Short-term native grassland compositional responses following liquid hog manure application

Abstract

Bork, E. W. and Blonski, L. J. 2012. Short-term native grassland compositional responses following liquid hog manure application. Can. J. Plant Sci. 92: 55–65. Intensive livestock operations (ILOs) are becoming more common in remote regions of the Canadian prairies in an effort to reduce conflict with other land uses. This has led to ILOs situated where the typical sink for manure application, cultivated land, is not available, leading to growing interest in using native grasslands for manure disposal. Significant opposition exists to this practice, in part due to limited information available on the impact of manure application to native grassland diversity and species composition. We examined plant species composition changes over two growing seasons following varying rates (∼9.5, 19, 38, 75 and 150 kg ha−1 available N), methods (surface broadcast vs. coulter injected) and timing (fall vs. spring) of one-time liquid hog manure (LHM) application. Our results revealed divergent responses between study sites, with metrics of plant diversity declining in mixed prairie but increasing in fescue grassland with increases in manure application rate. Both communities also demonstrated minor changes in plant species composition, primarily in response to LHM rate and manure application method. Responsive plant species included a mix of native grasses and dicots, some of which may be regarded as undesirable (e.g., Artemisia frigida): however, most vegetation responses were temporary and disappeared by the second year. Although invasion of non-native plant species was not observed, suggesting these communities are tolerant of LHM application, changes in the reproductive effort of dominant grasses (negative in Hesperostipa curtiseta; positive in Pascopyrum smithii and Festuca hallii) suggest LHM application could alter long-term grassland composition. Thus, despite exhibiting resilience to one-time LHM application, future use of native grasslands for manure disposal should be done cautiously.

Soil mineral nitrogen responses following liquid hog manure application to semiarid forage lands

“…In contrast, losses of N were low in native grasslands, including within broadcast treatments, apparently due to high infiltration of LHM into the well-developed surface mulch layer present at these sites (Bork and Blonski 2012). Finally, increases in residual soil mineral N from injection remained apparent 1 yr after LHM application (see Table 3).…”

“…As plant growth in this region may begin shortly after spring soil thaw, the option of fall application may be beneficial in increasing the window for LHM disposal, particularly if applications to growing vegetation are to be avoided to prevent smothering of plants (Stavast et al 2005). In any case, decisions on when to apply LHM should reflect the relative tolerance of vegetation to disturbance at that time, including any risk of undesirable changes in plant species composition within native grasslands (Bork and Blonski 2012).…”

“…Liquid hog manure application to native grassland has been associated with relatively short-term, temporary changes in plant composition (Bork and Blonski 2012). As native grasslands are typically situated in semi-arid regions where plant growth is limited by moisture rather than nutrients (Willms and Jefferson 1993), high manure rates may lead to larger and prolonged increases in soil nutrient availability, including soil mineral nitrogen (N).…”

Evaluation of greenhouse gas emissions from hog manure application in a Canadian cow–calf production system using whole-farm models

“…Although the application of animal manure on grassland increases land productivity (Wilson et al 2010;Bork and Blonski 2012), it is apparent that the concurrent increase in emissions of soil N 2 O occur through enhanced nitrification and denitrification (Ellis et al 1998;Chadwick et al 2000;Tenuta et al 2010). Therefore, the sustainability of manure application requires implementation of management practices that reduce soil N 2 O emissions.…”

“…For a cow-calf production system in a nutrient-poor landscape such as the Canadian prairie, where the largest proportion of the grazing land is unimproved (native) pasture (McCaughey et al 1999;Manitoba Agricultural Review 2001), addition of external sources of manure to grassland is essential to maintain and improve productivity (Wilson et al 2010;Bork and Blonski 2012). The use of animal manure as a source of N also provides a means to effectively utilise manure from intensive livestock operations and is a common practice in several parts of the world, including south-eastern Manitoba, Canada (Chadwick et al 2000;Petersen et al 2007;Wilson et al 2010;Bork and Blonski 2012). Furthermore, application of animal manure reduces the use of synthetic fertilisers and, therefore, the GHG emissions associated with production and use (Bouwman et al 2010).…”