Examining the Air-Surface Exchange in Field Edge Boundaries: Implications for African Smallholder Maize Fields

Issues of air-surface exchange are emerging in Africa where much of the population typically relies on small maize plots for subsistence. These farmers of small areas of land are one of the largest producers of food in the world but their methods of cultivation lack adequate scientific examination. Experience elsewhere indicates that maize field edges yield less than the field interiors, a finding that has confounded researchers for decades. While field edges are known to be more susceptible to insect pests and biological stressors, recent work in Tennessee indicates that additional mechanisms could be at play including the reduction in available CO2 for reproduction. Night-time pooling of CO2 is a common observation within and above crop canopies facilitated by the generation of stability regimes due to the aerodynamic roughness of the crop surface, especially during clear nights during the growing season. It is possible that at the field edges less pooling of CO2 will occur which will result in less photosynthetic activity in the field borders. This issue is of interest because it indicates that biological mechanisms peripheral to conventional surface boundary layer micrometeorological theory could affect surface energy budgets over heterogenous landscapes. Understanding this phenomenon better could result in farming systems that help establish more productive field edges using alternate crops including alley cropping with trees with heights similar to maize. The matter awaits additional experimental investigation and invites the attention of modelers.