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eturn to table of

eturn to table of contents CROP ROTATION & TILLAGE EFFECTS ON CORN YIELD: HYBRID SELECTION & PLANT POPULATION by Peter Thomison, Ph.D., Professor, Corn Cropping Systems Extension Specialist, Alex Lindsey, Ph.D., Assistant Professor, Allen Geyer, Research Associate, Horticulture & Crop Science Department, Ohio State University, and Kirk Reese, Agronomy Research Manager SUMMARY • The yield advantage of hybrids with greater drought tolerance varied among cropping sequences and locations. • Hybrid type, greater plant population, and no-tillage did not result in consistently greater residue accumulation. • Yield response to tillage ranged from no change to a 10% increase compared to no-tillage. • Corn yields were 3 to 13% greater following soybean than corn. 46

eturn to table of contents BACKGROUND Average plant population for corn in Ohio is continuously changing with rates increasing about 280 plants/acre/year according to the National Agricultural Statistics Service ( Plant populations in Ohio have increased 14% during the past 10 years and are closely associated with grain yield increases. In recent years, more questions have been posed concerning the impact of increased residues associated with higher plant populations in notillage and reduced-tillage cropping systems. Among farmers, a widespread perception exists that these greater residues, especially in no-tillage systems, adversely affect crop establishment and reduce yields. Effects of tillage systems on hybrid performance have received considerable attention since the introduction of no-tillage systems in the early 1970s. Seed companies have also identified hybrids with traits (including early season stress tolerance and disease resistance) that enhance performance in high-residue cropping systems. However, the performance of recently developed hybrids in no-tillage and reduced-tillage cropping systems, in which plant populations are often much greater than in the past, warrants renewed attention. DuPont Pioneer has worked to develop corn hybrids with improved drought tolerance in order to provide better yield stability on variable and droughty soils. Hybrids with higher levels of drought tolerance may provide greater yield stability for corn planted on heavy clay soils in no-tillage continuous corn. Corn crops planted on such soils using no-tillage are often susceptible to late season drought stress, especially when soil moisture is excessive at planting. Improving our understanding of the response of newer hybrids to plant population under different tillage and rotation systems and across different soil types will help improve our understanding of hybrid management and positioning. STUDY OBJECTIVES • Evaluate the response of hybrids with different drought tolerance ratings in different cropping sequences using no-tillage and conventional tillage. • Assess hybrid response to plant population in no-tillage and conventional-tillage continuous-corn production systems. • Determine the effects of increasing quantities of crop residues on corn and soybean performance in conventional and no-tillage cropping systems over time. STUDY DESCRIPTION Location: Research was conducted at Ohio State University research farms near South Charleston in southwest Ohio and Hoytville in northwest Ohio from 2013 to 2015. Plot Design and Measurements: The field experiment evaluating hybrid response to rotation and tillage was replicated four times in a randomized complete block, arranged in split-split-plot layout with the main plot - tillage, subplot - cropping sequence, and sub-subplot - hybrid. Plots consisted of 4 rows with 30-inch spacing, 40 feet in length. Two tillage systems were compared, no-tillage and conventional tillage. The conventional tillage system consisted of primary tillage with a chisel plow in the fall Greater corn residues in no-tillage systems have been associated with higher plant populations, transgenic insect traits, and greater use of foliar fungicides. and secondary tillage with a field cultivator before planting. A continuous corn and corn-soybean cropping sequence were compared. Four Pioneer ® brand corn products representing differences in maturity and drought tolerance were evaluated, including two Pioneer ® brand Optimum ® AQUAmax ® products and two comparative products. Hybrid/Brand 1 CRM Drought* P0210AM-R (AM, RR2) 102 9 (Optimum ® AQUAmax ® product) P1352AMX-R (AMX, RR2) 113 9 P1352AMXT (AMXT, RR2) (Optimum AQUAmax products) P0448AM1 (AM1, LL, RR2) 104 7 P1184AMX-R (AMX, RR2) 111 7 * Drought tolerance rating on a 1-9 scale; 9 = most tolerant, 1 = least tolerant. The field experiment evaluating hybrid responses to plant population and tillage was replicated four times in a randomized complete block, arranged in split-split-plot layout. The main plot was tillage, subplot – hybrid, and sub-subplot – seeding rate. Two tillage systems were considered: notillage vs. conventional tillage. Two hybrids were compared: Pioneer ® P0965AM1 brand corn (AM1, LL, RR2), representing hybrids with stable “defensive” yield performance across varying environmental conditions, and Pioneer ® hybrid P0993HR (HX1, LL, RR2), representing hybrids with high yield potential under favorable growing conditions. Plots consisted of 4 rows with 30-inch spacing, 40 feet in length. Plots were planted at seeding rates to achieve 4 target plant populations: 26,000; 34,000; 42,000; and 50,000 plants/acre. APPLIED QUESTIONS Did Hybrid Response to Cropping Sequence Differ in No- Till and/or Conventional Tillage Systems? Although average site yield levels varied considerably among locations and years, there was no evidence of interactions involving tillage, crop rotation, and hybrid at either location in 2013 to 2015. Tillage did not influence yield in any site-year 47

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