Conservation agriculture effects on plant nutrients and maize grain yield after four years of maize–winter cover crop rotations

Figures & data

Table 1: Summary of treatments used in the study

Type of cover crop (main plots)	Maize (subplots)	Treatment
Oat	Fertiliser applied	1
	No fertiliser applied	2
Vetch	Fertiliser applied	3
	No fertiliser applied	4
Fallow	Fertiliser applied	5
	No fertiliser applied	6

Figure 1: Winter cover crop type × fertiliser interaction effects on soil mineral nitrogen (N) (mg kg⁻¹)

Table 2: Effects of cover crop type, fertiliser and soil depth on extractable nutrients (mg l⁻¹). Means followed by the same superscript letter within the same column are not significantly different

Treatment	P	Mg	Ca	K	Cu	Mn	Zn
Cover crop type
Oat	30.9^b	389.9^a	1 329	112.4	4.62^a	25.2^b	6.38^a
Grazing vetch	39.9^a	330.4^b	1 347	118.7	4.36^a	31.8^a	7.05^a
Weedy fallow	19.8^c	376.7^a	1 397	102.2	3.96^b	22.6^b	4.40^b
	***	**	ns	ns	**	**	***
Fertiliser
Fertilised	32.5	341.8	1 319	113.3	4.27	27.0	6.53
Non fertilised	27.9	368.8	1 396	108.9	4.35	26.8	5.35
	*	**	ns	ns	ns	ns	*
Soil depth
0–5 cm	32.1	365.1	1 370	139.4	4.28	30.9	6.77
5–20 cm	28.2	345.5	1 345	82.8	4.35	22.9	5.96
	ns	ns	ns	***	ns	**	**

* p < 0.05, ** p < 0.01, *** p < 0.001, ns = not significant

Figure 2: Effects of cover crop type and fertiliser regime on maize grain yield across four seasons (2007–2011)

Figure 3: Winter cover crop type × fertiliser interaction effects on grain nitrogen (N) concentration

Table 3: Effects of winter cover crop type on grain nutrient concentration

Cover crop	Ca (%)	Mg (%)	P (%)	K (%)	Zn (mg kg^–1)	Cu (mg kg^–1)	Mn (mg kg^–1)
Vetch	0.034	0.106	0.297	0.318	25.0	1.748	8.36
Oat	0.031	0.112	0.307	0.305	27.2	1.313	8.42
p value	ns	ns	ns	ns	ns	ns	ns
CV (%)	25.2	8.4	8.8	10.3	20.9	27.5	15.6

ns = Not significant