Typical of dryland, where fallowed wheat yields range from 15 to 45
Bu/A, neither yield nor protein responses to nitrogen (N) fertilizer are
consistent (2, 3, 4, 8). Workers at the Tetonia and Aberdeen Branch
Stations in Intermountain Idaho began trials as early as the 1940's, but
there were no unifying concepts that would allow projection of trial
results to individual farm fields. Therefore, few reports have been
published, although trials have continued to date (1, 5, 8, 9).

The purpose of this paper is to summarize and interpret the data
collected over the entire period. We identified the two following goals:

1. The summary should be based on established agronomic relations,
and

2. The results of the analysis should improve predictions of yield
and protein responses to N fertilizer

Massee, T.W.

Painter, C.G.

USDA - ARS - NWISRL

135USING YIELD AND PROTEIN HISTORY FROM DRYLAND FIELDSTO IMPROVE NITROGEN FERTILIZER RECOMMENDATIONS 1T. W. Massee and C. G. Painter2INTRODUCTIONTypical of dryland, where fallowed wheat yields range from 15 to 45Bu/A, neither yield nor protein responses to nitrogen (N) fertilizer areconsistent (2, 3, 4, 8). Workers at the Tetonia and Aberdeen BranchStations in Intermountain Idaho began trials as early as the 1940's, butthere were no unifying concepts that would allow projection of trialresults to individual farm fields. Therefore, few reports have beenpublished, although trials have continued to date (1, 5, 8, 9).The purpose of this paper is to summarize and interpret the datacollected over the entire period. We identified the two following goals:1. The summary should be based on established agronomic relations,and2. The results of the analysis should improve predictions of yieldand protein responses to N fertilizer.METHODSAll data used in this report were from replicated field experimentswith either hard red winter or hard red spring wheat. The experimentswere conducted on both on- and off- station locations, so that the rangeof eastern Idaho dryland conditions were represented. Usually farmer'splantings were used for off-station trials. Early trials indicated thatthere were no wheat varietal differences to N response (8), and so dif-ferences in farm varieties was not considered a variable. Therefore,yield and grain protein increases from N treatments were, respectively,converted to bushel and percent protein increase per pound N per acreapplied. As final increments from high rates of N were expected toaffect behavior differently than initial rates, etc., yield and proteinchanges from added N were analyzed separately for each treatment levelwith applied N. For example, where plots received 0, 30, 60, and 90lb N/A, the 90 lb N/A plot was analyzed in comparison with the 60 lb N/Aplot to determine the effect of the last 30 lb of N. Thus, if the1 Proceedings, Thirtieth Annual Fertilizer Conference of theNorthwest, Spokane, Washington, July 17-19, 1979.2 Soil Scientist, Snake River Conservation Research Center, Scienceand Education Administration, USDA, Kimberly, Idaho; and Soils Specialist,Idaho Cooperative Extension Service, University of Idaho, Twin Falls,Idaho.190	 0qoO16q 000°S °0 5%daq °• •PROTEIN%	 14 o • a	 og •s	 rn,r. • %..oa	 ang•••nn •4? • „•n•.••_.••HSi • • 11•06 ••'• •9••s e I••••.• .n • •8 • •• •	 •2 4 6 8 16 12 14 16 18 20 22 24 A A k 32 3.4 36 38 40 48YIELD - 8u/Alib90 lb N/A plot produced 3 Bu/A more than the 60 lb N/A treatment, theunits recorded wereAY/AN = 3(Bu/A)/30 (lb N/A) 	 0.1where AY is change in yield and AN indicates change in N rate.We will show that this approach can be useful for any increment ofN if the AYAN value is compared with yield and protein content from thenext lower N rate, or, in field situations with the "historic" yieldand protein content.INTERPRETATION OF'RESULTSSpring and winter wheat were initially considered and analyzed asdifferent crops. However, regression trends indicated they were similar.Figure 1 shows that the yield:protein content relation is continuous,except that spring wheat is at the low yield:high protein content end ethe scatter diagram.Fig. 1. Protein content vs. yield from plots show a continuous trend.Open circles are spring wheat and solid circles are winter 00°•Another similarity (Fig. 2) comes from graphing yield increas es 4,caused by N, i.e. (AYAN), versus protein content (in this paper, 3 11""from next lower N increment or "historic") where data for the sprin g .wheat extends the distribution. Thus, spring and winter were analys oeand presented together.Figure 2 illustrates that the best response to additiona l N " 4*low protein wheat fields. This same phenomena has been reporte d pre'viously for Oregon and Washington (2, 3, 4, 6, 7). Agronomic allY,protein quantity reflects N availability. The more abundant wh eat the"carbohydrate content is quite dependent on moisture supply. 711"'A\-09 +19.3(4)2I /IN/r 2 • 0.684,2Bu/A RESPONSE Lb N APPLIED(2 TN )	 4.10137percent protein essentially compares protein to carbohydrate amounts andis a growing season integration of the nitrogen-to-moisture status. A"best fit" line for this relationship (Fig. 2) with the formula(AY/AN) = -0.09 + 19.3 (11% protein) 2indicates the (11% protein) term should be used in any further multipleregression approach.PROTEIN %Fig. 2. Comparison of AY/AN vs. percent protein, indicating that winterwheat (solid circles) and spring wheat (open circles) individ-ually and collectively show a trend. Highest AY/AN valueswere from plots where grain protein content was low.Better estimates of yield responses to N can be made by consideringboth yield and protein content of wheat. It was obvious from Fig. 1,where highest yields were from plots having the lowest protein, togetherwith Fig. 2 where low protein plots responded to N best, that the higheryielding plots should respond to N best (see also reference #6). Thefollowing equations might appear to depict just the opposite, and so anexplanation is given. If Fig. 1 had included the value of AY/AN for eachpoint plotted, a trend would have developed showing similar AY/AN valuesoccurring in bands (Fig. 3). These bands indicate that there is arelationship between yield and protein content which governed AY/AN. Ata given protein content, the largest AY/AN values are found with thelowest yields. The statistical analysis method used to study thisaspect was to relate yields vs. protein contents as a function whichseparated the positive from the negative AY/AN values. This line orfunction may be called the "line of zero return" (Fig. 4) because itrepresents the protein content - yield relation where no yield responsecan be expected from added N. Subtracting a protein level found fromthe "line of zero return" is done by the expression:[17.5 - 0.125 (Bu/A) - observed % protein'where both the Bu/A and observed % protein figures are inserted fromPROTEINPROTEIN000	0 00 0000aQ	 °c:1 % •05	 0 0 •	 S Dec__04 15 I. /41.	 •I,► •	 "ES0	 "V	 .• . Itr414: •• • Ai •$	 ••0	•	 ••••	 •	 •• • 	•• d Y	 • •	 05 •	 • S.• 44, Arcpc	 • •45es••• n •••••••20	 10YIELD - 9u/An•• •••138Fig. 3. Protein content vs. yield of wheat where lines group togethersimilar q T/AN values. The approximate mean value is indicatedbetween the lines.Fig. 4. A "line of zero return", having protein content as a functionof (17.5 - 0.125 (Bu/A)] indicates the yield and protein whereno changes in yields were found from added N.139field data. Regressing AY/AN on this expression indicates:(AY/AN) = 0.013 + 0.027 [17.5 - 0.125 (Bu/A) - observed % protein]= 0.49 - 0.003 (Bu/A) - 0.027 (observed % protein)r2 = 0.66This regression did not have as high a correlation coefficient aswhere (1/% protein) 2 was used previously. Thus, incorporating (11% pro-tein) 2 by multiple regression shows:(AY/AN) = 0.155 - 0.00147 (Bu/A) - 0.01176 (% protein) + 11.86(1/% protein) 2R2 = 0.71which was the best estimate found while adhering to the goals of thispaper.Changes in protein content from N fertilizer were also related toyield and protein content. Dividing yield by (% protein) 2 gave termsthat were negatively related to the change in percent protein P erlb N applied per acre, i.e. to AP/AN. As a second term for use in mul-tiple regression, % protein was also negatively related. Thus:Bu/A (ApAts).'0.14...0.069[]0.0072 (% protein)(% protein) 2R2 = 0.64This relation indicated that plots having low protein wheat respondedbest to N for producing a total protein (% protein x Bu/A) change, butonly after the potential yield increases from N were first acquired. Theaverage AP/AN for all plots was 0.037, or a 1.3% increase with a conserv-ative 35 lbs N/A rate.SUMMARY AND FIELD USEYield and protein changes from N fertilizer were estimated usinghistoric yield and protein content. It made little difference whetherspring or winter wheat was being analyzed, because their inherent dif-ferences in yield and protein content accounted for associated differ-ences in N response (spring wheat had less response than winter). Usinga conservative 35 lb N/A, from final equations shown, gave the calculatedresponses shown in Table 1.The interpretation in this report was derived from evaluating theeffects of individual increments of fertilizer N. These averaged near35 lb N/A. The corresponding yields and protein contents were takenahead of the increment in question. However, the equations given herecan also be used correctly to estimate responses from using higher Nrates. Doing this merely requires that the response to each incrementHistoric YieldBu/A153045710 (2.4)9 (1.6)9 (0.9)10	 13Bu/A and % protein16140of up to 35 lbs N/A be computed as separate steps until the rate Iliquestion is reached. That is, the change in yield and protein contentfrom the initial 35 lb N/A application should be added to the baseamounts before calculating the effect of a second N increment, etc.Usually it will be found that the effects of N become less and lesspronounced with additional N increments.Table 1. Expected increases in wheat yield (Bu/A) and protein (Z) (inparenthesis) from adding 35 lb N/A.Historic Protein Content - %Where stored soil moisture, date of planting, etc. are expected tochange the yield and protein from a "historic" value, this informationshould be used initially rather than a "historic" average.Thus, it has been shown that the wheat plant itself has expressedan integration of growth factors by its final yield and protein content,which also expresses how it would have responded differently had thenitrogen nutrition been different.141LITERATURE CITEDI. Fitzgerald, Paul J., F. H. Siddoway, and J. V. Mannering. 1958.The effect of nitrogen fertilization on yield and quality of hardred winter wheats grown on dryland in southern Idaho. Proc. 9thAnn. Fart. Conf. Pac. N.W. 9:21-28.2. Hunter, A. S., L. A. Albin, C. J. Gerard, W. E. Hall, and H. E.Cushman. 1961. Wheat fertilizer experiments in the ColumbiaBasin, 1953-57. Oregon Agric. Expt. Sta. Cir. of Info. 607.3. Jackson, T. L., D. F. Sundberg, E. F. Seeborg, and M. A. Barmore.1952. Effect of nitrogen fertilizer on wheat. Washington Agric.Expt. Sta. Cir. 188.4. Koehler, F. E. 1961. Fertilizers and wheat quality. Proc. 12thAnn. Pac. N.W. Fert. Conf. 12:73-78.5. McKay, Hugh. C. 1966. Nitrogen boosts wheat protein and wheatprofits. Idaho Current Info. Series 26. 2 p.6. Pumphrey, F. V. 1968. Wheat yield and protein content as predictorsfor nitrogen fertilization in northeast Oregon. /968. OregonAgric. Expt. Sta. Special Report 259. 8 p.7. Ramig, R. E. 1964. Protein content of wheat as influenced by someagronomic practices. Proc. 15th Ann. Pac. N.W. Fert. Conf.15:51-60.8. Schaeffer, R. J., and K. H. W. Klages. 1966. Nitrogen fertilizerimproves quality of hard red winter wheat in eastern Idaho. IdahoAgric. Expt. Sta. Bull. 461.9. Siddoway, F. H., H. C. McKay, and G. O. Baker. 1955. Review offertilizer situation on southern Idaho's drylands. Proc. 6th Ann.Fert. Conf. of Pac. N.W. 6:19-24.

Using yield and protein history from dryland fields to improve nitrogen fertilizer recommendations

Northwest Irrigation & Soils Research Laboratory Publications

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Using yield and protein history from dryland fields to improve nitrogen fertilizer recommendations

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