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Examining Corn Nutrient Uptake for Maximum Yield

19 May 2014

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Biotechnology, breeding, and agronomic advancements have propelled corn yields to new highs with little guidance as to how to fertilize these modern corn hybrids to achieve their maximum yield potential.


Fully-filled ears of corn—an indicator of successfully matching soil nutrient supply with crop demand.

Current fertilization practices, developed decades ago, may not match uptake capabilities of modern hybrids that contain transgenic insect protection now grown at population densities higher than ever before. A re-evaluation of nutrient uptake and partitioning can provide the foundation for fine-tuning our practices as we strive to achieve corn’s maximum yield potential.

As summarized by Bruulsema et al. (2012), optimizing nutrient management includes using the right source at the right rate, right time, and right place—the 4R approach. Research pertaining to primary macronutrient uptake, partitioning, and timing (Sayre, 1948; Hanway, 1962; Karlen et al., 1988), though fundamentally accurate for previous hybrids and management practices, may be unrepresentative of modern hybrids in higher yielding environments. The objective of this study was to determine how modern, transgenic insect-protected corn hybrids in high-yielding systems take up and utilize nutrients.

Nutrient contents of N, P, K, S, Zn, and B were determined at six incrementally spaced growth stages: V6 (vegetative leaf stage 6), V10, V14, R2 (blister), R4 (dough), and R6 (physiological maturity) (Hanway, 1963). Field experiments were conducted at the Northern Illinois Agronomy Research Center in DeKalb, Illinois and the Department of Crop Sciences Research and Education Center in Urbana, Illinois. A total of six hybrids ranging in relative maturity from 111 to 114 days were used with genetic resistance to feeding from Western Corn Rootworm (Diabrotica virgifera virgifera), European Corn Borer (Ostrinia nubilalis), and other species in the Lepidoptera order. In all cases, hybrids were seeded to obtain a fi nal stand of 34,000 plants/A. Representative plants were separated, analyzed, and evaluated in four tissue fractions: 1) stalk and leaf sheaths; 2) leaf blades; 3) tassel, cob, and husk leaves; and 4) corn grain, respectively referred to as stalk, leaf, reproductive, and grain tissues. Agronomic management at planting included a soil insecticide and a broadcast application of 150 lb P2O5/A as MicroEssentials® SZ™ along with 180 lb N/A as urea. This was followed by 60 lb N/A as Super-U (with urease and nitrification inhibitors) side-dressed at V6 and a fungicide at VT/R1 (tasseling/silking).

Nutrient Uptake and Removal

Across the two sites in 2010, these transgenic corn rootworm resistant hybrids yielded an average of 230 bu/A (range of 190 to 255 bu/A) and we will base our discussion of nutrient needs assuming this yield level.

When developing fertilizer recommendations, two major aspects of plant nutrition are important to understand and manage in high yield corn production including: 1) the amount of a given mineral nutrient that needs to be acquired during the growing season, referred to as “total nutrient uptake,” or nutrients required for production, and 2) the amount of that nutrient contained in the grain, referred to as “removed with grain” (Table 1). Our grain nutrient concentration values, in units of lb/bu (Table 1) are in agreement with those recently used by the fertilizer industry to determine replacement fertilizer rates (Bruulsema et al., 2012). In the past 50 years, however, the quantity of N, P, and K required for production and the amount of nutrients removed with the grain have nearly doubled across a variety of management systems used in the 1960s (Hanway, 1962).

Individual nutrient HI values were calculated, which quantify the percentage of total plant uptake that is removed with the grain. Nutrients with high requirements for production (N, P, K) or that have a high HI (P, Zn, S, N) allude to key nutrients for high yield (Table 1). In relation to total uptake for example, nearly 80 per cent of P is removed in corn grain compared to K and B, which are retained to a greater percentage in stover. For each nutrient, the fraction that is not removed with the grain remains in leaf, stalk, and reproductive tissues and constitutes the stover contribution that is returned to the fi eld. Production practices that utilize all or portions of aboveground stover (i.e. cellulosic ethanol, corn grown for silage) may remove an additional 20.8 lb N, 4.0 lb P2O5, 23.3 lb K2O, 1.9 lb S, 0.5 oz Zn, and 0.2 oz B per ton of dry matter.

Maximum Uptake Rates

Further improving fertility practices require matching in-season nutrient uptake with availability, a component of the right source applied at the right rate and right time. The maximum rate of nutrient uptake coincided with the greatest period of dry matter accumulation during vegetative growth (Figure 1) for all observed nutrients (Figures 2 to 7). Between V10 and V14, greater than one-third of total B uptake occurred, compared to the other nutrients which ranged from 20 to 30 per cent. During the V10 to V14 growth stages, corn required the availability of 7.8 lb N/day, 2.1 lb P2O5/day, 5.4 lb K2O/day, 0.56 lb S/day, 0.21 oz Zn/day, and 0.05 oz B/day. Fertilizer sources that supply nutrients at the rate and time that match corn nutritional needs are critical for optimizing nutrient use and yield.


Figure 1. Total maize dry matter production and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010).
GGDF = growing degree days (Fahrenheit)


Figure 2. Total maize N uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010).
GGDF = growing degree days (Fahrenheit)


Figure 3. Total maize P uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010).
GGDF = growing degree days (Fahrenheit)


Figure 4. Total maize K uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010).
GGDF = growing degree days (Fahrenheit)


Figure 5. Total maize S uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010).
GGDF = growing degree days (Fahrenheit)

Figure 6. Total maize Zn uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010).
GGDF = growing degree days (Fahrenheit)


Figure 7. Total maize B uptake and partitioning across four plant stover fractions: leaf, stalk, reproductive, and grain tissues. Each value is a mean of six hybrids across two site-years at Urbana, IL (2010) and DeKalb, IL (2010). GGDF = growing degree days (Fahrenheit)

Timing of Nutrient Uptake

Effectively minimizing nutrient stress requires matching nutrient supply with plant needs, especially in high-yielding conditions. Sulfur and N, for example, are susceptible to similar environmental challenges in the overall goal of improving nutrient availability and uptake. However, the timing of N uptake (Figure 2) in comparison to S (Figure 5) is surprisingly different, suggesting practices that are effective for one may not improve uptake of the other. Nitrogen uptake, unlike S, followed a more traditional sigmoidal (S-shaped) uptake pattern with two-thirds of the total plant uptake acquired by VT/R1. In contrast, S accumulation was greater during grain-filling stages with more than one-half of S uptake occurring after VT/ R1 (Figure 5). Potassium, like N, accumulated two-thirds of total uptake by VT/R1 (Figure 4). Interestingly, greater than one-half of total P uptake occurred after VT/R1 as well (Figure 3). These fi gures suggest that season-long supply of P and S is critical for corn nutrition while the majority of K and N uptake occurs during vegetative growth.

Unlike N, P, K, and S, which have a sigmoidal or relatively constant rate of uptake, micronutrients exhibited more intricate uptake patterns. Uptake of Zn and B, for example, began with a sigmoidal (S-shaped) uptake pattern in the early vegetative stages and plateaued at VT/R1 (Figures 6 and 7). Thereafter, Zn exhibited a constant uptake rate similar to that of P and S, while B uptake included a second major sigmoidal uptake phase concluding around R5 (dent). Zinc and B favored shorter periods of more intense uptake in comparison to macronutrients. During only one-third of the growing season, late vegetative and reproductive growth accounted for as much as 71 per cent of Zn uptake (Figure 6). A similar trend was noted for B; as much as 65 per cent of B uptake occurred over only one-fi fth of the growing season (Figure 7). Matching corn micronutrient needs in high-yielding conditions clearly requires supplying nutrient sources and rates that can meet crop needs during key growth stages.

Plant Nutrient Mobility

Unlike plant dry matter, specifi c nutrients possess mobility characteristics allowing them to be utilized in one tissue, then later transported (remobilized) and used in another (Sayre, 1948; Hanway, 1962; Karlen et al., 1988). For many nutrients, including N, P, S, and Zn, a large percentage of total uptake is stored in corn grain at maturity (Table 1). Nutrients with high HI values accumulated them from a combination of assimilation during grain fill (after VT/R1) and remobilization from other plant parts. Phosphorus, for example, accumulated more than one-half of total uptake after VT/R1 and remobilized a significant portion that was originally stored in leaf and stalk tissues (Figure 3). Nitrogen and S achieved similar HI values although through two different mechanisms. Post-flowering S uptake was the major source of grain S (Figure 5) compared to N, which was largely obtained from remobilization (Figure 2). Plant Zn exhibited a unique mobility characteristic in which stalk tissue served as a major, but temporal Zn source. By R6, nearly 60 per cent of stalk Zn was remobilized, presumably to corn grain. Similar to that of Karlen et al. (1988), leaf B content appeared to drop around VT/R1, indicative of its role in reproductive growth (Figure 7).

Optimization of Nutrient Management

Although nutrient management is a complex process, improving our understanding of uptake timing and rates, partitioning, and remobilization of nutrients by corn plants provides opportunities to optimize fertilizer rates, sources, and application timings. Unlike the other nutrients, P, S, and Zn accumulation were greater during grain-fill than vegetative growth; therefore, season-long supply is critical for balanced crop nutrition. Micronutrients demonstrated more narrow periods of nutrient uptake than macronutrients, especially Zn and B. As a percentage of total uptake, P was removed more than any other nutrient. In a corn-soybean rotation, it is commonplace in Illinois to fertilize for both crops in the corn production year. While farmers fertilize, on average, 93 lbs P2O5 for corn production (Fertilizer and Chemical Usage, 2011), the 80 per cent of soybean fields receiving no applied P would have only 13 lbs P2O5 remaining (Fertilizer, Chemical Usage, and Biotechnology Varieties, 2010). These data suggest a looming soil fertility crisis if adequate adjustments are not made in usage rates as productivity increases. This plant nutrition knowledge is critical in understanding our current nutrient management challenges.

Summary

As a result of improved agronomic, breeding, and biotechnological advancements during the last 50 years, yields have reached levels never before achieved. However, greater yields have been accompanied by a significant drop in soil macronutrient and micronutrient levels. The latest summary on soil test levels in North America by IPNI reported that an increasing percentage of US and Canadian soils have dropped to levels near or below critical P, K, S, and Zn thresholds during the last 5 years (Fixen et al., 2010). Soils with decreasing fertility levels coupled with higher yielding hybrids suggest that producers have not suffi ciently matched nutrient uptake and removal with accurate maintenance fertilizer applications. Integration of new and updated findings in key crops, including corn, will better allow us to achieve the fundamental goal of nutrient management: match plant nutritional needs with the right source and right rate at the right time and right place.

Acknowledgment

The authors wish to thank The Mosaic Company for their financial support of this research. This article is an excerpt from a research paper appearing in the Jan/Feb 2013 issue of Agronomy Journal.

References

Bruulsema, T.W., P.E. Fixen, and G.D. Sulewski. 2012. 4R Plant Nutrition Manual: A Manual for Improving the Management of Plant Nutrition, North American Version. International Plant Nutrition Institute, Norcross, GA, USA.

Fertilizer and Chemical Usage. 2011. National Agriculture Statistics Service, United States Department of Agriculture. Illinois Farm Report. 32:8.

Fertilizer, Chemical Usage, and Biotechnology Varieties. 2010. Bulletin As11091, Illinois Agricultural Statistics, National Agriculture Statistics Service, United States Department of Agriculture.

Fixen, P.E., T.W. Bruulsema, T.L. Jensen, R.L. Mikkelsen, T.S. Murrell, S.B. Phillips, Q. Rund, and W.M. Stewart. 2010. Better Crops 94(4):6-8.

Hanway, J.J. 1962. Agron. J. 54:217-222.

Hanway, J.J. 1963. Agron. J. 55:487-492.

Karlen, D.L. R.L. Flannery, and E.J. Sadler. 1988. Agron. J. 80:232-242.

Sayre, J.D. 1948. Physiol. Plant 23:267-281.

May 2014

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