Effect of Preplant Irrigation, Nitrogen Fertilizer Application Timing, and Phosphorus and Potassium Fertilization on Winter Wheat Grain Yield and Water Use Efficiency
Table 8
Water use efficiency (WUE) means and selected contrasts by year for plots with different fertilizer treatments and those received either their total N fertilizer preplant or topdressed midseason.
(a)
Fertilizer treatment
Year
2003
2004
2008
2011
WUE (kg ha−1 mm−1)
Preplant N
1
3.3
3.1
6.2
4.5
2
4.8
5.0
8.6
5.7
3
5.5
5.5
8.7
5.0
4
5.6
4.9
9.7
4.4
5
6.7
6.2
10.1
4.7
6
5.2
5.2
9.2
4.6
7
6.2
5.9
10.7
3.4
Topdress N
1
3.5
2.9
7.1
4.1
2
5.4
5.3
9.3
4.7
3
5.1
5.4
9.1
4.7
4
6.1
5.1
9.3
4.5
5
5.9
4.9
9.9
3.6
6
5.8
5.3
9.4
4.4
7
5.9
5.2
8.4
3.8
SED
0.3
0.4
0.7
0.3
(b)
Contrasts
Year
2003
2004
2008
2011
Sig
Dif
Sig
Dif
Sig
Dif
Sig
Dif
45 kg N ha−1 at preplant versus 45 kg N ha−1 at topdress
**
−0.6
ns
−0.2
ns
−0.2
ns
0.4
90 kg N ha−1 at preplant versus 90 kg N ha−1 at topdress
*
0.5
**
0.7
ns
0.7
ns
0.3
45 kg N ha−1 versus 90 kg N ha−1
**
−0.4
*
−0.4
ns
−0.2
***
0.5
Preplant 45 kg N ha−1 versus 90 kg N ha−1
***
−1.0
***
−0.8
*
−0.7
**
0.5
Topdress 45 kg N ha−1 versus 90 kg N ha−1
ns
0.1
ns
0.1
ns
0.2
*
0.5
P fertilizer with preplant N versus with topdress N
ns
−0.1
*
0.4
ns
0.6
ns
0.2
K fertilizer with preplant N versus with topdress N
ns
−0.2
ns
0.3
*
1.0
ns
−0.1
Preplant N-P fertilizer added versus no P fertilizer added
***
1.0
ns
0.3
**
1.2
**
−0.8
Topdress N-P fertilizer added versus no P fertilizer added
**
0.7
ns
−0.4
ns
0.4
**
−0.7
Preplant N-K fertilizer added versus no K fertilizer added
*
−0.5
ns
−0.1
ns
0.1
*
−0.5
Topdress N-K fertilizer added versus no K fertilizer added
ns
−0.2
ns
0.2
ns
−0.7
ns
0.1
Standard error of the difference for the interaction of N application timing and fertilizer treatment. * and ** are significant at the 0.1 level and 0.01 level, respectively. ns: not significant at the 0.1 level.
