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Nitrogen Removal by Delaware Crops

March 2024 | Written by: Amy L. Shober

 

 

Introduction

Effective nutrient management minimizes nutrient losses to the environment while maximizing the crop nutrient uptake. Valid numbers for all nutrient inputs and outputs are required to most effectively manage nutrients in agronomic and vegetable crop systems. The amount of nitrogen (N) removed by the harvested portion of the crop is needed to develop nutrient balances. However, N removal by crops can vary considerably from field-to-field and year-to-year. The purpose of this document is to provide average values of N uptake for common Delaware grain, forage, and vegetable crops for use in nutrient management planning activities. 

 

What is “Crop Nutrient Removal”? 

Crop nutrient removal is defined as the total amount of nutrients removed from the field in the harvested portion of the crop (e.g., grain, silage, hay). The term crop nutrient removal should not be confused with crop nutrient uptake, which is defined as the total amount of nutrients contained in the entire crop at maturity. For example, this would include N in the grain, stover, and roots of a corn crop. Crop nutrient removal is lower than crop nutrient uptake because a significant percentage of the nutrients taken up by a crop are returned to the soil in the form of crop residues. Nutrients remaining in crop residues are subsequently available for uptake by crops planted in the next season. 

 

Determining Crop Nitrogen Removal for Delaware Crops 

Removal of N by crops can be estimated using standard values for the N content in the harvested portion of the crop and crop yield. The USDA Natural Resources Conservation Service (NRCS) Crop Nutrient Uptake Tool (part of the PLANTS Database at https://plants.usda.gov/) provides standard values for estimating N removal for Delaware crops. However, the most accurate way to determine crop N removal is to have a representative sample of the harvested portion of the crop analyzed for N content. Analyzing crop samples for nutrient removal is different from routine plant tissue analysis, which is used to monitor the nutrient content of a crop or to identify nutrient deficiency or toxicity. For example, a subsample of the harvested grain that is collected from the combine or weigh wagon after yield determination is analyzed for N content to quantify N removal at harvest. In contrast, analysis of ear leaf samples collected at initial silking is useful to monitor corn nutrient content during the growing season. For vegetable crops, the use of standard values for N content may be preferable to harvested tissue analysis due to the difficulty encountered when trying to dry vegetables. Because of their high water content, a freeze drier is often required to prevent the vegetable samples from rotting during drying.

Laboratory nutrient analysis reports usually provide nutrient content of plant tissue samples on a dry weight basis (i.e., units of nutrient per unit of dry plant tissue). To determine crop N removal, these dry weight values must be adjusted to account for the moisture content of the crop. In addition, for crops where yield is reported in units other than pounds per acre, the N content of the harvested tissue must be adjusted based on the weight per unit (such as pounds per bushel). 

The following example illustrates how to determine crop N removal for corn grain containing 1.45% N based on results of lab analysis:

This value corresponds to 1.45 lb N per 100 dry lb of corn grain. Because this value is listed on a dry weight basis, it must be adjusted to account for the moisture content of the crop. For corn grain, if we assume a moisture content of 15.5%, which is equivalent to 84.5% dry matter or 0.845 lb dry corn grain per lb corn grain:

 



Crop N removal must then be adjusted (when applicable) based on the standard test weight. The standard test weight for corn grain is 56 lb/bu


 

Therefore, the actual nutrient removal for corn grain in this example would be 0.69 lb N per bushel.

 

Nitrogen Removal by Typical Delaware Crops

The N removal rates for typical Delaware grain crops listed in this document were determined by analyzing the harvested portion of selected crops in Delaware (Binford, 2008). Between 2003 and 2007, a total of 668 corn grain samples, 175 soybean samples, 322 winter wheat samples, and 117 winter barley samples were collected at harvest from locations throughout Delaware (with a small number of samples collected from farms located on the eastern shore of Maryland that share similar climate, soil, and cropping conditions as Delaware) and analyzed for N content (Binford, 2008). Nitrogen content of harvested grain samples in Delaware reported by Binford (2008) was comparable to standard values reported in the USDA-NRCS Crop Nutrient Removal database.

Only a small number of vegetable and forage harvest samples were collected from Delaware fields in 2004 due to issues related to drying samples for analysis. Nitrogen values in harvested tissue of the vegetable and forage crops data presented by Binford (2008) were in good agreement with values obtained from the USDA-NRCS Crop Nutrient Uptake Tool. Therefore, standard values for crop N removal of selected vegetable and forage crops from the USDA-NRCS Crop Nutrient Uptake Tool are reported in this publication. We then calculated the amount of N removed per acre by grain and forage crops (Table 1) and vegetable crops (Table 2) over a range of realistic yield goals for major Delaware crops, where removal is the product of N content and crop yield.

Table 1. Estimated Nitrogen Removal in the Harvested Portion of Selected Delaware Grain and Forage Crops.

 

Crop Yield Unit Crop N Content (lb N /yield unit) Yield (yield unit/ac) 40 Crop N Removal (lbs/ac) 30
Barley bu (48 lbs/bu @ 14% moisture) 0.76 40 30
60 46
80 61
100 76
Corn bu (56 lbs/bu @ 15.5% moisture) 0.69 50 35
100 69
150 104
200 138
Soybean bu (60 lbs/bu @ 13% moisture) 3.44 30 103
40 138
50 172
60 206
Wheat bu (60 lbs/bu @ 13% moisture) 1.05 40 42
60 63
80 84
100 105
Corn silage ton (@ 70% moisture) 7.75 15 116
20 155
25 194
30 233
Grass- legume hay ton (@12% moisture) 43.6 2 87
3 131
4 174
5 218
 

Table 2. Estimated Nitrogen Removal in the Harvested Portion of Selected Delaware Vegetable Crops.

 

Crop Yield Unit boxes (25 Crop N Content (lbs N/yield unit) Yield (yield unit/ac) 750 Crop N Removal (lbs/ac) 30
Bell pepper, fresh market lbs/box @ 92.5% moisture) 0.04 750 30
1000 40
1250 50
1500 60
Bell pepper processing lbs (@ 92.5% moisture) melons (6 0.002 18000 36
21000 42
23000 46
26000 52
Cantaloupe lbs/melon @ 96% moisture) 0.009 3500 32
5000 45
6500 59
8000 72
Cabbage cwt (@ 91% moisture) 0.32 100 32
115 37
120 38
125 40
Cucumber, pickler processing bu (50 lbs/box @ 95.5% moisture) 0.055 150 8
200 11
250 14
300 17
Eggplant boxes (32 lbs/box @ 93% moisture) 0.058 700 41
800 46
900 52
1000 58
Jalapeno pepper lbs (@ 92% moisture) 0.002 25000 50
30000 60
35000 70
40000 80
Lima bean lbs (@ 69% moisture) 0.011 1000 11
2000 22
3000 33
4000 44
Peas cwt (@ 79% moisture) 0.94 15 14
25 24
35 33
45 42
Potatoes cwt (@ 77.2% moisture) 0.37 150 56
200 74
250 93
300 111
 

 

Crop Yield Unit Crop N5 Content (lbs N/yield unit) Yield (yield unit/ac) 4 Crop N Removal (lbs/ac) 32
Sweet corn, processing tons (@ 75% moisture) 8 6 48
8 64
10 80
550 21
Squash, fresh market boxes (20 lbs/box @ 95% moisture) 0.038 600 23
650 25
700 27
12500 25
Squash, processing lbs (@ 95% moisture) 0.002 15000 30
17500 35
20000 40
750 29
Tomato boxes (25 lbs/box @ 94% moisture) 0.038 900 34
1050 40
1200 46
45000 45
Watermelon lbs (@ 91% moisture) 0.001 60000 60
75000 75
90000 90
   
 

Based on calculated N removal rates for Delaware crops, growers can estimate the amount of N removed in a planned crop rotation. The following are examples of estimated N removal for some common Delaware cropping systems. 

 

System #1: Corn-Wheat/Soybean-Corn, Dryland

 

Year Crop Yield Crop N Removal (lb/ac)
1 Corn 150 bu/ac 104
2 Wheat Soybean 70 bu/ac 35 bu/ac 74 120
Rotational Crop Removal 298
 

System #2: Corn-Wheat/Soybean-Corn, Irrigated

 

Year Crop Yield Crop N Removal (lb/ac)
1 Corn 275 bu/ac 190
2 Wheat Soybean 90 bu/ac 55 bu/ac 95 189
Rotational Crop Removal 474
 

System #3: Corn-Full Season Soybean

 

Year Crop Yield Crop N Removal (lb/ac)
1 Corn 225 bu/ac 155
2 Soybean 60 bu/ac 206
Rotational Crop Removal 361
 

System #4: Grain Crops and Vegetables

 

Year Crop Yield Crop N Removal (lb/ac)
1 Corn 150 bu/ac 104
2 Wheat Soybean 70 bu/ac 35 bu/ac 74 120
3 Peas Lima Beans 30 cwt/ac 2,500 lbs/ac 28 28
Rotational Crop Removal 354
 

Summary

The amount of N removed in the harvested portion of the crop can be determined using the standard crop removal values and the procedures presented above or by analyzing the N content of the harvested portions of the crop. If direct analysis is selected, one should keep in mind that results can be highly variable by field and year and difficult to perform for vegetable crops due to their high moisture content. Once crop N removal is determined, those removal rates can be used in subsequent nutrient management planning as part of an adaptive N management approach to determine the appropriate amounts of N to apply to a particular cropping system to maximize uptake and minimize losses to the environment.

 

References

Binford, G. 2008. Nutrient removal rates for common crops in Delaware: Final report. Submitted to the Delaware Center for the Inland Bays. University of Delaware. Newark.

USDA, NRCS. 2025. The PLANTS Database (http://plants.usda.gov, 3 March 2025). National Plant Data Team, Greensboro, NC 27401-4901 USA. 

 

About the Authors

Amy L. Shober (corresponding author), Professor and Extension Specialist, University of Delaware, Newark, DE (ashober@udel.edu)

 

About this Publication

Original Publication Date: 2013

Revision date(s): 2025

 

Peer Reviewers

Sydney Riggi, Extension Agent, University of Delaware Cooperative Extension, Dover, DE

Jennifer Volk, Extension Specialist, University of Delaware Cooperative Extension, Dover, DE

 


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