Oakes
Variety by row width by population
SOYBEAN ROW WIDTH AND POPULATION STUDY
W. Albus, L. Besemann and
H. Eslinger
From 1984-87 Walter Albus found irrigated soybeans at plant
populations of 100,000, 150,000 and 200,000 averaged 52, 53 and 55 bu/acre
respectively and 56 and 50 bu/acre in 15 and 30-inch rows respectively, at
the Oakes Irrigation Research Site.
With the introduction of roundup ready soybeans (RR) the effect of row
width and population needs to be revisited.
Increasing early soybean canopy through narrow rows and higher
populations for weed control is less of an issue with RR beans. The increased cost associated with RR beans
forces a more conservative approach to planting rates. Also increasing pressure from Sclerotinia
(white mold) has producers looking to 30-inch rows to provide better air-flow
for foliage to dry. Richard Greenland
initiated a row, population study in soybeans in 2005 to address these
issues. Results from 2005 showed no
significant impact of either row width (10, 20 and 30-inch) or plant population
(73,000, 108,000 and 143,000 plants/acre) on soybean yield. This study in 2006 produced similar results
as there was no difference in yield between 10, 20, and 30-inch rows or a yield
difference between 100,000, 150,000 and 200,000 plants/ac. Two soybean varieties, were grown at three
row widths; 10, 20 and 30-inch rows and at three populations; 100,000, 150,000
and 200,000 plants/acre in 2007
MATERIALS AND METHODS
|
Soil: |
Maddock sandy loam; pH=7.3; 1.8% organic
matter; soil-P was very high, soil-K was medium and soil-S was medium. |
|
Previous crop: |
2006 ‑ field corn; 2005 – field
pea, onion and potato; 2004 – potato and sweetcorn. |
|
Seedbed Preparation: |
Flailed, disked and coulter chiseled in the fall; Coulter chisel
lightly once on April 26 Multiweed (field cultivate) three times;
twice on May 8 to smooth the seedbed and to incorporate herbicide and once on
May 24 for control of small weeds and break crust. |
|
Planting: |
Planted Asgrow 801 and Croplan 995 on
May 24 in 10, 20 and 30-inch rows.
All beans were inoculated just prior to planting. |
|
Plots: |
Plots were 17 ft long by 10 ft. Plots in 10-inch rows had 10 rows per
plot, 20-inch row plots had 5 rows per plot and 30-inch row plots had 4 rows
per plot. Two varieties were planted
in each row width at 100K, 150K and 200K plant populations per acre. There were four reps. |
|
Fertilizer: |
November 2006, broadcast 9 lbs N/acre, 43 lbs P2O5/acre,
101 lbs K2O/acre and 13.5 lbs S/acre as 11-52-0, 0-0-60 and
90% elemental sulfur. |
|
Irrigation: |
Overhead sprinkler
irrigation as needed. |
|
Pest control: |
Trust (1½ pt/acre) on May 8, Cornerstone (32 oz/acre) + AMS (1
lb/10 gal) on June 19, Cornerstone (48 oz/acre) + AMS (1 lb/10 gal) + NIS
(0.5%v/v) on July 7; for weed control.
Topsin (1 lb/acre) July 11 for disease control. Lorsban (1 pt/acre) on August 3 for insect
control. |
|
Harvest: |
Harvested on October 4 with a Hege
plot combine. Harvest area 17 foot by
5 foot (30 inch = 2 rows; 20 inch = 3 rows; 10 inch = 6 rows). |
Croplan
995 and Asgrow 801 were planted in a split, split plot arrangement, variety as
main plots, row width as split plots and population as split, split plots. Harvest populations of 124,100, 189,800 and
233,400 were higher than the target populations of 100,000, 150,000 and 200,000
plants/acre. Croplan 995 and Asgrow 801
averaged 68 and 66 bu/ac, respectively.
Row width and plant population had no significant effect on yield. Lodging increased from a score of 2.7 in
10-inch rows to 4.7 in 30-inch rows.
Lodging was significantly more in 20-inch rows than in either 10 or
30-inch rows. Lodging score increased
with increasing plant population. There
was an interaction between variety and population. Lodging was lower in 801 than in 995 at low populations, but
higher at high populations. There also
was an interaction between row width and population. Lodging scores in 20-inch rows tended to increase more with
increasing population than the other row widths.
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Table 1. Results of the soybean row width and population study at the Oakes Irrigation Research Site in 2007.
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Irrigation Research Site 2007 Annual Report