Title: Berseem clover seed rate and harvest management effects on forage yields and nutrient uptake in swine-effluent spray field Authors
Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 4, 2013
Publication Date: N/A
Interpretive Summary: Bermudagrass is a warm-season perennial forage grown on swine-effluent application fields. Because bermudagrass survives the winter by lying dormant, winter cover crops can be over-seeded in the autumn for utilization during winter and spring. These could also be used to optimize phosphorus (P) uptake and to add nitrogen (N). Berseem clover can perform well as a winter cover crop because it begins to flower in early May, when conditions are generally favorable for hay curing. A team of scientists conducted field trials to determine the optimum seed rates for berseem clover harvested in two cutting regimes (once in May and twice in April and May) and any residual treatment effects on bermudagrass growth. Berseem clover was seeded at rates of 4, 8, 12, 16, 20 and 24 kg/ha in plots of bermudagrass fertilized with swine effluent in summer. Regression parameters were evaluated to determine the optimum seed rates for each forage component. Harvesting berseem clover once in May increased forage biomass, but recycled less P, Cu, and Zn from the swine effluent, as compared to harvesting clover in April and May. The optimum seed rate for hay yield is 14.0 kg/ha, for P uptake is 15.1 kg/ha, for Cu uptake is 14.6 kg/ha, and for Zn uptake is 15.3 kg/ha. The optimum rates were 4.5 to 5.3 kg/ha higher than the recommended 11.2 kg/ha rate for conventional seedings in Mississippi. While more costly for the grower, the heavier rates of seeding in sod of dormant bermudagrass were clearly advantageous to the growth of these forage crops, and hence, total nutrient uptake. Information supports nutrient management plans on commercial swine farms, where crop removal for a certain yield goal is used in making manure application decisions.
Technical Abstract: Research on how berseem clover (Trifolium alexandrium L.) seed rate (SR) affects winter and summer forage yields in swine-effluent spray fields is lacking for the southeastern USA. This 3-yr study determined optimum berseem SR for dry matter (DM) yield and nutrient uptake in the winter cover crop and summer perennial, bermudagrass [Cynodon dactylon L. (Pers.)], fertilized in April-October with swine effluent. ‘Bigbee’ berseem clover was drill-seeded in October at 4, 8, 12, 16, 20 and 24 kg/ha and harvested either twice in April and May or once in May. Yield of clover harvested twice was less than that harvested once (5410 vs. 7566 kg/ha), but N and P uptake were greater in double-harvest regime due to higher nutrient concentrations in less mature herbage. Clover responses to SR were described by quadratic trends, and for data pooled across years and harvest regimes, the optimum SR for DM yield is 16.5 kg/ha and for P, Cu and Zn uptake is 15.7, 14.8, and 16.0 kg/ha, respectively. Bermudagrass DM yield decreased linearly as berseem SR increased by approximately 6.3 and 66.7 kg DM/kg seed in the double- and single-harvest regimes, respectively. Increased DM of bermudagrass with double-harvest regime did not offset less clover yield. Results for total yields indicated the optimum berseem SR for DM yield is 14.0 kg/ha, and for P, Cu, and Zn uptake is 15.1, 14.6, and 15.3 kg/ha, respectively. For the treatments tested at this location, the combination of a berseem SR of between 15 and 16 kg/ha and two clover harvests, with the first cutting in April, appeared to be a best berseem clover management practice for remediation or control of P, Cu, and Zn concentrations in soil.