Opportunities and challenges of poplar-based agroforestry in the Four Corners region of New Mexico.

摘要

The Navajo Agricultural Products Industry (NAPI), a large commercial farm currently operating over 600 automatic center pivot irrigation systems on 25,000 ha of farmland, and Western Excelsior Corporation, a timber mill producing shredded aspen products, collaboratively intend to develop upwards of 1,000 ha of hybrid poplar under drip irrigation over a 10 year period. The broad objective of this dissertation is to contribute to the overall development of this emerging industry by: (1) identifying hybrids adaptable to a semi-arid environment having calcareous, elevated pH soils, (2) investigating the feasibility of industrial byproducts to cheaply remediate Fe-deficiency induced chlorosis, a consequence of these soils, and (3) calibrating instrumentation (SPAD chlorophyll meter) used in this study with actual chlorophyll values to establish literature values for specific hybrids.; In regards to adaptation potential, ten hybrids of P. deltoides, P. maximowiczii, P. nigra, and P. trichocarpa parentage were selected in 2002 to determine adaptability to growing conditions of the Four Corners region. Hybrids with P. nigra paternal parentage had low chlorosis ratings indicated by a Minolta 502 SPAD meter previously calibrated to two hybrids. Another notable hybrid was 58-280 (P. trichocarpa x P. deltoides).; To address micronutrient deficiencies, expensive Fe EDDHA fertilizer is used to correct Fe chlorosis in susceptible hybrids. The safe land application of coal combustion products and composted biosolids (sewage sludge), however, could supply a pool of micronutrients available for plant uptake from products otherwise landfilled. Byproducts were applied to a Doak sandy loam collected from Farmington to evaluate plant growth response in two greenhouse studies. Characterization of soil amendment mixtures indicated little potential for environmental concern but pH, salinity, and boron changes were observed depending on amendment. Results of greenhouse and field trials indicated that composted biosolids had the most benefit to hybrid poplar in terms of increasing leaf greenness and growth. With adaptable hybrids selected and management strategies better defined, hybrid poplar grown in the Four Corners provides crop diversification for NAPI while supplying timber needs in the region.