Kansas Field Research Kansas State University Agricultural Experiment Station and Cooperative Extension Service

Transcription

1 Kansas Field Research 2015 Kansas State University Agricultural Experiment Station and Cooperative Extension Service

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3 Contents Kansas Field Research East Central Kansas Experiment Field 5 Forage Sorghum Performance Trial 7 Late-Season Nitrogen Fertilizer Application in Soybean 9 Corn Yield Response to Plant Populations 12 Kansas River Valley Experiment Field 14 Effects of Seed Treatment on Sudden Death Syndrome Symptoms and Soybean Yield 18 Effects of an Experimental Seed Treatment from DuPont on Sudden Death Syndrome Symptoms and Soybean Yield 21 Soybean Sudden Death Syndrome Influenced by Macronutrient Fertility on Irrigated Soybean in a Corn/Soybean Rotation 25 Tillage Study for Corn and Soybean: Comparing Vertical, Deep, and No-Till 28 Grain Sorghum Yield Response to Water Availability 31 Department of Agronomy 31 Balanced Nutrition and Crop Production Practices for Closing Grain Sorghum Yield Gaps 35 Corn Yield Response to Water Availability 38 Cover Crop Impacts on Soil Water Status 43 Soybean Planting Date Maturity Group: Eastern Kansas Summary 1

4 Contributors E.A. Adee, Assistant Professor, Kansas River Valley Experiment Field, Topeka J.P. Broeckelman, Graduate Research Assistant, Dept. of Agronomy, Kansas State University. Manhattan I. Campitti, Assistant Professor, Dept. of Agronomy, Kansas State, University. Manhattan D.R. Hodges, Research Assistant, Dept. of Agronomy, Kansas State University. Manhattan J. Kimball, Plant Science Technician, East Central Experiment Field, Ottawa G. J Kluitenberg, Professor, Dept. of Agronomy, Kansas State University. Manhattan M. Kuykenkall, Graduate Research Assistant, Dept. of Agronomy, Kansas State University. Manhattan B. McHenry, Graduate Research Assistant, Dept. of Agronomy, Kansas State University. Manhattan J. L. Moyer, Professor, Southeast Agricultural Research Center, Parsons T. Newell, Graduate Research Assistant, Dept. of Agronomy, Kansas State University. Manhattan P.V.V. Prasad, Professor, Crop Physiology, Dept. of Agronomy, Kansas State University. Manhattan K.L. Roozeboom, Associate Professor, Cropping Systems, Dept. of Agronomy, Kansas State University. Manhattan D. Ruiz-Diaz, Associate Professor, Dept. of Agronomy, Kansas State University. Manhattan G. Sassenrath, Associate Professor, Southeast Agricultural Research Center, Parsons D. Shoup, Crops and Soils Specialist, Southeast Area Office, Chanute 2

5 East Central Kansas Experiment Field East Central Kansas Experiment Field Introduction The research program at the East Central Kansas Experiment Field is designed to keep area crop producers abreast of technological advances in agronomic agriculture. Specific objectives are to (1) identify top-performing varieties and hybrids of wheat, corn, soybean, and grain sorghum; (2) establish the amount of tillage and crop residue cover needed for optimum crop production; (3) evaluate weed and disease control practices using chemical, no chemical, and combination methods; and (4) test fertilizer rates, timing, and application methods for agronomic proficiency and environmental stewardship. Soil Description Soils on the field s 160 acres are Woodson. The terrain is upland and level to gently rolling. The surface soil is a dark gray-brown, somewhat poorly drained silt loam to silty clay loam over slowly permeable clay subsoil. The soil is derived from old alluvium. Water intake is slow, averaging less than 0.1 in./hour when saturated. This makes the soil susceptible to water runoff and sheet erosion Weather Information Precipitation during 2014 totaled (27.04 in.), which was 9.7 in. below the 35-year average (Table 1). Overall, the 2014 growing season was cooler than June and October were the only months receiving above the average rainfall for each period. The summer of 2014 had 30 days exceeding 90.0ºF, and three of those days exceeded 100.0ºF. The coldest temperatures occurred in January, February and November, with 28 days with low temperatures in single digits. The last freezing temperature in the spring was April 18 (average: April 18), and the first killing frost in the fall was October 31 (average: October 21). There were 196 frost-free days, which is more than the longterm average of 185. The early season growing conditions were very good until July after corn pollination. This is reflected in the short-season and full-season corn hybrid trials that averaged 172 and 195 bu/a, respectively. The drier July and August had a greater effect on soybean yields, with the soybean variety trial averaging 41 bu/a. 3

6 East Central Kansas Experiment Field Table 1. Precipitation at the East Central Kansas Experiment Field, Ottawa Month year avg. Month year avg in in January July February August March September April October May November June December Annual total

7 East Central Kansas Experiment Field Forage Sorghum Performance Trial J.L. Moyer and E.A. Adee Summary In our sorghum trials, production of forage was greater (P < 0.05) for FS 4 and AF 7401 than for AF 7202, possibly related to differences in maturity. Estimated grain production was greater for AF 7401 than for all others, except for AF Introduction Sorghums are an efficient genus of warm-season annual grasses. They are produced largely for forage but are considered a possible dedicated energy crop. This study was established to test cultivars for their adaptation to east central Kansas and to compare their productive and agronomic potential. Procedures Three sorghum hybrids entered by Advanta Seeds, Inc., and two other cultivars were planted at 100,000 seeds/a in 30-in. rows on May 29, 2014, at the East Central Kansas Agronomy Experiment Field. Plots were 30 ft 10 ft and were arranged in a randomized, complete block with three replications. The area was fertilized preplant with 150 lb nitrogen (N)/a as urea, and sprayed preemergence on May 22 with 1.6 lb a.i./a of S-metolachlor. Plants were thinned to 35,000 plants/a on June 17. Date of half-bloom was recorded for each plot. Measurements of height to flag leaf, number of tillers per plant, and lodging were taken at harvest, along with an estimate of relative grain production. Two rows were harvested on September 23 at 2- to 3-in. height for a length of 20 ft per plot. Subsamples were dried at 140 F for moisture content. Results Maturity of the hybrids differed significantly (P > 0.05), in terms of both bloom date and forage dry matter content at harvest (Table 1). By both measurements, AF 7202 was earlier maturing than FS 4 and AF Forage production was greater for FS 4 and AF 7401 than for AF 7202, perhaps partly because of the difference in maturity (Table 1). Estimated grain production was greater for AF 7401 and AF 7102 than for the other hybrids. Plant height was greater for FS4 than the other entries, and greater for Atlas than for the rest. Although lodging differences were not significant, even at the 10% level, the greater height of FS 4 had no apparent effects on its tendency to lodge. The earlier maturity of AF 7202 may have contributed to its tendency to lodge. 5

8 East Central Kansas Experiment Field Table 1. Bloom date, dry matter (DM), yield, and other agronomic traits in 2014 for forage sorghum, Ottawa Experiment Field, Department of Agronomy Cultivar Bloom date, Julian day 1 DM, % Yield, lb DM/a Grain production, Plant 0 to 10 2 height, in. Lodging, % 3 AF AF AF FS Atlas Average LSD NS 1 Julian day 229 occurred on August Visually rated from 0 to 10, where 0 = no head and 10 = head fully filled with grain. 3 Tillers lodged per 100 primary plants. 6

9 East Central Kansas Experiment Field Late-Season Nitrogen Fertilizer Application in Soybean D. Hodgins, E. Adee, and I.A. Ciampitti Summary Field experiments were conducted at the Kansas River Valley Experiment Field, located near Rossville and Topeka, KS, in the summer of 2014 to evaluate effects of late-season nitrogen (N) fertilizer application on modern soybean genotypes. A unique fertilizer N source (urea) was applied at five N rates (0, 40, 80, 120, and 160 lb N/a) to soybean at the R3 growth stage. The main objective was to determine if late-season N application has an agronomical benefit to soybean producers. Overall soybean yields ranged from 43.7 to 57.5 bu/a considering both experimental fields. At Rossville, sudden death syndrome (SDS) affected the final soybean yield potential. Application of late-season N fertilizer did not significantly increase soybean yields at the evaluated sites. Maximum soybean yields, 46 bu/a at Rossville and 57 bu/a at Topeka, were documented at the 0-N fertilizer rate. Introduction Increasing soybean yields is associated with larger N demand. The ability to sustain N fixation by the rhizobia during the late season can be compromised, restricting the capability of the crop to supply all of the N required for optimum grain-filling and final grain N content. Previous studies investigating the effects of late-season N fertilizer application have shown contrasting outcomes. A common pattern is to report fertilizer N responses in sites where average soybean yields were above 50 to 60 bu/a. Therefore, the effects of extra N application late in the crop growing season might be important to consider in high-yielding soybean systems. Procedures The Topeka experiment was conducted on Eudora silt loam soil. The soybean variety was Asgrow 3833, which was planted on May 21 with a Kinze split-row planter in 15-in. rows at a population 140,000 seeds/a, with no fertilizer applied before planting. Fertilizer N rates were applied at 0, 40, 80, 120, and 160 lb/a. Each fertilizer treatment was replicated four times, providing a total of 20 plots per experiment. Plot size was 20 ft (16 rows) 30 ft. Fertilizer N was applied close to the R3 growth stage (August 18). The soybean was harvested on October 15. The Rossville experiment was conducted on Eudora silt loam soil. Midland 3633N soybean was planted on May 14 with a Kinze split-row planter in 15-in. rows at a population 140,000 seeds/a, with no fertilizer applied before planting. Fertilizer N rates were applied at 0, 40, 80, 120, and 160 lb/a. Each fertilizer treatment was replicated four times, providing a total of 20 plots per experiment. Plot size was 10 ft (8 rows) 20 ft. Fertilizer N was applied close to the R3 growth stage (August 18). The soybean was harvested on September 24. 7

10 East Central Kansas Experiment Field Results Late-season N fertilizer application did not statistically increase soybean yield in either location (Table 1). Overall yield level was 45 bu/a at Rossville and 56 bu/a at Topeka. In these environments, the application of extra N late in the season did not increase soybean yields over the no-n application check (0-N) treatment. Table 1. Late-season nitrogen (N) application rates and yields at Rossville and Topeka, Kansas River Valley Experiment Field, 2014 N rates, lb/a Rossville Topeka Yields at 13% moisture, bu/a P > 0.05 NS 1 NS 1 Not significant, P >

11 East Central Kansas Experiment Field Corn Yield Response to Plant Populations D.E. Shoup, E.A. Adee, and I.A. Ciampitti Summary Corn hybrid development with a focus on drought tolerance has emerged in recent years, and producers have questions about their yield performance across a range of plant populations. A two-year study was conducted to determine the yield of corn hybrids across several plant populations. Corn hybrids responded differently in 2013 and In 2013, a lower yield environment occurred. The hybrid with drought tolerance had the greatest yield of 95 bu/a at a plant population of 21,500 plants/a, whereas the non-drought-tolerant hybrid s greatest yield was 90 bu/a at a plant population of 13,500 plants/a. In 2014, the yield environment was significantly higher. The hybrid with drought tolerance had the greatest yield of 174 bu/a at the greatest plant population of 35,500 plants/a, and the non-drought-tolerant hybrid s greatest yield was 169 bu/a at a plant population of 29,500 plant/a. Introduction Corn yield can be affected by many factors in Kansas, including soil quality, fertility, crop production practices (planting date, plant population, and hybrid), and weed and pest management. The most significant factors that affect corn yield in Kansas are often related to moisture and heat stress. Several seed companies have devoted considerable resources to breeding hybrids with improved drought tolerance. Although the method of achieving drought tolerance in corn hybrids may differ among companies, the goal of improving water use efficiency can help increase yields of corn grown in water-limited environments. Producers have many questions surrounding the newer corn hybrids labeled as drought-tolerant, and data comparing yields across a range of plant populations need to be evaluated. A two-year study was conducted at the East Central Experiment Field in Ottawa to evaluate two corn hybrids and their yield responses to various plant populations. Procedures The experimental site was located on a Woodson silt loam. Plots were strip-till-fertilized into soybean stubble with a mix of 120 lb nitrogen/a, 40 lb P 2 O 5 /a, and 15 lb K 2 O/a. Corn was planted on 30-in. rows on April 4, 2013, with Channel hybrids (non- DroughtGuard) and 198 (DroughtGuard) and on April 9, 2014, with Dekalb hybrids DKC50-48 (non-droughtguard) and DKC51-20 (DroughtGuard) (Monsanto, St. Louis, MO). The experiment was a randomized complete block design with four replications in a strip-plot arrangement. Plant population was the main factor, and hybrid was the subfactor. Plots were four rows wide, 35 ft long, and planted at 36,000 seeds/a. At the V6 growth stage when the growing point was above the soil surface, plots were thinned to several plant populations. In 2013 because of low plant emergence, plots were thinned to five populations: 10,000; 13,500; 17,500; 21,500; and 27,500 plants/a. In 2014, seedling emergence was improved and plant populations were thinned to 17,500; 23,500; 29,500, and 35,500 plants/a. Plots were maintained weed-free throughout the season. Corn plots were harvested by plot combine, plot weights were determined, and yields were adjusted to 13% moisture. 9

12 East Central Kansas Experiment Field Results Corn hybrids responded differently in 2013 and 2014 (Figures 1 and 2). In 2013, a lower yield environment occurred because of drier than normal weather. In 2013, only 1.37 in. of rain fell through the month of June and the first three weeks of July. The hybrid with drought tolerance had the highest yield of 95 bu/a at a plant population of 21,500 plants/a, whereas the non-drought-tolerant hybrid s highest yield was 90 bu/a at a plant population of 13,500 plants/a. In 2014, the yield environment was considerably better because of cooler and wetter than normal conditions. The hybrid with drought tolerance had a peak yield of 174 bu/a at the highest plant population of 35,500 plants/a, and the non-drought-tolerant hybrid s highest yield was 169 bu/a at a plant population of 29,500 plants/a. The excellent growing conditions in 2014 resulted in above-average corn yields. The highest plant population of 35,500 plants/a was likely not high enough to maximize yield with the drought-tolerant hybrid in 2014 and may have benefited from an increased seeding rate. 120 Hybrid Hybrid 198DG 100 Corn yield, bu/a ,000 13,500 17,500 21,500 27,500 Corn population, plants/a Figure 1. Corn yield response to plant populations in Corn hybrids included drought-tolerant (Channel hybrid 198; Monsanto, St. Louis, MO) and non-droughttolerant (Channel hybrid ) traits. 10

13 East Central Kansas Experiment Field Corn yield, bu/a Hybrid DKC50-48 Hybrid DKC ,500 23,500 29,500 35,500 Corn population, plants/a Figure 2. Corn yield response to plant populations in Corn hybrids included drought-tolerant (Dekalb hybrid DKC51-20; Monsanto, St. Louis, MO) and nondrought-tolerant (Dekalb hybrid DKC50-48) traits. 11

14 Kansas River Valley Experiment Field Kansas River Valley Experiment Field Introduction The Kansas River Valley (KRV) Experiment Field was established to study management and effective use of irrigation resources for crop production in the KRV. The Paramore Unit consists of 80 acres located 3.5 miles east of Silver Lake on U.S. Highway 24, then 1 mile south of Kiro, and 1.5 miles east on 17th street. The Rossville Unit consists of 80 acres located 1 mile east of Rossville or 4 miles west of Silver Lake on U.S. Highway 24. Soil Description Soils on the two fields are predominately in the Eudora series. Small areas of soils in the Sarpy, Kimo, and Wabash series also occur. Except for small areas of Kimo and Wabash soils in low areas, the soils are well drained. Soil texture varies from silt loam to sandy loam, and the soils are subject to wind erosion. Most soils are deep, but texture and surface drainage vary widely Weather Information The year was cooler and wetter than the previous year, although there were more frostfree days. The frost-free season was 194 days at the both units (average = 173 days), and 30 and 31 days in single digits at Paramore and Rossville, respectively. The last spring freeze was April 18 (average = April 21), and the first fall freeze was October 29 (average = October 11). There were 30 and 31 days above 90 F at Paramore and Rossville, respectively, and 3 of those days were above 100 F at Rossville. Precipitation was below normal at both fields for the year (Table 1) but was above average for several months during the growing season. For the year, the rainfall deficit for Rossville was 3.35 in., and 8.7 in. for Paramore. The irrigated corn hybrid and soybean variety trials averaged 266 and 41 bu/a, respectively. The corn yields responded well to the cooler weather; however, the high amount of rainfall in June contributed to sudden death syndrome, a major yield-limiting factor in irrigated soybeans at KRV. Dryland corn hybrid and soybean variety trials averaged 195 and 59 bu/a, respectively, indicating a good growing season unless disease was present. 12

15 Kansas River Valley Experiment Field Table 1. Precipitation at the Kansas River Valley Experiment Field Rossville Unit Paramore Unit Month year avg year avg in January February March April May June July August September October November December Total

16 Kansas River Valley Experiment Field Effects of Seed Treatment on Sudden Death Syndrome Symptoms and Soybean Yield E.A. Adee Summary Sudden death syndrome (SDS) is a soybean disease that perennially limits yields in the Kansas River Valley. The presence of soybean cyst nematode (SCN) and saturated soils have been implicated in contributing to the severity of the disease. Selecting varieties with some degree of tolerance to SDS is the only cultural practice that can potentially reduce the severity of SDS and improve yields. Variety selection alone, however, cannot improve the production of soybeans to make them profitable. The challenge of trying to manage irrigation scheduling to avoid saturated soils further complicates efforts to increase productivity with irrigation while still avoiding SDS. A study with seed treatments applied to soybean was conducted at the Kansas River Valley Experiment Field in 2014, with treatments applied to a soybean variety with a high level of tolerance to SDS. The study was irrigated earlier and more often than normal to promote the disease. The most severely infested plots had more than 50% of the leaf area expressing symptoms of SDS by the R6 growth stage. Treatments with ILeVO from Bayer CropScience (Research Triangle Park, NC) reduced foliar symptoms and increased yields up to 12 bu/a, or more than 25%. These results are similar to those in a 2013 study of varieties with SDS tolerance ranging from very susceptible to more tolerant; the yield increase was up to 16 bu/a, or 40% with the ILeVO seed treatment. Introduction Soybean SDS is caused by the fungus Fusarium virguliforme, which infects plants through the roots, primarily before they start to flower. Foliar symptoms generally begin to show up as interveinal chlorosis and necrosis in the leaves at growth stage R3, after the seed has started to develop in the pods. An interaction between SDS and SCN has been reported, and SCN is prevalent in the soils of the Kansas River Valley. Saturated soils also have been implicated as contributing to the development of SDS. Depending on how early the symptoms begin to be visible and the symptoms severity, yield losses can be very significant. In severe cases, plants in which the symptoms begin early (i.e., before the seed development stage) can fail to produce any seed. This disease has been a perennial problem in the Kansas River Valley, causing severe yield reductions to the point that soybean cannot be profitably produced in some fields. Crop rotations and tillage have had little effect on reducing the severity of the disease and reducing the subsequent yield loss. No soybean varieties are totally resistant to the fungus, but some varieties have varying degrees of tolerance that can reduce yield losses. Irrigating soybean at the wrong time also could increase the severity of SDS, further complicating production in the Kansas River Valley, where irrigation is often necessary to produce a profitable crop. 14

17 Kansas River Valley Experiment Field Another method of trying to increase soybean productivity in fields with a risk of SDS is seed treatment at planting. Seed treatments could help protect the roots against initial infection by F. virguliforme. Procedures Soybean was planted into a field with a history of SDS at the Rossville Unit of the Kansas River Valley Experiment Field in Seed treatments were applied by Bayer CropScience (Research Triangle Park, NC) to a soybean variety with a high level of tolerance to SDS, Stine 42RE02 (Stine Seed Co., Adel, IA). The treatments included: ILeVO 0.15 mg/seed and ILeVO mg/seed in combination with other seed treatment products, a check with Poncho/Votivo or Gaucho, and a test product. Soybean was planted May 6 at 140,000 seeds/a into ft plots, with four replications in a randomized complete block design. The soil was Eudora silt loam, and the previous crop was soybean. Irrigation with a linear-move sprinkler irrigation system was started on June 24. Total irrigation was 7.81 in., and 21.4 in. of rain was received during the growing season. Preemergence herbicide applied at planting was Authority Maxx (FMC Corporation Agricultural Products Group, Philadelphia, PA) (5 oz) and Cinch (Syngenta Crop Protection, LLC, Greensboro, NC) (1.5 pt). Postemergence herbicide was Roundup PowerMax (Monsanto Company) (22 oz), Assure II (DuPont, Wilmington, DE) (12 oz), and Warrant (Monsanto Company) (1.5 qt). Foliar symptoms of SDS were rated weekly starting August 6, when the soybean crop was at the R4 (pods full length) to September 3 at the R6 (full seed) growth stages. Ratings were based on incidence and severity of the symptoms. An area under the disease progress curve (AUDPC), a unitless number describing the development of defoliation effects over time, was derived by plotting periodic measurements of disease over time and integrating the area under the disease curve. A GreenSeeker meter (Trimble Navigation, Ag Division, Westminster, CO) was also used to collect normalized difference vegetation index (NDVI) readings from each plot at the R6 growth stage. The NDVI readings are higher when plants have abundant green leaves to absorb the light used in photosynthesis. The plots were harvested September 30. Results The severity of the disease ratings, using both AUDPC and NDVI, correlated with yield (Figures 1 and 2). The figures also show that the more traditional ratings with the AUDPC and the NDVI are nearly equal in their relationship with yield. As the AUDPC increased, the yield decreased, with the AUDPC explaining more than 28% of the change in yield. The NDVI readings explained more than 16% of the change in yields, with soybean yields increasing as the NDVI increased. The seed treatments with ILeVO increased yields from 3 to 12 bu/a, depending on the rate of the product and the additional seed treatments (Table 1). The greatest yields were with the higher rates of ILeVO. Disease severity ratings show that the environment in which this study was conducted was very favorable for SDS, with nearly 50% of the leaves showing symptoms in the most affected plots with this variety that is highly tolerant to SDS (Table 1). To have a more than 25% yield increase owing to seed treatment with this level of severity is promising. These data are similar to a study with ILeVO conducted in 2013, indicat- 15

18 Kansas River Valley Experiment Field ing that this product can consistently decrease soybean yield loss due to SDS. This seed treatment in combination with a variety with a high tolerance to SDS could make soybean more sustainable as a crop in the presence of SDS. Table 1. Influence of seed treatment for sudden death syndrome (SDS) on yield of soybean on Stine 43RE02, Kansas River Valley Experiment Field, Rossville, 2014 Seed treatments Yield SDS severity SDS severity NDVI 1 bu/a % leaf area at R6 AUDPC 2 Poncho/Votivo check 47.4 g 3 52 a 696 ab bc ILeVO 4 (0.15 mg)+ Poncho/Votivo 59.6 a 16 bc 146 c ab ILeVO (0.075 mg)+ Poncho/Votivo 57.0 d 31 ab 443 bc bc Gaucho 600 check 54.0 d 25 bc 814 a c ILeVO (0.15 mg)+ Gaucho c 16 bc 192 c ab ILeVO (0.075 mg)+ Gaucho d 7 c 153 c a ILeVO (0.15 mg)+ Gaucho Agriplier 58.3 b 13 bc 148 c a Poncho/Votivo + test compound 50.1 f 21 bc 572 ab bc LSD Normalized difference vegetation index. 2 Area under the disease progress curve, a unitless number describing the development of defoliation effects over time. 3 Values followed with different letters are significantly different at P < Bayer CropScience (Research Triangle Park, NC). 16

19 Kansas River Valley Experiment Field Yield, bu/a y = x R² = ,000 1,200 1,400 AUDPC Figure 1. The severity of soybean sudden death syndrome disease ratings as shown by area under the disease progress curve (AUDPC, a unitless number describing the development of defoliation effects over time) correlated with yield, Kansas River Valley Experiment Field, Rossville, Yield, bu/a y = x R² = NDVI at R6 Figure 2. The severity of soybean sudden death syndrome disease ratings as shown by normalized difference vegetation index (NDVI) at growth stage R6 correlated with yield, Kansas River Valley Experiment Field, Rossville,

20 Kansas River Valley Experiment Field Effects of an Experimental Seed Treatment from DuPont on Sudden Death Syndrome Symptoms and Soybean Yield E.A. Adee Summary Sudden death syndrome (SDS) is a soybean disease that perennially limits yields in the Kansas River Valley. Soybean cyst nematode (SCN) and saturated soils contribute to the severity of the disease. Selecting varieties with some degree of tolerance to SDS is the only cultural practice that can reduce the severity of SDS and improve yields. Variety selection alone, however, doesn t necessarily make soybean production profitable; an added complication is managing irrigation scheduling to avoid saturated soils. A study with seed treatments applied to soybean was conducted at the Kansas River Valley Experiment Field in 2014, with treatments applied to two soybean varieties susceptible to SDS. The study was irrigated earlier and more often than normal for soybean to promote the disease. In the most severely infested plots, more than 50% of the leaf area expressed symptoms of SDS by the R6 growth stage. Treatments with an experimental seed treatment from DuPont (Wilmington, DE) reduced the amount of foliar disease in all varieties and increased yields up to 10 bu/a, or more than 25%. Introduction Soybean SDS is caused by the fungus Fusarium virguliforme, which infects plants through the roots, primarily before they start to flower. Foliar symptoms generally begin to show up as interveinal chlorosis and necrosis in the leaves at growth stage R3, after the seed has started to develop in the pods. An interaction between SDS and SCN has been reported, and SCN is prevalent in the soils of the Kansas River Valley. Saturated soils also have been implicated as contributing to the development of SDS. Depending on how early the symptoms become visible and their severity, yield losses can be very significant. In severe cases, plants in which the symptoms begin early (i.e., before the seed development stage) can fail to produce any seed. This disease has been a perennial problem in the Kansas River Valley, causing severe yield reductions in soybean to the point that the crop cannot be profitably produced in some fields. Crop rotations and tillage have had little effect on reducing the severity of the disease and reducing the subsequent yield loss. No soybean varieties are totally resistant to the fungus, but some varieties have varying degrees of tolerance that can reduce yield losses. Irrigating soybean at the wrong time also could increase the severity of SDS, further complicating production in the Kansas River Valley, where irrigation is often necessary to produce a profitable crop. Another method of trying to increase soybean productivity in fields with a risk of SDS is seed treatment applied to the seeds at planting. Seed treatments could help protect the roots against initial infection by F. virguliforme. 18

21 Kansas River Valley Experiment Field Procedures Soybean was planted into a field with a history of SDS at the Rossville Unit of the Kansas River Valley Experiment Field in Seed treatments were applied by DuPont (Wilmington, DE) to two soybean varieties susceptible to SDS, Sloan and Pioneer 93Y91 (Pioneer Hi-Bred, Johnston IA). The treatments included: the DuPont experimental seed treatment at 0.65X, 1.0X, 2.0X, 3.0X; a competitor s seed treatment; and an untreated check. Soybean was planted May 6 at 140,000 seeds/a into 10-ft 30-ft plots, with four replications in a randomized complete block design. The soil was Eudora silt loam, and the previous crop was soybean. Irrigation with a linearmove sprinkler irrigation system was started on June 24. Total irrigation was 7.81 in., and 21.4 in. of rain was received during the growing season. Preemergence herbicide applied at planting was Authority Maxx (FMC Corporation Agricultural Products Group, Philadelphia, PA) (5 oz) and Cinch (Syngenta Crop Protection, LLC, Greensboro, NC) (1.5 pt). Postemergence herbicide was Roundup PowerMax (Monsanto Company, St. Louis, MO) (22 oz), Assure II (DuPont, Wilmington, DE) (12 oz), and Warrant (Monsanto Company) (1.5 qt). Foliar symptoms of SDS were rated weekly starting July 21, when the soybean crop was at the R4 (pods full length) stage, through August 18, when plants were at the R6 (full seed) growth stage. Ratings were based on incidence and severity of the symptoms. An area under the disease progress curve (AUDPC), a unitless number describing the development of defoliation effects over time, was derived by plotting periodic measurements of disease over time and integrating the area under the disease curve. A GreenSeeker meter (Trimble Navigation, Ag Division, Westminster, CO) was also used to collect normalized difference vegetation index (NDVI) readings from each plot at the R6 growth stage; NDVI readings are higher when there are abundant green leaves to absorb the light used in photosynthesis. The plots were harvested September 22. Results The experimental seed treatment from DuPont reduced the severity of foliar symptoms of SDS (Table 1). The single rating at R6 on August 18 and the AUDPC, which measured disease severity throughout the season, both showed a reduction in SDS severity. The NDVI rating taken at R6 also showed higher ratings for the treatments with the experimental product from DuPont, especially at higher application rates. Yields were higher with the two higher rates of the experimental product (Table 1), which agrees with the higher NDVI ratings and the lower severity ratings for SDS. There was no interaction between variety and seed treatment (data not shown) because the product performed similarly with both varieties. These data suggest the experimental product from DuPont has the potential to increase soybean yield in the presence of SDS. The environment was very favorable for SDS, and both varieties in the trial were highly susceptible to SDS, showing that this product can reduce yield loss even when the pressure from SDS is severe. Caution should be used in drawing strong conclusions because these data are from only one site, but the results are promising. 19

22 Kansas River Valley Experiment Field Table 1. Influence of an experimental seed treatment for sudden death syndrome (SDS) on soybean yield, Kansas River Valley Experiment Field, Rossville, 2014 Seed treatments Yield SDS foliar at R6 SDS severity NDVI 1 bu/a % AUDPC 2 DuPont 3 experimental treatment, 0.65X 29.7 c b 410 b bc DuPont experimental treatment, 1.0X 31.9 bc 45.3 b 377 b ab DuPont experimental treatment, 2.0X 35.3 ab 41.0 b 326 b a DuPont experimental treatment, 3.0X 40.0 a 26.6 b 232 b a Competitor s product 28.4 c 68.0 a 806 a c Untreated check 29.6 c 71.1 a 777 a c LSD Normalized difference vegetation index determined by a GreenSeeker meter (Trimble Navigation, Ag Division, Westminster, CO). 2 Area under the disease progress curve, a unitless number describing the development of defoliation effects over time. 3 DuPont (Wilmington, DE). 4 Values with the same letter are not statistically different at P <

23 Kansas River Valley Experiment Field Soybean Sudden Death Syndrome Influenced by Macronutrient Fertility on Irrigated Soybean in a Corn/Soybean Rotation E.A. Adee and D. Ruiz Diaz Summary The effects of nitrogen (N), phosphorus (P), and potassium (K) fertilization on a corn/ soybean cropping sequence were evaluated from 1983 to 2014, with corn planted in odd years. We observed a relationship between the P rate applied during the corn years and the severity of sudden death syndrome (SDS) in 2014 soybean. Introduction A study was initiated in 1972 at the Topeka Unit of the Kansas River Valley Experiment Field to evaluate the effects of N, P, and K on furrow-irrigated soybean. In 1983, the study was changed to a corn/soybean rotation with corn planted and fertilizer treatments applied in odd years. Study objectives were to evaluate the effects of N, P, and K applications on a corn crop on grain yield of corn, yield of the following soybean crop, and soil test values. Procedures The initial soil test in March 1972 on this silt loam soil was 47 lb/a available P and 312 lb/a exchangeable K in the top 6 in. of the soil profile. Rates of P were 50 and 100 lb/a P 2 O 5 ( ) and 30 and 60 lb/a P 2 O 5 ( ), except in 1997 and 1998, when a starter of 120 lb/a of (12 lb/a N + 41 lb/a P 2 O 5 ) was applied to all plots of corn and soybean. Rates of K were 100 lb/a K 2 O ( ), 60 lb/a K 2 O ( ), and 150 lb/a K 2 O ( ). Nitrogen rates included a factorial arrangement of 0, 40, and 160 lb/a of preplant N (with single treatments of 80 and 240 lb/a N). The 40 lb/a N rate was changed to 120 lb/a N in Treatments of N, P, and K were applied every year to continuous soybean ( ) and every other year (odd years) to corn ( , ). Soil cores were pulled from each plot in the spring of 2014, prior to planting. Analyses for macronutrients were performed from soil for each 1-ft increment to a depth of 4 ft. Soybean varieties planted in even years were: Douglas (1984), Sherman (1986, 1988, 1990, 1992, 1996, 1998), Edison (1994), IA 3010 (2000), Garst 399RR (2002), Stine (2004), Stine (2006), Midland 9A385 (2008), Asgrow 4005 (2010), Asgrow 3832 (2012), and Asgrow 3833 (2014). Soybean was planted in early to mid- May. Herbicides were applied preplant each year, and postemergent herbicides were applied as needed. Plots were cultivated, furrowed, and furrow-irrigated through 2001 and sprinkler-irrigated with a linear-move irrigation system from 2002 to Percentage of leaf area infested by SDS was rated visually, and normalized difference vegetation index (NDVI) ratings were measured with a GreenSeeker meter (Trimble 21

24 Kansas River Valley Experiment Field Navigation, Ag Division, Westminster, CO) on August 28 at growth stage R6. A plot combine was used to harvest grain. Results The severity of foliar SDS symptoms in soybean was related to the rate of P applied to the corn in the corn/soybean rotation for the previous years (Table 1). The SDS was most severe, and the NDVI (measure of greenness), heights, and yields decreased as the rate of P decreased. The level of P in the soil was different at the different rates in a soil sample taken in the spring of 2014 (Table 2). The largest difference between P rates was in samples collected from the top foot of soil. There was no effect of N, K, nor any interactions of the three macronutrients with these four measurements (data not shown). SDS had not been observed to this degree in these plots in previous years. In addition, the effect of P on yield has not been this great, with average yield response for 1984 to 2012 from the check to the 60 lb rate less than 6 bu/a. The development of SDS was probably related to the above-average rainfall in June of 8.26 in., which is 3.62 in. more than the 30-year average. The negative correlation between foliar symptoms of SDS and NDVI was very strong (-0.82, <0.0001; Figure 1). The NDVI measurements are an objective measurement based on near-infared light reflectance off the crop canopy, which can be affected by the greenness of leaves and density of the canopy, both of which can be influenced by multiple factors. Height of plants, development of branches, number and size of leaves, and amount of chlorophyll in leaves are some of the factors that can affect NDVI readings. The visual ratings of foliar symptoms tend to be more subjective but can focus on a single aspect of crop health, in this case foliar symptoms of SDS. The strength of this correlation indicates that SDS was a primary factor affecting the health of this crop, even though height differences were related to P rates. Yield of soybean correlated well with both the visual rating for SDS (-0.74, <0.0001) and NDVI (0.83, <0.0001) (Figures 2 and 3). This result suggests that SDS was a major factor affecting yield of soybean in this study. Combined with the strong relationship between the rate of P applied during the corn year of the rotation with yield and NDVI, the negative relationship with foliar symptoms of SDS indicates that P had a significant role in the severity of SDS and subsequent yield loss. To our knowledge, this relationship between P applied as a fertilizer and SDS has not been previously reported. 22

25 Kansas River Valley Experiment Field Table 1. Effects of phosphorus (P) applied to corn on sudden death syndrome (SDS) and yield of soybean, Kansas River Valley Experiment Field, 2014 P rate on corn SDS severity NDVI 1 Height Yield lb/a % foliage affected in. bu/a LSD (0.05) Normalized difference vegetation index. Table 2. Soil test values for phosphorus (P) in macro-fertility study, Kansas River Valley Experiment Field, 2014 P rate 1st ft 2nd ft 3rd ft 4th ft lb/a LSD (0.05) NS 1 1 Not significant NDVI R² = SDS severity August 28, % leaf area infested Figure 1. Relationship between visual ratings for severity of foliar symptoms of sudden death syndrome (SDS) and normalized difference vegetation index (NDVI) measurements with a GreenSeeker meter (Trimble Navigation, Ag Division, Westminster, CO) in a longterm macronutrient fertility study at the Kansas River Valley Experiment Field,

26 Kansas River Valley Experiment Field Yield, bu/a y = x R² = SDS severity August 28 at R6, % leaf area infested Figure 2. Relationship between foliar symptoms of sudden death syndrome (SDS) and yield of soybean at the Kansas River Valley Experiment Field, Yield, bu/a y = 259.1x R² = NDVI reading August 28 Figure 3. Relationship between normalized difference vegetation index (NDVI) and yield of soybean at the Kansas River Valley Experiment Field,

27 Kansas River Valley Experiment Field Tillage Study for Corn and Soybean: Comparing Vertical, Deep, and No-Till E.A. Adee Introduction The need for tillage in corn and soybean production in the Kansas River Valley continues to be debated. The soils of the Kansas River Valley are highly variable, with much of the soil sandy to silty loam in texture. These soils tend to be relatively low in organic matter (<2%) and susceptible to wind erosion. Although typically well drained, these soils can develop compaction layers under certain conditions. A tillage study was initiated in the fall of 2011 at the Kansas River Valley Experiment Field near Topeka to compare deep vs. shallow vs. no-till vs. deep tillage in alternate years. Corn and soybean crops are rotated annually. This is intended to be a long-term study to determine if soil characteristics and yields change in response to a history of each tillage system. Procedures A tillage study was laid out in the fall of 2011 in a field that had been planted with soybean. The tillage treatments were (1) no-till, (2) deep tillage in the fall and shallow tillage in the spring every year, (3) shallow tillage in the fall following both crops, and (4) deep tillage followed by a shallow tillage in the spring only after soybean, and shallow tilled in the fall after corn. The fall of 2010, prior to the soybean crop, the entire field was subsoiled with a John Deere (John Deere, Moline, IL) V-ripper. After soybean harvest, 30-ft 100-ft individual plots were tilled with a Great Plains (Great Plains Mfg., Salina, KS) TurboMax vertical tillage tool at 3 in. deep or a John Deere V-ripper at 14 in. deep. Spring tillage was with a field cultivator. In the fall of 2012, the treatments were with the TurboMax or a Great Plains Sub-Soiler Inline Ripper SS0300. Spring tillage in 2013 and 2014 was with the TurboMax on the required treatments. Each tillage treatment had four replications. Dry fertilizer ( and nitrogen-phosphorus-potassium, or NPK) was applied at 200 lb/a for each product to the entire field prior to fall tillage. Nitrogen (150 lb in 2012 and 2013, 185 lb in 2014) was applied in March prior to corn planting. Corn hybrid Pioneer 1395 was planted at 30,600 seeds/a on April 12, 2012; P1498HR on April 30, 2013; and P1105 at 32,000 seeds/a on April 21, Soybean variety Pioneer 93Y92 was planted at 155,000 seeds/a on May 14, 2012; P94Y01 on May 15, 2013; and Asgrow 3833 at 140,000 on May 21, Soybean was planted after soybean in the setup year. Irrigation to meet evapotranspiration (ET) rates began May 26 and concluded August 1 for corn, and began July 5 and concluded August 23 for soybean in Irrigation for corn started June 24, 2013, and concluded August 1. Irrigation for soybean in 2013 started June 30 and concluded September 8. Irrigation in 2014 started July 1 and ended Aug 16 for corn, and started July 22 and ended August 22 for soybeans. Two yields were taken from each plot from the middle 2 rows of planter passes. Corn was harvested on August 31, 2012; September 25, 2013; and September 11, Soybean was harvested on October 5, 2012; October 10, 2013; and October 9,

28 Kansas River Valley Experiment Field Results Yields of corn or soybean did not differ due to tillage in the setup year of the study (Table 1). The yields were respectable considering the extreme heat and drought experienced this growing season. Growing conditions were better in 2013, resulting in higher yields in both corn and soybean, but no significant differences were detected among tillage treatments (Table 2). In 2014, corn yields were very good and soybean yields were lowered by sudden death syndrome (SDS), but no differences were detected among tillage treatments (Table 3). Combining data from 2013 and 2014 for analysis did not result in any differences among tillage treatments (Table 3). We anticipate that it will take several years for any characteristics of a given tillage system to build up to the point of influencing yields. Table 1. Effects of tillage treatments on corn and soybean yields, Kansas River Valley Experiment Field, 2012 Tillage treatment Corn yield Soybean yield bu/a No-till Fall subsoil/spring field cultivation Fall vertical till LSD 0.05 NS 1 NS 1 Not significant. Table 2. Effects of tillage treatments on corn yields, Kansas River Valley Experiment Field, 2013 and 2014 Corn yield Tillage treatment Average bu/a No-till Fall subsoil/spring field cultivation Fall vertical till Fall subsoil after soybean/vertical till after corn LSD 0.05 NS 1 NS NS 1 Not significant. 26

29 Kansas River Valley Experiment Field Table 3. Effects of tillage treatments on soybean yields, Kansas River Valley Experiment Field, 2013 and 2014 Soybean yield Tillage treatment Average bu/a No-till Fall subsoil/spring field cultivation Fall vertical till Fall subsoil after soybean/vertical till after corn LSD 0.05 NS 1 NS NS 1 Not significant. 27

30 Kansas River Valley Experiment Field Grain Sorghum Yield Response to Water Availability J. Broeckelman, E. Adee, K. Roozeboom, G. Kluitenberg, and I.A. Ciampitti Summary Yield effects of irrigation on sorghum and corn were compared, but this report is merely focused on the sorghum phase of the crop rotation. Mean yield based on 12.5% grain moisture for irrigated sorghum was 168 bu/a, whereas dryland yield was 145 bu/a. The latter represents a yield improvement of 23 bu/a, an increase of approximately 2 bu/a per unit (in.) of water applied (considering a total of 11 in. of water applied in the irrigation block). The irrigated sorghum used a mean of 7.8 in. more water than the dryland, which suggests that the dryland sorghum consumed 3.4 in. more water from the soil profile than the irrigated sorghum (this value assumes no water losses due to runoff or deep percolation and is calculated from total precipitation and irrigation as well as changes in profile water status). Water use efficiency, or WUE, was calculated as the ratio of yield to water use. A trend for superior WUE of 6.5 bu/in. was documented under dryland conditions, compared with 5.6 bu/in. for irrigated sorghum. Introduction Decreases in available irrigation water and increased water restrictions necessitate exploration of more economical ways to use available irrigation water. Under lowyielding environments (<80 bu/a grain sorghum), sorghum has a yield advantage over corn because of its lower input costs and superior WUE and heat tolerance. Sorghum s yield potential is not as high as corn s, however, so the goal of this study is to determine at what point in available water, both under dryland and irrigation management scenarios, it is better to plant sorghum rather than corn. Procedures In a randomized complete block design, grain sorghum was planted in dryland and fully irrigated blocks at the Topeka Unit of the Kansas River Valley Experiment Field. Within each block, three treatments of different grain sorghum hybrids were planted (Pioneer 84G62, Pioneer 85Y40, and DKS 53-67) with four replications. The plot size was 10 ft 30 ft, and sorghum was planted in 30-in. rows (four rows per plot). The center two rows were harvested to determine final grain yield and its components. Plant populations and fertility were based on yield goals of 170 bu/a for the fully irrigated and 130 bu/a for the dryland. Grain sorghum was planted on May 21 with seeding rates based on a goal of 90,000 plants/a in the irrigated block and of 60,000 plants/a in the dryland block. Fertilizer was applied based on recommendations for corn because sorghum fertilizer recommendations for the target yield were lower, and we wanted to eliminate variables that would cause different yields for corn vs. sorghum. Nitrogen (N) was applied preplant at 142 lb/a on both the dryland and the irrigated treatments and 28