Denitrification from Soils of a Year‐Round Forage Production System Fertilized with Liquid Dairy Manure

Abstract

Denitrification is an important potential sink for N in liquid manure and the amount of denitrification may affect sustainability of crops grown with liquid manure as a nutrient source. This study examined gaseous N loss by denitrification and the changes in soil N pools after liquid manure application. Liquid dairy manure was applied at four N rates (246, 427, 643, and 802 kg N ha−1 yr−1) to four quadrants of a center‐pivot in a year‐round forage production system. Denitrification (using the acetylene block technique on intact cores) and soil N pools were determined before and for 2 yr after beginning liquid manure application. Nitrous oxide evolution from soil cores was compared to denitrification for a third year of the study. Denitrification rates and soil N pools increased after manure application at all rates of application. The two highest rates of manure had highest denitrification rates, although differences in soil moisture due to soil and drainage properties complicated the interpretation of manure rate effects. At the two highest rates of N application and two lowest rates of N application, the quadrant with higher soil moisture had higher denitrification. Nitrous oxide emissions accounted for about 29% of total denitrification. Denitrification ranged from 11 to 37% of total N applied in the manure. Highest rates of denitrification and highest proportions of total N denitrified were found with the second highest manure application rate because these soils were wetter. Annual denitrification totals ranged from 32 to 114% of the excess N (application‐crop uptake) available.

Effect of land management practices and environmental parameters on growing season denitrification rates under dairy crop rotations in Atlantic Canada

“…Our discussion of the denitrification results will be restricted to treatment effects, temporal patterns, and relationships with soil parameters rather than an overall mass balance of N lost by denitrification. Other studies have similarly used AIT in this manner (Paul and Zebarth 1997b;Lowrance et al 1998;Marshall et al 1999;Sullivan et al 2005;Drury et al 2008;Mkhabela et al 2008;Miller et al 2012). Acrylic sleeves measuring 10 cm in length by 6.0 cm inside diameter and perforated with 2.0 mm holes, 1.0 cm apart to facilitate gas exchange (Burton and Beauchamp 1984) were inserted into a soil corer fitted with a drop hammer to facilitate penetration into the soil.…”

“…Marshall et al (1999) found that spring additions of poultry manure to pasture resulted in cumulative denitrification losses of up to 4.9 kg N ha −1 for a 150-day growing season, equivalent to a mean DDR of 32.0 g N ha −1 day −1 . In a study involving LDM applications to a Bermudagrass-rye-silage corn rotation applied at a rate of 246 kg total N ha −1 , Lowrance et al (1998) reported mean DDRs of 20.2-63.1 g N ha −1 day −1 over a 2-year period, representing 3.0-9.3% of total manure N applied. Sullivan et al (2005) measured denitrification rates ranging from 0.10 to 0.14 in a low year and 0.14-0.41 g N ha −1 day −1 in a high year following application of swine effluent to Bermudagrass at rates of 112-218 kg Total N ha −1 .…”

“…It is generally accepted that denitrification losses are higher when organic N sources such as LDM are used for crop fertility in place of inorganic N fertilizers due to the increased availability of labile C and N compounds for use as energy sources and substrates for biological denitrification (e.g., Lowrance et al 1998). However, mean DDRs across all three rotations in 2008 and 2011, the 2 years in which no LDM was applied, were not lower than average when compared with the means for the manure years 2007, 2009, 2010, and 2012.…”

“…When organic N sources such as LDM are used instead of inorganic N fertilizers, most authors have reported significantly higher denitrification losses. Lowrance et al (1998) for example found that high rates of LDM applied to year-round forage production systems resulted in denitrification rates 10-100 times higher than those with inorganic N fertilizer. There are fewer studies quantifying denitrification losses from manure-fed dairy crop rotations in humid ecozones such as Atlantic Canada where both N leaching and denitrification losses are of concern, and no comprehensive studies comparing and quantifying losses between rotations with different NUEs, such as perennial hayfield and cornsoybean-wheat rotations with or without tillage as a major land management practice.…”

Liquid Cattle Manure Application to Soil and Its Effect on Crop Growth, Yield, Composition, and on Soil Properties

“…Bechini & Marino (2009) reported that nitrification and NO 3 -production was extremely rapid after LCM application on unsaturated soils, regardless of soil texture. Loro et al (1997) and Lowrance et al (1998) reported that denitrification and N 2 O production after soil application of LCM was positively correlated with the soil water content and the cumulative production of N 2 O was found to be higher for the solid than the liquid cattle manure (Loro et al, 1997). Rochette et al (2008) found no differences between LCM and solid cattle manure in respect to N 2 O emissions and reported that the N 2 O emissions were affected by soil texture in conjunction to weather conditions.…”