The effects of root-pruning on productivity in an alley cropping system in the Georgia Piedmont, USA
Reichlen, Jonathan Joseph
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A non-irrigated alley cropping system, with Albizia julibrissin (mimosa) as the hedgerow tree species and Zea mays (field corn) as the alley crop, was studied during a two year period (2002-2003) to examine the effects of root interactions on productivity. Three randomly placed treatments were established within 4 separate blocks to determine the effects of root interactions on crop and hedgerow productivity. In one block all biomass was retained from hedgerow prunings and crop residue on the soil surface within the alleys (biomass addition). Three blocks had hedgerow prunings and crop residues excluded for the purpose of accentuating the effects of root interactions (biomass exclusion). Treatments consisted of a rootprune and installation of a root barrier (barrier), a root-prune without a root barrier (trench), and a control with neither a root-prune nor a root barrier (control). Maize biomass and height during 2002 was significantly greater for both the barrier and the trench treatment when compared to the control. There were no differences between treatments during 2003 for any of the biomass exclusion blocks, but the biomass addition block did have significantly greater height for both the barrier and the trench when compared to the control. Maize biomass and height were greater in 2003 than in 2002. Total N concentrations in both maize plants and roots showed no difference between treatments for 2002 or 2003, but did show a significant difference between years, with 2002 being greater than 2003. Total N concentration in soils showed no difference between treatments, blocks, or years. Results of soil water content comparison between treatments showed no differences for either 2002 or 2003, but the biomass addition block had greater soil water content, for 8 of the 9 sampling dates, than any of the three biomass exclusion blocks during the experiment. There were also no differences between treatments or blocks for mimosa pruning biomass production. A five year drought in Georgia concluded at the end of 2020, and rainfall was above average during the growing season during 2003, therefore results from root-pruning between years is assumed to be an effect of soil water content availability and competition. Root-pruning appears to have a positive effect on productivity for non irrigated alley cropping systems in the Georgia Piedmont. Additionally, there is a positive effect on productivity with the retention of aboveground biomass within the alley cropping system. Further study would enhance the efficacy of results from this experiment for both drought years and average rainfall years.