Fertility and Fertilization
Many researchers have found switchgrass can be high yielding but not as responsive to applied nutrients as improved grasses, such as bermudagrass and tall fescue. However, most of those studies were based on short term observations (e.g., two to three years). Longer studies are needed to clarify how switchgrass uses nutrients.
High yields of switchgrass will not be sustained if adequate nitrogen (N) or other nutrients are not applied because it removes significant amounts of nutrients from the soil. Table 4-1 shows the average major nutrient content of mature switchgrass harvested in late fall or winter. The nutrient content of mature biomass is much less than that harvested earlier for forage. It is believed that N and other nutrients are translocated to the rhizomes for storage after switchgrass reaches maturity. Therefore, most nutrients will remain in the rhizomes for the following years growth if the harvested portion is only the dry stems, leaves, and seed heads. However, the potential for optimum yield, maintenance of stand, maximum weed control, and sustainable production could be compromised if adequate soil fertility and soil pH are not maintained.
Major plant nutrients removed by switchgrass
when harvested at maturity as a biofuel crop.
| Yield (tons) |
Nitrogen (lbs N) |
Phosphorus (lbs P2O5) |
Potassium (lbs K2O) |
|---|---|---|---|
| 1 | 20 | 8 | 20 |
| 4 | 80 | 32 | 80 |
| 8 | 160 | 64 | 160 |
