Open sumanager56 opened 1 year ago
julieshortridge
commented
1 year ago Thanks Suman, this is very helpful to see. The comparison of 0N and 180N N uptake, dry matter, and grain yield look pretty good to me. @ryestewart what do you think of the N balance numbers? Is there anything that looks unreasonable in those tables to you?
ryestewart
commented
1 year ago Sorry for the late reply, but the mass balance looks pretty good, except what is the ammonium outflux term? Is that leaching? Those numbers seem like they might be high if so. Typically nitrate is assumed to be much more mobile than NH4 since the latter will be held in the CEC. But with sandy soils the CEC will likely be relatively low.
On Wed, Feb 22, 2023 at 11:52 AM julieshortridge @.***> wrote:
Thanks Suman, this is very helpful to see. The comparison of 0N and 180N N uptake, dry matter, and grain yield look pretty good to me. @ryestewart https://github.com/ryestewart what do you think of the N balance numbers? Is there anything that looks unreasonable in those tables to you?
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sumanager56
commented
1 year ago Thanks, Dr. Stewart. Yes, the NH4 outflux term is the leaching component - I also think that it might be a little high. I will check if I can reduce this component while keeping the overall uptake and yield similar.
sumanager56
commented
1 year ago Hi Dr. Shortridge, & Dr. Stewart, I spend some time looking into the difference between irrigated and non-irrigated N uptake yields for both 0-N and 180-N treatments. It was interesting to see that the response to irrigation can be just opposite for 0-N and 180-N treatments. For example, irrigation could cause an increase in yield and N uptake for 180-N treatment but at the same time cause marginal reduction in these values for 0-N treatment. The highly influencing parameters are:
1) Nitrification coefficient -
2) Transpiration concentration stream factor (TCSF_N) - Used to calculate NH4-N uptake when NH-4 concentration in soil is limiting.
3) Thickness of soil layer considered for simulation of OM and N-dynamics (dz_WSN).
Most importantly, how I schedule irrigation also has a negative or positive impact on yields. Below is a result when I schedule irrigation based on pressure head criterion (-350 cm as critical pressure head and irrigate to FC = -160 cm). Plants starts experiencing drought stress at -300 cm (-400 cm in CN model) and there's no water extraction at -2000 cm (soil moisture content at -2000cm is almost same as that at -10,000 cm but creates more stress for the same value of -300 cm)
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| Ammendments | Total N uptake | Total dry matter yield | Grain yield | Grain yield_potential | Dry matter yield_potential -- | -- | -- | -- | -- | -- | -- | kg/ha | lb/acre | lb/ha | bu/acre | bu/acre | lb/acre No irrigation | 180-N | 137.4905 | 19199.78 | 193.6 | 241 | 23887.76 Irrigation | 180-N | 148.0262 | 20666.39 | 203.8 | 241 | 23887.76 | | | | | | No irrigation | 0-N | 56.59482 | 9238.588 | 38.7 | 241 | 23887.76 Irrigation | 0-N | 56.26 | 9208.256 | 38.8 | 241 | 23887.76 ### N-balance for 180-N treatment (no irrigation) NH4-N | | | | NO3-N | | | -- | -- | -- | -- | -- | -- | -- | -- Input | | Output | | Input | | Output | Ammendments | 87.36 | Volatilisation | 8.55 | Ammendments | 45.5 | | Crop Residues | 0 | Plant uptake | 97.87 | Crop Residues | 0 | Plant uptake | 56.25 Mineralisation | 52.3 | Nitrification | 48.15 | Nitrification | 48.15 | Denitrification | 0.08 Influx top | 29.75 | Outflux | 12.97 | Influx top | 29.75 | Outflux | 54.22 Influx lat | 0 | | | Influx lat | 0 | | Influx bot | 0 | | | Influx bot | 0 | | Total | 169.41 | Total | 167.54 | Total | 123.4 | Total | 110.55 | | Diff.Stor | 1.87 | | | Diff.Stor | 12.85
@julieshortridge @ryestewart As discussed in our last meeting, I was seeing a lot of mineralization component in our N balance that was contributing to N uptake and losses and therefore minimizing the effect of applied N fertilizer.
Changes made in CranMais.snp file
Firstly, mineralization depend on soil water content, there's a parameter "WFPSCrit" in CranMais.snp file that controls this process, so I changed reduced this value to reduce the mineralization process. It helped some, but I also had to change/reduce the overall organic matter content in the soil to reduce the overall NH4 and NO3 contents in soil (I assumed a 1.5% OM - around 20 kg/m3 and divided it into different pools as suggested by WOFOST). I also adjusted the nitrification and denitrification rates, and the thickness of the soil layer (dz_WSN) considered for simulation of soil organic matter and nitrogen dynamics (0.3 suggested for grassland, and as high as 1 m for winter wheat - I used 0.7m for ours).
Changes made in CranMais.sme file
Secondly, I adjusted dates of N application based on Lal's document - 25% N application on April 20 (45 kg/ha) and 75% on June 02 (135kg/ha). A volatilization fraction of 0.25 is considered by WOFOST, but I reduced it to 0.15 and 0.10 in first and second application, respectively (Since, it was side-dressed close to the peak uptake time, volatilization loss will be less).
Changes made in GmaizeD.crp file
1) TSUMEA (temperature sum from emergence to anthesis) = 900 2) TSUMAM (temperature sum from anthesis to maturity) = 850 Base temperature of 10 degreeC was considered in calculating the GDD's. 3) TDWI (Initial total crop dry weight) = 25kg/ha (largely controls potential yields) (https://anketor.com/how-many-kilos-of-maize-seed-per-acre/) 4) SPAN (life span uder leaves under optimum conditions) - default is 33, calibrated to 44 (increased both potential yield and actual yield) - Frequently calibrated parameter in the literature. 5) CVO (efficiency of converting assimilates into storage organs)-default is 0.67, calibrated to 0.87 which is inline with literature values for corn. This parameter significantly increased actual and potential grain yield. 6) AMAXTB (maximum CO2 assimilation rate as a function of development stage) - default is 21-70, calibrated to 21-79, which is in line with literature value.
Nitrogen USE section
7) DVSNLT (development stage above which no crop nitrogen uptake does occur. I set this to highest (2.0) for more N uptake and saw same value used in example of SWAP/WOFOST manual. 8) DVSNT (development stage above which nitrogen translocation to storage organs does occur) - 1.0 (this seemed reasonable reading about N translocation to grains after tasseling period starts at 1.0) 9) NLUE/NPART/NSLA - all are coefficient for reduction due to N stress; Used for calibration because all other parameters would make changes in yields(actual) for both 0N and 180N applied setting in the same way, but I wanted the yield to reduce only when there were no fertilizer application in the field (0N setting). 10) NMAXSO (maximum N concentration in storge organs) -only changes actual yield keeping potential yield same. Also used to adjust N uptake rates.
Overall, I did all the calibration using the following references: 1) Actual dry matter yield under 0N and 180 N kg/ha fertilizer treatment. 2) Actual corn yield under 0N and 180 kg/ha fertilizer treatment. 3) Total N uptake under 0N and 180 N kg/ha fertilizer treatment. 4) Reasonable LAI values for corn under both scenarios (3.9 under 180 N application and 2.3 under 0N). These values were highly fluctuating with different parameters. LAI can go as high as 6 under irrigated treatment.
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Simulated corn yield and N uptake
Ammendments | Total N uptake | Total dry matter yield | Grain yield | Grain yield_potential | Dry matter yield_potential -- | -- | -- | -- | -- | -- kg/ha | lb/acre | lb/ac | bu/acre | bu/acre | lb/acre 0 | 54.7 | 8033 | 37.5 | 234 | 22074 180 | 167 | 19664 | 193.78 | 234 | 22074 ### Field-observed corn yield and N uptake Ammendments | Total N uptake | Total dry matter yield | Grain yield -- | -- | -- | -- kg/ha | lb/acre | lb/ac | bu/acre 0-N | 102 | 8992.6 | 46.1 0-N | 50 | 5854.9 | 23.5 0-N | 50 | 5888.1 | 34.4 0-N | 40 | 4367.3 | 35.4 180-N | 431 | 23551.1 | 202.5 180-N | 175 | 19904.3 | 131.4 180-N | 210 | 19998.4 | 190.8 180-N | 151 | 17597.4 | 202.4 ### No fertilizer application. NH4-N and NO3-N balance NH4-N | | | | NO3-N | | | -- | -- | -- | -- | -- | -- | -- | -- Input | | Output | | Input | | Output | Ammendments | 0 | Volatilisation | 0 | Ammendments | 0 | | Crop Residues | 0 | Plant uptake | 44.41 | Crop Residues | 0 | Plant uptake | 16.88 Mineralisation | 83.65 | Nitrification | 34.11 | Nitrification | 34.11 | Denitrification | 2.66 Influx top | 29.9 | Outflux | 29.18 | Influx top | 29.9 | Outflux | 36.9 Influx lat | 0 | | | Influx lat | 0 | | Influx bot | 0 | | | Influx bot | 0 | | Total | 113.55 | Total | 107.7 | Total | 64.01 | Total | 56.44 | | Diff.Stor | 5.85 | | | Diff.Stor | 7.57 ### 180kg/ha mineral fertilizer applied. NH4-N and NO3-N balance NH4-N | | | | NO3-N | | | -- | -- | -- | -- | -- | -- | -- | -- Input | | Output | | Input | | Output | Ammendments | 90 | Volatilisation | 10.1 | Ammendments | 90 | | Crop Residues | 0 | Plant uptake | 105 | Crop Residues | 0 | Plant uptake | 82.15 Mineralisation | 88 | Nitrification | 48.1 | Nitrification | 48.2 | Denitrification | 5.43 Influx top | 29.7 | Outflux | 34.5 | Influx top | 29.7 | Outflux | 66.49 Influx lat | 0 | | | Influx lat | 0 | | Influx bot | 0 | | | Influx bot | 0 | | Total | 207.7 | Total | 197.7 | Total | 167.9 | Total | 154.07 | | Diff.Stor | 10 | | | Diff.Stor | 13.83 ### No fertilizer application  ### 180kg/ha fertilizer application 