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In northern and central Illinois, early April to mid-May is the optimum planting window that may allow 97 to 100% realization of potential yield.1,4 Planting before this optimum window, even when conditions are fit, incurs risks such as cold temperatures or frost after emergence, thus increasing the vulnerability of seeds/seedlings to diseases, insects, and animal predators which can impact yield.2 Planting towards the early part of the window can permit more days for plant development, reduced pest pressure from some insects and diseases, earlier pollination to help avoid heat stress, improved standability due to shorter plant height, and earlier maturity and faster dry down.4 Late planting can lead to a potential yield loss of around 1 to 2 bu/acre for each day beyond the optimum planting window.1
Regardless of planting date, yield is affected by seeding rate and harvest population. Modern corn products are better capable of withstanding stresses and can produce an ear on every plant. Therefore, more plants per acre should lead to more ears per acre which, with adequate kernel number and weight, can provide higher yields.3 The purpose of this demonstration was to investigate the interactions between planting date and plant population for yield optimization.
A corn demonstration trial was conducted at the Monsanto Learning Center near Monmouth, IL comparing two planting dates and two planting populations. The trial was planted with a 113 RM Genuity® SmartStax® RIB Complete® corn blend product.
The trial was conducted on soybean rotated ground. Soil was prepared under conventional tillage with a chisel plow in the fall followed by a soil finisher in the spring. Plot sizes were 10 ft x 100 ft (0.023 acre)/treatment. Corn was planted in 30-inch single rows, 4 rows/treatment with 2 replications. A pre-emergent herbicide application of Harness® Xtra 5.6L at 2.75 qt/acre was done on April 23, 2014 for early planting, and on May 22, 2014 for late planting. Post-emergent herbicide applications of Roundup PowerMAX® at 22 fl oz/acre + AMS at 17 lb/100 gal were done on June 4, 2014 for early planting, and on June 25, 2014 for late planting. The trial was harvested October 20, 2014, and yield data was adjusted to 15% moisture content.
Figure 1. Effects of planting date on corn yield response to plant population.
There was an interaction between planting date and plant population (Figure 1). At 42,000 seeds/acre, early planting yielded 19 bu/acre more than late planting. At 36,000 seeds/acre, early planting yielded 8 bu/acre more than late planting.
Across plant populations, early planting yielded 14 bu/acre more than late planting. Across planting dates, 42,000 seeds/acre yielded 7 bu/acre more than 36,000 seeds/acre (Figure 2).
Figure 2. Mean corn yield response to planting date and plant population.
Overall, this trial provided the following findings:
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1Nebraska - Cool temperatures and corn planting. Alert, Technology Development & Agronomy, 04222013LGM. 2Determining when to begin corn and soybean planting. Spotlight, Technology Development & Agronomy, 03312014CRB. 3Populations and variable rate seeding for corn. Spotlight, Technology Development & Agronomy, 03132014JEH. 4The risks associated with planting corn before the optimum window – IA, IL, IN. Spotlight, Technology Development & Agronomy, AMB032112. 5Nafziger, E. 2008. Thinking about corn planting date and population. Issue 1, Article 7. The Bulletin. University of Illinois.