1. Plant-to-Plant Variability in Corn Production K.L. Martin, P.J. Hodgen, K.W. Freeman, Ricardo Melchiori, D.B. Arnall, R.K. Teal, R.W. Mullen, K. Desta, S.B. Phillips, J.B. Solie, M.L. Stone, Octavio Caviglia, Fernando Solari, Agustin Bianchini, D.D. Francis, J.S. Schepers, J. L. Hatfield, W.R. Raun

2. Objectives 1. Evaluate by-plant corn grain yield variability over a range of production environments 2. Determine the relationships among mean grain yield, standard deviation of yield, coefficient of variation of yield, and yield range 3. Evaluate the relationship between NDVI and corn grain yields.

3. Variability in by-plant corn grain yields Delayed and uneven emergence variable depth of planting variable depth of planting double seed drops double seed drops wheel compaction wheel compaction location of the seed within the furrow location of the seed within the furrow surface crusting surface crusting random soil clods random soil clods soil texture differences soil texture differences variable distance between seeds variable distance between seeds variable soil compaction around the seed variable soil compaction around the seed insect damage insect damage moisture availability moisture availability variable surface residue variable surface residue variable seed furrow closure variable seed furrow closure Ames, Iowa

4. 2003 Corn Data FAO and National Corn Growers Association Corn Grain Production Avg. YldArea Corn Grain Production Avg. YldArea Mg/hamillion ha World4.5142 USA8.928 Argentina6.42.3 Mexico2.57.8 Iowa9.8 4.8 Nebraska9.23.1 Ohio8.71.2 Virginia7.20.2 Oklahoma7.80.1 Mg/hamillion ha World4.5142 USA8.928 Argentina6.42.3 Mexico2.57.8 Iowa9.8 4.8 Nebraska9.23.1 Ohio8.71.2 Virginia7.20.2 Oklahoma7.80.1

5. Methods By-plant Corn Grain Yields By-plant Corn Grain Yields Argentina Mexico Iowa Nebraska Ohio Virginia Oklahoma Data collected: Grain yield, yield range, standard deviation and coefficient of variation. Data collected: Grain yield, yield range, standard deviation and coefficient of variation. Transects: corn rows ranging from 8 to 30 m in length Transects: corn rows ranging from 8 to 30 m in length Individual plants marked at most sites at or before V8 to ensure detection of barren, and/or lost plants at harvest (60-85 days later depending on the maturity) Individual plants marked at most sites at or before V8 to ensure detection of barren, and/or lost plants at harvest (60-85 days later depending on the maturity) At the time plants were tagged, a tape measure was extended the length of the row and cumulative distances were recorded for each plant At the time plants were tagged, a tape measure was extended the length of the row and cumulative distances were recorded for each plant

6. At most sites (based on row spacing) the area occupied by each plant was calculated. At most sites (based on row spacing) the area occupied by each plant was calculated. Each plant determined to occupy half the distance to and from its nearest neighbor Each plant determined to occupy half the distance to and from its nearest neighbor Where: Where: Ai is the area occupied by the ith plant Ai is the area occupied by the ith plant Di-1,di,di+1 are the distances to the i-1, i, and i+1 plants Di-1,di,di+1 are the distances to the i-1, i, and i+1 plants R is the row spacing R is the row spacing Ears harvested individually, dried, and weighed Ears harvested individually, dried, and weighed > one ear per plant, total weight was recorded on a by-plant basis > one ear per plant, total weight was recorded on a by-plant basis Sites where actual distances between plants were not recorded: Avg. distance occupied per plant was determined based on row spacing and total transect or row distance and number of plants harvested per row. Sites where actual distances between plants were not recorded: Avg. distance occupied per plant was determined based on row spacing and total transect or row distance and number of plants harvested per row. Methods

7. Mean Yield vs Std. Dev. Average corn grain yield plotted against the standard deviation from by-plant yield over 46 transects in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma.

8. Mean Yield vs. CV Average corn grain yield plotted against the coefficient of variation from by-plant yields over 46 transects in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma.

9. Mean Yield vs. Yield Range Average corn grain yield plotted against the by-plant yield range (maximum minus minimum yield) in 46 transects ranging from 10.5 to 30m in length, in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma.

10. Distance Averaged vs. Error Effect of averaging plant yields over a specified distance along the row on the absolute error incurred when using the average corn yield for estimating the by-plant yield. Yields were normalized by the average yield along the entire row.

11. Average corn grain yields plotted by plant, every 2 plants, every 3 plants and every 4 plants, using measured distances between plants, Ames, IA 2004. Measured Distances

12. Fixed Distances Average corn grain yields computed using fixed distances of 23.5, 47.0, 70.6, and 94.1 cm at Ames, IA 2004

13. NDVI vs Yield NDVI versus corn grain yield determined for every 4 plants using linear regression and associated 95% confidence intervals, east row, Ames IA, 2004. +/- 1000 kg/ha

14. Location Statistics Minimum, maximum, mean, standard deviation, maximum/minimum and CV for by-plant corn grain yields from 46 transects in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma, 2002-2004. ________________________________________________________________________________________________________ LocationYearsTransectsMin Yield Max Yield Mean YieldStdevMax/MinCV ------------------------ kg ha-1-----------------------% El Batan, Mexico2002360694404268193522.445.3 OK, <6000 kg ha-12003-412112891694652172410.037.2 OK, >6000 kg ha-12003-481947141207050216711.630.5 Ames, IA, Shelton, NE200441872211738320366014.146.0 Wooster, OH20041206619458975943679.450.2 Parana, Argentina2003928062805811478421115.036.8 Painter, VA200344753245521194331715.226.7 Phillips, NE200457098214921438329263.220.3 -------------------------------------------------------------------------------------------------------------- All Sites 2002-04462752172818495276511.134.3 ________________________________________________________________________________________________________ 44 bu/ac

15. Summary Errors associated with predicting yield at V8 were dwarfed in comparison to the recorded by-plant yield differences Errors associated with predicting yield at V8 were dwarfed in comparison to the recorded by-plant yield differences Can N management at this scale help since yield potential can be predicted. Can N management at this scale help since yield potential can be predicted. By-plant nutrient management could be eliminated by developing production systems that homogenized plant stands, and emergence By-plant nutrient management could be eliminated by developing production systems that homogenized plant stands, and emergence Over all sites, plant-to-plant variation in corn grain yield averaged 2765 kg/ha (44.1 bu/ac). Sites with the highest average corn grain yield (11478 and 14383 kg/ha, Parana Argentina, and Phillips, NE), had plant-to-plant variation in yields of 4211 kg/ha (67 bu/ac) and 2926 kg/ha (47 bu/ac) Over all sites, plant-to-plant variation in corn grain yield averaged 2765 kg/ha (44.1 bu/ac). Sites with the highest average corn grain yield (11478 and 14383 kg/ha, Parana Argentina, and Phillips, NE), had plant-to-plant variation in yields of 4211 kg/ha (67 bu/ac) and 2926 kg/ha (47 bu/ac)