Establishment of Alleycropped Hybrid Aspen “Crandon” in Central Iowa, USA: Effects of Topographic Position and Fertilizer Rate on Aboveground Biomass Production and Allocation

William Headlee,Ronald Zalesny,Richard Hall

doi:10.3390/su5072874

William Headlee, Ronald Zalesny + Show 1 more

Open Access

https://doi.org/10.3390/su5072874

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Abstract

Hybrid poplars have demonstrated high productivity as short rotation woody crops (SRWC) in the Midwest USA, and the hybrid aspen “Crandon” (Populus alba L. × P. grandidenta Michx.) has exhibited particularly promising yields on marginal lands. However, a key obstacle for wider deployment is the lack of economic returns early in the rotation. Alleycropping has the potential to address this issue, especially when paired with crops such as winter triticale which complete their growth cycle early in the summer and therefore are expected to exert minimal competition on establishing trees. In addition, well-placed fertilizer in low rates at planting has the potential to improve tree establishment and shorten the rotation, which is also economically desirable. To test the potential productivity of “Crandon” alleycropped with winter triticale, plots were established on five topographic positions with four different rates of fertilizer placed in the planting hole. Trees were then harvested from the plots after each of the first three growing seasons. Fertilization resulted in significant increases in branch, stem, and total aboveground biomass across all years, whereas the effects of topographic position varied by year. Allocation between branches and stems was found to be primarily a function of total aboveground biomass.

Highlights

Using baseline scenarios, the U.S Department of Energy estimates that forestlands in the contiguous United States have the capability to produce 298 million dry Mg of biomass annually by the year 2030 [1]
Short rotation woody crops (SRWC) are purpose-grown trees that are a vital component of this potential woody biomass supply
―Crandon‖ grown in an alleycropping system with winter triticale was evaluated at multiple topographic positions with different rates of fertilizer placed in the planting hole

Summary

Introduction

The baseline estimate for perennial crops (woody and herbaceous) on agricultural lands was 346 million dry Mg of biomass annually, with estimates for high-yield scenarios reaching 705 million dry Mg annually. Production from both land cover types will be vital to meet the nation’s demands for biofuels, bioenergy, and bioproducts. Adequate woody feedstock supply is necessary for achieving our national goal of 16 billion gallons of cellulosic biofuels by 2022, established under the U.S Energy Independence and Security Act of 2007. One approach is targeting marginal agricultural lands upon which traditional crops often perform poorly [6]. The hybrid aspen ―Crandon‖ (Populus alba L. × P. grandidenta Michx.) appears especially promising, due to both its high productivity and its adaptability to sloping marginal lands [7]

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