The Lower Mississippi Alluvial Valley (LMAV) contains extensive agriculture subject to intense nitrogen (N) fertilization which contributes to water quality degradation and seasonal hypoxia in the Gulf of Mexico. Marginal lands exist throughout the LMAV that are less suitable for conventional agriculture due to periodic flooding and seasonally high water tables. On such inundated sites, short rotation woody crops (SRWCs) may be an opportunity to diversify landowner income while simultaneously providing ecosystem services such as excess N uptake, sediment interception, and carbon sequestration. Nevertheless, research is necessary to determine how both waterlogging and soil water stress influence production and nutrient removal of candidate biofuel crops such as eastern cottonwood (Populus deltoides) and black willow (Salix nigra).
Therefore, this study aims to determine the most suitable SRWC species/genotypes that can achieve high productivity on marginal alluvial lands of the southern US. Six cottonwood and five willow varieties (with a total of 600 individuals, 300 cottonwoods and 300 willows) were strategically planted at the interface between agriculture and waterways in the riparian area of the LMAV in June, 2018. Establishment success and survival potential were analyzed in conjunction with environmental conditions including water and soil quality.
Results/Conclusions
The establishment rates (i.e., one-month survival) of cottonwoods and willows were 62% and 98% respectively. After one year, the rates of survival for individuals that had successfully established were 99% and 98% for cottonwoods and willows, respectively. After one year, willows (1.7 m) were taller than cottonwoods (1.3 m), while the average diameter of cottonwoods (7.9 cm) was greater than that of willows (6.2 cm).
In the late growing season when water can be limiting, groundwater levels were within 1 m of the surface, whereas the site was continuously inundated in the dormant season. Soil and water quality data are still pending.
Willows established better than cottonwoods, however, the year-one survival of established cottonwoods paralleled that of established willows. Continued monitoring of the site will provide more evidence about the growth performance of selected SRWC species/genotypes and their potential for N mitigation. Future research will investigate the interactions among soil, hydrology, physiology, and nutrient cycling of SRWCs for recommending optimal agroecosystem management options.