Influence of common lambsquarters ( Chenopodium album) densities and phosphorus fertilization on lettuce

Abstract

Field trials were conducted in organic soils to determine the effects of different phosphorus fertilization programs and common lambsquarters ( Chenopodium album L.) densities on ‘South Bay’ lettuce ( Lactuca sativa L.) yield loss. Phosphorus was applied either banded (125 kg P/ha) or broadcast (250 kg P/ha) prior to lettuce planting. Common lambsquarters population densities of 0, 2, 4, 8 or 16 plants/6 m row (5.4 m 2) interfered with lettuce for 10 weeks. Two rectangular hyperbola models characterized the relationship between common lambsquarters density and lettuce yield loss. When phosphorus was applied broadcast, predicted lettuce yield losses were 39%, 50%, 59% and 65% for 2, 4, 8 and 16 common lambsquarters plants/6 m row, respectively. However, when the phosphorus rate was reduced by 50% and was applied in bands beneath lettuce rows, these predicted losses were 23%, 30%, 35%, and 38% for the same common lambsquarters densities. Based on the lettuce yield loss models, if a single common lambsquarters plant interferes with lettuce every 6 m row, then predicted lettuce yield losses could be approximately 27% and 16% for broadcast and banded phosphorus applications, respectively.