Plant population effects on yield and yield components of maize hybrids bred for response to high plant population

Jason W Lee, Purdue University


In an effort to increase yield seed companies are breeding corn (Zea mays L.) hybrids to tolerate high plant populations (>93,000 plants ha -1) as well as encouraging producers to plant high seeding rates to take advantage of this selected characteristic. Our objective was to compare yield and yield components of two hybrids, one marketed as “highly-responsive” (Stine 9733) to high plant populations and the other considered “less-responsive” (Stine 9728), across a range of seeding rates (61,750 to 113,620 seeds ha -1 in four increments of 17,290 seeds ha-1) in 76 cm rows. The second objective was to document plant population effects on plant nutrient uptake and nutrient allocation to the grain. This study was conducted in 2013 and 2014 at four locations that varied in soil type, management practices, and weather conditions. The actual plant population for each intended seeding rate varied among locations. Due to the variation in actual plant population among locations and years, each location-year was analyzed separately. At silking (R1), increased plant population had little to no effect on the total number of ovules ear-1 (TNOE) at seven of the eight locations, with only a minimal decrease (≤50 ovules ear-1) at one location. The TNOE for both hybrids responded similarly to increased plant populations. At physiological maturity (R6) total kernel number ear-1 (TKNE) decreased by approximately 28% as plant population increased. However, the two hybrids did not differ in TKNE throughout the range of plant populations across all locations. The two hybrids did not differ in kernel weight (KW) at seven of the eight locations when plant populations increased. At all locations, KW decreased in a curvilinear fashion as plant population increased. The yield response for both hybrids varied depending on location. The calculated optimum plant population ranged from 74,176 to 97,194 plants ha-1 and from 64,656 to 102,152 plants ha-1 for Stine 9733 and Stine 9728, respectively, at four of the eight locations. At only one of these locations was the grain yield for Stine 9733 significantly higher at the highest plant population than the grain yield for Stine 9728. Both hybrids yielded the same at the remaining four locations irrespective of plant population. When averaged across locations, the average optimum plant population was approximately 83,000 plants ha-1,which is approximately 4,000 plants ha-1 higher than the reported average optimum plant population for Indiana (Nielsen et al., 2015). Overall, the two hybrids examined responded similarly to plant population for all parameters other than yield. Despite marketing claims, the grain yield response to increased plant population did not consistently show that Stine 9733 had a greater tolerance to high plant population than Stine 9728. Nutrient uptake was assessed based on nutrient concentration in the ear leaf at silking (R1). In general, this study found that increased plant population had the greatest effect on ear leaf N concentration, and little to no effect on ear leaf P and K concentrations. Ear leaf N concentrations decreased on averaged by approximately 3 g kg-1 between the lowest and highest plant populations. At physiological maturity (R6), grain N and P concentrations decreased as plant populations increased at six and five of the locations, respectively. However, grain N and P concentration primarily differed at the two lowest plant populations. Increased plant population had very little effect on K concentration in the grain.




Nielsen, Purdue University.

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