Crop Rotation and Tillage Effects on Corn Yield: What Role Do Hybrid Selection and Plant Population Play?
Field Facts written by Peter Thomison, Ph.D.1, Alex Lindsey, Ph.D.2, Allen Geyer3, and Kirk Reese4
Key Research Findings
- 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.
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 no-tillage and reduced-tillage cropping systems. Among farmers, a widespread perception exists that 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.
Greater corn residues in no-tillage systems have been associated with higher plant populations, transgenic insect traits, and greater use of foliar fungicides.
- 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.
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 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.
|P0210AM-R™ (AM, RR2) - (Optimum® AQUAmax® product)||102||9|
|P1352AMX-R™ (AMX, RR2) - (Optimum® AQUAmax® product)||113||9|
|P1352AMXT™ (AMXT, RR2) - (Optimum® AQUAmax® product)||113||9|
|P0448AM1™ (AM1, LL, RR2)||104||7|
|P1184AMX-R™ (AMX, RR2)||111||7|
1All Pioneer products are hybrids unless designated with AM1, AM, AMT, AMRW, AMX and AMXT, in which case they are brands.
2Drought 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: no-tillage 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.
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 of this specific evaluation. In five of six site-years, corn yields were greater following soybean than corn. Corn yields were 3 to 11% greater following soybean at S. Charleston and 5% to 13% greater following soybean at Hoytville. Corn yield was not affected by cropping sequence at Hoytville in 2013.
At S. Charleston averaged across years, yields following soybean were 10% and 5% greater than those following corn for no-tillage and conventional tillage, respectively. At Hoytville, the yield increase associated with crop rotation was nearly the same (5%) in conventional tillage and no-tillage. Differences among hybrids were observed in three of the six site-years. In 2013, there was no difference in yield among hybrids at S. Charleston, whereas at Hoytville, Pioneer® P0448AM1™ and P1352AMXT™ brand corn out-yielded Pioneer® P1184AM1™ brand corn. In 2014 at S. Charleston, Pioneer® P1352AMX-R™ brand corn out-yielded Pioneer® P0210AM-R™ and P0448AM1™ brand corn by 4 to 5%, but no difference in yield occurred between P1184AMX-R™ and P1352AMX-R™ and between P0210AM-R™ and P0448AM1™. No differences in yield were present among hybrids at Hoytville in 2014. In 2015, there was no difference in yield among hybrids at S. Charleston, whereas at Hoytville, P0210AMX™, P0448AMX™, and P1352AMXT™ out-yielded P1184AM1™. When examined by drought tolerance designation, an interaction between hybrid type and rotation was observed when averaged across years at each location (Table 1).
Table 1. Grain yield from Optimum AQUAmax products and comparative products grown in continuous-corn or corn-soybean cropping sequence. Letters within a column denote similar yield values (P<0.05).
The Optimum AQUAmax products produced 4% greater yield than the comparative products when grown in continuous corn and produced similar yield when rotated with soybeans at Hoytville. At S. Charleston, comparative products produced similar yield to the Optimum AQUAmax products in the continuous-corn cropping sequence, but the Optimum AQUAmax products produced 5% greater yield than the comparative products when rotated with soybeans. The Optimum AQUAmax products, P0210AM-R™ and P1352AMXT™, individually did not exhibit consistently greater yields than the comparative products, but in experiments where product affected yield, P1352AMXT™ out-yielded one or more of the other products. The drought tolerance and later maturity of P1352AMXT™ may have contributed to its higher yields.
Did Hybrid Response to Plant Population Differ in No-Till and Conventional Tillage Systems in Continuous Corn?
Although yields were 50 to 100 bu/acre greater at S. Charleston than Hoytville over the 3 years, there was no evidence of interactions between tillage, population, and hybrid for yield at either location. Corn products showed similar yield responses to plant population in no-till and conventional tillage at both sites across a range of growing conditions (Table 2). Yield response to no-tillage and conventional tillage was similar in four of the six experiments. Yields were about 3% greater in conventional tillage than no-tillage at Hoytville in 2013 and 10% greater in conventional tillage than no-tillage at S. Charleston in 2014.
A difference in yield between the two corn products was evident in two of the six experiments with yields of Pioneer® hybrid P0993HR, averaged across tillage and plant population, greater than Pioneer® P0965AM1™ brand corn. Although P0965AM1™ was characterized as having more stable “defensive” yield performance across varying environmental conditions, its yields were either less or comparable to those of P0993HR. Although P0993HR was characterized as having the higher yield potential under favorable growing conditions, its yield in 2013 was not different from P0965AM1™ at S. Charleston where yield levels were 40% greater than Hoytville. The absence of a yield difference between P0993HR and P0965AM1™ in 2013 may be related to greater root lodging™, which was evident at both locations (32% vs. 17% at S. Charleston and 36% vs. 22% at Hoytville), associated with P0993HR compared to P0965AM1.
In 2013, increasing plant population resulted in higher yields, but no yield response to plant population was evident above 42,000 plants/acre. Increasing plant population from 26,000 to 42,000 plants/acre increased yields 11% and 13% at S. Charleston and Hoytville, respectively. In 2014, there was no response to plant population at either location. In 2015, yield was affected by population, but population responses were highly erratic, especially at Hoytville, which may be related to the uneven and inconsistent plant growth associated with excessive soil moisture. In 2013, higher plant populations also increased root lodging, which increased from 12 to 34% at S. Charleston and 20 to 40% at Hoytville. Tillage, hybrid, and plant population effects on grain moisture, stalk lodging, test weight, and percent barren/nubbin ears were generally small and inconsistent.
Did Increasing Quantities of Crop Residue Affect Corn Performance in Conventional and No-Tillage Cropping Systems Over Time?
Continuous no-till corn and high corn plant populations — the experimental treatments expected to result in greater residue accumulation — did not affect crop performance consistently. After three years of residue accumulation, corn yields in 2015 were similar for no-till and conventional tillage. In the study evaluating hybrid response to rotation and tillage, post-harvest residue cover in the conventional tillage continuous corn plots was about 30 to 40% of the coverage in the no-tillage continuous corn plots at S. Charleston and Hoytville in 2013 and 2014. No differences in percent residue cover were evident on plots following corn or soybean at S. Charleston in 2013 and 2014 and Hoytville in 2014. At Hoytville in 2013, residue cover was slightly greater in plots following corn.
Although hybrids differed in plant height and maturity, differences in plot residue cover associated with hybrids were detected in only one site-year. At S. Charleston in 2015, the residue cover associated with Pioneer® P1352AMX-R™ brand corn, a full season product, was greater than Pioneer® P0210AM-R™ brand corn, an earlier maturing, shorter product. In the study evaluating hybrid responses to plant population and tillage, residue cover in 2014 and 2015 in the conventional tillage continuous corn plots was about 30 to 40% of the coverage in the no-tillage continuous corn plots at S. Charleston and Hoytville. Plant population effects on post-harvest residue were only present at Hoytville in 2013. Plant population affected percent residue cover, but the differences in residue coverage between plant populations did not correspond to changes in plant density. The post-harvest residue cover measurements for 34,000 plants/acre exceeded those of the lower and higher plant densities.
Table 2. Tillage, hybrid, and plant population effects on yield. S.Charleston and Hoytville, OH, 2013 to 2015.
No differences in plot residue cover were associated with hybrids, although they differed in plant height (P0993HR greater than P0965AM1™). Past descriptions of P0965AM1™ suggested that this hybrid’s shorter plant stature might result in less plant residue to manage following harvest. Measurements of residue cover biomass collected early in 2014 and 2015 did not detect differences in the quantity of crop residue produced by the two products at high and low plant populations in the conventional and no-till treatment. Outcomes may be expected to differ under less favorable growing conditions and with greater residue accumulation over a longer time period, especially in no-tillage with high plant populations.
What Are the Overall Management Implications of the Study?
There was no advantage to selecting hybrids based on interaction with the tillage, cropping sequence, and plant population. Drought-tolerant hybrids performed better in different rotations at different locations, but the variation in hybrid performance makes it difficult to produce a specific recommendation. Hybrids with defensive and high-yield designations showed similar responses to tillage and plant population. Corn yields averaged across locations, tillage, and hybrids were about 7% greater following soybean than corn. The yield advantage associated with crop rotation was the same or greater for corn grown using no-tillage than conventional tillage. Residue accumulation was not consistently greater in the no-tillage, continuous corn, and high plant population treatments.
Research conducted by Peter Thomison, Alex Lindsey, and Allen Geyer; Horticulture and Crop Science Department, The Ohio State University as a part of the Pioneer Crop Management Research Awards (CMRA) Program. This program provides funds for agronomic and precision farming studies by university and USDA cooperators throughout North America. The awards extend for up to four years and address crop management information needs of DuPont Pioneer agronomists and customers and Pioneer sales professionals.
Peter Thomison, Ph.D.1 - Professor, Corn Cropping Systems Extension Specialist, Horticulture & Crop Science Department, Ohio State University
Alex Lindsey, Ph.D.2 - Assistant Professor, Horticulture & Crop Science Department, Ohio State University
Allen Geyer3 - Research Associate, Horticulture & Crop Science Department, Ohio State University
Kirk Reese4 - Agronomy Research Manager, DuPont Pioneer