|Andrae, John -|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 2012
Publication Date: July 2, 2012
Citation: Stone, K.C., Bauer, P.J., Andrae, J., Busscher, W.J., Millen, J.A., Strickland Jr, E.E., Evans, D.E. 2012. Irrigation and nitrogen impact on bermudagrass yield response in the southeastern Coastal Plain. Transactions of the American Society of Agricultural and Biological Engineers. 55(3):969-978. Interpretive Summary: In the Southeast US, sustainable hay production for the cattle industry is needed. The industry may be more sustainable using irrigation to alleviate water deficit stress during the short periods of drought that are common in the region. In this study, we investigated the impact of irrigation management practices and nitrogen fertility levels on Tifton 85 bermudagrass yield and forage quality. We evaluated four irrigation rates designed to alleviate water deficit stress and three nitrogen fertilization rates for each irrigation rate. We harvested the hay at 4- and 8- week intervals. As expected the nitrogen fertilizer significantly increased hay yield, nutrient concentrations, and forage quality. We also found that during harvest intervals without sufficient rainfall to maintain adequate soil moisture levels, hay yields increased linearly with irrigation rate. These harvests also had significant forage quality trends with increasing irrigation rate. Additionally, for the non-irrigated treatments, we observed that hay yields decreased linearly as the soil moisture was depleted. Irrigation management to maintain acceptable soil moisture can sustain and potentially increase bermudagrass hay production in the southeastern Coastal Plain.
Technical Abstract: In the southeastern region of the US, the cattle industry has a critical need for sustainable hay production. Yet, this production is threatened by frequent short-term regional drought. This drought threat can be mitigated by properly managed irrigation. In this study on Tifton 85 bermudagrass, irrigation management, nitrogen fertility levels, and harvest interval were evaluated for their impact on hay quality and yield. The experimental treatments were arrayed in a split-plot design with harvest interval as main treatment; irrigation by N levels were the subplots. Treatments had four replicates and were repeated for two years. The optimal irrigation rate was set to maintain soil water potentials below -30 kPa. When needed, the full irrigation treatment received a 12.5-mm irrigation application. The reduced irrigation treatments received water in rates of 0, 33, and 66% of the full irrigation rate. In addition, each irrigation treatment had nitrogen rates of 168, 336, and 504 kg N/ha. The irrigation and nitrogen treatments were harvested at 4- or 8-week intervals. Total harvest per year ranged from 3 to 6. Over both years and for all harvests, there was no irrigation-nitrogen interaction for hay yield. Over all harvests, nitrogen significantly increased bermudagrass hay yield, nutrient concentrations, and forage quality. Forage quality was higher for the 4-week harvest interval. Throughout the study, forage quality was maintained within desired industry standards. When irrigation was required, it significantly increased hay yields. Moreover, hay yield increased linearly with increasing irrigation rate. The 4-week harvest interval was more responsive to irrigation. Additionally, we observed a linear relationship between non-irrigated bermudagrass hay yields and average soil water potential. As soil moisture was depleted, non-irrigated hay yields decreased 31 kg/ha per kPa. Timely supplemental irrigation to maintain soil water potentials below -20 to -30 kPa can increase bermudagrass yields. Thus, irrigation management should be critically assessed for its potential role in sustaining hay production in the southeastern Coastal Plain.