Location: Northwest Irrigation and Soils Research
Title: Manure and fertilizer effects on organic and inorganic carbon losses and budget for an irrigated corn field Authors
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 2014
Publication Date: June 10, 2014
Citation: Lentz, R.D., Lehrsch, G.A. 2014. Manure and fertilizer effects on organic and inorganic carbon losses and budget for an irrigated corn field. Soil Science Society of America Journal. 78:987-1002. Interpretive Summary: A greater understanding of nutrient cycling in cropping systems, and the effects of agricultural byproducts and amendments on nutrient cycling, is vital to fine-tuning commercial fertilizer and manure nutrient and carbon (C) management practices, and improving the sustainability of the agricultural systems. This study is the first to determine the complete C budget of an irrigated corn field; and identify the relative size of transfers among the atmosphere, crop, soil, runoff-water and percolation-water C pools. Manure applications increased short-term C stores in the soil and the use of mineral fertilizer caused soil C depletion. While the addition of organic-rich manure amendments increased soil C emissions from the soil, these C losses were partially offset by decreases in particulate runoff C, and dissolved percolate C. Thus, the fraction of total C that remained in the manure-amended field at the end of each growing season was larger than anticipated due to the indirect effects of manure on soil characteristics and properties, such as aggregate stability. This work contributes to a broader understanding of nutrient and C cycling within animal and cropping systems, and will help producers develop management approaches that maximize soil C storage and minimize soil greenhouse gas emissions and nutrient losses.
Technical Abstract: Little is known about inorganic fertilizer or manure effects on organic carbon (OC) and inorganic C (IC) losses from a furrow irrigated field, particularly in the context of other system C gains or losses. In 2003 and 2004, we measured dissolved organic and inorganic C (DOC, DIC), particulate OC and IC (POC, PIC) concentrations in irrigation inflow, runoff, and percolation waters (6-7 irrigations/y); C inputs from soil amendments and crop biomass; harvested C; and gaseous C emissions from field plots cropped to silage corn (Zea mays L.) in southern Idaho. Annual treatments included: (M) 13 (y 1) and 34 Mg/ha (y 2) stockpiled dairy manure; (F) 78 (yr 1) and 195 kg N/ha (y 2) inorganic N fertilizer; or (NA) no amendment--control. The mean annual total C input into M plots averaged 16.1 Mg/ha, 1.4-times greater than that for NA (11.5 Mg/ha) or F (11.1 Mg/ha), while total C outputs for the three treatments were similar, averaging 11.8 Mg/ha. Thus, the manure plots ended each growing season with an average net gain of 3.8 Mg C/ha (a positive net C flux), while the control (-0.5 Mg C/ha) and fertilizer (-0.4 Mg C/ha) treatments finished the season with a net C loss. Atmospheric CO2 incorporated into the crop biomass contributed 96% of the mean annual C input to NA and F plots but only 68% to M plots. We conclude that nutrient amendments substantially influence the short-term carbon balance of our furrow-irrigated system. Amendments had both direct and indirect influences on individual C components, such as the losses of DIC and POC in runoff and DOC in percolation water, producing temporally complex outcomes which may depend on environmental conditions external to the field.