Greenhouse Gas Emissions from Cut Grasslands Renovated with Full Inversion Tillage, Shallow Tillage, and Use of a Tine Drill in Nasu, Japan

Abstract

To restore the productivity of a deteriorated sward due to weed invasion, renovation (re-sowing) is necessary. However, the renovation method used can affect the sward’s greenhouse gas (GHG) emissions and herbage yield. This study compared the effects of renovation using full inversion tillage (F), shallow tillage (S), or a tine drill (T) on the GHG emissions and herbage yield of a grassland in Nasu, Japan. Two adjacent grasslands were renovated in September 2015 (year 1) and 2016 (year 2). In each year, F, S, and T plots (5 m × 20 m each) were arranged in a randomized complete block design with four replications and then orchardgrass (Dactylis glomerata L.) was seeded. All plots received 40 kg-N ha−1 for renovation and 190 kg-N ha−1 y−1 the following year. Carbon balance (i.e., the difference between C input through crop residue and C output through heterotrophic respiration), methane (CH4) and nitrous oxide (N2O) emissions, and herbage yield were measured over a period of 411 or 412 days. Cumulative N2O emissions were significantly smaller from F and S plots than from T plots, however, there was no significant difference in the sum of GHG emissions (i.e., C balance plus cumulative CH4 and N2O emissions) among F, S, and T plots. The cumulative total herbage yields of the F, S, and T plots did not differ significantly from each other. Consequently, the GHG intensity—i.e., the sum of GHG emissions per cumulative total herbage yield—was not significantly different among the F, S, and T plots.