Effect of Preplant Irrigation, Nitrogen Fertilizer Application Timing, and Phosphorus and Potassium Fertilization on Winter Wheat Grain Yield and Water Use Efficiency

Table 5

Grain yield 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	2008	2011
		Grain yield (kg ha^−1)
Preplant N	1	1575	2582	1055
	2	2332	3593	1342
	3	2671	3669	1252
	4	2749	4058	1099
	5	3274	4238	1129
	6	2498	3849	1125
	7	2989	4498	857
Topdress N	1	1688	2902	964
	2	2584	3848	1103
	3	2435	3753	1133
	4	2955	3863	1069
	5	2882	4106	840
	6	2753	3885	1015
	7	2877	3533	898
	SED^a	176	259	91

(b)

Contrasts	Year
	2003		2008		2011
	Sig	Dif	Sig	Dif	Sig	Dif
45 kg N ha^−1 at preplant versus 45 kg N ha^−1 at topdress	*	−238	ns	−32	ns	127
90 kg N ha^−1 at preplant versus 90 kg N ha^−1 at topdress	*	247	*	338	ns	122
45 kg N ha^−1 versus 90 kg N ha^−1	**	−210	ns	−117	***	107
Preplant 45 kg N ha^−1 versus 90 kg N ha^−1	***	−452	*	−301	*	109
Topdress 45 kg N ha^−1 versus 90 kg N ha^−1	ns	33	ns	68	*	105
P fertilizer with preplant N versus with topdress N	ns	10	*	314	ns	97
K fertilizer with preplant N versus with topdress N	ns	−72	*	465	ns	35
Preplant N-P fertilizer added versus no P fertilizer added	***	510	**	517	**	−183
Topdress N-P fertilizer added versus no P fertilizer added	**	409	ns	183	**	−163
Preplant N-K fertilizer added versus no K fertilizer added	*	−268	ns	26	*	−123
Topdress N-K fertilizer added versus no K fertilizer added	ns	−104	ns	−275	ns	2

aStandard error of the difference for the interaction of N application timing and fertilizer treatment.
*, **, and *** are significant at the 0.1, 0.01, and 0.001 level, respectively.
ns: not significant at the 0.1 level.