Abstract
Soils of northwest New Mexico have an elevated pH and CaCO3content that reduces Fe solubility, causes chlorosis, and reduces crop yields. Could biosolids and fly ash, enriched with Fe, provide safe alternatives to expensive Fe EDDHA (sodium ferric ethylenediamine di-(o-hydroxyphenyl-acetate)) fertilizers applied toPopulushybrid plots? Hybrid OP-367 was cultivated on a Doak sandy loam soil amended with composted biosolids or fly ash at three agricultural rates. Fly ash and Fe EDDHA treatments received urea ammonium nitrate (UAN), biosolids, enriched with N, did not. Both amendments improved soil and plant Fe. Heavy metals were below EPA regulations, but high B levels were noted in leaves of trees treated at the highest fly ash rate. pH increased in fly ash soil while salinity increased in biosolids-treated soil. Chlorosis rankings improved in poplars amended with both byproducts, although composted biosolids offered the most potential at improving Fe/tree growth cheaply without the need for synthetic inputs.
Highlights
The New Mexico State University Agricultural Science Center at Farmington, San Juan County, has been exploring short rotation hybrid poplar trees for fiber and timber production, biofuel, and phytoremediation purposes
Fly ash plus urea ammonium nitrate (UAN) significantly increased SPAD values and plant Fe in hybrid poplars even though soil Fe remained statistically similar to the control soil
Despite the increase in soil pH from fly ash additions, which would imply even lower solubility of micronutrients, and the fact that N from UAN remained constant among the fly ash, the uptake of Fe in fly ashamended poplars was likely related to an acidulation of the rhizosphere from UAN applications which made Fe more available just at the root/soil interface
Summary
The New Mexico State University Agricultural Science Center at Farmington, San Juan County, has been exploring short rotation hybrid poplar trees for fiber and timber production, biofuel, and phytoremediation purposes. Fe deficiency chlorosis (interveinal yellowing of juvenile leaves) has been observed because soil pH can exceed 8 with moderate to high CaCO3 levels. Under these conditions, soil iron is mostly in the form of well-crystallized iron oxides (e.g., hematite and goethite) and almost insoluble and unavailable to plants [1]. On our research plots, chelated iron fertilizer in the form of Fe EDDHA is applied to alleviate chlorosis symptoms. Considering that 5 kg Fe EDDHA material—enough to cover approximately 1 ha season−1—costs approximately $200, fertilizing large-scale plantations may be cost prohibitive
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