MISSISSIPPI SOYBEAN PROMOTION BOARD PROJECT NO (YEAR 2) 2013 Annual Report

Transcription

1 MISSISSIPPI SOYBEAN PROMOTION BOARD PROJECT NO (YEAR 2) 2013 Annual Report Title: Yield and economic response of soybean to irrigation initiation on a clay soil in Mississippi Project Leader: H. C. Pringle, III--lpringle@drec.msstate.edu EXECUTIVE SUMMRY In 2013, irrigation initiated at any time prior to stage R3.5 increased yields and net returns above those from a nonirrigated treatment. At all sites in 2013, statistically highest yields and greatest net returns to irrigation for MG 4 soybean varieties were achieved when irrigation was initiated at the late R2 R3 growth stages. Irrigation water savings of 2.5 to 5.5 acre-inches were realized by delaying irrigation initiation until the above stages. BACKGROUND AND OBJECTIVES Recent concerns over the sustainability of the Mississippi Delta s shallow alluvial aquifer, which serves as the water source for most agricultural irrigation in the Mississippi Delta, emphasizes the need for increasing agriculture s irrigation efficiency. Increased emphasis is being placed on proper irrigation scheduling for all crops in the Delta so that producers can produce maximum economical yields with the least amount of water. Proper irrigation scheduling begins with timely irrigation initiation. Significant shifts in soybean production from conventional soybean production systems (CSPS) to early soybean production systems (ESPS) and from varieties of MG s 5-7 to earlier MG 4 varieties warrant investigating irrigation initiation in an ESPS and MG 4 production environment. Previous research indicated yields could be maximized by initiating irrigations at beginning bloom (R1) on MG s 5-7 in the CSPS. Objective: Determine the relationship of irrigation initiation to soybean yield and economic response of MG 4 varieties grown in the ESPS with irrigation on Mississippi Delta soils. Procedures REPORT OF PROGRESS/ACTIVITY Three irrigation initiation x variety field studies were conducted in 2013 on three different soil types. The Bosket Dubbs SiL site at Stoneville, MS was sprinkler-irrigated (Site 1). A Dundee Forrestdale SiCL at Tribbett, MS (Site 2) and a Sharkey SiCL site at Stoneville, MS (Site 3) were both furrow-irrigated. Site 1 was conducted in a randomized complete block design with a split-plot arrangement of treatments in three replicates. Irrigation initiation treatments were randomized within replicates and varieties were randomized within initiation treatments. Plots were inch-wide rows that were 67 feet long.

2 Site 2 and 3 were conducted in a randomized complete block design with a factorial arrangement of treatments in four replicates. Plots were six 40-inch-wide rows that were feet long. At Site 3, two rows were left unplanted between all plots to provide a non-shrinking buffer zone between the irrigation treatments. Site 1 was planted on April 23 with HBK RY4620 and P94Y82 varieties. Site 2 was planted on April 30 with AG4632 and HBK RY4620 varieties. Site 3 was planted May 30 with Halo Liberty Link soybean 4:65 and 4:94. No difference in growth stages was observed between P94Y82 and RY4620 or AG4632 and RY4620 from bloom through maturity for these MG 4.6 to 4.8 varieties. Halo 4:65 was approximately 9-10 days ahead of Halo 4:94. Weeds were managed so that weed competition was not a factor limiting crop production in any study. Watermark soil water potential sensors were installed in two replicates of each irrigation initiation x variety treatment of each study. They were installed at three depths (8, 16, and 24 inches in furrow-irrigated plots; 6, 15, 24 inches in sprinkler-irrigated plots). Each site was instrumented with dataloggers that were set to read and store data every hour. The first irrigation initiation treatment of each study was initiated when soil water potential readings (SWP) averaged over all three depths were in the range of -20 to -40 kpa. Once the first irrigation initiation treatment was initiated, subsequent initiation treatments were initiated 4 days apart for sprinkler-irrigated and 5 days apart for furrow-irrigated plots except when rain occurred. The irrigation initiation dates and the approximate growth stage for each irrigation initiation treatment are given in Table 1, a-c. In general, subsequent irrigations for each initiation treatment were applied on a 4-day interval for sprinkler-irrigated and a 10-day interval for furrow-irrigated plots except when rain occurred. Estimated total water applied to each of the irrigation initiation treatments for each initiation study is given in Table 1, a-c. Soil water deficit (SWD) during the growing season was calculated by creating a water balance spreadsheet that used weather data to calculate crop water use (FAO 56 Method). Measurements of rainfall and water pumped were then used to estimate effective rainfall and irrigation. Whole plant samples from one square meter were taken approximately midway of each plot the week before harvest of each study. Plant height, plant number, nodes/plant, pods/plant, seed/plant, pods/m -2, and seed/m -2 were obtained from each sample. The two middle rows of each plot were harvested with a plot combine at Site 1. For the large plots in Sites 2 and 3, the upper and lower ends of the field were trimmed before plots were harvested. The middle four rows of Site 2 and the middle six rows of Site 3 of each plot were harvested with a commercial combine and seed were augured into a weigh cart to determine yield. A sample from each plot was taken for harvest moisture, test weight, and seed weight. Yields were adjusted to 13% moisture content. Data were subjected to analysis of variance and the means were separated by the least significant difference (LSD) procedure at the 5% level of significance. The economic analysis for all three field studies is based on partial budgeting of net returns above irrigation and hauling costs since all other factors of production were held constant and no difference in the seed cost by variety was assumed. Irrigation cost estimates are based on MSU budgets for sprinkler irrigation with a ¼ mile center pivot system and for furrow irrigation of a

3 160-acre tract using roll-out pipe (MSU Department of Agricultural Economics Budget Report , Appendix 13 & 14). The average reported soybean price for the week including the harvest date in the Delta area (USDA Market News- JK_GR110) is used to set the soybean price in the analysis for each study. Weather Winter rainfall (October 1, 2012 March 31, 2013) at Stoneville, MS was 2 inches above the 99- year average of 28 inches, indicating that likely the entire rooting profile was recharged to start the season on all sites. Monthly rainfall during the growing season was normal or near normal for all months except June and July, when the combined total was 5.56 inches, which was1.83 inches lower than the 99-year average of 7.39 inches. This included a period of no rainfall from June 6 to July 9. In 2013, one of the coolest growing seasons on record (2 nd lowest for the period April 1 July 31), average maximum air temperature was 81.6 F, which was 2.5 F lower than the 84- year average of 85.1 F. The low rainfall period occurred during peak water use of the soybean crop, thus requiring supplemental irrigation. Cooler maximum air temperatures enhanced yields. Seed Yield Site 1 Table 1-A. Average soybean yields of 89 and 88 bu/acre for P94Y82 and RY4620, respectively, were not significantly different. All irrigated treatments had average yield of 88 to 93 bu/acre, which was significantly greater than the 78 bu/acre non-irrigated (NI) treatment yield. This higher yield was due to an increase in seed weight (P>0.0002). No difference in yield was found among irrigation treatments initiated at or before June 25, or the late R2 growth stage. Site 2 Table 1-B. Average yield for both AG4632 and RY4620 was 75 bu/acre. Irrigated treatments had an average yield of 76 to 82 bu/acre, which was significantly greater than the 51 bu/acre from the NI treatment. This higher yield was due to an increase in seed weight (P>0.0001). The irrigation treatments initiated at or before June 24, or mid-r2 growth stage, were not significantly greater than yields from treatments with later irrigation initiation. Site 3 Table 1-C. Average yield for both Halo 4:65 and Halo 4:94 was 51 bu/acre. The average NI yield of 31 bu/acre was significantly lower than yields from all irrigated treatments, which averaged 53 to 60 bu/acre. This was due to reduced seed weights (P>0.0001) and reduced number of seed (seed/m^2, P>0.0002) in the NI treatment. The lower yields from both the irrigated treatments and the NI treatment from this site compared to Sites 1 & 2 are likely the result of the May 30 planting date. There was a significant difference in yields between the July 6 and July 11 initiation treatments, but those yields were not significantly different from the yield from the July 22 initiation treatment. Rainfall occurring on July 11, 14 and 19 (0.35, 0.79, and 0.26 inches) may have had some negative affect on the July 11 initiation treatment yields due to soil staying saturated longer. Rainfall also delayed the next initiation to July 22. With this rainfall, initiations could be delayed to as late as July 22 at R3 or R2 for Halo 4:65 and Halo 4:94, respectively, and yields were not significantly different from yields from the earlier initiations. Economic Analysis Estimated variable and fixed irrigation costs to set up for sprinkler irrigation are estimated at $76.12/acre, with additional fixed and variable costs of $5.56/acre-inch of water applied.

4 Estimated variable and fixed irrigation costs for furrow irrigation are estimated at $66.27/acre, with additional fixed and variable costs of $2.99/acre-inch applied. Estimated total irrigation costs per acre for each treatment for each study are shown in Table 2A- C. Soybean prices of $14.12, $13.63, and $13.42 were used for harvest dates of September 10, September 18, and October 23 at Sites 1, 2 and 3, respectively. Soybean hauling costs were estimated at $0.27/bu (MSU Department of Agricultural Economics Budget Report , Appendix 4). The mean and standard deviation, along with maximum and minimum expected net returns above irrigation and hauling costs for each treatment, are shown in Table 3a-c. Site 1 Table 3-A. There was no difference (P>0.25) in net returns among varieties. However, there was a significant difference among initiation dates at the P>0.06 level (LSD=$61/acre). All initiation treatments had statistically similar net returns, and all were greater than net return to the NI treatment. Site 2 Table 3-B. There was no significant difference in net returns between varieties (P>0.96), but there was a significant difference in net returns among irrigation initiation dates (P>0.0001). All irrigation treatments had a significantly higher net return per acre (LSD=$30/acre) than did the NI treatment. There was also a significant difference between irrigation treatments initiated before June 24 and irrigation treatments initiated on July 3. Site 3 Table 3-C. There was no significant difference (P>0.9944) in net returns between varieties, but there was a significant difference among irrigation initiation dates (P>0.0001). All irrigation treatments had a significantly higher net return per acre (LSD=$60/acre) than did the NI treatment. Soil Water Potential and Soil Water Deficit In each study there are three to four initiation treatments where yields were maximized, yet there was no statistical difference in yield or net return. Thus, the drier the soil is allowed to get within this Window of Opportunity, the less water will be applied without a negative effect on yield or net return. From 2013 results, irrigations should be initiated at or before average Watermark SWP readings in the active rooting zone reached -60, -75, and -50 kpa and before soybean reach R3 for Sites 1, 2, and 3, respectively (Figure 1A-C). When using an irrigation scheduler program, irrigations should generally should have been initiated at or before estimated SWD reached -4.2, -3.6, and -4.6 inches, respectively, for the three studies in 2013 (Figure 2 A-C). Results from 2012, which was conducted on a Sharkey SiCL soil, indicated irrigations should be initiated at or before average SWP readings reached -50 kpa or estimated SWD reached -2.6 inches. Due to variation in weather from year to year, additional years of data are needed to provide more definitive results. IMPACTS AND BENEFITS TO MISSISSIPPI SOYBEAN PRODUCERS Results from this project will help determine trigger value recommendations of when to initiate irrigations when using Watermark soil water potential sensors and irrigation scheduling programs, and when to apply water more timely in order to maximize economic yield while using the least amount of water. This should reduce irrigation (water and pumping costs) on all

5 irrigated soybean acreage. One less furrow irrigation will save approximately 3 acre-inches and would reduce irrigation operation costs by approximately $9.50/acre. End Products-Completed or Forthcoming A publication will be forthcoming after the conclusion of the project. Soybean and Corn Field Day, Stoneville, MS, July 18, Soybean and Corn Field Day, Stoneville, MS, July 19, Results have been referred to in support of other work presented by Jason Krutz in Irrigation Symposiums at: Tunica on February 10 Stoneville on February 26 Delta Area Water Conservation Meetings in Cleveland on February 17 in Sumner on February 18 in Indianola on February 20 in Belzoni on February 21 Mississippi, Arkansas, and Louisiana Extension Agent In-Service Training in Stoneville on February 24-25, 2013.

6 Table 1-A. Initiation date, yield, stage of growth, and water applied by initiation treatment from sprinkler irrigated initiation study on a Bosket Dubbs SiL soil, Delta Research and Extension Center, Stoneville, MS, Init 1 Init 2 Init 3 Init 4 Init 5 Variety June 13 June 17 June 21 June 25 June 29 NI Avg. Yield bu/acre P94Y a RY a Avg. 93 a 93 a 89 ab 91 ab 88 b 78 c Stage of Growth R2 R2 R2 R2 R3 R6.5 Water pumped in./acre LSD for comparing varieties = 2.4; LSD for comparing irrigation treatments = 4.5 Table 1-B. Initiation date, yield, stage of growth, and water applied by initiation treatment from furrow irrigated initiation study on a Dundee - Forrestdale SiCL soil, Tribbett, MS, Init 1 Init 2 Init 3 Init 4 Init 5 Variety June 14 June 19 June 24 June 29 July 3 NI Avg. Yield bu/acre AG a RY a Avg. 82 a 82 a 80 ab 78 b 76 c 51 d Stage of Growth R2 R2 R2 R2 R3 R6.5 Water pumped in./acre LSD for comparing varieties = 1.3; LSD for comparing irrigation treatments = 2.2 Table 1-C. Initiation date, yield, stage of growth, and water applied by initiation treatment from furrow irrigated initiation study on a Sharkey SiCL soil, Delta Research and Extension Center, Stoneville, MS, Init 1 Init 2 Init 3 Init 4 Variety July 6 July 11 July 22 Aug 6 NI Avg Yield bu/acre Halo 4: a Halo 4: a Average 60 a 56 b 56 ab 53 b 31 c Stage of Growth Halo 4:65 R2 R2 R3 R3.5 R6.5 Halo 4:94 V5 V7 R2 R3 R6.5 Water pumped in./acre LSD for comparing varieties = 2.8; LSD for comparing irrigation treatments = 4.5

7 Table 2. Estimated Irrigation Costs by Treatment. Initiation Inches Date Applied Cost/Acre A Sprinkler irrigated initiation study on a Bosket Dubbs SiL soil, Delta Research and Extension Center, Stoneville, MS June $128 June $124 June $119 June $114 June $109 NI - - B--Furrow irrigated initiation study on a Dundee Forrestdale SiCL soil, Tribbett, MS June $125 July $119 July $113 July $105 July $100 NI - - C Furrow irrigated initiation study on a Sharkey SiCL soil, Delta Research and Extension Center, Stoneville, MS July $113 July $99 July $99 August $92 NI - -

8 Table 3. Net Returns above Irrigation and Hauling Costs by Variety and Treatment. Initiation Date Mean Return Std Dev Max Min A Sprinkler irrigated initiation study on a Bosket Dubbs SiL soil, Delta Research and Extension Center, Stoneville, MS June 13 $1163 a $37 $1225 $1124 June 17 $1159 a $50 $1241 $1087 June 21 $1113 ab $51 $1174 $1025 June 25 $1152 a $31 $1194 $1099 June 29 $1103 ab $73 $1181 $1008 NI $1081 b $83 $1187 $943 LSD for comparing irrigation treatments = $61/acre. B Furrow irrigated initiation study on a Dundee Forrestdale SiCL soil, Tribbett, MS June 14 $964 ab $17 $983 $939 June 19 $974 a $21 $1009 $952 June 24 $958 ab $30 $997 $917 June 29 $941 bc $23 $977 $901 July 3 $913 c $22 $946 $887 NI $679 d $57 $768 $612 LSD for comparing irrigation treatments = $30/acre. C Furrow irrigated initiation study on a Sharkey SiCL soil, Delta Research and Extension Center, Stoneville, MS July 6 $680 a $18 $713 $660 July 11 $633 ab $21 $670 $607 July 22 $641 ab $47 $706 $568 August 6 $607 b $73 $688 $506 NI $405 c $90 $515 $214 LSD for comparing irrigation treatments = $60/acre.

9 a) b) c) Figure 1. Relative yield and soil water potential at initiation of irrigation. Window of Opportunity indicates no significant difference among yield and economic net returns.

10 a) b) c) Figure 2. Relative yield and estimated soil water deficit at initiation of irrigation. Window of Opportunity indicates no significant difference among yield and economic net returns.