Soybean plants have a remarkable ability to fill empty spaces, so maximum yield can be achieved with a minimum amount of seed, say researchers at McNeese State University, Lake Charles, LA. But they point out that low seeding rates result in thicker stems, reducing quality.
Research has shown that soybean seeding rates within the normal range for southwestern Louisiana (100,000-180,000 seeds/acre) yield about the same amount of forage. But little information was available on the impact of lower rates.
Two studies were conducted in 2011 to identify the optimum seeding rate and growth stage at harvest. Big Fellow forage soybeans were planted in irrigated and non-irrigated plots at 42,000, 84,000 and 144,000 seeds per acre.
Stems were more than ½” thick at the lowest seeding rate, perhaps enabling livestock to separate and reject them, say the researchers. As plants aged, leaf-to-stem ratios declined while dry matter content and stem length increased.
“Overall, the data support planting 84,000 seeds per acre and harvesting at reproductive stage 4 to attain the optimum forage quantity and quality desired for livestock production,” say the researchers.