Nutrient Uptake of Four Spring Wheat Varieties Grown Under Varying Nitrogen Stress

Study author(s): Daniel Kaiser, Albert Sims, Jochum Wiersma, and Apurba Sutradhar
Years of study: 2011 – 2014
Location(s): n/a

Important: for the complete report, including all tables and figures, please download using the link(s) to the right.

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SUMMARY OF MAIN POINTS

Uptake of macro- and micronutrients tend to follow similar patterns. However, some elements such as B and Cu appeared to delay their uptake until later in the growing season while K and Ca were found to be at maximum near Anthesis.
Tissue concentration in flag leaves declined over time for many elements. The greatest decrease was for P which was reduced to nearly half the amount contained at Anthesis at 20 days post Anthesis.
There was significant correlation between N and other elements, in particular micronutrients. The two other primary macronutrients, P and K, showed more independence from the uptake of N. Overall, sufficiency or deficiency of N could lead to lower concentration of other nutrients as indicated by plant tissue tests.
Varieties differed in their nutrient concentration and uptake over the growing season. There was no one variety that had consistently higher concentrations for all elements.
Nitrogen sufficiency level impacted the total uptake of other nutrients due to the impact of nitrogen on plant biomass production. Nutrient partitioning was not greatly impacted by the amount of nitrogen fertilizer applied to the soil.
The uptake of all nutrients followed a similar pattern with the lower fraction accumulating nutrients until around anthesis and then seeing a redistribution of nutrients to the developing reproductive structure until harvest or a loss of plant biomass later in the growing season even from the penultimate and flag leaf. Plant parts near the top of the plant (the flag leaf) exhibited less redistribution than older plant structures.
The total amount of nutrients at the end of the season in the head accounted for 40% or more of the total uptake for most nutrients except for K and Ca which had higher concentration in the stem and leaf fraction.

INTRODUCTION

Recent trends have been to utilize plant analysis for assessing nutrient status of fields to recommend fertilizer for the correction of hidden deficiencies. Plant analysis can be a useful tool for confirming nutrient deficiencies within fields. In most cases specific plant parts are used for plant analysis procedures. Additionally, most samples are taken when it is too late to apply fertilizer to correct nutrient deficiencies. Identifying when and where to use plant analysis is important to provide farmers with information how to use this management tool.

Plant varieties can differ in their growth patterns and potentially nutrient uptake at a specific time. Generally overall growth and nutrient uptake follow a similar pattern. Uptake is in typically consistent across a growing season, as plants grow and mature nutrient levels in specific plant parts can significantly change throughout the growing season. Identifying optimal nutrient concentrations is difficult if specific plant parts are not sampled. Also, plant stress caused by insects or drought can impact the nutrient status of plant tissues. In some circumstances plant tissue analysis could indicate a deficiency when the problem may only be temporal.

As farmers strive for higher yields they are looking for specific yield limiting factors that may not be apparent. Plant analysis is starting to be used to understand nutrient deficiencies that may not be display foliar symptoms. In order for this to be functional a database of plant nutrient concentrations needs to be built and correlated to crop yield response. This type of data has not been completed recently in Minnesota with current varieties. Also, data needs to be presented to show farmers the pitfalls of attempting to utilize plant analysis to make management decisions. Spring wheat typically has not been over fertilized for N, determining the effect of various rates of N on the nutrient status of other nutrients in the plant. Also, understanding the rate of nutrient uptake and partitioning within the plant is important to know when nutrients should be applied for maximum effect within a growing season.

Objectives

Study the uptake and partitioning of macro- and micronutrients in spring wheat.
Compare macro- and micronutrient uptake between four wheat varieties with varying yield and protein potentials.
Study the uptake of plant nutrients in wheat varieties in the presence of nitrogen stress.

materials and methods

The proposed study is an extension of a current project submitted by Drs. Albert Sims and Jochum Wiersma and funded by AFREC. This study consists of 4 hard red spring wheat varieties Faller, Glenn, Samson, and Vantage, which vary in their protein and yield potentials. Four nitrogen rates (0, 60, 120, and 180 lbs N/ac) were applied over each variety for a total of 16 variety x N rate combinations. Plant samples were collected started with sampling the entire plant at first node, at anthesis (flowering), 10 day post anthesis, 20 days post anthesis, and at maturity. Starting with the anthesis samples the whole plant samples were separated into different plant parts prior to analysis. These parts included the peduncle and head (HEAD), the flag leaf (FLAG LEAF), the penultimate leaf (2ND LEAF), and all the vegetative biomass from the lower section of the plant (LOWER). For simplicity, uptake of nutrients in the Flag Leaf and 2nd leaf were added to the lower fraction. The lower fraction consisted of all plant material except for the head.

The funded project analyzed samples for total N to determine uptake and partitioning of this nutrient for different varieties and the potential impact on grain protein. One full year has been conducted on the funded study with an additional year to be completed in 2011. Plant samples collected were dried, ground, and weighed. In addition sampling weight was recorded in order to determine the total nutrient uptake in terms of pounds per acre. This report includes data from the first two years of the N rate study. Analysis of the third year of data collected in the Sims and Wiersma study was approved for funding and will be analyzed and included in a final report for the three years of this study. Because not all of the data is yet run from the third year not all of the statistical analysis may be complete for this project looking at the full partitioning of nutrients over time.

results and discussion

Macro- and Micronutrient Uptake

Total uptake of macronutrients are given for phosphorus (P), potassium (K), calcium (Ca), Magnesium (Mg), and sulfur (S) in Figure 1 and Table 1 through 5. Data in Figure 1 summarizes across all varieties only for the average of the 60, 120 and 180 lb N rates. The date of sampling was converted to a growing degree unit since the actual dates sampled varied by year. Nutrient uptake was low early in the season and progressively increased until Anthesis. For potassium and calcium total uptake of these nutrients was at maximum by Anthesis. There was a small increase in Ca uptake for the 10 and 20 days post measurement but this was small compared to P, Mg, and S which did not maximize until the 20 days post Anthesis sampling.

Uptake curves for the micronutrients studied; boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) are given in Figure 2. The pattern of total uptake was similar for B, Mn, and Zn compared to P, S, and Mg. Manganese slightly differed from B and Zn in that it appeared to maximize total uptake earlier in development. Two of the nutrients, Fe and Cu, have been problematic to model. For Fe, the uptake at the earliest sampling data is high in relation to the anthesis sampling. This could be due to some contamination of the samples with soil particles. If soil is in the sample the iron in the soil would be picked up in the digestion and analysis. If this cannot be cleaned up we likely will have to analyze this data without this sample timing. The remaining points seemed cleaner and more closely followed the sigmoid relationship. The other problem nutrient was Cu. In this case there is a large decrease in the total uptake between the last two sampling dates. This drop is likely due to the loss of the leaves between the last two sampling dates. Since Cu is an immobile nutrient a decrease in the concentration and amount of Cu in the leaves would not be expected. Thus, if the leaves are lost a significant amount of Cu may be lost in the sample. We have been attempting to model the uptake of the nutrients to estimate the final concentrations that may be in the flag and penultimate leaves and the lower section of the plant. While the lower section was measured for the final sampling it included the nodes where the flag and penultimate leaves were located which were included with the leaf samples for the measurements taken at anthesis and 10 and 20 days after. Hopefully this can be cleaned up with the additional year of data.

Individual uptake by variety and N rate based on time of sampling are given in Tables 1 through 10 for each of those nutrients. One of the important questions we wanted to address is whether the rate of N significantly affected the uptake of nutrients and whether these affect varied by variety. In the tables the two main effects, variety and nitrogen rate, are summarized. If there was a significant interaction between variety and N rate (N rate response varied by variety) it was noted in the tables. For the most part even if the varieties differed there was no evidence of an interaction between variety and N rate. The only time the interaction was significant was for the early whole plant samples and harvest samples for K uptake. This indicates that while total uptake may vary the rate of uptake is consistent for the varieties. The main effect of nitrogen rates was significant for at least one of the sample timings for all nutrients. In general there were few differences of importance for the early whole plant samples. The main difference when significant came from the 60 lb N rate resulting in higher uptake of nutrients which is likely an effect of higher plant mass for some unexplained reason. This difference can be discounted as a result of random plot variability and for the most part there were few differences. For most elements, the 0 fertilizer rate differed from the other rates starting at anthesis and for some nutrients the 60 lb rate started to differentiate from the 0 and the 120 and 180 as development progressed. The 180 lb N rate typically resulted in the greatest uptake of nutrients and only differed from the 120 lb rate by harvest for Ca, S, and Mn. The only instances where all rates differed from the 0 control but not each other by harvest was for P, Fe, and Zn which indicates that the supply of N does affect the uptake of other nutrients.

Similar to N rate effects, the main effect of variety was significant for at least on sample timing for all of the nutrients sampled. While there is a significant amount of variation in the ranking of the varieties in total uptake by timing two things clearly stood out. First, there was seldom any effect of variety at the early whole plant stage. Since a small percentage of the total uptake occurs by this time it would make sense that the varieties would not fully differentiate from each other in terms of total uptake of nutrients. Second, the variety Glenn tended to have one of the lowest total uptake of elements at anthesis. In some cases, Glenn took up more nutrients in the 10 and 20 days post anthesis time period to give it one of the highest uptakes. Sulfur for instance (Table 5), Glenn had the lowest uptake at anthesis but ended with the greatest uptake 20 days later. A similar effect was seen for Cu (Table 7) where Glenn had the highest total uptake at Harvest. From the evidence it appears that Glenn may have a slightly higher uptake rate post anthesis than the other varieties.

N Rate Effects on Flag Leaf Tissue Concentrations

Flag leaf tissue concentrations were studied since they are the most likely plant part to be sampled during the growing season. Data for individual nutrients are summarized in Tables 11 through 20. For P, the concentration in flag leaves significantly decreased over time past Anthesis. Faller and Glenn tended to have the highest concentrations of P in the flag leaves over time versus Samson and Vantage. If sampling were delayed past Anthesis the tissue concentration would have been low if the same correlation data were used. There was no effect of N rate on flag leaf P concentration until 20 days post anthesis which was a marginal difference at best. This indicates that sampling beyond the recommended time frame can lead to possible low readings from P concentrations in flag leaves and that P concentration tends to remain relatively constant if other factors may be varied. For K, again Faller and Glenn tended to have the highest tissue concentrations over time. In all cases the K concentration in the flag leaves was considered sufficient. Nitrogen rate did influence the amount of K in the flag leaves. For the 10 and 20 day post Anthesis sampling the difference was between the 0 N rate and all others. For Ca, there was no effect of N rate or variety on Ca concentration in the tissue. Only Glenn differed from the other three varieties in tissue Mg concentration while N rate resulted in differences in Mg concentration for the first two sampling. Nitrogen rate affected tissue S concentration for all three of the timings, with the 180 lb N rate resulting in the highest concentration. Tissue S concentration only varied for Glenn, which was greater at the Anthesis sampling compared to the other varieties.

Flag leaf micronutrient concentration is summarized in Tables 16 through 20. There was no effect of variety or N rate on tissue B or Fe concentration. Leaf Cu concentration differed between varieties for the earliest sampling and for N rate only to the sampling 10 days post anthesis. Tissue Mn concentration varied by N rate for all three samplings and by variety for the first and last sampling only where Glenn and Samson tended to have higher concentrations of Mn than the other varieties. For Zn, the effect of variety and N rates were only significant for the first and last sampling. The middle sampling showed similar trends to the other two times but failed to reach statistical significance.

A summary of N rate effects on flag leaf tissue concentration for the anthesis and 10 and 20 day post samplings was averaged across variety and given in Figures 3 and 4. Each figure shows the sufficiency range that is relevant for the Anthesis samplings. No data is available for the later sampling dates. Macronutrient concentrations trended lower for the later samplings for P and K and were similar for Ca, Mg, and S. This follows closely to the mobility of nutrients in the plant and shows that nutrients are being drawn out of the flag leaf tissue as the grain is developing. All of the N rates resulted in sufficient levels of P, K, Ca, and Mg at Anthesis. However the 0 lb N rate resulted in a S concentration which would be considered low and the other rates were marginally sufficient. It should be noted that the samples were run with ICP. We currently are studying whether the ICP may give lower values than the methods used to initially establish the sufficiency levels. Therefore the range used may not be representative to the sufficiency of S in the flag leaves. For the micro-nutrients, only Mn and Zn showed any evidence of a decrease in concentrations later in the growing season. For the most part, all levels would be considered sufficient. However, B and Cu concentrations were at the low end of the sufficiency range for their respective ranges. The important message from this data is that the time of sampling is crucial when using a tissue concentration to establish the sufficiency of a particular element. Since data were developed based on a set sampling time, delaying the time of sampling could result in low levels in the tissue that are not related to a specific nutrient deficiency.

Relationship between Tissue N Concentration and Other Nutrients

Tables 21 through 23 summarize correlation coefficients between tissue nutrient concentrations for the flag leaves sampled around Anthesis. Within the tables, coefficients between -0.48 and 0.48 are not considered significant meaning the concentration are independent of each other. For the Anthesis sampling, there was a significant correlation with N for S, Ca, Mg, Fe, Mn, Cu, and Zn. In the case of P, K, and B, there was no correlation between these nutrients and N concentration in the plant. Similar relationships were seen up to 10 days post Anthesis. At 20 days post Anthesis the only two elements not related to N were Cu and B. At this time K and N concentration were related across varieties and P concentration was only significantly related to P for Samson and Vantage. Since this study focused on N the greatest differences in yield would be due to this nutrient. The correlation between other elements and N indicate that if N is considered deficient it is likely that other elements will be lower in concentration. They may not be deficient but the larger question is if multiple elements are considered low along with N would corrected the N deficiency also lead to increases in other nutrients or should they be applied. This alone is one of the difficulties interpreting sufficiency levels for plant analyses. While it is not guaranteed, correcting the larger deficiency alone may be enough to increase yield.

Nutrient Partitioning for the 180 lb N rate

Nutrient uptake was low early in the growing season for all wheat varieties evaluated in this study. Most nutrient uptake occurred during the period of pre-flowering stages. A common uptake pattern was observed for most nutrients in which acquisition of nutrients progressively increased over time until harvest. Tissue samples collected from anthesis to harvest were divided in to head and lower sections. In the head section, acquisition of all nutrients increased as the plant headed to maturity. Nutrient uptake patterns varied in the lower section of the plant. In most cases nutrient accumulation increased until 20 days post anthesis. Thereafter, uptake dropped sharply at harvest.

Phosphorus accumulation was greatest at anthesis in all wheat varieties (Figure 5). A total of 72- 77% of P uptake occurred during pre-flowering stages. After anthesis, uptake slowed down. Except for Samson, the amount of P uptake for other varieties from 10 days post anthesis to 20 days post anthesis was similar. The P uptake rate for Samson was 5% higher at 20 days post anthesis compared to 10 days post anthesis. Accumulation of P was slowest (< 7%) during the time of 20 days post anthesis to harvest. Overall, head section of the plant contained 88 to 91% of total P at harvest. These results suggested that most P was translocated to head section during grain development. All four varieties followed similar uptake patterns. The increase in P uptake as the growing season progressed attributed to greater dry matter accumulation and late reproductive developments. In the lower section of the plant, P accumulation spiked at anthesis and gradually decreased to its low at harvest. The reduction in the lower section is consistent with the increase rate in the head section which means most P transported to head at maturity.

Like P, most K, S, Ca, and Mg accumulation occurred during the vegetative growth stages. Total uptake of these nutrients ranged from 68-78% from the one node stage until anthesis. Potassium uptake decreased by 8% after anthesis until 10 days post anthesis and then increased by 17% at 20 days post anthesis. Potassium accumulation was higher (15-42%) in the lower section of the plant at harvest. Early vegetative growth stages are the critical time for K nutrition when demand is greatest. For S, Ca, and Mg, uptake rate increased up to 50% between the time of 10 days post anthesis and 20 days post anthesis. Most S and Mg accumulated in the head section of the plant while most Ca accumulated in the lower section of the plant at harvest.

Except Fe, most accumulation of micronutrients evaluated in this study occurred before anthesis. At anthesis, total accumulation of these nutrients ranged from 68 to 85%. Zn uptake gradually decreased in all varieties between anthesis and harvest stage. Among all micronutrients, Fe uptake at the earliest sampling data was higher in relation to the anthesis sampling. This could due to luxury consumption of Fe occur until when the plant was one node stage. It is more likely that the high Fe concentration early in the season was a result of contamination of the samples with fine soil particles that adhered to the plant tissue following cleaning. If soil was in the tissue samples the Fe in the soil would be picked up in the digestion and analysis. After one node stage, Fe uptake slowed down. From one node stage until anthesis, Faller and Samson accumulated 26 and 23% of total Fe, respectively. There was no Fe accumulation in Glenn and Vantage during this time of vegetative development. From anthesis Fe accumulation slowed until harvest in Faller. In Glenn, and Vantage, Fe uptake were higher at 20 days post anthesis compared to 10 days post anthesis and harvest. Manganese uptake increased at 20 days post anthesis in Faller but gradually decreased in the other varieties from anthesis to harvest.

Nutrient Partitioning for the 0 lb N rate

Seasonal uptake pattern for each of the nutrient for plots where no N fertilizer was applied are summarized in Figures 15 through 24. The variations in uptake were nutrient and variety specific associated with vegetative and reproductive growth stages. However, it should be noticed that most nutrients showed similar uptake patterns in all wheat varieties.

Nutrient uptake was low early in the growing season for all macronutrients. In the head section, accumulation of nutrients increased as the plants progressed from tillering (whole plant) through maturity. At harvest, the amounts of nutrients in the plant tissues were greatest for all wheat varieties. Nutrient uptake patterns were different in the lower section of the plant. Phosphorus uptake was higher at anthesis for Faller and Vantage while P uptake was higher at 10 days after flowering for Glenn and Samson. Potassium uptake spiked at anthesis in Faller, Samson, and Vantage. In Glenn, K uptake was highest at 20 days after flowering. Sulfur, Ca, and Mg uptake pattern in the lower section of the plant did not differ among timing and varieties. Most uptake of these three elements occurred 20 days after flowering. Nutrient uptake dropped sharply and reached their lowest values at harvest.

The apparent increase in post-flowering nutrient accumulation may be attributed to greater dry matter production during the late reproductive development and grain filling. While wheat growth and yield depend on season-long accumulation of P, S, and Mg, accumulation of K and Ca primarily occurred during vegetative growth stages. The magnitude of K and Ca accumulation in the head section were less than the accumulation in the lower part. The reduction of P, S, and Mg in the lower section is consistent with the increase rate in the head section which means most of these nutrients were transported to head at maturity.

Micronutrients accumulation varied considerably among plant parts, timing, and varieties. Overall Zn uptake was greater in the head compared to uptake in the lower section. In the head section, Zn accumulation was highest during harvest indicating that Zn was likely transported to head during grain filling period. In the lower section, Zn uptake was highest at anthesis in Faller and Vantage. In Glenn and Samson, uptake was higher from anthesis until 10 days post-anthesis.

Among all nutrients, early stage Fe uptake was higher relative to Fe uptake at other growth stages. This could be due to the luxury consumption of Fe occurred until when the plant was one node stage. It is also likely that the high Fe concentration early in the growing season was a result of contamination of the samples with fine soil particles that adhered to the plant tissue following cleaning. If soil was in the tissue samples the Fe in the soil would picked up in the digestion and analysis. In the head section, Fe accumulation progressively increased toward harvest from anthesis in all four varieties. In the lower section, most Fe accumulation occurred at 10 days after flowering in Faller, and 20 days after flowering in Glenn, Samson, and Vantage.

Manganese uptake varied depending on wheat varieties. In the head section, Mn uptake was greatest in Faller when samples were collected at 20 days after post anthesis. Manganese uptake was highest in Glenn and Samson during harvest. Manganese uptake was same at 20 days post- harvest sampling and during harvest in Vantage. In the lower section of the plant Mn accumulation was generally greatest at anthesis and lowest during harvest. Greater Mn accumulation was also observed from anthesis to 20 days post-anthesis to 20 days post-anthesis in Glenn and Samson.

Early uptake of Cu and B was very low and did not differ among varieties. The differences in nutrient uptake were very small between timing, plant parts, and varieties. In the head section, Cu accumulation was generally higher during harvest in all varieties except Vantage. In Vantage, Greatest accumulation of Cu in the head section occurred after 20 days of flowering. In the lower section, Cu accumulation was greatest at 20 days post anthesis. Boron uptake in the head part was greatest during harvest in all varieties. In the lower section, B accumulation was higher mostly 20 days after flowering.

When comparing data collected from the 180 lb N rates (Figures 5 through 14) to those of the 0 lb N rates, there was little effect of the rate of N on the relative uptake of P, S, Ca, Mg, Mn, Cu, and B. This indicates that uptake and translocation of these nutrients is relatively constant in spite of a deficiency of N. It should be noted that the total amount of these nutrients were less when 0 N was applied due to reductions in plant growth.

There were slightly differences that were noticeable for K, Zn, and Fe. For K, the primary difference occurred in the lower fraction where, starting at Anthesis, the amount of K decreased over time when 0 N was applied while it increased when 180 lb N was applied. A similar effect occurred for Zn. For Fe, there was a greater reduction in the amount of Fe in the lower fraction from the whole plant sampling taken at tillering to the lower fraction sampled at Anthesis. It is reasonable to assume that having less plant material would have a greater impact on contamination of Fe due to more raindrops hitting the soil surface due to less biomass coverage per unit area. In the end the three different responses were all minor and in the end we can assume that the overall partitioning of nutrients was not greatly impacted by the level of N applied.

Partitioning of the individual plant parts for the 180 lb N rate

Partitioning data were summarized only for the treatments with the highest rate of N (180 lbs). Nitrogen rate affected the total amount of nutrients taken up (not shown) but there was no evidence that there was a difference in the relative impact of nitrogen on the partitioning of nutrients among the four varieties. Data in Figure 25 and 26 summarize macro- and micronutrient uptake over time, respectively. Time is represented as the percent growing degree day (GDD) accumulation. Julian day and growing degree day were utilized but differences in planting date and GDD accumulation by year made it difficult to model the uptake of nutrients. The percent GDD accumulation normalized the data and made it possible to model the uptake of all nutrients for each plant fraction.

Data are partitioned out summarizing uptake for the lower stem and leaves (lower), penultimate leaf (2nd leaf), flag leaf, and the head (including grain). One challenge in summarizing this data was the lack of points collected before the first sampling. In most cases, the model used to predict uptake indicated a large increase in uptake until tillering in the lower fraction followed by a significant decrease in the amount of nutrients in the lower fraction as the head developed. The decrease in nutrient concentration in the lower fraction is likely due to remobilization of nutrients. A more gradual uptake of nutrient resembling a S shaped curve, similar to what is shown in Figures 1 and 2, would have been expected and likely would have occurred had additional sampling early and later in the growing season.

Nutrient uptake in the penultimate and flag leaves, and the lower fraction were estimated at the time the studies were terminated. The lower fraction was measured but any remaining penultimate and flag leaves were not separated from the stem fraction. This resulted in a greater total uptake of most nutrients in the lower fraction compared to the sampling 20 days post anthesis. Thus, the information provided for nutrient uptake at the end of the growing season is was calculated for all tissue samples except for the head fraction.

Total uptake of nutrients typically proceeded with the least total uptake in the lower fraction, followed by the penultimate leaf, the flag leaf, and finally the head fraction. The exception was for K and Ca was, at the end of the season, the total uptake into the head was less than the leaf fraction (Table 25). For the remaining nutrients, the head accounted for 40% or greater of the total uptake of nutrients by the end of the growing season. The greatest partitioning of nutrients occurred for P, Mn, and Zn where 60% or more of the total uptake occurred in the head. In most cases the uptake of nutrients in the head was linear indicating that nutrients were still being taken up or partitioned into the head until the end of the growing season. There was no evidence that the uptake of nutrients in any of the lower or leaf fractions continued to increase over time except for B which showed linear increases over time for all plant fractions.

conclusions

Uptake of macro- and micronutrients tend to follow similar patterns. However, some elements such as B and Cu may delay their uptake until later in the growing season while K and Ca were found to be at maximum near Anthesis. Tissue concentration in flag leaves tended to decline over time for many elements. The greatest decrease was for P which was nearly half the concentration 20 days post Anthesis. When sampling plant tissue such as wheat, taking a sample at the proper time is key in order to get the best data from the sample taken. There was significant correlation between N and other elements, in particular micronutrients. At or 10 days after Anthesis concentrations of P and K were independent, but were correlated at 20 days post Anthesis. Varieties did differ in their nutrient concentration and uptake over the growing season. There were no varieties that had consistently higher concentrations for all elements. If varieties do significantly differ in their uptake on nutrients gathering tissue concentration data across many locations will be needed in order to determine if the differences is due to the location and conditions at that location or due to the varieties themselves.

Nitrogen sufficiency level impacted the total uptake of other nutrients due to the impact of nitrogen on plant biomass production. Nutrient partitioning was not greatly impacted by the amount of nitrogen fertilizer applied to the soil. While the plant may exhibit luxury uptake of some nutrients, this luxury uptake is relative to the total overall uptake and redistribution of nutrients by the plant. The uptake of all nutrients followed a similar patter with the lower fraction accumulating nutrients until around anthesis and then seeing a redistribution of nutrients to the developing reproductive structure until harvest or a loss of plant biomass later in the growing season. Plant parts near the top of the plant exhibited less redistribution than older plant structures. Boron is the only nutrient where uptake appeared to be constant to all plant parts across the entire growing season. The total amount of nutrients at the end of the season in the head accounted for 40% or more of the total uptake for most nutrients except for K and Ca.

acknowledgements

The authors would like to thank the Minnesota Agricultural Fertilizer Research and Education Council for the support of this project. We would also like to thank our cooperators for their current and future support on the project along with the crop consultants which also were instrumental in helping locate and establish the trials. We also would like to thank the field crew from the Department of Soil, Water, and Climate for their technical support on the research project.