Effect of row spacing, plant population and nitrogen rate on corn yields.

Charles Shapiro, Soil Scientist, NEREC Mark Langrud, Graduate Student, UNL

Agronomy Research Team, NEREC

July 2, 1997

Objective: Determine if corn would respond to increased management inputs and increase yield under lateral move irrigation at the Northeast Research and Extension Center.

Material and Methods:

A split-split plot arrangement of treatments in three replications was used to compare 25,000, 30,000 and 35,000 plant populations in 20 and 30 inch rows with 0, 75, 150 and 225 lbs N per acre. The first split was population, the second split was row spacing and nitrogen rate was randomized within each sub-sub plot. A John Deere Max-Emerge 8 row planter was used for the 30" rows and a 12 row John Deere 7300 vacuum system was used for the 20". The experiment was planted May 30, 1996 with Pioneer 3394. Plots were 10 feet wide and 40 feet long. Nitrogen was applied with a 10 foot Barber Spreader. Nitrogen was applied as 34-0-0 on June 11 at rates of 0, 75, 150, and 225 lbs N/acre.

Initial soil tests indicated that the experimental sites had a pH of 6.7, organic matter of 2.5 %, soil texture of silty clay loam, Bray phosphorus of 35, potassium 381 and DTPA zinc of 0.70. Soil nitrates averaged 10.1 ppm to a depth of 30 inches. The University of Nebraska nitrogen recommendation for a 150 bushel yield goal was 80 lbs N per acre.

The experiment was hand harvested by taking 40 feet of row, shelling and taking a moisture sample. Five ears were taken for further analysis. Yields shown below are slightly lowered due to the five ears being removed before shelling. The relationship between treatments should remain constant.

Results:

The two planters could not be set at exactly the same planting rate. The 30'' planter dropped 27,700, 32,000 and 37,700 seeds and the 20" planter dropped 26000, 31500, and 38000 seeds for the 25000, 30000 and 35000 population treatments. Analysis of variance of final population indicated no significant Population x Rowspacing interaction. However, final stand was less than the target populations. The average population at harvest was 25230, 28400, and 32980 for the 25000, 30000, and 35000 treatments.

Yields were decreased by late planting due to unavailability of equipment. The narrow row corn increased yield about 9 bushels and was significant at the 0.08 level. Population did not affect yield. Nitrogen rate increased yields from 129 bu/acre for the zero nitrogen rate to 145 bu/acre for the 225 lbs N rate. Yield did not plateau at the 225 lb N rate in this experiment. There was no interaction between nitrogen rate and population or nitrogen rate and row spacing.

Examination of the three way interaction between rowspacing, population and nitrogen rate indicates that the narrow rows yielded better without nitrogen at the low populations and the wide rows yielded better without nitrogen at the high population.

Analysis of Variance
Source	df	Pr>F
Rep (R)	2	-----
Pop (P)	2	0.484
R x P (error A)	4	----
Row Spacing (S)	1	0.076
P x S	2	0.750
R x P x S (error B)	6	----
N Rate (NR) N linear 1 N quad 1	3	0.015 0.002 0.475
P x NR	6	0.943
S x NR	3	0.983
P x S x NR	6	0.056
Residual error	36	----
CV (%)		10.3

Effect of plant population, row spacing and nitrogen rate on corn grain yield at Northeast Research and extension Center. 1996.

	Population (plants/acre)
	25000	30000	35000	Mean
Nitrogen Rates (lbs N/acre)
20 inch rows	---------------------bu/acre--------------------
0	137	145	116	133
75	154	135	136	142
150	148	152	139	146
225	148	151	150	150
Mean	147	146	135	143
30 inch rows
0	117	126	135	126
75	130	146	123	133
150	140	134	136	137
225	149	142	128	140
Mean	134	137	131	134

Summary: Conclusions can't be drawn from one year data, however, narrow rows did increase yields at the 7% probability level. This experiment will continue in 1997. Timely planting will be based on availability of equipment.