Invasion of broad-leaved weeds into alfalfa stand during time of utilisation of alfalfa stands in low-input farming system
Institute of Agricultural and Environmental Sciences, Estonian Agricultural University, Kreutzwaldi 56, 51014 Tartu, Estonia; e-mail: email@example.com
The objective of the investigation was to determine the percentage and yield of weeds in lucerne stands during the productive period. Different cutting regimes (first and final cut date and cutting frequency) were applied as treatments for estimating the extent of the invasion of weeds. Experiment 1 was conducted in 1980–1995 with the locally-bred alfalfa cv. Jõgeva 118 to study the connection between the invasion of broad-leaved weeds in the stand and weather conditions. Experiment 2 was carried out in 1991–2003 to investigate the impact of the first cut date and cutting frequency on the total DM yield of the alfalfa stand (cv. Karlu), partial DM yield of weeds, and the percentage of weeds in the stand. Experiments 3 and 4, Medicago sativa type WL 252 HQ variety (US), were sown in Tartu and Koonu to study weed spreading and alfalfa production at different locations. The results showed that management system had a strong impact on the productivity and competition ability of alfalfa and the invasion of weeds into the stand. Decreasing cutting frequency to 2–3 harvest times per season and performing the final cut in the second half of September or in early October allowed us to successfully depress the weeds in the alfalfa stands under Estonian pedoclimatic conditions. It is especially important to avoid more intensive management when extremely rainy and cool, or opposite droughty, weather conditions (total precipitation from May to September below the equivalent of 200 mm) dominate during vegetation period.