Interseeded Crimson Clover or Red Clover Did Not Reduce Pumpkin Yield

Pumpkins (Cucurbita pepo L.) are grown with wide between-row spacing. The inter-row soil may not be covered by the pumpkin canopy until August in Minnesota, and the pumpkin canopy dies at frost (typically October). This provides spatiotemporal availability for growing cover crops, especially frost-tolerant and shade-tolerant species like clover (Trifolium sp.). However, ensuring minimal interference with the pumpkin crop is important. A 2-year study was conducted to gain a better understanding of the potential for crimson (T. incarnatum L.) or red (T. pratense L.) clover to be sown between pumpkin rows without impacting pumpkin yield. ‘Cotton Candy’ and ‘Kratos’ pumpkins were grown on 10-foot row spacing, and crimson clover or red clover seeds were sown between rows before pumpkin vines elongated. Pumpkin yield and clover fall biomass and nitrogen content were measured. Clovers had no meaningful impact on pumpkin fruit size, size variability, or yield. ‘Kratos’ fruits were larger (9.2 kg) and yielded more by weight (45 Mg/ha) than ‘Cotton Candy’ (25 Mg/ ha, 2.5 kg/fruit). Clovers accumulated less biomass (0.39 Mg dry matter/ha) and aboveground nitrogen (4.8 kg nitrogen per ha) under the more vigorous ‘Kratos’ plants, but there were large differences in clover and pumpkin growth attributable to spring flooding and late-summer drought in the second year. Crimson clover fall biomass (2.1 Mg/ha) and nitrogen contribution (42.1 kg nitrogen/ha) were greater than those of red clover in 2023, but spring regrowth of red clover was not studied. The results are discussed in the context of intercropping in vegetable and row-crop systems.