Long-term manure application and forages reduce nitrogen fertilizer requirements of silage corn-cereal cropping systems
Nyiraneza, J., Chantigny, M.H., N'Dayegamiye, A., Laverdière, M.R. (2010). Long-term manure application and forages reduce nitrogen fertilizer requirements of silage corn-cereal cropping systems, 102(4), 1244-1251. http://dx.doi.org/10.2134/agronj2009.0480
Assessment of the soil N supply capacity is essential to optimize fertilizer N use. We investigated soil N supply capacity and fertilizer N recovery for three cropping systems established in 1977: silage corn (Zea mays L.)-cereal without (CC) and with 20 Mg ha-1 yr-1 manure (CCM), and silage corn-forage (3-yr) with manure (CFM). During the present study (2005-2008), manure applications were suspended and a silage corn-silage corn-barley (Hordeum vulgaris L.)-wheat (Triticum aestivum L.) sequence was imposed to all systems. Fertilizer (15NH415NO3, 3.1 atom % 15N) was applied in 2005 to silage corn (160 kg N ha-1) and in 2007 to barley (80 kg N ha-1). The 15N recovery in silage corn and barley ranged from 40 to 59%, with the lowest values measured in CFM. Compared to the CC systems (47 kg N ha-1) in 2005, soil-derived N in silage corn was two times higher under CCM (98 kg N ha-1), and four times higher under CFM (208 kg N ha-1). These differences decreased over years, but were still noticeable at the end of the experiment. Twenty-two to 58% of applied 15N was recovered in the soil at harvest. More than 50% of this residual N was present in macroaggregates (>0.25 mm), whereas <20% was present in particulate organic matter (POM). Up to 75% of residual 15N was lost during the winter period, and little residual N was transferred to the following crop. These findings indicate that soil macroaggregates may be a preferential sink for residual fertilizer N, but this N is not present in stable forms and is vulnerable to environmental loss. © 2010 by the American Society of Agronomy.
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