Modified Relay Intercropping (MRI) is the planting of soybeans into headed wheat that may occur up to 6 weeks or more prior to wheat harvest; whereas Double Cropping (DC) is the planting of soybeans after wheat harvest. Vyn et al, found that relay intercropping of soybeans yielded better than double cropping of soybeans north of I - 70 in Indiana (http://www.agry.purdue.edu/staffbio/AY316.pdf).
There are pros and cons with each system. In both systems, two crops, wheat and soybeans are harvested in the same growing season. In 2014, MRI and DC systems were planted at two locations; one in central Ohio at South Charleston (SC) and another at Bucyrus in north central Ohio.
Average yields over soybean and wheat in the two systems may offer a general comparison.
MRI vs DC Soybean Yields in 2014
|
Crop |
MRI 15 inch rows (SC) |
MRI Twin Rows (Bucyrus) |
DC (SC) |
DC (Bucyrus) |
|
Soybean Yields (bu/ac) |
35 |
35 |
27 |
8 |
|
Average |
35 bu/ac |
18 bu/ac |
||
MRI soybean yields were similar for the two sites in this trial (over all soybean plot yield averages (bu/ac) were 43 and 33 at SC and Bucyrus respectfully). Planting dates for DC soybeans were: July 11 at SC and Bucyrus. Rainfall from June 1 to August 31 was 9.9 inches at SC and 12.2 from 5/11 to 8/31 at Bucyrus. Stands were excellent at both locations; however soil types differed with SC being a Crosby and Bucyrus a Blount. Yield differences might also be related to the length of the growing season. Bucyrus DC soybeans had been killed by frost up to 10 days earlier than SC and were harvested 11/3, whereas SC soybeans were not harvested (not ready) until 11/11.
Interseeding vs No interseeding on Wheat Yield
|
Crop |
MRI 15 inch rows Wheat (SC)** |
MRI 10 inch Wheat - 3 year average (Bucyrus)* |
15 inch row Wheat at (SC)** |
10 inch row wheat – 3 years average (Bucyrus)* |
|
Wheat Yields (bu/ac) |
79 |
85 |
86 |
87 |
|
Average |
82 |
87 |
||
* 2011-2013 time period; ** 2014
There is a negative interseeding effect on wheat yield in the row spacing used above. The effect will depend on many factors such as: when wheat was interseeded, equipment operation and set up and wheat row spacing. In 2014 , a 7 bushel difference in wheat yield was observed in 15 inch rows . In 10 inch rows, for 3 years at Bucyrus, there was a 2 bushel difference.
In summary, DC soybeans with a shorter growing season are at greater risk to adverse weather over rainfall and growing season length. However, DC will almost always be expected to have better wheat yields. For more information on the Modified Relay Intercropping go to: http://ohioline.osu.edu/agf-fact/0504.html