Response of Soil CO₂ Emission and Summer Maize Yield to Plant Density and Straw Mulching in the North China Plain

Table 2

Grain yield and yield components under different mulching and density treatments in 2012 and 2013 summer maize growing seasons.

Treatment	Spike number		Rows per spike		Kernels per row		1000-kernel weight		Grain yield
	(spikes m^−2)		(rows spike^−1)		(Kernels row^−1)		(g)		(g m^−2)
	2012	2013	2012	2013	2012	2013	2012	2013	2012	2013
M1	9.67^a	9.89^a	16.78^a	15.39^ab	27.37^d	27.45^c	294.18^c	309.04^b	1143.92^ab	1140.01^ab
N1	9.63^a	9.81^a	16.11^ab	14.44^b	27.81^cd	26.92^c	296.71^c	296.13^bc	1083.53^b	969.73^bc
M2	7.93^b	7.63^b	16.29^ab	16.17^a	30.85^b	30.16^b	326.03^b	325.7^ab	1255.44^a	1168.85^a
N2	7.63^c	7.63^b	15.82^b	16.06^a	29.52^bc	29.28^bc	299.82^c	265.3^c	1043.53^bc	906.25^c
M3	5.44^d	5.63^c	16.63^ab	16.33^a	35.37^a	35.7^a	343.11^a	358.92^a	1072.95^b	1159.73^a
N3	5.41^d	5.22^d	16.67^a	16.28^a	33.85^a	35.33^a	322.08^b	315.82^b	936.13^c	878.06^c
M	7.67^a	7.72^a	16.56^a	15.96^a	31.20^a	31.10^a	321.10^a	331.22^a	1157.44^a	1156.19^a
N	7.57^a	7.56^b	16.20^a	15.59^a	30.39^a	30.51^a	306.20^b	292.42^b	1021.06^b	918.01^b
1	9.65^a	9.85^a	16.44^ab	14.92^b	27.59^c	27.19^c	295.45^c	302.59^b	1113.72^a	1054.87^a
2	7.78^b	7.63^b	16.06^b	16.11^a	30.19^b	29.72^b	312.92^b	295.50^b	1149.49^a	1037.55^a
3	5.43^c	5.43^c	16.65^a	16.31^a	34.61^a	35.52^a	332.59^a	337.37^a	1004.54^b	1018.89^a

Means in the same column followed by different letters denote significant differences (LSD, 𝑃<0.05).