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Long Term Sugarcane Crop Residue Retention Offers Limited Potential to Reduce Nitrogen Fertilizer Rates in Australian Wet Tropical Environments.

Meier EA, Thorburn PJ - Front Plant Sci (2016)

Bottom Line: Soil carbon increased in trash blanketed soils relative to SOC in soils with burnt trash.Simulated N fertilizer rates were able to be reduced from conventional rates regardless of trash management, because of low yield potential in the wet tropics.While these savings in N fertilizer use were modest at the field scale, they were potentially important when aggregated at the regional level.

View Article: PubMed Central - PubMed

Affiliation: Agriculture & Food Unit, Commonwealth Scientific and Industrial Research Organisation (CSIRO), St. Lucia QLD, Australia.

ABSTRACT
The warming of world climate systems is driving interest in the mitigation of greenhouse gas (GHG) emissions. In the agricultural sector, practices that mitigate GHG emissions include those that (1) reduce emissions [e.g., those that reduce nitrous oxide (N2O) emissions by avoiding excess nitrogen (N) fertilizer application], and (2) increase soil organic carbon (SOC) stocks (e.g., by retaining instead of burning crop residues). Sugarcane is a globally important crop that can have substantial inputs of N fertilizer and which produces large amounts of crop residues ('trash'). Management of N fertilizer and trash affects soil carbon and nitrogen cycling, and hence GHG emissions. Trash has historically been burned at harvest, but increasingly is being retained on the soil surface as a 'trash blanket' in many countries. The potential for trash retention to alter N fertilizer requirements and sequester SOC was investigated in this study. The APSIM model was calibrated with data from field and laboratory studies of trash decomposition in the wet tropics of northern Australia. APSIM was then validated against four independent data sets, before simulating location × soil × fertilizer × trash management scenarios. Soil carbon increased in trash blanketed soils relative to SOC in soils with burnt trash. However, further increases in SOC for the study region may be limited because the SOC in trash blanketed soils could be approaching equilibrium; future GHG mitigation efforts in this region should therefore focus on N fertilizer management. Simulated N fertilizer rates were able to be reduced from conventional rates regardless of trash management, because of low yield potential in the wet tropics. For crops subjected to continuous trash blanketing, there was substantial immobilization of N in decomposing trash so conventional N fertilizer rates were required for up to 24 years after trash blanketing commenced. After this period, there was potential to reduce N fertilizer rates for crops when trash was retained (≤20 kg N ha(-1) per plant or ratoon crop) while maintaining ≥95% of maximum yields. While these savings in N fertilizer use were modest at the field scale, they were potentially important when aggregated at the regional level.

No MeSH data available.


Related in: MedlinePlus

Soil mineral nitrogen (SMN) for the small plot field experiments at the HS and FS used to parameterize the model. Measured SMN is shown as symbols with bars for the mean and range of values; simulated SMN is shown as lines. Trash was retained on the soil surface (TS), incorporated (TI) or removed and the soil left bare (B) as a surrogate for burnt trash. RMSE, index of agreement (d) and ME are included.
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Figure 3: Soil mineral nitrogen (SMN) for the small plot field experiments at the HS and FS used to parameterize the model. Measured SMN is shown as symbols with bars for the mean and range of values; simulated SMN is shown as lines. Trash was retained on the soil surface (TS), incorporated (TI) or removed and the soil left bare (B) as a surrogate for burnt trash. RMSE, index of agreement (d) and ME are included.

Mentions: Average SMN measured in the surface 0.3 m of soil in the small plots ranged from 14 to 70 kg N ha–1 at HS and 12 to 95 kg N ha–1 at FS (Figure 3) during the experiment. There was substantial variability in SMN between replicate plots on individual measurement dates (3–51 kg N ha–1 at HS and 3–74 kg N ha–1 at FS). The greatest variability in replicates occurred during summer where high rainfall and temperatures may have promoted high rates of mineralization within some plots. An increase in the variability of measured SMN has similarly been observed in other sugarcane experiments during the summer period (Allen et al., 2010) and under wet tropical conditions (Webster et al., 2012). The variability of replicates led to low model performance values (e.g., ME = –7 at HS, Figure 3), although the overall trend in SMN was captured.


Long Term Sugarcane Crop Residue Retention Offers Limited Potential to Reduce Nitrogen Fertilizer Rates in Australian Wet Tropical Environments.

Meier EA, Thorburn PJ - Front Plant Sci (2016)

Soil mineral nitrogen (SMN) for the small plot field experiments at the HS and FS used to parameterize the model. Measured SMN is shown as symbols with bars for the mean and range of values; simulated SMN is shown as lines. Trash was retained on the soil surface (TS), incorporated (TI) or removed and the soil left bare (B) as a surrogate for burnt trash. RMSE, index of agreement (d) and ME are included.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940410&req=5

Figure 3: Soil mineral nitrogen (SMN) for the small plot field experiments at the HS and FS used to parameterize the model. Measured SMN is shown as symbols with bars for the mean and range of values; simulated SMN is shown as lines. Trash was retained on the soil surface (TS), incorporated (TI) or removed and the soil left bare (B) as a surrogate for burnt trash. RMSE, index of agreement (d) and ME are included.
Mentions: Average SMN measured in the surface 0.3 m of soil in the small plots ranged from 14 to 70 kg N ha–1 at HS and 12 to 95 kg N ha–1 at FS (Figure 3) during the experiment. There was substantial variability in SMN between replicate plots on individual measurement dates (3–51 kg N ha–1 at HS and 3–74 kg N ha–1 at FS). The greatest variability in replicates occurred during summer where high rainfall and temperatures may have promoted high rates of mineralization within some plots. An increase in the variability of measured SMN has similarly been observed in other sugarcane experiments during the summer period (Allen et al., 2010) and under wet tropical conditions (Webster et al., 2012). The variability of replicates led to low model performance values (e.g., ME = –7 at HS, Figure 3), although the overall trend in SMN was captured.

Bottom Line: Soil carbon increased in trash blanketed soils relative to SOC in soils with burnt trash.Simulated N fertilizer rates were able to be reduced from conventional rates regardless of trash management, because of low yield potential in the wet tropics.While these savings in N fertilizer use were modest at the field scale, they were potentially important when aggregated at the regional level.

View Article: PubMed Central - PubMed

Affiliation: Agriculture & Food Unit, Commonwealth Scientific and Industrial Research Organisation (CSIRO), St. Lucia QLD, Australia.

ABSTRACT
The warming of world climate systems is driving interest in the mitigation of greenhouse gas (GHG) emissions. In the agricultural sector, practices that mitigate GHG emissions include those that (1) reduce emissions [e.g., those that reduce nitrous oxide (N2O) emissions by avoiding excess nitrogen (N) fertilizer application], and (2) increase soil organic carbon (SOC) stocks (e.g., by retaining instead of burning crop residues). Sugarcane is a globally important crop that can have substantial inputs of N fertilizer and which produces large amounts of crop residues ('trash'). Management of N fertilizer and trash affects soil carbon and nitrogen cycling, and hence GHG emissions. Trash has historically been burned at harvest, but increasingly is being retained on the soil surface as a 'trash blanket' in many countries. The potential for trash retention to alter N fertilizer requirements and sequester SOC was investigated in this study. The APSIM model was calibrated with data from field and laboratory studies of trash decomposition in the wet tropics of northern Australia. APSIM was then validated against four independent data sets, before simulating location × soil × fertilizer × trash management scenarios. Soil carbon increased in trash blanketed soils relative to SOC in soils with burnt trash. However, further increases in SOC for the study region may be limited because the SOC in trash blanketed soils could be approaching equilibrium; future GHG mitigation efforts in this region should therefore focus on N fertilizer management. Simulated N fertilizer rates were able to be reduced from conventional rates regardless of trash management, because of low yield potential in the wet tropics. For crops subjected to continuous trash blanketing, there was substantial immobilization of N in decomposing trash so conventional N fertilizer rates were required for up to 24 years after trash blanketing commenced. After this period, there was potential to reduce N fertilizer rates for crops when trash was retained (≤20 kg N ha(-1) per plant or ratoon crop) while maintaining ≥95% of maximum yields. While these savings in N fertilizer use were modest at the field scale, they were potentially important when aggregated at the regional level.

No MeSH data available.


Related in: MedlinePlus