Relationship between Interseeded Red Clover Biomass and Plant Number

Developing robust relationships between dry matter (DM) and plant number (PN) in interseeded red clover (Trifolium pratenseL.) and winter cereal systems are useful for predicting potential DM. Predicting DM months in advance enhances producers’ ability to determine forage requirements. Data from five winter cereal and red clover studies conducted during the period 2003 to 2009 were synthesized to develop robust relationships between red clover DM and PN using treatments that included different winter cereal species and variety, winter cereal seeding rate, red clover variety, tillage, and soil amendment. Dry matter data were collected during two 40‐d harvests after winter cereal harvest. The relationship between red clover PN and DM was described mathematically by a two‐phase regression for both harvests following winter cereal harvest. During the first harvest, the relationship was described by a parabola in the first line segment while the second line segment had no slope. In the second harvest, the first line segment was a simple positive linear relationship and the second line segment also had no slope. The join point for the first harvest occurred at 90.3 plants m−2while the second harvest join point occurred at 42.3 plants m−2. Red clover PN above 80 plants m−2likely provide around 90% of total maximum DM while red clover PN around 50 plants m−2likely only provides about 70% of total maximum DM.