The problems of low NUE in organic agriculture are more complex than the simple adjustment of fertilization methods. In the absence of synthetic N application, N uptake depends on the size of the root absorbing area and root uptake efficiency, existing inorganic N and potential N mineralization reserves in the soil (Spiertz & De Vos, 1983). Since the principle is based on utilization of already existing ecological systems and recycling process, the main concept in the improvement of NUE in organic agriculture is to maintain existing residual N as well as to recycle on-farm materials such as green manure, and incorporate plant residue from previous crops which are available for a long mean residual time (Spiertz & De Vos, 1983; Drinkwater, 2004;
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Plough-in legume or other plant residues are eventually decomposed by responsible soil microorganisms, and released N from these residues is prone to leaching when the N supply and crop demand …show more content…
Tillage is an important regulator of SOM decomposition and thus N mineralization. Tillage is used to exploit soil organic nutrient reserves to increase crop yield (Martens 2001). In organic systems, producers often use tillage as weed control. Inclusion of tillage with fallow in crop rotation promotes N leaching (Kessavalou et al., 1998; Sainji et al., 2009). This occurs through leaching, volatilization and denitrification (Sainji et al., 2009). Tillage has a similar impact as fallow on N leaching and also affects SOM content, soil structure and soil biological activities (Martens, 2001). As main channels for N losses, N volatilization, leaching and denitrification become prominent when N mineralization activity occurs under favourable conditions for these N losses. Tillage provides necessary aeration and optimum moisture for soil microbial decomposition of SOM, thus the practice likely results in promoting the loss of soil organic N. Due to N conservation awareness and increased fuel costs, no-till has been widely implemented to conserve N pool (Porter et al., 1996; Ortega et al., 2005; Spargo et al., 2008). Under no-till management, soil near the surface is likely to be cooler, wetter and less aerobic relative to tilled soil, limiting microbial activities that are responsible for mineralization (Nyborg & Malhi, 1989; Doran et al., 1998; Spargo et al., 2008). Organic matter derived
Plough-in legume or other plant residues are eventually decomposed by responsible soil microorganisms, and released N from these residues is prone to leaching when the N supply and crop demand …show more content…
Tillage is an important regulator of SOM decomposition and thus N mineralization. Tillage is used to exploit soil organic nutrient reserves to increase crop yield (Martens 2001). In organic systems, producers often use tillage as weed control. Inclusion of tillage with fallow in crop rotation promotes N leaching (Kessavalou et al., 1998; Sainji et al., 2009). This occurs through leaching, volatilization and denitrification (Sainji et al., 2009). Tillage has a similar impact as fallow on N leaching and also affects SOM content, soil structure and soil biological activities (Martens, 2001). As main channels for N losses, N volatilization, leaching and denitrification become prominent when N mineralization activity occurs under favourable conditions for these N losses. Tillage provides necessary aeration and optimum moisture for soil microbial decomposition of SOM, thus the practice likely results in promoting the loss of soil organic N. Due to N conservation awareness and increased fuel costs, no-till has been widely implemented to conserve N pool (Porter et al., 1996; Ortega et al., 2005; Spargo et al., 2008). Under no-till management, soil near the surface is likely to be cooler, wetter and less aerobic relative to tilled soil, limiting microbial activities that are responsible for mineralization (Nyborg & Malhi, 1989; Doran et al., 1998; Spargo et al., 2008). Organic matter derived