Empire (MN) Alley (IMAGE) American Society of Agronomy Caption This is an alley cropping system at Empire, MN in June 2013. Alternating blocks of willow (foreground) and poplar can be seen, with four herbaceous perennial biomass crops nested within each block of woody crops. Credit Photo credit Joshua Gamble. Usage Restrictions Please use with story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.