Soluble Organic Carbon and Carbon Dioxide Fluxes in Maize Fields Receiving Spring‐Applied Manure

Abstract

More than 19 million Mg of dairy manure are produced annually in the Canadian provinces of Quebec and Ontario, and most of it is spread on agricultural fields. Quantitative information on the impact of manure management practices on levels of soluble organic carbon (SOC) and emissions of CO2 is important for assessing whether this management significantly contributes to increasing atmospheric CO2 concentrations. The objective of this study was to measure the effects of dairy cattle manure (applied at 0, 56, and 112 Mg ha−1) on SOC levels in, and soil surface CO2 fluxes from, a typical maize (Zea mays L.) field in central Canada, from April to October. The higher rate of manure increased both the CO2 emissions and the SOC levels by a factor of two to three compared with the control. Fluxes of CO2 were very low immediately after thaw, increased sharply following manure application and increased again in mid‐June at the time when temperature and soil moisture increased; thereafter, fluxes declined throughout the rest of the season. Over the season, which was drier than normal, SOC was not a good predictor of CO2 flux. Carbon dioxide flux increased proportionately less for the second 56 Mg ha−1 increment of manure added than for the first increment. Factors other than the quantity of S OC limited soil respiration at the highest manure application rate. Carbon dioxide is contributed to the atmosphere at a lower rate, and proportionately more manure C is retained in soil with increasing levels of manure applied.

Dynamics of soil water-extractable organic C following application of dairy cattle manures

“…For example, small (Rochette et al 2000) and large increases in K 2 SO 4 -extractable organic C were reported in a loamy soil receiving liquid hog manure. Similarly, manureinduced increases in soil WEOC content are much smaller in the present study than those observed by Gregorich et al (1998) and Rochette and Gregorich (1998) in a loamy soil receiving solid dairy cattle manure. Greater soil C extraction efficiency with 0.5 M K 2 SO 4 solution (Gregorich et al 1998; Rochette and Gregorich 1998), compared with the 5 mM CaCl 2 used in the present study, may partly explain the difference (Zsolnay 1996;Chantigny 2003).…”

“…On average for the 2 yr, soil WEOC content was 6.7 mg kg -1 greater with liquid manure and 7.2 mg kg -1 greater with solid manure than with the control; differences between the two manures were not statistically significant. Many others have reported an immediate increase in soil C extractable with aqueous solutions following amendment with animal manure (Kirchmann and Lundvall 1993;Gregorich et al 1998;Rochette and Gregorich 1998;Rochette et al 2000Rochette et al , 2004; however, the magnitude of the response among studies was variable. For example, small (Rochette et al 2000) and large increases in K 2 SO 4 -extractable organic C were reported in a loamy soil receiving liquid hog manure.…”

“…Several studies in agricultural soils have shown close relationships between WEOC concentration and soil processes such as denitrification (e.g., Burford and Bremner 1975), microbial respiration (e.g., Gregorich et al 1998;Rochette and Gregorich 1998), heavy metal binding and transport (e.g., McBride et al 1999), and P (e.g., Fox and Comerford 1992) and N cycling (Murphy et al 2000).…”

“…Manures can contain up to 35% of their total C as soluble forms (Kirchmann and Lundvall 1993;Chantigny et al 2001Chantigny et al , 2004 and applying animal manure to soils usually results in an increase in soil C extractable with aqueous solutions (Kirchmann and Lundvall 1993;Gregorich et al 1998;Rochette and Gregorich 1998;Rochette et al 2000Rochette et al , 2004. However, the magnitude of manure-induced changes in soil WEOC appears variable and few studies have investigated the shortterm recovery of manure WEOC applied to soil.…”

Soil dissolved organic carbon: Influences of water-filled pore space and red clover addition and relationships with microbial biomass carbon

“…Red clover has been found to increase yields in the subsequent year by improving soil structure and microbial activity, by accelerating the decomposition of wheat straw (Drury et al 1999), by providing organic N through N 2 fixation (Bruulsema and Christie 1987), and by adding a large amount of organic C to the soil. Addition of organic compounds and fertilization has been shown to increase the content of SDOC by a factor of 2.7 to 3.2 Gregorich et al 1998). In manured soils, soluble C increased dramatically after manure application, followed by a gradual decrease over time .…”