Increasingly, crop people are planting their corn with the goal of harvesting the highest possible energy forage supporting profitable livestock production. For folks who do not (or may not) use herbicides, it’s critical that such stands be cultivated on a timely basis so that weeds don’t overwhelm the crop.
The problem with repeated cultivation is that it loosens the soil, which in turn oxidizes organic matter (OM) vital to the soil’s health and structure. (Introducing some oxygen to the soil is good; introducing lots of oxygen to the soil proves to be too much of a good thing when it degrades soil OM.) Loose soil on slopes is very vulnerable to rain, which washes away its most productive components.
The biggest problem with corn culture is that multiple cultivations come at the same time, demanding the same nice weather as the hay crop needing cutting. Critical hay harvest is delayed for the corn’s benefit. When hay is at peak quality, the most important chore on the farm is harvesting and storing that homegrown nutrition. Growers lose money each day the harvest is delayed. But folks who don’t use chemicals must cultivate or risk forfeiting their crop to weeds. An alternative that research in the last decade revealed – and more organic farms are considering – is the use of brown midrib (BMR) male-sterile sorghum instead of corn for livestock forage programs.
As was shown in an earlier column, nutrient-enhanced male-sterile BMR forage sorghum with delayed harvest has nearly the same energy and potentially more protein than corn silage. It is not genetically modified and is available as untreated seed. On a per-acre basis, its costs are a fraction of seed corn’s. BMR sorghum yields equal or exceed those of corn silage. Unlike corn’s and soybean’s, sorghum’s fine fibrous roots enhance, rather than deteriorate, soil structure.
Sorghum, sudangrass, their hybrids and millets maintain existing OM; with increased OM comes increased water storage capacity. I can’t overstress the importance of protecting OM and topsoil. Since 1850, Iowa has lost so much OM and topsoil that its water storage capacity has been reduced by a gallonage equivalent to that of Cayuga Lake.
Planted correctly, sorghum can be successfully grown without herbicides. It’s critical that sorghum be planted when the soil is at least 65º F and the forecast is for continued warmer temperatures the next week to 10 days. This allows sorghum to rapidly germinate, rapidly emerge and quickly shade out potential weeds. Planted into warm soil, followed soon by warm rains, seedlings break ground in as little as three days.
If there are any spots that light is getting through, sorghum quickly sends out lateral shoots to fill in, so the resulting canopy completely shades the ground, also helping retain moisture. These warm soil temperatures usually occur after winter forage, cool season grasses, red clover and alfalfa have achieved peak quality. Thus, we recommend growers harvest all their haylage/baleage first at its highest quality. Then return to incorporate manure to help meet sorghum’s critical nitrogen needs.
Immediately incorporating manure increases the plant’s vital available nitrogen by about 75% compared to surface spreading. When the soil temperature and the weather forecast are right, then plant.
At some point, some growers may no longer need corn planters. A good quality press-wheel drill that can plant accurately below 8 lbs. of seed/acre, with sleeved drop tubes planting in narrow rows, is perfect for rapid shading of the ground, stealing sunlight from weeds. Annual grasses hardly germinate when incoming solar radiation is reduced by more than 40%. The same drill can be used to grow the increasingly popular, soil-enhancing, high forage quality winter triticale the other half of the year.
By drilling in narrow rows, the sorghum seeds/plants are spaced uniformly. An 8-inch drill at suggested 100,000 seeds/acre is a seed every 7.8 inches in the row. This maximizes the rapid shading of soil. It also maximizes the stalk size so the male-sterile plant can stand for eight weeks after heading without going down. Top-heavier fertile seedheads would be prone to lodging.
Utilizing a stale seedbed planting system will further enhance weed control. Here the grower applies then immediately incorporates manure and rolls the field. This makes ideal conditions to encourage small weeds to sprout and start growing. By allowing the field to sit for a week or so, and then lightly harrowing, most sprouted weed seeds are killed.
When using a press-wheel drill, only the soil over the sorghum seed is compacted to enhance seed germination. In between the row remains loose harrowed soil, causing poorer sprouting conditions for small weed seeds. Soil temperature, stale seedbed, drill spacing and press-wheels combine to enhance the crop’s emergence while discouraging that of weeds.
BMR male-sterile forage sorghum can be harvested as a single, direct cut system. This reduces harvesting cost and doubles the yield while enhancing nutrient content compared to a multi-cut system. If you must multi-cut to harvest as round bales, then BMR pearl millet or sudangrass may be a better crop. Further cost savings come from the fact that a processor is not needed and would actually prove detrimental to making quality sorghum silage/baleage.
For energy approximately the same as corn silage, it’s critical that the harvest is delayed for eight weeks after the male-sterile sorghum heads. This delay is key to enhancing the energy of the forage. It is the same timeframe we use with corn silage, which is chopped eight weeks after tasseling.
It’s necessary to select the correct season length for your climatic area and time of planting. As soon as the crop is harvested, you can immediately use your drill to no-till plant triticale into the sorghum stubble for a winter crop. Rolling coulter injection of manure into the triticale in November or December can meet all the winter forage’s spring nitrogen needs.