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Double‐crop systems have the potential to generate additional feedstocks for bioenergy and livestock utilization, and also to reduce NO 3 –N leaching relative to sole‐crop systems. Field studies were conducted near Ames, IA, during 2005–2007 to evaluate productivity and crop and soil nutrient dynamics in three prototypical bioenergy double‐crop systems, and in a conventionally managed sole‐crop corn system. Double‐cropping systems evaluated in the study included fall‐seeded forage triticale (X Triticosecale Wittmack), succeeded by one of three summer‐adapted crops: corn ( Zea mays L.), sorghum‐sudangrass Sorghum bicolor (L.) Moench, or sunn hemp ( Crotalaria juncea L.). Total dry matter production by triticale/corn and triticale/sorghum‐sudangrass was 25% greater than sole‐crop corn, which in turn produced 21% more dry matter than triticale/sunn hemp. Potential ethanol yield was greatest for triticale/corn, which was estimated to have the capacity to produce 1080 L ha −1 more ethanol than sole‐crop corn. Crop N uptake was greater in double‐crop systems during April‐June, greater in the sole‐crop corn system during July–August, and greater again in double‐crop systems during September–October. Relative to sole‐crop corn, potentially leachable soil N was reduced in double‐crop systems by 34 and 25%, respectively, in the spring (mid‐April) and fall (late October). High nutrient density of biomass coupled with high productivity for triticale/corn and triticale/sorghum systems also resulted in the removal of 83, 41, and 177% more N, P, and K, respectively, compared with sole‐crop corn. Sustained removal of large quantities of nutrient‐dense biomass from double‐cropping systems would necessitate increased fertilization or integration with nutrient recycling mechanisms.
Heggenstaller et al. (Sat,) studied this question.