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Nutrient Sufficiency Concepts for Modern Corn Hybrids: Impacts of Management Practices and Yield LevelsIgnacio A. Ciampitti* and Tony J. Vyn

AbstractOver the last 70 years, national corn yield gains have occurred because of superior genetic yield potentials and management improvements such as improved water management, higher plant densities, and earlier planting dates. Some management recommendations, such as those from seed companies that promote optimum plant densities, are often environment, hybrid, and/or yield-range specific. Nitrogen rate recommendations for corn are updated annually in the Corn Belt states and are sometimes adjusted for regions or soil zones within a state. In contrast, nutrient guidelines for nutrients other than N are assumed to be constant per unit of yield produced, and have generally not been updated in key corn-producing states. Some recent studies providing nutrient content values for corn grain and/or stover did not account for management practices and yield levels for which nutrient replacement recommendations would be pertinent. The purpose of this report is to illustrate how macro- and micronutrient contents for modern corn hybrids can change in the context of diverse plant densities, N rates, and accompanying yield range influences in certain environments. The information presented here can be used to better understand nutrient content and removal for more precisely implementing best nutrient management practices for current corn hybrids at diverse yield ranges.

Optimum nutrient management (recently popularized as using the “4Rs” approach involving selection of right rate,

time, placement and source [IPNI, 2012]) should be pursued to increase corn yields in a sustainable manner. Current nutrient management decisions for nutrients other than N are typi-cally based on publicly available information that may be more pertinent for corn hybrids and management in earlier decades (Chandler, 1960; Hanway, 1962a, 1962b; Jordan et al., 1950; Karlen et al., 1987, 1988; Sayre, 1948), although there have been some more recent recommendations for specific nutri-ents (Bundy, 2004; Fernández, 2012; Sawyer and Mallarino, 2007). Total plant nutrient content or grain nutrient removal calculations are now based on constant nutrient concentration

Published in Crop Management DOI 10.2134/CM-2013-0022-RS © 2014 American Society of Agronomy

and Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

I.A. Ciampitti, Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506, and T.J. Vyn, Agronomy Dep., Purdue Univ., West Lafayette, IN 47906. Received 18 Sept. 2013. *Corresponding author (ciampitti@ksu.edu).

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assumptions that may not be accurate. This report will illustrate the changing plant nutrient requirements/removals in corn at different yield levels resulting from varying plant density and N rate management systems in certain recent Indiana studies.

FIELD STUDIESNutrient content was determined six times during the growing season, corresponding with V5, V10, V15, R1, R3, and R6 growth stages as defined by Hanway (1963). Four field experiments were conducted with conservation-till corn following no-till soybean in west- and north-central regions in Indiana (West Lafay-ette, and Wanatah, respectively) (Ciampitti and Vyn, 2013; Ciampitti et al., 2013). Two Mycogen triple-stack hybrids (2T789 and 2M750) were evaluated with simi-lar characteristics (comparative relative maturity at 114 days) under three seeding rates to obtain a final plant density of 22,000; 32,000; and 42,000 plants (pl)/A, and with three fertilizer N rate levels to promote different N supply scenarios: 22N, 100, and 200 lbs/A. The sole N source employed was urea–NH4NO3 (UAN, 28–0–0). All treatments received 22 lbs N/A (10–34–0 or 19–17–0 as N– P2O5–K2O) as banded starter fertilizer at planting. The remainder of the N application rate was delivered

as sidedressed UAN at about the V6 growth stage. Plot sizes were six rows, 15 ft wide (30-inch row spacing) and 105 ft in length. Pest management was implemented as needed to avoid any confounding effect from weeds, dis-eases, and insects. Soil pH (which ranged from 5.8 to 6.5 units), available P (>33 mg P kg-1), exchangeable K (>112 mg P kg-1), and all micronutrient concentrations were well above critical levels; thus, those nutrients were not expected to constrain crop productivity (Ciampitti and Vyn, 2013; Ciampitti et al., 2013).

The experimental design was a split-split-plot with six replications (blocks). At each specific site-year, the factors evaluated were hybrid (main-plot), plant density (PD; sub-plot), and fertilizer N rate (sub-sub-plot). The site, years, and all treatment factors (hybrid, PD, and N rate) were used as fixed factors because the utilization of only two sites and two years were not sufficiently comprehensive to accurately conclude that these factors were random. Blocks within each experiment were considered as a ran-dom factor. For yield, biomass, and total plant nutrient concentrations, an ANOVA was performed using SAS PROC MIXED (SAS Institute, 2004) (Table 1). The main factors were the PD and N rate (due to the minor hybrid effect; Ciampitti and Vyn, 2013) and its interaction.

Table 1. Grain yield (15.5% moisture) from combine harvest (bu/A), total plant biomass (lbs/A), and total plant nutrient concentration (%, g nutrient per 100 g dry matter [DM]) at maturity across two maize hybrids grown at three plant densities (PD) and N rate (Nr) levels across two locations (at Pinney-Purdue Agricultural Center and Purdue University Agronomy Center for Research and Education) and two growing seasons (2010 and 2011).

Plant nutrient concentration N rates Yield Biomass N P2O5 K2O S Zn Mg

bu/A lbs/A ––––––––––––––––––––––––––––––%––––––––––––––––––––––––––––––Low PD (22,000 pl/A)

22N 123 13,712 0.89 0.55 1.13 0.08 0.22 0.22100N 175 17,039 1.03 0.55 1.06 0.09 0.18 0.18200N 197 18,898 1.20 0.60 1.08 0.10 0.17 0.17

Medium PD (32,000 pl/A)

22N 109 14,380 0.87 0.57 1.22 0.08 0.22 0.22100N 168 17,889 0.97 0.57 1.13 0.08 0.16 0.16200N 210 20,536 1.13 0.55 1.05 0.09 0.15 0.15

High PD (42,000 pl/A)

22N 97 14,962 0.87 0.53 1.19 0.08 0.21 0.21100N 164 19,094 0.94 0.50 1.16 0.08 0.16 0.16200N 199 20,728 1.12 0.53 1.12 0.09 0.15 0.15

ANOVAPD *** * * ns ns ns ns ns

N rate *** *** *** ns ns ** ** **PD ´ N rate *** ns† ns ns ns ns ns ns

*Significant at the 0.05 probability level.

**Significant at the 0.001 probability level.

***Significant at the 0.0001 probability level.†ns = not significant (P > 0.05).

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NUTRIENT CONTENT DYNAMICS (IN RECENT INDIANA RESEARCH)In this paper, we will adapt selected information recently published (Ciampitti and Vyn, 2013; Ciampitti et al., 2013) to outline new approaches to determination of nutrient sufficiency for modern hybrids. The focus of this article is on a single PD level since grain yield was maxi-mized at the normal PD (32,000 pl/A) and total plant biomass and N uptake did not substantially differ among the plant density levels evaluated (Table 1). At normal PD (32,000 pl/A) with optimum N supply (200 lbs N/A), corn grain yield averaged 210 bu/A across four site years (i.e., average of 203 bu/A with Mycogen 2M750 and 217 bu/A for Mycogen 2T789). Starter fertilizer N was applied at a rate of 22 lbs N/A for all treatments. For this article, the 22N treatment received 22 lbs N/A as a starter; while the 100N and 200N treatments received 78 and 178 lbs N/acre as a side-dress N fertilizer application. When no side-dress N was applied (22N), grain yield averaged 100 bu/A less than under optimum N (i.e., yields of 109 bu/A with 22N), while yield was also reduced by 40 bu/A when an intermediate fertilizer N rate (100 lbs N/A) was employed (i.e., mean yield of ~168 bu/A). Nutrient content dynamics were tightly linked to the final plant biomass and yield levels (Table 1; Fig. 1) attained at each specific N rate (ranging from 109 to 210 bu/A for the 22N to 200 lbs N/A levels at the intermediate plant density of 32,000 pl/A).

Corn biomass accumulation was rapid from early vegetative (V5 stage) to early reproductive (R3 stage) during the growing season. The N rate factor signifi-cantly influenced total plant biomass accumulation and N uptake from V10 towards the end of the season. The effect of sidedressed N was already evident at a mid-veg-etative growth stage (V10) (yellow-blue vs. red lines) with progressively more biomass as the crop season advanced. The advantage in biomass gain between the highest (200N) versus the intermediate (100N) N scenarios was more obvious at flowering time (R1 stage), but was espe-cially reflected in greater biomass accumulation during the reproductive period. Across all N rates evaluated, 56% of the total biomass was accumulated during the vegetative period before flowering (R1) with 44% accu-mulated during the reproductive period relative to the total biomass attained at the end of the crop season.

The rate of uptake, the total amount of each nutrient at each growth stage, and the proportion of total uptake at the time of flowering (timing) were greatly influenced by the N rate applied. The effect of better N nutrition was already reflected early in the season (from V5 onward), with higher N content with 200 lbs N/A as compared with both the 100 and 22 lb N rates. From V15 towards maturity, the plant N uptake ranking was unmodified, with a significantly greater N uptake for 200N > 100N > 22N (Fig. 1). Across the three N rates, approximately 71% of total N was accumulated before flowering. The highest

Figure 1. Biomass and nutrient content during the corn growing season under a normal plant density level (32,000 pl/A) and three N rates (22, 100, and 200 lbs/A) across two hybrids, two sites, and two years. The arrows for each panel indicate the average flowering time across N rates. Percentages are proportions (averaged across three N rates) of vegetative-stage nutrient contents relative to total contents at maturity. (Ciampitti et al., 2013; Ciampitti and Vyn, 2013).

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N rate helped to sustain a greater N content during the reproductive period (yellow lines; Fig. 1) as compared to both the intermediate (100 lbs N/A) and low N (22 lbs N/A) levels (blue and red lines). Therefore, the highest N rate promoted higher grain yield, biomass, and total N content mostly because of accumulating more mass and N after flowering.

The timing and quantities of whole-plant uptake for nutrients other than N were also impacted by N rates. Phosphorus (P), S, K, Zn, and Mg accumulations during the reproductive period were much higher with the 200 lbs N/A as compared with lower N rates (Fig. 1). For K and S, a clear separation in nutrient uptake among N rate levels (ranking 200N > 100N > 22N) was documented from V10 onward; while for P, the N rate influence was evident from V15 towards maturity. For Zn and Mg, the N rate effect was delayed until flowering (R1) but then it also persisted until the end of the season (R6, maturity). In terms of the timing of nutrient uptake, S followed a very similar pattern as reported for biomass, with 58% of S accumulated before flowering. Phosphorus and Zn were quite similar in overall timing of nutrient content, with 45% of P and Zn being taken up before flowering; while the Mg content pattern was similar to that observed for N since 71% was taken up before flowering. However, corn plant K content timing was much different; 90% of all plant K content occurred before flowering.

Higher plant densities (ranging from 22,000 to 42,000 pl/A) promoted more nutrient content before flowering but, as presented below, there was very little change in whole-plant nutrient content at maturity for the three plant densities evaluated across hybrids, N rates, and environments (Table 1).

WHOLE PLANT NUTRIENT CONTENT REQUIREMENT AT DIVERSE YIELD LEVELSThe information related to the whole-plant nutrient con-tent needed per unit of yield produced can complement existing diagnostic tools to predict fertilization needs and more precisely define the right rate to be applied for a target yield level in a specific environment. In most of the scientific papers and extension reports, simple mean values are reported as a constant nutrient content require-ment per unit of crop yield (Bundy 2004; Fernández, 2012; Sawyer and Mallarino, 2007; Vitosh et al., 2000). Although those values can be useful from a practical viewpoint, more science-based information including the nutrient requirements of current hybrids could be used in preci-sion agriculture technologies to help produce more valid variable rate fertilizer maps. The key issue is whether those crop nutrient requirements change across diverse yield levels and, if so, what is the direction of change (e.g., do specific nutrient requirements increase or decrease as yields change?). Information from our published papers (Ciampitti and Vyn, 2013; Ciampitti et al., 2013) were used to demonstrate the patterns for corn plant content of N,

P, K, and S nutrients at progressively higher yield levels in response to management practices (Fig. 2).

Whole-plant nutrient content of N, P, K, and S per unit of yield increased rather substantially in these genetic/environment/management situations as total crop grain yield improved. For example, crop nutrient requirement of N increased from 0.4 to 1.3 lbs N/bu within a yield range from 87 to 299 bu/A (with comparable threefold variations for plant N and corre-sponding yields). However, plant Zn and Mg content per unit of grain was relatively unchanged (Fig. 2). The main changes in crop nutrient requirement documented for N, P, K, and S are related to major changes in total plant and grain mass as yields improved (e.g., under diverse N rates; Table 1), while for Zn and Mg improvements in yield were accompanied by overall declining plant nutrient concentrations (Table 1), resulting in a general unchanging crop nutrient requirement throughout the diverse yield ranges explored (Fig. 2).

Consultants or agronomists often use the mean nutrient requirement value (e.g., more specifically for N) obtained from public or private research institutions to calculate the amount of nutrient needed for a specific yield target. Available soil nutrient levels need to be determined first, but a common nutrient management strategy is to maintain given soil P, K, and S nutrient levels by replac-ing nutrients removed in the harvested grain. Estimation of the nutrients removed is usually based on a common mean grain nutrient concentration, but this approach is not valid if grain nutrient concentrations vary with yield levels. Table 2 compares corn nutrient requirements based on a “constant approach,” to replace nutrient removal in grain using a mean value for N, P, and K whole-plant nutrient content from recent literature (Bender et al., 2013) (overall corn yield of 230 bu/A) versus a yield-specific approach estimated from values presented in Fig. 2.

The assumptions of constant nutrient removal rates of 1.11 lbs N/bu, 0.44 lbs P2O5/bu, and 0.78 lbs K2O/bu that are consistent across yield levels (Bender et al., 2013) were employed to calculate the nutrient requirement at diverse yield levels (Table 2). In the “variable approach” data from Fig. 2 was also used to estimate nutrient requirements in the same yield range levels. At certain intermediate yield levels, both approaches provide similar estimations of whole-plant nutrient contents for N, P, and K (Table 2). Nonetheless, below and above these yield ranges, the “constant approach” overestimated and underestimated nutrient content for low and high yields, respectively. The relative variation between the two methods for estimating crop nutrient requirement seemed to be largest for N and K and smallest for P.

In summary, corn at diverse yield levels can, in certain cases, require quite different nutrient content quantities per unit of yield for N, P, K, and S, but probably not for Mg and Zn. Farmers, consultants, and agronomists should acknowledge that high-yielding cropping systems may result in a substantially higher demand for some nutrients than those estimated by a “constant approach,” and that

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the proportional nutrient requirement change may not be a simple and stable constant for all major- and micronu-trients per unit of yield change. The “constant approach” tends to overestimate the total plant N requirement per unit of yield under more yield ranges (from 87 to 207 bu/A) as compared to the “variable approach”. For P and K, the “constant approach” also overestimated nutrient removals, but across a smaller yield range (<150 bu/A for P and <110 for K). However, the use of the “constant approach” tends to underestimate total plant nutrient needed per unit of yield for N under high-yielding corn environments (>210 bu/A) and under diverse yield ranges for P and K (Table 2). Management research, like that described above, should

be conducted in many additional environments with other hybrids, soil test nutrient concentrations, and weather conditions. Nevertheless, results from these sites suggest that producers in high yield corn systems may need to alter requirement assumptions for specific nutrients whose total plant nutrient content is more likely to be “yield responsive.”

GRAIN NUTRIENT REMOVALEstimation of nutrient quantities removed in the grain has often been used to estimate nutrient replace-ment rates on individual fields, or portions of fields, to maintain soil test levels. Grain nutrient removal is the

Figure 2. Whole-plant nutrient content per unit of yield, expressed in lbs/bu, under diverse yield ranges (expressed in 15.5% moisture, bu/A) produced at the end of the crop season across plant density, N rate, hybrid, sites, and years. The upper and lower ends of the boxes for each nutrient displays the first and third quartiles, the horizontal line represents the median for each plant nutrient uptake per unit of yield ratio, and the ends of the whiskers portrays maximum and minimum boundaries for the entire dataset evaluated in each specific yield range level. The values presented above each box, under each specific yield range, represent the median whole-plant nutrient content per unit of yield (lbs/bu). The numbers in parentheses refer to the individual number of data points collected from each individual yield range (total observations were 216 points) (Ciampitti et al., 2013; Ciampitti and Vyn, 2013).

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outcome of new nutrient content during the reproduc-tive period and nutrients that are remobilized from other plant structures (such as leaf and stem organs). The coef-ficient that has the most impact on the amount of nutri-ent present in the grain compared to the whole-plant nutrient content is the nutrient harvest index (HI). In our research, nutrient HIs displayed higher efficiency at normal plant density than at high density even though high densities can increase overall content of some nutri-ents (such as N and K; Table 3). From the plant nutrient content perspective, N and K are the two most abundant nutrients needed for corn hybrids but they differ consid-erably in timing of nutrient uptake (Fig. 1) as well as in the final nutrient HI. In terms of efficiency, P, S, N, and Zn (in that order) reflected the highest nutrient HIs with more than 58% of total plant content being removed in the grain. In contrast, less than a third of the plant K content is removed in the grain. Grain nutrient removal (lbs/bu) was very similar across plant densities (Table 3). Overall nutrient removal values seemed to be more related to the yield than to any particular influence of the diverse density or N rate management treatments evalu-ated in this research project.

Nutrient removals for P2O5 and K2O shown in Table 3 are above the standard values previously docu-mented by Vitosh et al. (2000). The latter outcome seems

to be a consequence of the higher yields explored in this research project, but may be associated with other genetic changes over time and the expected interac-tions with the environments and management practices employed. Ideally, similar research resulting in a wide range of actual yields within experiments should be undertaken with a broader range of current commer-cial hybrids and in diverse production environments. Average nutrient removal values in certain production regions may need to be updated to fairly reflect yield improvements experienced at the cropping system level. Nevertheless, as documented for the whole-plant nutri-ent requirement (Table 1), nutrient removals presented in Table 3 may be most accurate as reference values in the 200 to 210 bu/A yield range.

SUMMARYFrom a practical viewpoint, nutrient fertilizer recom-mendations at the state (or multi-state) level could be improved if more nutrient content and harvest index information from applied research studies are sum-marized using modern hybrids under varying yield ranges. Three main points are noteworthy from this investigation: (i) high-yielding cropping systems may require more whole-plant nutrient content (with empha-sis on N, P, K, and S nutrients) per unit of yield (thus

Table 2. Whole-plant nutrient (e.g., N, P, and K nutrients) content as related to the yield level calculated using two different approaches with constant crop nutrient requirement compared with the “observed” data collected from recent Purdue University research (Ciampitti et al., 2013). For the “variable approach,” the values within parenthesis represent one standard deviation from the mean crop nutrient requirement obtained from Fig. 2.

Whole-plant nutrient content related to the yield levelN P2O5 K2O

Nutrient/mean yield

Constantapproach

Variableapproach

Constantapproach

Variableapproach

Constantapproach

Variableapproach

–––––––––––––––––––––––––––––––––––––––––––––lbs/A–––––––––––––––––––––––––––––––––––––––––––––87† 97† 37†

(33, 42)38† 27†

(22, 32)68† 52†

(38, 65)

108† 120† 54†

(49, 59)48† 37†

(30, 43)84† 75†

(61, 90)

148† 164† 98†

(85, 111)65† 56†

(44, 68)115‡ 119‡

(91, 148)

175† 194† 138†

(115, 161)77‡ 77‡

(57, 97)137§ 170§

(130, 210)207† 230† 199†

(171, 228)91§ 102§

(82, 122)161§ 189§

(150, 228)238‡ 264‡ 259‡

(232, 287)105§ 121§

(95, 147)186§ 235§

(192, 279)

271§ 301§ 324§

(296, 352)119§ 166§

(133, 200)211§ 373§

(325, 421)

299§ 332§ 399§

(375, 423)132§ 178§

(133, 223)233§ 411§

(342, 481)†The “constant approach” recommends a greater whole-plant nutrient content relative to the “variable approach.”‡Both approaches predict very similar nutrients contents.§The “constant approach” underestimates nutrient content relative to the “variable approach.”

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demonstrating a less than proportional yield-nutrient content relationship); (ii) the primary impact of man-agement practices such as plant density and N fertilizer rates on the dynamics of corn plant nutrient content was attributed to the cropping system influence on bio-mass production and yield levels; and (iii) actual grain yield level appeared to be the main factor defining grain nutrient contents (because of both higher grain nutrient concentrations and higher nutrient HI for some nutri-ents), and thus the nutrient removal rates. Because, for some essential nutrients, whole-plant nutrient content increases with biomass production, ensuring adequate nutrient supplies for modern hybrids may benefit from the use of integrated decision aids such as the prelimi-nary “variable approach” proposed here.

Considerably more information is still required, but using this data to better understand nutrient content and removal may assist in implementing, in a more precise manner, the best management practices for fertilizer and nutrient management to help meet needs of modern corn hybrids at a wide range of yield levels.

AcknowledgmentsFunding was primarily provided by Dow AgroSciences and supplemented by the USDA National Institute of Food and Agriculture (NIFA award no. 2010-85117-20607), the Purdue Bilsland Dissertation Fellowship, and the Potash Corporation. The Mosaic Company provided special funding for the data analyses and interpretation on comparative nutrient evaluations beyond N alone. We express our thanks to numerous graduate students, visiting scholars, field technicians, research agronomist, and volunteers for their extensive help in both the field and laboratory.

ReferencesBender, R.R., J.W. Haegele, M.L. Ruffo, and F.E. Below. 2013. Nutrient

uptake, partitioning and remobilization in modern, transgenic insect-protected maize hybrids. Agron. J. 105:161–170. doi:10.2134/agronj2012.0352

Bundy, L.G. 2004. Corn fertilization. Ext. Bull. A3340. Online. Univ. of Wisconsin-Ext, Madison, WI.

Chandler, W.V. 1960. Nutrient uptake by corn in North Carolina. Tech. Bull. 43. North Carolina Agric. Exp. Stn., Raleigh.

Ciampitti, I.A., and T.J. Vyn. 2013. Maize nutrient accumulations and partitioning in response to plant density and nitrogen rate: II. Calcium, magnesium, and micronutrients. Agron. J. 105:1645. doi:10.2134/agronj2013.0126

Ciampitti, I.A., S.T. Murrell, J.J. Camberato, and T.J. Vyn. 2013. Maize nutrient accumulations and partitioning in response to plant den-sity and nitrogen rate: I. Macronutrients. Agron. J. 105:783–795. doi:10.2134/agronj2012.0467

Fernández, F.G. 2012. Nutrient removal rates of new hybrids and variet-ies. Agronomy Day 2012: 56th Annual Agronomy Day, 16 Aug. 2012, Univ. of Illinois, Urbana-Champaign. Urbana, IL. p. 22–23.

Hanway, J.J. 1962a. Corn growth and composition in relation to soil fertil-ity: II. Uptake of N, P, and K and their distribution in different plant parts during the growing season. Agron. J. 54:217–222. doi:10.2134/agronj1962.00021962005400030011x

Hanway, J.J. 1962b. Corn growth and composition in relation to soil fertil-ity: III. Percentages of N, P, and K in different plant parts in relation to stage of growth. Agron. J. 54:222–229. doi:10.2134/agronj1962.00021962005400030012x

Hanway, J.J. 1963. Growth stages of corn (Zea mays L.). Agron. J. 55:487–492. doi:10.2134/agronj1963.00021962005500050024x

IPNI. 2012. 4R Plant Nutrition: A manual for improving the management of plant nutrition. International Plant Nutrition Institute. IPNI, Peachtree Corners, GA.

Jordan, H.V., K.D. Laird, and D.D. Ferguson. 1950. Growth rates and nutrient uptake by corn in a fertilizer-spacing experiment. Agron. J. 42:261–268. doi:10.2134/agronj1950.00021962004200060001x

Karlen, D.L., R.L. Flannery, and E.J. Sadler. 1988. Aerial accumula-tion and partitioning of nutrients by corn. Agron. J. 80:232–242. doi:10.2134/agronj1988.00021962008000020018x

Karlen, D.L., E.J. Sadler, and C.R. Camp. 1987. Dry matter, nitrogen, phosphorus, and potassium accumulation rates by corn on Norfolk loamy sand. Agron. J. 79:649–656. doi:10.2134/agronj1987.00021962007900040014x

SAS Institute. 2004. SAS/STAT 9.1 user’s guide. SAS Inst., Cary, NC.Sayre, J.D. 1948. Mineral accumulation in corn. Plant Physiol. 23:267–281.

doi:10.1104/pp.23.3.267Sawyer, J., and A. Mallarino. 2007. Nutrient removal when harvesting

corn stover. Online. Univ. Ext. Iowa State Univ., Ames.Vitosh, M.L., J.W. Johnson, and D.B. Mengel. 2000. Tri-state fertilizer rec-

ommendations for corn, soybeans, wheat and alfalfa. Online. Ext. Bull. E-2567. Michigan State Univ. Ext., East Lansing, MI.

Table 3. Total whole-plant nutrient content, grain nutrient content, nutrient harvest indices, and nutrient removal coefficient (grain nutrient content to grain yield ratio) at normal (32,000 pl/A) and high (42,000 pl/A) plant density levels at the highest fertilizer N rate applied (200 lbs/A) across all environments evaluated. Grain yields were 210 bu/A under normal density and 200 bu/A with high density.

Plant nutrient content

Grain nutrient content Harvest index Nutrient removal

“Tri-state”†

removal

Plant density

Nutrients Normal High Normal High Normal High Normal High

––––––––––––––––––lbs/A–––––––––––––––––– –––––––%––––––– ––––––––––––––lbs/bu––––––––––––––

N 232 233 148 142 64 61 0.70 0.71 –

P2O5 115 108 96 87 83 81 0.46 0.44 0.37

K2O 217 233 71 67 33 29 0.34 0.34 0.27

S 19 18 12 11 65 63 0.06 0.06 –

Zn 0.48 0.48 0.3 0.3 60 58 0.001 0.001 –

Mg 31 30 15.2 13.5 49 45 0.07 0.07 –†Vitosh et al. (2000).