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Advancing Intensive Management of Corn Systems in Minnesota

Study author(s): Jeff Coulter, University of Minnesota, Department of Agronomy and Plant Genetics
Years of study: 2018
Location(s): Waseca, MN

Important: for the complete report, including all tables and figures, please download using the links to the right.

1) goals and objectives obtained

a) Establish treatments and manage plots. Plots were established. Weeds were controlled using pre- and post-emergence herbicides. Plots were end-trimmed and staked, and corn stand counts were taken. In-season nitrogen (N) fertilizer and foliar fungicide applications were made at the appropriate times for the respective treatments.

b) Collect and analyze in-season plant samples. Corn plant samples were collected at the V10 stage, processed, and analyzed for nutrients.

c) Harvest plots for grain, cob, and stover, and analyze plant samples collected at harvest. Plots were harvested in early October. Corn grain, cob, and stover samples were processed and analyzed for nutrients.

d) Collect soil samples after harvest and analyze. Plots were soil sampled after harvest in mid-October to a depth of 40 inches and samples were analyzed for bulk density and nutrients.

e) Manage plots in the fall. Following soil sampling, corn stalks were chopped, partial stover removal was conducted in the appropriate plots, phosphorus and potassium fertilizers were applied as appropriate, and the trial area was disk-ripped.

f) Present oral update to AFREC Council. An oral update was presented to the AFREC council on December 11, 2018 at Minneapolis, MN.

g) Present research results to farmers and agricultural professionals and Extension meetings. Results from this research were presented to farmers and agricultural professionals at Extension meetings across Minnesota.

2) Activities performed

a). The goal/objective “establish treatments and manage plots” was accomplished through the activities described in this section.

This project compares two levels of agronomic management: 1) farmer-practice agronomics and 2) a high-yield system that is also environmentally responsible, referred to as sustainable intensification. For both of these, standard fertilizer management in line with university guidelines is compared with advanced fertilizer management. Within these four main-plot treatments, split plots are with and without N fertilizer for evaluation of N use efficiency parameters.

Treatment details are in Table 1. Compared to farmer-practice agronomics, sustainable intensification includes partial removal of corn stover after harvest, a longer-season corn hybrid, a greater planting rate, and foliar-applied fungicide at the VT corn stage. Compared to standard fertilization, the advanced fertilization treatment includes phosphorus and potassium application based on grain removal, surface-banded starter fertilizers, and in-season N applications that more closely align with corn N uptake.

Following discussions with crop advisors and farmers, and based on recommendations from AFREC, treatment upgrades were made to this experiment at Waseca, MN for the 2018 growing season. These included different hybrids, foliar fungicide applied at the VT corn stage with a high-clearance applicator in the sustainable intensification treatment, increasing the rate of sulfur application in all plots, and increasing the total rate of N application to 180 lb N/ac in the standard fertilizer management treatment and 220 lb N/ac in the advanced fertilizer management treatment.

In addition, the advanced fertilizer management treatment had an additional in-season N application added at the V14 corn stage for a total of two in-season N applications (V6 and V14). The N application at V14 is 40 lb N/ac as 28-0-0 that is surface-banded near corn rows using the ‘360 Y-DROP’ system. Based on observed changes in soil-test values and an economic analysis, the basis for P fertilization in the advanced fertilizer management treatment was changed from 100% of grain removal to 50% of grain removal.

Sulfur and urea were broadcast according to Table 1 prior to pre-plant tillage. Corn was planted in 30-inch rows on May 8, 2018 using a custom built 4-row John Deere 7300 MaxEmerge II planter. Pioneer P0157AMXT [101 comparative relative maturity (CRM)] was planted in the farmer-practice agronomics treatments and Pioneer P0589AMXT (105 CRM) was planted in the sustainable intensification treatments. Planting rates for target corn populations and starter fertilizers were applied according to Table 1.

Weeds were controlled using pre- and post-emergence herbicides. Corn stand counts were taken at the V3 corn stage. Final corn populations were 34,000 plants/acre for the farmer-practice agronomics treatments and 39,000 plants/acre for the sustainable intensification treatments. In-season N fertilizer and foliar fungicide applications were made at the appropriate times for the respective treatments.

Monthly total precipitation in 2018 at Waseca, MN was near the 30-year average during April through August (Table 2), but was 6.87 inches above the 30-year average in September. Adequate, but not excessive precipitation, from April through August, combined with warmer than normal air temperature during May and June, near-normal air temperature during July and August, and modestly above-normal air temperatures during September, resulted in robust corn growth and development during vegetative stages and limited stress during kernel set and grain filling. This resulted in a maximum yield of 229 bu/acre in this trial (Table 4).

b) To accomplish the goal/objective “Collect and analyze plant samples,” whole plant samples were collected from each plot at the V10 corn stage for determination of dry matter yield and nutrient uptake. Eight whole plants were collected from the non-harvest rows of each plot, weighed wet, ground, and subsampled for determination of plant moisture content and calculation of whole plant dry matter yield. A dry subsample of ground plant material from each plot was analyzed for total N, phosphorus, potassium, calcium, sulfur, magnesium, boron, manganese, iron, zinc, copper, and aluminum. Corn nutrient uptake at the V10 corn stage was calculated as the product of plant dry matter yield and nutrient concentration, and is shown in Table 3. Differences among treatments at the V10 corn stage are shown in Photos 1-8.

Greatest corn dry matter yield at the V10 stage was obtained with all combinations of fertilizer and agronomic management when N fertilizer was applied (Table 3). On average, corn dry matter yield at the V10 stage was 68% greater with N fertilization. The non-N-fertilized control treatments are included in this study for evaluation of N use efficiency indices.

For N-fertilized treatments, corn uptake of N, sulfur, boron, and manganese at the V10 stage was less with standard fertilizer management + farmer-practice agronomics compared to treatments including advanced fertilizer management or sustainable intensification (Table 2). Similarly, corn uptake of phosphorus, potassium, and copper was greater with advanced compared to standard fertilizer management for both levels of agronomic management.

c) To accomplish the goal/objective “harvest plots for grain, cob, and stover, and analyze plant samples collected at harvest,” whole-plant corn samples were collected from each plot at the R6 growth stage (physiological maturity). Ears were separated from the rest of the plant (stover). Ears were dried, weighed, and shelled, after which grain and cobs were weighed separately. Stover was weighed, chipped, sub-sampled in the field, with sub-samples weighed wet and again after drying. These data were used to calculate corn silage yield at 65% moisture content. In early-October, plots were end-trimmed and harvested using a plot combine. Grain yield was adjusted 15.5% moisture content. A dry subsample of ground grain, cobs, and stover from each plot was analyzed for total N, phosphorus, potassium, calcium, magnesium, sulfur, boron, copper, iron, manganese, and zinc. Corn nutrient uptake was calculated as the product of plant dry matter yield and nutrient concentration and is shown in Tables 4-5.

Parameters of corn N uptake and N use efficiency were calculated as:

i) Apparent N fertilizer uptake efficiency = [(aboveground N uptake in treatment with N fertilization – aboveground N uptake in corresponding treatment without N fertilization) / (N fertilizer rate in treatment with N fertilization – N fertilizer rate in corresponding treatment without N fertilization)]
ii) Physiological N use efficiency = [(grain yield in treatment with N fertilization – grain yield in corresponding treatment without N fertilization) / (aboveground N uptake in treatment with N fertilization – aboveground N uptake in corresponding treatment without N fertilization)]
iii) Agronomic N use efficiency = [(grain yield in treatment with N fertilization – grain yield in corresponding treatment without N fertilization) / (N fertilizer rate in treatment with N fertilization – N fertilizer rate in corresponding treatment without N fertilization)]

With N fertilization, corn grain yield was greatest with advanced fertilizer management and either farmer-practice agronomics or sustainable intensification (average = 227 bu/acre) (Table 4). This was 5% greater than that with standard fertilizer management (average = 216 bu/acre).

With N fertilization, corn silage yield was maximized with sustainable intensification + advanced fertilizer management (30.8 tons/acre) (Table 4). This was 8% greater than that with standard fertilizer management + farmer-practice agronomics or sustainable intensification (average = 28.5 tons /acre). Among treatments with N fertilization, silage yield was least with advanced fertilizer management + farmer-practice agronomics. With N fertilization, grain and silage yields averaged 2.0- and 1.4-fold greater, respectively, compared to when no N fertilizer was applied.

Grain moisture at harvest averaged 3.9 percentage points greater with sustainable intensification than farmer-practice agronomics (Table 4). This is attributed to the later-maturity hybrid (105-day) with sustainable intensification compared to farmer-practice agronomics (101-day).

Apparent fertilizer N uptake efficiency, or the increase in corn N uptake per pound of N fertilizer applied, was greatest with standard fertilization + either level of agronomic management and least with advanced fertilization + farmer-practice agronomics (Table 4). Physiological N use efficiency, or bushels gained per one-pound increase in corn N uptake when N fertilizer was applied, was not affected by the treatments in this study. Agronomic N use efficiency was greatest with standard fertilizer management + sustainable intensification. This is attributed to moderately high yield (218 bu/acre) achieved with relatively low N fertilizer input (180 lb N/acre). Agronomic N use efficiency was less with the other treatments.

Corn nutrient uptake in grain, cobs, and stover at maturity was affected by agronomic management, fertilizer management, and N fertilization. Aboveground corn nutrient uptake averaged 0.2- to 3.1-fold greater with N fertilization compared to without N fertilization for all nutrients measured in this study except zinc and aluminum (Tables 4 and 5). These increases in corn nutrient uptake were associated with greater grain and whole-plant yields.

When N fertilizer was applied, advanced fertilization + sustainable intensification maximized corn uptake of each nutrient measured in this study (Tables 4 and 5). Corn uptake of N and potassium was greatest with advanced fertilization + either level of agronomic management. Greatest corn uptake of phosphorus occurred with advanced fertilization + either level of agronomic management and with standard fertilization + farmer-practice agronomics. For magnesium and manganese, greatest uptake by corn occurred with standard fertilization + either level of agronomic management and with advanced fertilization + sustainable intensification. Corn uptake of sulfur, iron, zinc, and aluminum was not significantly influenced by fertilizer management or agronomic management.

d) To accomplish the goal/objective “collect soil samples after harvest and analyze,” soil samples were collected after harvest in mid-October to a depth of 40 inches and were processed and analyzed for bulk density and nutrients. When N fertilizer was applied, residual soil nitrate-N in the 0- to 40-cm depth was greatest with advanced fertilization + farmer-practice agronomics and least with standard fertilization + sustainable intensification; the difference between these treatments was 20 lb/acre (Table 4).

Soil-test levels from the fall of 2018 show that the treatments in this study did not affect soil organic matter, cation exchange capacity, electrical conductivity, calcium, sulfur, magnesium, boron, manganese, iron, zinc, copper, or sodium for any depth increment within the 0- to 40-inch soil profile (Tables 6-9). On average, there was no significant difference between standard and advanced fertilizer management for pH for any depth increment within the 0- to 40-inch soil profile.

Within the 0- to 2-, 2- to 4-, and 4- to 8-inch depths, Bray-1 phosphorus averaged 53, 40, and 13 ppm greater with advanced compared to standard fertilizer management, respectively (Table 7). Within the 0- to 2-, 2- to 4-, and 4- to 8-inch depths, Olsen phosphorus averaged 35, 25, and 8 ppm greater with advanced compared to standard fertilizer management, respectively. Within the 0- to 2- and 2- to 4-inch depths, soil-test potassium averaged 62 and 22 ppm greater with advanced compared to standard fertilizer management, respectively. There was no significant difference between standard and advanced fertilizer management for Bray-1 or Olsen phosphorus for depth increments below 8 inches, or for potassium for depth increments below 4 inches.

e) To accomplish the goal/objective “manage plots in the fall,” plots were managed as appropriate. This involved chopping corn stalks following soil sampling, partial stover removal in the appropriate plots, application of phosphorus and potassium fertilizers as appropriate based on the treatments, and disk-ripping the trial area.

f) To accomplish the goal/objective “present oral update to AFREC council,” an oral update was presented to the AFREC council on December 11, 2018 at Minneapolis, MN.

g) To accomplish the goal/objective “research results to farmers and agricultural professionals and Extension meetings,” results from this research were presented to farmers and agricultural professionals at Extension meetings across Minnesota.

3) MULTI-YEAR SUMMARY FOR KEY METRICS OF CROPPING SYSTEM PERFORMANCE

Key findings for grain yield:

  1. There was a yield gap of 16 to 64 bu/acre between treatments with highest and lowest yields. Averaged across years, this yield gap was 36 bu/acre or 19%.
  2. Greatest 6-year average yield occurred with advanced fertilizer management applied to sustainable intensification.
  3. Intermediate 6-year average yield occurred with either advanced fertilizer management or sustainable intensification alone.

Key findings for economic net return:

  1. When compared to farmer-practice agronomics + standard fertilizer management, economic net return was significantly greater with sustainable intensification alone in 2 of 6 years.
  2. When compared to farmer-practice agronomics + standard fertilizer management, economic net return was significantly less in 4 of 6 years and on average with advanced fertilizer management alone or in combination with sustainable intensification. This was associated with the cost of applying phosphorus and potassium fertilizers at greater rates, especially during the first 5 years of the study.

Key findings for agronomic N use efficiency:

  1. Averaged across years, agronomic N use efficiency was greater with sustainable intensification compared to farmer-practice agronomics for standard fertilizer management, but not for advanced fertilizer management. Across years and both levels of fertilizer management, agronomic N use efficiency was greater with sustainable intensification compared to farmer-practice agronomics. Greater agronomic N use efficiency was associated with greater corn N recovery efficiency.

Key findings for corn N recovery efficiency:

  1. For standard fertilizer management, corn N recovery efficiency was greater with sustainable intensification compared to farmer-practice agronomics in 4 of 6 years and on average. For advanced fertilizer management, corn N recovery efficiency was greater with sustainable intensification compared to farmer-practice agronomics in 1 of 6 years. Across years, corn N recovery efficiency was not significantly different between standard and advanced fertilizer management for either level of agronomic management.

Key findings for residual soil nitrate-N after harvest in the 0- to 40-inch depth:

  1. Across years, residual soil nitrate-N after harvest in the 0- to 40-inch depth was not significantly different between farmer-practice agronomics and sustainable intensification. For farmer-practice agronomics, residual soil nitrate-N was less with standard compared to advanced fertilizer management in 3 of 6 years and on average. For sustainable intensification, residual soil nitrate-N was less with standard compared to advanced fertilizer management in 2 of 6 years and on average.

4) CHALLENGES ENCOUNTERED

There were no significant challenges encountered.

5) FINANCIAL INFORMATION

A detailed financial report will be submitted by the University of Minnesota Sponsored Financial Reporting group.

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