High N2O variations induced by agricultural practices in integrated weed management systems

Abstract

Integrated weed management aims to decrease the dependence of cropping systems on herbicides by using a combination of several agricultural practices. Environmental impacts of individual practices under various conditions are already known. However, there is scarce knowledge on the impact of combining several practices. Therefore, we studied N 2 O emissions of weed management cropping systems that use differing practices such as crop diversity, tillage, and herbicide pressure, during about 1 year. Data were compared with a conventionally managed cropping system. Results were also simulated using the NOE model. Results show a large variation of N 2 O emissions, ranging from 177 g N 2 O-N/ha for intensive tillage integrated weed management to 362 g N 2 O-N/ha for the conventional cropping system, 777 g N2O-N/ha for the no herbicide cropping system and 5226 g N 2 O-N/ha for no-till integrated weed management. Most N 2 O emissions occurred in spring, despite the absence of fertilizing related N 2 O peaks. The lowest emissions occurred in autumn and winter. Emissions are explained by interactions between specific soil potential denitrification rate, soil bulk density, temperature, soil water, and inorganic N contents. N 2 O emissions are accurately predicted by the model NOE, with a global Nash-Sutcliffe coefficient of efficiency equal to 0.80.

N₂O Emission Pattern in A Legume-Based Agroecosystem

“…Nevertheless, daily peaks reached 130.0 g N 2 O ha -1 d -1 . N 2 O emissions were of the same order of magnitude as those measured at the same experimental site and in similar tilled cropping systems, with values ranging from 0.0 to 30.0-50.0 g N 2 O ha -1 d -1 [18,20]. Although our measurements represent on average only 60% of the days in each period, N 2 O emissions appear to be of the same magnitude as measurements made under comparable pedoclimatic conditions in Eastern France [21] or under crop rotations including legumes [4,22,23].…”

“…In this study, the amounts of N residues incorporated in the soil as well as their C:N ratio were different among legume species and cereals (Table S3), but these characteristics did not affect N 2 O emissions. However, in the current experiment [20], the amounts of N mineralized from crop residues were related to wheat N uptake. In addition, these authors showed by modeling that some significant amounts of nitrate were lost by leaching during the fallow period and may explain the low N 2 O emissions during wheat cultivation with probably insufficient amounts of nitrate remaining in the soil to induce higher N 2 O emissions which may in turn explain the absence of differences between experimental treatments.…”