Oklahoma State UniversityNitrogen Use Efficiency, Nitrogen Fertilizers, NUE, Nitrogen and the Environment

RESOLUTION TRIAL

Objectives

To determine at which scale should spatial variability be treated using in-season nitrogen algorithms.

To determine the benefits of treating the identified unit individually.

Treatment Structure arranged in Complete Randomized Design

 

Treatment No. N Rate, kg ha-1 Method Fertilizer Application Resolution, m2
1 0 check -
2 90 Preplant -
3 90 Topdress -
4 * midseason NFOA 0.836
5 * midseason NFOA 13.37
6 * midseason NFOA 26.67

* Average mid-season N rate applied

 

Field Activities

 

Flagging off plots treated at high resolution (0.836 m2)

 

Each microplot is sensed at Feekes 5. NDVI values are used to calculate in-season yield potential.

 

Mid-season fertilizer rate is computed based on predicted yield potential.

 

Urea-ammonium nitrate (UAN) is applied variably with a pulse-modulated sprayer.

 

2003-2004 Results

Grain yield and NUE data at Tipton, OK.

Treatment Preplant N Topdress N Grain Yield N Use Efficiency
  kg/ha kg/ha Mg/ha %
Check 0 0 3.4 -
90-Pre 90 0 4.7 37
90-Top 0 90 4.7 41
0-NFOA 1 0 34 4.3 43
0-NFOA 13 0 37 4.3 56
0-NFOA 26 0 35 4.1 49

Average check sensor CV = 17.2% with average NDVI = 0.61 at Feekes 5.

 

Grain yield and NUE data at Chickasha, OK.

Treatment Preplant N Topdress N Grain Yield N Use Efficiency
  kg/ha kg/ha Mg/ha %
Check 0 0 1.2 -
90-Pre 90 0 1.7 21
90-Top 0 90 1.8 27
0-NFOA 1 0 41 1.6 26
0-NFOA 13 0 50 1.7 30
0-NFOA 26 0 47 1.8 31

Average check sensor CV = 12.1% with average NDVI = 0.28 at Feekes 5.

 

2004-2005 Results

Grain yield and NUE data at Tipton, OK.

Treatment Preplant N Topdress N Grain Yield Profit N Use Efficiency
  kg/ha kg/ha Mg/ha $/ac %
Check 0 0 1.2   -
90-Pre 90 0 2.1   17
90-Top 0 90 2.6   32
0-NFOA 1 0 39 1.9   36
0-NFOA 13 0 62 2.1   31
0-NFOA 26 0 61 2.2   34

 

Grain yield and NUE data at Chickasha, OK.

Treatment Preplant N Topdress N Grain Yield Profit N Use Efficiency
  kg/ha kg/ha Mg/ha $/ac %
Check 0 0 3.0   -
90-Pre 90 0 3.6   28
90-Top 0 90 4.0   39
0-NFOA 1 0 90 4.2   40
0-NFOA 13 0 81 4.2   47
0-NFOA 26 0 82 4.2   37