Planting Corn or Soybeans
Following a First-cut Hay Harvest

With some alfalfa stands being marginal this spring, producers are considering planting corn or soybeans in alfalfa fields following a first-cut hay harvest. There are two important concerns regarding this management practice. First, the alfalfa (and dandelions, quackgrass, etc.) use a significant amount of soil moisture by early June. Also, both corn and soybeans respond to planting date in terms of increased yield so don't count on a "bin buster" (even for silage) with this strategy. Nevertheless, there will be situations in a year such as this where the combination of the hay harvested plus the subsequent corn or soybean crop result in good use of available resources.

Corn:

Corn yield reductions can be expected from a later planting date and reduced early season moisture availability. Unless the corn will be harvested as silage, a shift to short season hybrids is recommended.

At the Arlington Research Center during 1985 to 1987, UW researchers compared moldboard plowing to a no-till system for corn planted in late May or early June following a hay harvest. Surprisingly, control of perennial species as not a major problem for no-till corn after alfalfa. Herbicides (Roundup and 2,4-D) did an adequate job of controlling the existing alfalfa, quackgrass, and dandelions. Corn emergence was reduced 8 to 20 percent under no-till compared to the plowing treatment. Poorest corn emergence occurred in the dry years of 1985 and 1987 in the no-till system. Although stands were overplanted to compensate for stand differences, crop yields were reduced 60 percent in 1985 and 20 percent in 1987 (the dry years) under no-till compared to moldboard plowing. Corn grain yields were similar between the two systems in 1986 when adequate moisture fell following planting. The actual results were as follows:

1985
1986
1987
Conv.
Till
No-
Till
Conv.
Till
No-
Till
Conv.
Till
No-
Till
Emergence %
98
78
94
86
95
87
Grain Moisture %
36.4
40.9
31.3
30.4
32.4
36.1
Grain Yield, bu/ac
107
41
140
137
107
82

Soybean:

Soybeans can also be planted following a first-cut hay harvest. Again, the bigest concern is available soil moisture. After June 1, something less than a full-season variety needs to be planted. The biggest disadvantage to planting soybeans after alfalfa is that the crop will not make efficient use of the nitrogen fixed by the alfalfa. However, this extra nitrogen will not hinder soybean growth. Remember that all soybean seed needs to be inoculated before planting. Alfalfa inoculum will not be effective for soybean.

For more information contact Mike Rankin
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