1. NFOA for Wheat and Corn

2. Yield Potential

6. Definitions INSEYIn Season Estimated Yield = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) = YP0 GDDGrowing Degree Days = (Tmin + Tmax)/2 – 4.4°C RI NDVI = NDVI from plots receiving adequate but not excessive preplant N, divided by NDVI from the farmer check (specific to that field) where preplant N may or may not have been applied. RI HARVEST = Maximum observed grain yield (treatment average with N fertilizer) divided by the observed grain yield from plots where no N was applied either preplant or topdress RI SV = Estimate of RI (spatial variability), using the average NDVI value from a random sensor sample (100 m in length) collected in a farmers field + 1 standard deviation, divided by the average NDVI value minus 1 standard deviation. YP MAX = Maximum obtainable yield level for a specific environment determined by the farmer, or previously defined as a biological maximum by research agronomists for that crop, and for that region (units: Mg/ha) YP 0 = Predicted or potential yield based on growing conditions up to the time of sensing, that can be achieved with no additional (topdress) N fertilization (units: Mg/ha) YP N = Predicted or potential yield that can be achieved with additional (topdress) N fertilization based on the in-season response index (RINDVI) (units: Mg/ha) = (YP 0 )/ (1/RI NDVI ) = (YP 0 )*(RI NDVI ) Definitions INSEYIn Season Estimated Yield = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) = YP0 GDDGrowing Degree Days = (Tmin + Tmax)/2 – 4.4°C RI NDVI = NDVI from plots receiving adequate but not excessive preplant N, divided by NDVI from the farmer check (specific to that field) where preplant N may or may not have been applied. RI HARVEST = Maximum observed grain yield (treatment average with N fertilizer) divided by the observed grain yield from plots where no N was applied either preplant or topdress RI SV = Estimate of RI (spatial variability), using the average NDVI value from a random sensor sample (100 m in length) collected in a farmers field + 1 standard deviation, divided by the average NDVI value minus 1 standard deviation. YP MAX = Maximum obtainable yield level for a specific environment determined by the farmer, or previously defined as a biological maximum by research agronomists for that crop, and for that region (units: Mg/ha) YP 0 = Predicted or potential yield based on growing conditions up to the time of sensing, that can be achieved with no additional (topdress) N fertilization (units: Mg/ha) YP N = Predicted or potential yield that can be achieved with additional (topdress) N fertilization based on the in-season response index (RINDVI) (units: Mg/ha) = (YP 0 )/ (1/RI NDVI ) = (YP 0 )*(RI NDVI )

7. GDD and rainfall data for 23 experiments over 4 years. Location/YearPlantingTotal number ofNumber of days from ---------------------Rainfall--------------------- ExperimentDatedays from plantingplanting to sensing Planting toPlanting toFeekes 5 to to sensingwith GDD>0MaturityFeekes 5Harvest --------------------------mm---------------------- Tipton S&N1998Oct 07, 1997142104415277138 Perkins S&N1998Oct 21, 199716799638396242 Perkins N&P1998Oct 21, 199716395638396242 Perkins N&P1999Oct 12, 1998142113655244411 - - - - - - - - -2000Oct 08, 199912299514203311 - - - - - - - - -2001Nov 17, 200016591444208236 Stillwater 2221999Oct 13, 1998133102759305454 - - - - - - - - -2000Oct 07, 1999150114810292518 - - - - - - - - -2001Nov 20, 200015580341171170 Stillwater_Efaw 3011999Oct 15, 1998159122759309450 - - - - - - - - -2000Oct 07, 1999150114588292296 - - - - - - - - -2001Nov 16, 200016688341171170 Stillwater_Efaw AA1999Nov 09,199813496596146450 - - - - - - - - -2000Oct 07, 1999150114810292518 - - - - - - - - -2001Nov 22, 200016087341171170 Haskell 8011999Oct 16, 19981571231016600416 - - - - - - - - -2000Oct 10, 1999157127703342361 - - - - - - - - -2001Oct 04, 2000191115823561262 Lahoma 5021999Oct 09, 1998146107882337545 - - - - - - - - -2000Oct 12, 1999152109536317219 - - - - - - - - -2001Dec 01, 200013455362167195 Hennessey AA2000Oct 07, 1999157119603341262 - - - - - - - -2001Nov 11, 200014472387195192

8. N Fertilizer Optimization Algorithm (NFOA): 1. Predict potential grain yield or YP 0 (yield achievable with no N fertilization) INSEY = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) YP 0 = 0.74076 + 0.10210 e 577.66(INSEY) 2. Predict response to N fertilization (In-Season-Response-Index, or RI NDVI ). RI NDVI = NDVI from non-N-limiting fertilized plots divided by NDVI in farmer check plots 3. Determine predicted yield that can be attained with added N (YP N ) based on in-season response index (RI NDVI ) and potential yield with no added N fertilization YP N = YP 0 * RI NDVI RI NDVI cannot exceed 2.0 YP N cannot exceed maximum obtainable yield (YP MAX ) 4. Predict percent N in the grain (PNG) based on YP N (includes adjusted yield level) PNG = -0.1918YP N + 2.7836 5. Calculate predicted grain N uptake (predicted percent N in the grain multiplied times YP N ) GNUP = PNG*(YP N /1000) 6. Calculate predicted forage N uptake from NDVI FNUP NDVI = 14.76 + 0.7758 e 5.468NDVI 7. Determine topdress N requirement (FNR)= (Predicted Grain N Uptake - Predicted Forage N Uptake)/0.70 Procedure applies more N to areas with high yield potential, & reduced N to areas with lower yield potential. N Fertilizer Optimization Algorithm (NFOA): 1. Predict potential grain yield or YP 0 (yield achievable with no N fertilization) INSEY = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) YP 0 = 0.74076 + 0.10210 e 577.66(INSEY) 2. Predict response to N fertilization (In-Season-Response-Index, or RI NDVI ). RI NDVI = NDVI from non-N-limiting fertilized plots divided by NDVI in farmer check plots 3. Determine predicted yield that can be attained with added N (YP N ) based on in-season response index (RI NDVI ) and potential yield with no added N fertilization YP N = YP 0 * RI NDVI RI NDVI cannot exceed 2.0 YP N cannot exceed maximum obtainable yield (YP MAX ) 4. Predict percent N in the grain (PNG) based on YP N (includes adjusted yield level) PNG = -0.1918YP N + 2.7836 5. Calculate predicted grain N uptake (predicted percent N in the grain multiplied times YP N ) GNUP = PNG*(YP N /1000) 6. Calculate predicted forage N uptake from NDVI FNUP NDVI = 14.76 + 0.7758 e 5.468NDVI 7. Determine topdress N requirement (FNR)= (Predicted Grain N Uptake - Predicted Forage N Uptake)/0.70 Procedure applies more N to areas with high yield potential, & reduced N to areas with lower yield potential.

9. Growth Stages in Cereals TilleringTillering Stem Extension HeadingHeading RipeningStageRipeningStage

10. N Fertilizer Optimization Algorithm (NFOA): 1. Predict potential grain yield or YP 0 (yield achievable with no N fertilization) INSEY = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) YP 0 = 0.74076 + 0.10210 e 577.66(INSEY) N Fertilizer Optimization Algorithm (NFOA): 1. Predict potential grain yield or YP 0 (yield achievable with no N fertilization) INSEY = NDVI (Feekes 4 to 6)/days from planting to sensing (days with GDD>0) YP 0 = 0.74076 + 0.10210 e 577.66(INSEY)

11. INSEY vs Grain Yield (24 locations, 1998-2001)

12. 2. Predict response to N fertilization (In-Season- Response-Index, or RI NDVI ) RI NDVI = NDVI from non-N-limiting fertilized plots divided by NDVI in farmer check plots 2. Predict response to N fertilization (In-Season- Response-Index, or RI NDVI ) RI NDVI = NDVI from non-N-limiting fertilized plots divided by NDVI in farmer check plots

13. Fertilize whole field with 40 lbs N/ac preplant Before exiting the field, apply one strip with 80 (non- N-limiting) Fertilize whole field with 40 lbs N/ac preplant Before exiting the field, apply one strip with 80 (non- N-limiting)

14. 3. Determine predicted yield that can be attained with added N (YP N ) based on in-season response index (RI NDVI ) and potential yield with no added N fertilization YP N = YP 0 * RI NDVI RI NDVI cannot exceed 2.0 YP N cannot exceed maximum obtainable yield (YP MAX )

15. OctoberFebruaryJune 0120240 days 50 lb N /ac 100 lb N/ac 67 lb N/ac N uptake, lb/ac INSEY: Rate of N uptake over 120 days, > ½ of the total growing days and should be a good predictor of grain yield INSEY: Rate of N uptake over 120 days, > ½ of the total growing days and should be a good predictor of grain yield 45 bu/ac, 2.5% N in the grain days with GDD>0?

16. NDVI at F5 In-Season Estimated Yield (INSEY)   days from planting to F5 (GDD>0) Hard Red Winter Wheat (Oklahoma) Soft Red Winter Wheat (Virginia)

17. YP 0 YP N YP MAX

18. YP 0 YP N (RI=1.5) YP MAX YP N (RI=2.0)

19. 4. Predict percent N in the grain (PNG) based on YP N (includes adjusted yield level) PNG = -0.1918YP N + 2.7836 4. Predict percent N in the grain (PNG) based on YP N (includes adjusted yield level) PNG = -0.1918YP N + 2.7836

21. 5. Calculate predicted grain N uptake (predicted percent N in the grain multiplied times YP N ) GNUP = PNG*(YP N /1000) 5. Calculate predicted grain N uptake (predicted percent N in the grain multiplied times YP N ) GNUP = PNG*(YP N /1000)

22. 6. Calculate predicted forage N uptake from NDVI FNUP NDVI = 14.76 + 0.7758 e 5.468NDVI (CALCULATE Grain N uptake, YP 0 ) 6. Calculate predicted forage N uptake from NDVI FNUP NDVI = 14.76 + 0.7758 e 5.468NDVI (CALCULATE Grain N uptake, YP 0 )

23. Genetic Improvements in NUE Moll et al. (1982) reported that the differences between corn hybrids for NUE could largely be attributed to variation in the use of accumulated N before anthesis, especially under low N supply. Water use efficiency generally paralleled nitrogen use efficiency in corn (Eghball and Maranville, 1991). In wheat, varieties with a high harvest index and low forage yield were noted to have low plant N loss and increased NUE (Kanampiu et al., 1997). Higher NUE was observed with high harvest index (Bufogle et al., 1997) Karrou and Maranville (1993) indicated that wheat varieties with more seedling dry matter with greater N accumulation are not necessarily the ones that use N more efficiently. N assimilation after anthesis is needed to achieve high wheat yields (Cox et al., 1985) and high NUE. Genetic selection is often conducted with high fertilizer N input in order to eliminate N as a variable, however this can mask efficiency differences among genotypes to accumulate and utilize N to produce grain (Kamprath et al., 1982). This is consistent with Earl and Ausubel (1983), noting that high yielding varieties of corn, wheat, and rice released during the Green Revolution were selected to respond to high N inputs. Consequently, continued efforts are needed where plant selection is accomplished under low N, often not considered to be a priority by plant breeders and uncharacteristic of agricultural experiment stations. Genetic Improvements in NUE Moll et al. (1982) reported that the differences between corn hybrids for NUE could largely be attributed to variation in the use of accumulated N before anthesis, especially under low N supply. Water use efficiency generally paralleled nitrogen use efficiency in corn (Eghball and Maranville, 1991). In wheat, varieties with a high harvest index and low forage yield were noted to have low plant N loss and increased NUE (Kanampiu et al., 1997). Higher NUE was observed with high harvest index (Bufogle et al., 1997) Karrou and Maranville (1993) indicated that wheat varieties with more seedling dry matter with greater N accumulation are not necessarily the ones that use N more efficiently. N assimilation after anthesis is needed to achieve high wheat yields (Cox et al., 1985) and high NUE. Genetic selection is often conducted with high fertilizer N input in order to eliminate N as a variable, however this can mask efficiency differences among genotypes to accumulate and utilize N to produce grain (Kamprath et al., 1982). This is consistent with Earl and Ausubel (1983), noting that high yielding varieties of corn, wheat, and rice released during the Green Revolution were selected to respond to high N inputs. Consequently, continued efforts are needed where plant selection is accomplished under low N, often not considered to be a priority by plant breeders and uncharacteristic of agricultural experiment stations.

25. 7. Determine topdress N requirement (FNR)= (Predicted Grain N Uptake - Predicted Forage N Uptake)/0.70 Procedure applies more N to areas with high yield potential, & reduced N to areas with lower yield potential. 7. Determine topdress N requirement (FNR)= (Predicted Grain N Uptake at YP N - Predicted Grain N Uptake at YP 0 )/0.70 7. Determine topdress N requirement (FNR)= (Predicted Grain N Uptake - Predicted Forage N Uptake)/0.70 Procedure applies more N to areas with high yield potential, & reduced N to areas with lower yield potential. 7. Determine topdress N requirement (FNR)= (Predicted Grain N Uptake at YP N - Predicted Grain N Uptake at YP 0 )/0.70

26. Wheat grain yield, 1999, 2000, 2001. 1999200020012001YieldNUE TrtN rateCovingtonMorrisonChickashaCovingtonAvg.Avg. (kg/ha)Method-------------------------------- (kg/ha) --------------------------------(%) 10check11222786103315621625- 245mid-season1268348513811994203221 390mid-season1846391214382461241420 49045 preplant, 45 mid-season--16772744221018 590preplant--17762329205316 6( )mid-season-NFOA2395 (77.0)3601 (25.1)1410 (19.8)2553 (58.6)2489 (45.1)54

27. Farmer Inputs: Date of planting Applicator inputs: Date of sensing, days from planting where GDD>0, RI, YP MAX Field requirments: Regular practice, 2X Strip Claims: 1. Topdress N based on INSEY and NFOA which can increase grain yields at lower N rates (INSEY computed and applied to each 1m 2 ). Increases N use efficiency (decreased N applied where forage N uptake was already high) when the production system allows for in-season application of fertilizer N. 2. Process to optimize plant yield where variability is treated at the spatial resolution occurring in the field. When spatially precise estimates of yield potential are made, they correspond to the resolutions where differences in soil test parameters are found. At coarse resolutions (>30 m), variation in yield potential will be masked by averaging, and benefits realized in treating the variability are lost.