respective adoption percentage in *** The demonstration project data in this analysis is modified by taking average of center pivot data from the demonstrations and estimated furrow data weighted by the adoption percentage of center pivot and furrow irrigation systems in the region in 2013.

17 Percentage change from the baseline (%) It can be observed from Table 6 that during , bushels of corn was produced per acre with inch of irrigation water (28.94 inch of total water). This indicates an improvement in water use efficiency in the recent time period with the production of 9.67 bushels of corn per inch of irrigation and 6.73 bushels per inch of total water applied compared to 8.78 and 5.78, respectively, during the baseline period. Also shown in Table 6, corn productivity was the highest in 2013 with bushels per acre and was the lowest in 2012 with bushels per acre. The yield per inch of irrigation was the highest in 2010 with bushels of corn production per acre-inch of irrigation, whereas it was lowest in 2011 with only 8.05 bushels of corn produced per acre-inch irrigation. The yield per inch of irrigation was the highest in 2013 (7.25 bushel/ inch) and was the lowest in 2010 (6.10 bushels/ inch). Among the different demonstration projects, EPIC recorded the highest yield ( bushels per acre) while MC4TD registered the lowest yield ( bushels per acre). The demonstration project showed the highest water use efficiency with 10.2 bushels of corn production per inch of irrigation and 6.94 bushels per inch of total water. The percentage changes in yield and water use efficiency relative to the baseline for the recent data in Scenario II is illustrated in Figure 3. The amount of irrigation was 8.6% lower and the amount of total water applied was 8.7% lower than the baseline. Even with this lower amount of water, the corn productivity increased by 4.1% increasing water use efficiency. The results showed a 10.11% increase in yield per acre-inch of irrigation and 13.12% increase in the yield per acre-inch of total water applied Irrigation (inch) Total Water (inch) Yield (bu/acre) Yield / inch irrigation Yield / inch total water -10 Figure 3. The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water for data from the baseline (Scenario II) 16

18 Percentage change from the baseline (%) Analysis of the data by year was also performed to identify the year to year differences in yield and water use efficiency. The results of the annual analysis are presented in Figure 4. Irrigation was 46.5% lower than the baseline in 2010 and in spite of that the yield increased by 1.2% leading to a staggering 77.3% increase in the yield per inch of irrigation. In 2013, the yield went up by 12.9% although irrigation and total water applied decreased by 9.7 and 8.4%, respectively. This resulted in increase in yield per inch of irrigation by 17.2% and yield per inch of total water by 21.9%. On the other hand, the yield was lower than the baseline in 2011 and 2012 by 1.3 and 1.6%, respectively. The yield per inch of irrigation decreased by 8.3% in 2011 whereas it decreased by 1.6% in Figure 4. The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch of total water for different years from the baseline (Scenario II). There were differences in gains in yield and water use efficiency among different demonstration projects in Scenario II. The analysis by project that shows percentage change in water use, yield, and water use efficiency for each demonstration project from the baseline in Scenario II, is provided in Appendix A (Figure A-2). Analyses conducted in Scenario I and Scenario II show very significant year to year differences in water use, yield, and water use efficiency in the recent years. Therefore, it is important to investigate if there are considerable differences in weather parameters during any of the recent years that may bias the estimates. Scenario III takes the impact of weather into consideration and further refines the estimates of gains in corn yield and water use efficiency obtained in Scenario II. Scenario III Irrigation (inch) Total Water (inch) Yield (bu/acre) Yield / inch irrigation Yield / inch total water High temperature during the growing season negatively influences the corn yield. Years 2011 and 2012 were unusually warm, which may be the reason for yield and water use efficiency reduction during these years. The monthly average of daily maximum temperature (Tmax) for each month from May to September for 2010, 2011, 2012, and 2013 are presented in Figure 5 along with that for the baseline (average for ). 17

19 Average of daily maximum temperateure ( o F) It can be observed from Figure 5 that 2011 and 2012 were much warmer than the baseline period and the rest of the recent years. Particularly 2011 was considerably warmer than the baseline throughout the corn growing season. This may be the reason for the low yield during 2011 even with higher irrigation leading to a reduction in water use efficiency. Similarly, the temperature was higher than the baseline during 2012 also, especially during the early and flowering stage of corn. This may be a contributing factor to the low corn productivity during The significantly higher air temperature during 2011 and 2012 warrants an analysis where the normal (2010 and 2013) and the warmer (2011 and 2012) years are considered separately May June July August September Baseline Figure 5. The average of the daily maximum temperature (Tmax) for each month from May to September for 2010, 2011, 2012, 2013, and for the baseline (average of ). Since the high temperature may have adversely affected the yield and water use efficiency during 2011 and 2012, an analysis was performed to look at these years (warm years) and the rest (normal years; 2010 and 2013) separately. The abnormally warm years of 2011 and 2012 may have adversely affected corn yield and water use efficiency leading to underestimation of the yield and efficiency improvements. Because 2010 and 2013 had temperature similar to the baseline the data, these years may provide better indication of extent of the yield and efficiency improvements relative to the baseline. The data on irrigation, yield, and water use efficiency for the warmer and normal years are provided along with the baseline in Table 7. During the normal years (2010 and 2013), corn yield of bushels per acre was achieved from only 19.3 acre-inch of irrigation. The water use efficiency was considerably higher during these years with 11.2 bushels of corn produced per acre per acre-inch of irrigation and 7.1 bushels per inch of total water applied. On the other hand, during the warm years of 2011 and 2012, the corn yield (178.9 bushels per acre) was lower than the baseline yield (181.6 bushels per acre) although the amount of irrigation was more or less the same as the baseline. This suggests that the yield and efficiency gains are not fully expressed by the average of these four years and the mean of 2010 and 2013 may provide a more realistic estimate of the yield and efficiency improvements. 18

20 Percentage change from the baseline (%) Table 7. Data on water use, production, and water use efficiency for normal (2010 and 2013) and warm (2011 and 2012) years along with the baseline (Scenario III). Project / Year Number of observations Water (acre-inches) Total Irrigation Water* Production (Bushels per acre) Yield/ inch Yield irrigation Yield/ inch total water 2010 and 2013*** and 2012*** BASELINE** *The total water is the sum of irrigation, rainfall, and soil profile contribution. **The baseline in this analysis the weighted average of the data from center pivots and furrow irrigated fields from the AgriPartners data from weighted by the respective adoption percentage in *** The demonstration project data in this analysis is modified by taking average of center pivot data from the demonstrations and estimated furrow data weighted by the adoption percentage of center pivot and furrow irrigation systems in the region in Since the weather during 2011 and 2012 were so much different from the baseline, it was felt that the estimates will be more realistic if these years were dropped from the analysis and only the normal years (2010 and 2013) considered. The percentage change in water use, yield, and water use efficiency for the normal (2010 and 2013) years from the baseline is provided in Figure % % % Irrigation (inch) Total Water (inch) Yield (bu/acre) Yield / inch irrigation Yield / inch total water % % Figure 6. The percentage changes in irrigation, total water, yield, yield per inch of irrigation, and yield per inch total water for normal (2010 and 2013) years from the baseline (Scenario III). In this analysis, the irrigation decreased by 16.07% and the total water applied decreased by 7.57% during the normal years compared to the baseline. The corn yield was 10.9% higher than the baseline (Figure 6). The improvement in the water use efficiency also is 19