Skip to content

Influence of Nitrogen Fertilizer Rate, Source, and Time of Application on Improving N Efficiency: Silt Loam

Influence of Nitrogen Fertilizer Rate, Source, and Time of Application on Improving N Efficiency: Silt Loam published on No Comments on Influence of Nitrogen Fertilizer Rate, Source, and Time of Application on Improving N Efficiency: Silt Loam

H.J. “Rick” Mascagni, Jr. and Brenda Tubana

Introduction

            Nitrogen (N) fertilization is a critical cultural practice required for producing maximum corn yield. Many factors, including soil type and crop management systems, determine optimum N rates. Nitrogen is typically knifed-in soon after the crop has emerged and an adequate stand established. Growers often times split N fertilizer applications as part of their management system or, in some cases, due to uncontrollable factors such as excessive or lack of rainfall, may produce soil conditions conducive to N fertilizer loss through denitrification and/or inefficient plant N uptake.  If N is topdressed with a fertilizer containing urea losses may occur due to volatization, which depends to a large extent on climatic and soil factors. If irrigated or rainfall occurs (0.5 inch or greater) within about three days, the fertilize is incorporated and no or minimal volatization losses will occur  Sometimes N applications are delayed or omitted due to inclement weather, while at other times, growers apply the recommended N rate for an expected yield potential. However, as the crop develops yield potential may be higher than expected and additional N may be required. In each of the above situations the question arises, how late can N fertilizer be applied and be effective? The fertilizer N source is also an important component of an effective fertility program. Products are also available such as urease inhibitors (i.e., Agrotain) that minimize urea volatization losses for 7 to 10 days. The objective of this trial was to evaluate N applications, N sources, and an urease inhibitor at different growth stages on a Mississippi River silt loam.

 Procedures

            A field experiment was conducted in 2011 on Commerce silt loam at the Northeast Research Station near St. Joseph to evaluate the influence of N rate, timing, and fertilizer source on corn yield and N fertilizer use efficiency (NFUE). Early-season N rates were injected at about the 3-leaf growth stage (April 16) as 30-0-0-2 solution (UAN) at N rates of 0, 120, 150, 180, and 210 lb N/acre. Urea, with and without Agrotain (3 qts/ton urea), was also hand-broadcast at the rate of 120 lb N/acre at the 3-leaf growth stage. For the early-season N rate of 120 lb/acre using 30-0-0-2, supplemental N rates of 30 and 60 lb/acre were applied at about the 12-leaf (May 23) and early-silk growth stages (June 7). Urea, with and without Agrotain, was hand-broadcast  and 30-0-0-2, with and without Agrotain, was hand-dribbled (to simulate a dribble application) at the 12-leaf and early-silk applications. There were a total of 23 treatments (see Table 2). REV® 28HR20 was planted on March 24 at 32,000 seed/acre. Cotton was the previous crop and all LSU AgCenter recommended cultural practices were followed.

             The experimental design was a randomized complete block with four replications. Grain yield, yield components, plant N, seed N, NFUE, and remote sensing data were determined. Grain yield was determined by machine harvest from the two middle rows of four-row plots and reported at 15.5% moisture. Yield components, seed weight (g/100 seed) and ear size (seed/ear) were also determined from the two middle rows.  Ear-leaf samples were collected at the early- silk growth stage to determine the influence of treatments on the N status of the plant. Seed samples were also collected at harvest. Total N was determined in the plant tissue and harvested seed by the LSU AgCenter’s Soil and Plant Testing Lab. Seed-N uptake (lb N/acre) was calculated by multiplying seed-N concentration by grain yield. NFUE was calculated using the following formula: (seed-N uptake for a given N rate – seed-N uptake for the no-N control) / N rate.   Remote sensing data using a SPAD meter were also determined at the 3- and 12-leaf growth stages. Statistical analyses were performed using the GLM procedure of SAS using a probability level of 0.10.

 Results and Discussion

            Rainfall was extremely low in May with a only a total of 4.9 inches in May and June in this dryland trial (Table 1). However, overall yields were extremely good averaging over 150 bu/acre (Table 2).

             At early-season, urea, urea + Agrotain, and UAN were compared at the 120 lb N/acre rate. Yield response had the following rank: UAN = urea + Agrotain > urea (Table 2). Evidently, there was some N loss due to volatization for the urea fertilizer. There was a 10 day interval between application and the first rainfall event. For the late N applications at the 12-leaf growth stage and early silk, both the 30 and 60 lb N/acre rates increased yields across sources. Yields tended to be a little higher for the early silk compared to 12-leaf applications. There were 11 and 2 day intervals between application and rainfall for the 12-leaf and early-silk applications, respectively. There was a yield response to urea + Agrotain for the 30 lb N/acre late application at the 12-leaf growth stage. When comparing equivalent N rates applied either once early season or split between early season and 12 leaf or early-silk growth stages, yields were similar. The treatment influence on kernel weight and ear size (kernel number) are shown in Table 2.

 Plant and seed N data are presented in Table 3. Leaf N, seed N, seed N uptake, and NFUE had the following rank for the early-season N treatments: UAN>urea+Agrotain>urea. Similar to yield responses, there were only small differences between the 12-leaf and early-silk late N applications for each N trait. Nitrogen fertilizer use efficiency (NFUE) was extremely high, ranging from 0.36 to 0.78 (Table 3). There were no differences in NFUE between the single and split applications, when comparing equivalent N rates. SPAD readings reflected treatment effects similar to yield responses (Table 4).

 

Table 1. Rainfall in St. Joseph, 2011.

Month

Rainfall

 

inches

 

 

March

8.3

April

3.0

May

0.9

June

4.0

July

4.4

August

1.3

 

Table 2. Influence of N fertility treatments on corn yield and yield components on Commerce silt loam, 2011.

 

 

 

N rate

 

 

 

 

 

 

 

ESN1 rate

ESN

source2

 

12-leaf

Early silk

Late N

source

Total N

applied

 

Yield

 

Ears

Kernel

weight

 

Kernels

lb/a

 

———lb/a——

 

lb/a

bu/a

no/a

g/100

no/ear

 

 

 

 

 

 

 

 

 

 

0

0

39.6

31,390

31.7

124

120

Urea

120

116.7

32,700

32.0

293

120

Urea + Ag

120

141.9

32,700

33.4

329

120

UAN

120

145.8

33,350

34.4

365

 

 

 

 

 

 

 

 

 

 

120

UAN

30

Urea

150

160.7

33,350

34.7

327

120

UAN

30

Urea+Ag

150

169.4

32,700

34.1

386

120

UAN

30

UAN

150

165.8

30,740

34.7

423

120

UAN

30

UAN+Ag

150

165.6

32,700

36.0

385

Average

 

 

 

 

165.4

32,370

34.9

380

 

 

 

 

 

 

 

 

 

 

120

UAN

60

Urea

180

170.0

32,050

35.2

386

120

UAN

60

Urea+Ag

180

176.8

34,010

36.2

397

120

UAN

60

UAN

180

160.3

33,350

35.2

357

120

UAN

60

UAN+Ag

180

166.2

32,700

35.1

378

Average

 

 

 

 

168.3

33,030

35.4

380

 

 

 

 

 

 

 

 

 

 

120

UAN

30

Urea

150

168.5

34,660

35.1

361

120

UAN

30

Urea+Ag

150

151.8

33,350

34.9

368

120

UAN

30

UAN

150

168.7

32,700

35.7

389

120

UAN

30

UAN+Ag

150

168.0

33,350

34.3

386

Average

 

 

 

 

164.3

33,520

35.0

376

 

 

 

 

 

 

 

 

 

 

120

UAN

60

Urea

180

177.0

32,700

35.6

403

120

UAN

60

Urea+Ag

180

172.8

34,010

34.4

383

120

UAN

60

UAN

180

166.5

33,350

34.1

381

120

UAN

60

UAN+Ag

180

170.0

32,700

35.1

393

Average

 

 

 

 

171.6

33,190

34.8

390

 

 

 

 

 

 

 

 

 

 

150

UAN

150

166.2

34,010

34.3

374

180

UAN

180

169.8

30,740

33.9

432

210

UAN

210

178.8

34,010

36.7

380

 

 

 

 

 

 

 

 

 

 

LSD (0.10):

 

 

 

 

14.7

NS3

2.7

53

                                                 

1ESN, early-season N injected at about 3-leaf growth stage.

2Ag = Agrotain; UAN = 30-0-0-2;

3NS = Non-significant at the 0.10 probability level

 

Table 3. Influence of N fertility treatments on N nutrition of corn on Commerce silt loam, 2011.

 

 

 

N rate

 

 

 

 

 

 

ESN1 rate

ESN

source2

 

12-leaf

Early silk

Late N

source

Total N

applied

 

Leaf N

 

Seed N

Seed N

uptake

 

NFUE3

lb/a

 

———lb/a——

 

lb/a

%

%

lb N/a

 

 

 

 

 

 

 

 

 

 

 

0

0

1.18

1.28

39.7

120

Urea

120

1.57

1.22

82.0

0.36

120

Urea + Ag

120

1.86

1.38

107.9

0.57

120

UAN

120

2.24

1.43

133.0

0.78

 

 

 

 

 

 

 

 

 

 

120

UAN

30

Urea

150

2.30

1.40

116.9

0.52

120

UAN

30

Urea+Ag

150

2.23

1.43

135.0

0.64

120

UAN

30

UAN

150

2.26

1.44

141.7

0.68

120

UAN

30

UAN+Ag

150

2.32

1.45

143.5

0.69

Average

 

 

 

 

2.28

1.43

134.3

0.63

 

 

 

 

 

 

 

 

 

 

120

UAN

60

Urea

180

2.32

1.50

142.4

0.57

120

UAN

60

Urea+Ag

180

2.27

1.55

166.4

0.71

120

UAN

60

UAN

180

2.15

1.50

138.1

0.55

120

UAN

60

UAN+Ag

180

2.36

1.52

145.4

0.59

Average

 

 

 

 

2.28

1.52

148.1

0.61

 
 

 

 

 

 

 

 

 

 

 

 
120

UAN

30

Urea

150

1.40

135.0

0.64

 
120

UAN

30

Urea+Ag

150

1.44

136.1

0.64

 
120

UAN

30

UAN

150

1.48

146.9

0.72

 
120

UAN

30

UAN+Ag

150

1.48

143.7

0.70

 
Average

 

 

 

 

1.45

140.4

0.68

 
 

 

 

 

 

 

 

 

 

 

 
120

UAN

60

Urea

180

1.47

151.7

0.63

 
120

UAN

60

Urea+Ag

180

1.53

149.8

0.61

 
120

UAN

60

UAN

180

1.47

139.1

0.56

 
120

UAN

60

UAN+Ag

180

1.45

142.4

0.58

 
Average

 

 

 

 

1.48

145.8

0.60

 
 

 

 

 

 

 

 

 

 

 

 
150

UAN

150

2.28

1.45

139.3

0.67

 
180

UAN

180

2.50

1.49

146.9

0.60

 
210

UAN

210

2.48

1.48

154.4

0.55

 
 

 

 

 

 

 

 

 

 

 

 
LSD (0.10):

 

 

 

 

 

0.16

0.10

21.7

0.14

 
                                                   

1ESN, early-season N injected at about 3-leaf growth stage.

2Ag = Agrotain; UAN = 30-0-0-2;

3NFUE = N fertilizer use efficiency

Table 4. Influence of N fertility treatments on SPAD readings taken early season and at 12-leaf growth stage on Commerce silt loam, 2011.

 

 

 

N Fertilizer Source

 

 

 N rate1

 

Total N

 

Urea

Urea + Agrotain

 

UAN2

UAN + Agrotain

 

Average

lb/acre   ———————————SPAD Readings ————————————-
 

 

 

 

 

 

 

 

 

 

Early-Season N Application

 

 

 

 

 

 

 

 

120

120

38.5

44.0

46.9

43.1

150

150

48.5

48.5

180

180

51.1

51.1

210

210

52.4

52.4

 

 

 

 

 

 

 

 

 

 

     12-leaf Growth Stage N Application

 

 

 

 

 

 

30

150

49.2

46.4

50.0

50.4

49.0

60

180

50.1

52.2

48.4

51.2

50.5

Average

 

49.7

49.3

49.2

50.8

 

 

 

 

 

 

 

 

LSD (0.10):

 

 

 

3.8

 

 

                   

1N rate applied early-season (3-leaf) and 12-leaf growth stage

2UAN = 30-0-0-2 fertilize solution

 

Leave a Reply

Your email address will not be published. Required fields are marked *

Secondary Sidebar