History of Predicting Yield Potential Oklahoma State University

Outline Yield Goals and Potential Yield Soil Test vs. Sensor Based Sufficiency: Mobile vs. Immobile Nutrients Bray’s mobility concept How to generate nutrient recommendations What should we learn from soil testing Subsoil nutrient availability Soil Testing: Correlation/Calibration/Recommendation Models for Interpretation of Response Interfering agronomic factors

Yield Goal/Potential Yield Yield Goal: yield per acre you hope to grow (Dahnke et al., 1988) Potential yield: highest possible yield obtainable with ideal management, FOR specific soil and weather conditions Maximum Yield: grain yield achievable when all manageable growth factors (nutrients, insects, disease, and weeds) are nonlimiting and the environment is ideal

Yield Goals in the Literature Yield per acre you hope to grow (Dahnke et al. (1988). Highest yield attained in the last 4-5 years and that is usually 30-33% higher than avg. yield (J. Goos, 1998). Aim for a 10-20% increase over the recent average (Rehm and Schmitt, 1989). Yield goal should be based on how much water is available (stored soil water to 1.5m, Black and Bauer, 1988). When Yield Goals are used it explicitly places the risk of predicting the environment (good or bad) on the producer.

Value of Using Yield Goals Nutrient removal can be reliably estimated for a given yield level in specific crops. Selected Yield Goal defines the risk the producer is willing to take. Yield Goal can define the limits in terms of economic inputs when considering herbicides, insecticides, etc.

Importance of Predicting Potential Yield Seasonal N need directly related to observed yield. NUE decreases with increasing N rate. Known Potential Yield = Known N Input = Highest NUE.

Potential Yield with N, YPN Max Yield YPMAX Average Yield +30% Yield Goal Grain yield Potential Yield YP0 Potential Yield with N, YPN Bound by Environment and Management

Predicting N Needs Use of Yield Goals. Based on past season yields. May take into account current-year preplant conditions of available moisture and residual N. Seldom is adjusted for midseason conditions to alter N inputs. Use of Potential Yield. Reliability of predicting final yield (and N requirement) from existing soil and crop conditions should increase as harvest approaches.

Yield Goals Average of the last 3 or 5 years + 20% versus observed yield

Spatial Variability and Yield Potential Significant soil variability at distances less than 30 m apart (Lengnick, 1997) In order to describe the variability encountered in field experiments, soil, plant and indirect measures should be made at the 1m or submeter resolution Significant differences in soil test P, organic C, and pH were found at distances <0.30m (OSU)

Crop Response/Models to Predict Yield (N need) CERES (Crop-Environment Resource Synthesis) crop response model was not useful in predicting wheat grain yield (Moulin and Beckie, 1993) Complicated. Total N uptake at Feekes growth stage 5 was found to be a good predictor of yield (Reeves et al., 1993) Worked some, but not all years.

Growth Stages in Cereals Stem Extension Ripening Stage Heading Tillering

and should be a good predictor of grain yield 50 lb N /ac 100 lb N/ac 75 lb N/ac N uptake lb/ac 45 bu/ac, 2.5% N in the grain INSEY: Rate of N uptake over 120 days, > ½ of the total growing days and should be a good predictor of grain yield

Adjusting Yield Potential October 1 Benchmark Planting Date Planting Date F4 Date F5 Date Adj. Index 42+20=62 29+6=35 Perkins 42 20 143 185 Tipton 29 6 116 145

Feekes growth stage SF45 = (NDVI4 + NDVI5)/days from F4 to F5 YIELD POTENTIAL  growth NDVI min F4 F5 Maturity Feekes growth stage

INSEY INSEY = (NDVI = (NDVI + NDVI + NDVI )/GDD T1 to T2 14 14 12 12 10 10 8 8 Above ground dry Above ground dry S S NDVI NDVI 6 6 T1 T2 T1 T2 4 4 weight weight 2 2 GDD GDD 500 500 1000 1000 1500 1500 2000 2000 2500 2500 Cumulative growing degree days Cumulative growing degree days Rickman, R.W., Sue E. Waldman and Betty Klepper. 1996. Rickman, R.W., Sue E. Waldman and Betty Klepper. 1996. MODWht3: A development MODWht3: A development - - driven wheat growth simulation. driven wheat growth simulation. Agron J. 88:176 Agron J. 88:176 - - 185. 185.

6 experiments (NDVI F4 + NDVI F5/GDD from F4 to F5

Normalized Difference Vegetation Index (NDVI) = NIR ref – red ref / NIR ref + red ref (up – down) excellent predictor of plant N uptake Units: N uptake, kg ha-1

Normalized Difference Vegetation Index (NDVI) Reasonably good predictor of final grain yield

+ NDVI NDVIT2 Estimated Yield (EY) = GDD from T1 to T2 +Good predictor of final grain yield - Requires two sensor readings +GDD y = 0.4554e344.12x R2 = 0.62

NDVI at F5 = days from planting to F5 In-Season Estimated Yield (INSEY)1 = days from planting to F5 +Good predictor of final grain yield +Requires only one sensor reading Units: N uptake, kg ha-1 day-1

NDVI at F5 = days from planting to F5 In-Season Estimated Yield (INSEY)1 = days from planting to F5 Hard Red Winter Wheat (Oklahoma) Soft White Winter Wheat (Virginia)

NDVI at F5 = In-Season Estimated Yield (INSEY)2 days from planting to F5, GDD>0 GDD = ((Tmin + Tmax)/2)-4.4°C Units: N uptake, kg ha-1 day-1 where GDD>0

Need for GDD Is growth possible on all days (October to May)? Days where average temp did not exceed 4.4°C (40°F) Count only those days where growth was possible What if GDD was high, but moisture was limiting? Under irrigation, use cumulative GDD

NDVI at F5 = In-Season Estimated Yield (INSEY)2 days from planting to F5, GDD>0 +Good predictor of final grain yield +Requires only one sensor reading +Appears to work over different regions Units: N uptake, kg ha-1 day-1 where GDD>0

NDVI at F5 = In-Season Estimated Yield (INSEY)2 days from planting to F5, GDD>0 Hard Red Winter Wheat (Oklahoma) Soft White Winter Wheat (Virginia)

Winter Wheat 24 locations in Oklahoma 1998-2001 Spring Wheat 4 locations in Ciudad Obregon, MX 2001 Soft White Winter Wheat 7 locations in Virginia, 2001

INSEY vs Grain Yield (24 locations in Oklahoma, 1998-2001)

Can We Predict Yield with No Additional N Applied? YP0 Can We Predict The Yield Increase If We Apply N in a Given Year? YPN Can We Predict if Harvested Yield will be Less than Predicted Yield? YP?

Post-maturity yield loss 12 10 8 6 4 2 Above ground dry weight Harvest Cumulative growing degree days

VEGETATIVE REPRODUCTIVE R-NH2 NO3 NH4 R-NH2 moisture heat NH3 Total N moisture heat Total N NH3 Safety valve amino NO NO NH 3 2 3 acids nitrate reductase nitrite reductase NO3- + 2e (nitrate reductase) NO2- + 6e (nitrite reductase) NH4+

Rainfall Disease Frost 12 10 8 6 4 2 Rainfall Disease Frost Above ground dry weight Harvest Cumulative growing degree days

NEXT Section…… ???? Predicting the Increase in Yield due to Applied N N uptake, lb/ac 40 N 0 N October February June