Dairy manure nitrogen availability in eroded and noneroded soil for sugarbeet followed by small grains

Authors: Lentz, Rodrick; Lehrsch, Gary; BROWN, B - University Of Idaho; JOHNSON-MAYNARD, J - University Of Idaho; Leytem, April

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2011
Publication Date: 3/2/2011
Citation: Lentz, R.D., Lehrsch, G.A., Brown, B., Johnson-Maynard, J., Leytem, A.B. 2011. Dairy manure nitrogen availability in eroded and noneroded soil for sugarbeet followed by small grains. Agronomy Journal. 103:628-643.

Interpretive Summary: The U.S. dairy herd of 9 million animals produces 22 million tons of manure annually, much of which is applied directly to cropland either directly, or as composted manure. To maximize their use of manure and minimize losses of nitrogen (N) to the environment, growers need to understand how soil N availability is influenced by a one-time application of manure or composted manure and how availability may vary with soil erosion status, i.e. between whole (non-eroded) and eroded soils in the intermountain West US. This study applied manure or compost to soils and measured the nitrogen (N) made available via microbial breakdown and the N taken up by crops over three years. After the fall addition of manure or compost to soils, we observed a strong cyclical pattern where N was immobilized by microbes as soil warmed in early summer followed by a peak in N mineralization and increased N availability to crops in late summer. Also, net N mineralization in the 12-to-24-in soil layer below the zone of manure incorporation, was increased by manure application. This indicated that organic C and N from manure had moved from the surface soil deeper into the soil profile, where it was mineralized by microbial populations. Manure increased net N mineralization more in eroded soils than in whole soil (compared to respective controls). This research is the first to demonstrate that manure application can substantially increase net N mineralization in soil beneath the depth of incorporation, and determined that the type of organic amendment, soil erosion status, seasonal temporal N cycles, and subsoil N mineralization need to be considered when assessing N availability from manure amendments.

Technical Abstract: Efficient recycling of abundant manure resources from regional dairy industries in the semiarid West requires a better understanding of N availability in manure-amended soils. We measured net N mineralization using buried bags, and crop biomass, N uptake, and yields for sprinkler-irrigated, whole (noneroded) and eroded Portneuf soils (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) subject to a one-time manure application. Treatments included a control, fertilizer, two rates of composted dairy manure (28.4, 64.3 Mg ha–1, dry wt.), and two rates of stockpiled dairy manure (23.3, 45.7 Mg ha–1, dry wt.) applied in the fall before the Year 1 cropping season. Plots were planted to sugarbeet (Beta vulgaris L.), winter wheat (Triticum aestivum L.), and spring barley (Hordeum vulgare L.) during the 3-yr study. Overall, net N mineralization rates were low to moderate during winter through spring, decreased in early summer due to N immobilization, then increased to a maximum in late summer, followed by a decrease in fall. Th e mean mineralization rate (as a percentage of the added organic N) for Years 1, 2, and 3 was –4.2 (N immobilization), 4.3, and 4.8% for compost and 17.4, 17.0, and 11.4% for manure, respectively. Relative to controls, compost and manure treatments as a group increased total 3-yr net N mineralization more for eroded (1.77×) than for whole soils (1.55×). At higher rates, manure also increased immobilization and mineralization in 30- to 60-cm soil depths (below the zone of incorporation). To optimize the use of N mineralized in southern Idaho’s manure-amended soils, one should consider the type manure employed and the erosion status of the soil receiving the amendment.