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Study site and soil information for the rice N-response trials on silt loam soils.

 
Year Site Soil series Soil classification Previous crop Location†
2004 1 Calhoun fine-silty, mixed, active, thermic Typic Glossaqualf soybean ES
2004 2 Dewitt fine smectitic, thermic Typic Albaqualf soybean ES
2004 3 Dewitt fine smectitic, thermic Typic Albaqualf soybean ES
2004 4 Hilleman fine-silty, mixed, active, thermic, albic Glossic Natraqualf soybean ES
2005 5 Calhoun fine-silty, mixed, active, thermic Typic Glossaqualf soybean ES
2005 6 Dewitt fine smectitic, thermic Typic Albaqualf soybean ES
2005 7 Hilleman fine-silty, mixed, active, thermic, albic Glossic Natraqualf soybean ES
2006 8 Calloway fine-silty, mixed, active, thermic Aquic Fraglossudualf soybean ES
2006 9 Dewitt fine smectitic, thermic Typic Albaqualf soybean P
2006 10 Dewitt fine smectitic, thermic Typic Albaqualf soybean ES
2006 11 Hilleman fine-silty, mixed, active, thermic, albic Glossic Natraqualf soybean ES
2007 12 Calhoun fine-silty, mixed, active, thermic Typic Glossaqualf soybean ES
2007 13 Foley fine-silty, mixed, active, thermic, albic Glossic Natraqualf catfish P
2007 14 Dewitt fine smectitic, thermic Typic Albaqualf soybean ES
2007 15 Hillemann fine-silty, mixed, active, thermic, albic Glossic Natraqualf soybean P
2007 16 Dexter fine-silty, mixed, active, thermic Ultic Hapludalf fallow P
2007 17 Dewitt fine smectitic, thermic Typic Albaqualf soybean P
2007 18 Dewitt fine smectitic, thermic Typic Albaqualf soybean P
2008 19 Dewitt fine smectitic, thermic Typic Albaqualf soybean ES
2008 20 Calhoun fine-silty, mixed, active, thermic Typic Glossaqualf fallow ES
2008 21 Calloway fine-silty, mixed, active, thermic Aquic Fraglossudualf rice ES
2008 22 Dewitt fine smectitic, thermic Typic Albaqualf soybean P
2008 23 Dewitt fine smectitic, thermic Typic Albaqualf soybean P
2008 24 Hillemann fine-silty, mixed, active, thermic, albic Glossic Natraqualf soybean ES
2008 25 Forestdale fine, smectitic, thermic Typic Endoaqualf fallow ES
Designates whether experiments were located on experiment stations (ES) or in production fields (P).



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Soil pH and selected N chemical characteristics by depth for the soils at the 25 sites.

 
Site pH† NH4–N‡ NO3–N‡ TN§
0–15 15–30 30–45 45–60 Soil sample depth (cm) 0–15 15–30 30–45 45–60
0–15 15–30 30–45 45–60 0–15 15–30 30–45 45–60
mg N kg soil−1
1 7.5 7.3 6.9 6.9 19 6 6 7 3 3 1 < 1 1100 220 480 280
2 6.8 6.5 6.6 6.0 10 6 5 7 11 5 3 < 1 820 660 890 870
3 5.9 6.1 6.0 5.6 9 5 4 5 < 1 4 < 1 < 1 900 840 720 820
4 7.0 6.8 6.9 7.0 11 6 3 4 1 3 < 1 < 1 850 850 550 430
5 8.1 7.5 7.1 6.9 21 4 4 5 19 < 1 < 1 < 1 1030 470 390 470
6 6.7 6.5 6.2 6.3 20 4 4 7 6 3 < 1 1 1070 750 640 740
7 6.8 6.9 14 10 8 6 1000 960
8 7.0 7.2 6.9 6.1 9 7 5 5 10 8 8 7 870 450 330 350
9 6.0 6.5 6.3 5.8 5 2 2 3 9 4 4 2 880 760 790 730
10 5.7 6.1 6.1 5.8 6 4 3 4 10 8 5 4 680 600 490 590
11 7.2 6.9 7.3 7.6 4 2 2 2 4 4 2 2 890 570 370 450
12 6.7 6.5 5.6 5.6 3 1 2 2 20 10 8 6 883 462 554 489
13 6.9 7.5 7.5 7.6 40 168 132 97 76 21 16 7 1384 756 822 667
14 6.7 7.1 7.0 6.1 9 4 5 6 14 10 9 9 963 741 747 806
15 6.5 6.5 6.4 6.4 6 4 3 4 5 6 4 4 957 577 646 608
16 5.2 5.2 5.4 5.0 7 4 4 5 18 18 19 16 1366 604 646 539
17 6.7 7.1 7.1 5.9 8 6 6 10 17 13 13 9 799 715 639 734
18 6.6 6.6 5.3 5.3 8 4 5 6 16 13 11 12 1006 722 757 901
19 6.6 7.2 7.1 5.9 4 2 3 3 9 7 6 5 852 692 709 657
20 7.1 6.8 6.8 6.9 1 < 1 1 1 8 5 5 7 710 271 235 240
21 7.0 6.9 6.6 6.5 < 1 1 1 1 10 6 5 5 463 206 179 191
22 6.8 6.4 5.6 5.4 2 1 2 2 15 9 7 2 978 511 571 571
23 6.9 6.2 6.0 6.3 1 < 1 < 1 < 1 13 4 4 3 888 582 496 457
24 6.6 6.4 6.3 6.2 1 < 1 1 2 5 6 7 5 970 614 732 620
25 5.1 5.0 5.6 5.7 4 1 2 1 19 12 9 6 1542 765 489 439
Soil/water ratio, 1:2.
Determined by salicylate colorimetric techniques, MULVANEY (1996).
§Total nitrogen (TN) determined by dry combustion technique, NELSON and SOMMERS (1996).



View Full Table | Close Full ViewTable 3

Mean and standard deviations for alkaline hydrolyzable-N (AH-N) as determined by the Illinois Soil Nitrogen Test (ISNT) and direct steam distillation (DSD) for each soil depth increment; total N uptake, check plot grain yield, and percentage of relative grain yield (RGY) of rice receiving no N; and the N rate predicted to achieve 95% RGY for the 25 sites used in the study.

 
Site ISNT† DSD† Total N uptake‡ Check plot yield‡ RGY‡ N rate to achieve 95% RGY‡
Soil sample depth (cm)
0–15 15–30 30–45 45–60 0–15 15–30 30–45 45–60
mg N kg soil−1 kg N ha−1 kg rice ha−1 % kg N ha−1
1 141 ± 7.0 45 ± 5.4 42 ± 4.3 36 ± 2.1 156 ± 6.7 66 ± 4.1 60 ± 4.0 42 ± 1.5 53 4710 44 150
2 134 ± 3.4 84 ± 2.8 124 ± 2.7 134 ± 3.5 136 ± 4.0 94 ± 1.8 136 ± 3.6 146 ± 2.1 147 8948 83 58
3 118 ± 7.7 96 ± 6.8 101 ± 7.1 109 ± 5.3 127 ± 2.1 109 ± 2.4 100 ± 1.4 116 ± 1.6 100 6882 61 114
4 144 ± 8.8 96 ± 8.6 42 ± 9.1 38 ± 4.2 151 ± 5.4 103 ± 4.8 55 ± 1.3 47 ± 0.9 46 3921 48 84
5 136 ± 2.1 50 ± 1.7 39 ± 1.1 35 ± 0.9 144 ± 1.9 78 ± 0.7 51 ± 0.8 51 ± 1.1 45 4389 40 138
6 148 ± 3.0 78 ± 2.9 77 ± 2.1 113 ± 1.6 157 ± 2.2 81 ± 2.6 92 ± 5.3 118 ± 1.2 63 4106 37 100
7 151 ± 8.0 109 ± 4.2 155 ± 5.7 137 ± 2.9 81 6392 74 73
8 99 ± 6.8 59 ± 5.1 43 ± 2.3 43 ± 2.8 113 ± 5.7 77 ± 2.1 56 ± 1.6 54 ± 1.8 54 2810 29 177
9 107 ± 6.3 93 ± 4.9 97 ± 3.8 91 ± 5.1 115 ± 3.0 101 ± 4.2 105 ± 2.6 103 ± 3.5 119 3717 62 104
10 104 ± 7.9 84 ± 4.2 76 ± 3.5 92 ± 6.2 111 ± 6.0 95 ± 4.9 88 ± 5.2 98 ± 3.9 81 2949 38 109
11 127 ± 7.4 77 ± 3.9 48 ± 1.6 44 ± 2.0 132 ± 5.9 90 ± 4.5 63 ± 2.4 59 ± 1.4 75 4393 49 141
12 131 ± 5.6 73 ± 4.9 60 ± 4.6 50 ± 3.2 131 ± 4.0 83 ± 2.1 70 ± 1.6 59 ± 1.0 62 4385 43 155
13 181 ± 8.2 240 ± 11 211 ± 9.8 165 ± 6.3 210 ± 5.3 280 ± 7.1 243 ± 6.9 205 ± 4.3 153 9321 100 0
14 137 ± 5.9 97 ± 4.1 100 ± 4.4 111 ± 4.8 143 ± 5.8 107 ± 5.5 102 ± 4.9 115 ± 3.7 102 4413 46 100
15 161 ± 6.1 112 ± 5.8 104 ± 3.4 112 ± 5.1 152 ± 3.7 110 ± 2.6 109 ± 2.3 108 ± 2.1 121 7006 74 92
16 217 ± 9.2 91 ± 4.1 95 ± 3.9 84 ± 2.8 230 ± 7.6 106 ± 3.3 108 ± 4.5 85 ± 3.5 156 9878 93 19
17 137 ± 3.6 99 ± 2.7 120 ± 2.3 134 ± 2.0 146 ± 4.5 105 ± 3.9 103 ± 3.4 129 ± 3.1 98 6854 61 95
18 138 ± 8.4 96 ± 6.5 95 ± 5.9 120 ± 5.6 141 ± 4.6 98 ± 4.9 124 ± 5.6 141 ± 3.4 119 7052 71 77
19 113 ± 7.6 93 ± 6.8 105 ± 4.2 96 ± 5.7 130 ± 8.1 111 ± 7.3 117 ± 6.8 114 ± 5.9 71 3830 48 104
20 97 ± 3.2 44 ± 4.6 37 ± 1.0 28 ± 0.8 122 ± 4.2 72 ± 3.5 63 ± 2.0 57 ± 1.1 64 3982 37 146
21 61 ± 3.2 28 ± 0.8 26 ± 0.6 22 ± 0.5 91 ± 2.1 59 ± 0.7 54 ± 1.1 51 ± 1.2 31 1966 19 185
22 102 ± 6.7 59 ± 3.1 62 ± 4.5 49 ± 3.2 133 ± 4.6 102 ± 5.2 88 ± 4.1 82 ± 5.6 90 6905 61 119
23 119 ± 7.2 59 ± 5.4 71 ± 5.0 93 ± 4.6 149 ± 3.1 97 ± 3.6 106 ± 4.1 121 ± 3.0 81 5494 49 101
24 123 ± 5.2 80 ± 3.4 97 ± 3.8 86 ± 6.4 143 ± 5.8 110 ± 6.4 116 ± 2.4 105 ± 3.7 53 4133 52 95
25 177 ± 9.1 78 ± 6.3 42 ± 5.7 35 ± 6.7 212 ± 7.2 111 ± 4.3 77 ± 4.9 67 ± 4.0 170 9223 96 41
Mean of three replicate determinations.
Mean of four replicate determinations.



View Full Table | Close Full ViewTable 4

Regression models for the relationship between total N uptake, check plot grain yield and percentage of relative grain yield (RGY) with alkaline hydrolyzable-N (AH-N) quantified by the Illinois Soil Nitrogen Test (ISNT) and direct steam distillation (DSD).

 
Relationship Soil sample depth ISNT DSD
Regression model r2 Regression model r2
cm
Total N uptake† 0–15 −12.9 + 0.77x 25 0.41*** 4.87 + 0.60x 25 0.40 ***
15–30 42.8 + 0.55x 25 0.31** 39.3 + 0.48x 25 0.26**
30–45 43.6 + 0.58x 24 0.36** 31.9 + 0.61x 24 0.39**
45–60 47.2 + 0.53x 24 0.48*** 36.1 + 0.57x 24 0.33**
0–30 −3.3 + 0.86x 24 0.48*** −0.2 + 0.74x 24 0.45***
0–45 5.0 + 0.86x 24 0.47*** −2.5 + 0.81x 24 0.46***
0–60 13.6 + 0.81x 24 0.46*** 4.1 + 0.79x 24 0.48***
Check Plot Yield‡ 0–15 −1058 + 49.2x 24 0.51*** 84 + 37.8x 24 0.49***
15–30 2299 + 38.9x 24 0.17* −378 + 59.7x 24 0.25*
30–45 3011 + 30.9x 23 0.18* 1531 + 42.4x 23 0.26*
45–60 37 + 21.3x 23 0.14 3029 + 25.3x 23 0.15
0–30 1222 + 63.2x 23 0.45*** −1930 + 62.1x 23 0.52***
0–45 955 + 66.5x 23 0.42*** −4757 + 92.8x 23 0.61***
0–60 765 + 50.9x 23 0.34** −1663 + 67.7x 23 0.48***
% RGY§ 0–15 −5.5 + 0.46x 24 0.53*** 5.5 + 0.35x 24 0.50***
15–30 14.5 + 0.51x 24 0.34** −16.5 + 0.74x 24 0.45***
30–45 30.2 + 0.32x 23 0.25* 15.0 + 0.44x 23 0.33**
45–60 38.5 + 0.20x 23 0.15 32.5 + 0.24x 23 0.16
0–30 −12.7 + 0.65x 23 0.57*** −17.0 + 0.61x 23 0.60***
0–45 −10.2 + 0.68x 23 0.53*** −46.4 + 0.93x 23 0.73***
0–60 8.2 + 0.51x 23 0.42*** −14.7 + 0.67x 23 0.57***
*Statistical significance at p < 0.05 levels.
**Statistical significance at p < 0.01 levels.
***Statistical significance at p < 0.001 levels.
x, Alkaline hydrolyzable-N (mg N kg soil−1); y, total N uptake from check plots (kg N ha−1).
x, Alkaline hydrolyzable-N (mg N kg soil−1); y, check plot grain yield (kg rice ha−1).
§x, Alkaline hydrolyzable-N (mg N kg soil−1); y, percentage of relative grain yield (%RGY).
n, number of sites.



View Full Table | Close Full ViewTable 5

Regression models for the relationship between the N rate to achieve 95% relative grain yield (95% RGY) with alkaline hydrolyzable-N (AH-N) quantified by the Illinois Soil Nitrogen Test (ISNT) and direct steam distillation (DSD).

 
Relationship Soil sample depth ISNT DSD
Regression model† r2 Regression model† r2
cm
95% RGY 0–15 237– 1.00x 24 0.58*** 214– 0.77x 24 0.56 ***
15–30 202– 1.21x 24 0.45*** 264– 1.64x 24 0.52**
30–45 165– 0.76x 23 0.32** 200– 1.03x 23 0.43**
45–60 152– .57x 23 0.28* 167– 0.65x 23 0.28**
0–30 259– 1.45x 23 0.68*** 265– 1.34x 23 0.69***
0–45 256– 1.57x 23 0.66*** 337– 2.10x 23 0.89***
0–60 219– 1.23x 23 0.57*** 269– 1.56x 23 0.73***
*Statistical significance at p < 0.05 level.
**Statistical significance at p < 0.01 level.
***Statistical significance at p < 0.001 level.
x, Alkaline hydrolyzable-N (mg N kg soil−1); y, N fertilizer rate to achieve 95% relative grain yield (95%RGY) (kg N ha−1).
n, number of sites.