Bicultures of oat (Avena sativa L.) and grazing vetch (Vicia dasycarpa L.) cover crops increase contents of carbon pools and activities of selected enzymes in a loam soil under warm temperate conditions

Figures & data

Table 1. Average annual cover crop maize biomass inputs across seasons and maize yields (2010/2011), as affected by the different cover crop treatments.

	Average annual dry matter added (kg ha^−1)^&
Treatment	Cover crop	Maize	Total	Maize yield^$ (kg ha^−1)
100% oat	5985^b	10580^b	16565^b	5277^ab
90% oat + 10% vetch	7730^c	10730^bc	18460^c	5489^ab
70% oat + 30% vetch	7689^c	12400^c	20089^e	6368^b
50% oat + 50% vetch	6624^b	11871^bc	18495^cd	5604^ab
100% vetch	6947^bc	12397^c	19344^de	5497^ab
Weedy fallow	3608^a	8964^a	12572^a	4961^a

^&Annual dry matter added is an average biomass value for 2009 and 2010 for cover crops and 2009/2010 and 2010/20110 summer for maize. Total biomass input is the sum of the average annual inputs from cover crops and maize. Oat is Avena sativa L., vetch is Vicia dasycarpa L. and maize is Zea mays L. ^$Maize yields are from Muzangwa et al. (2015). Different letters within a column indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 2. Average concentrations of carbon (C), nitrogen (N) and phosphorus (P) and C:N and C:P ratios of the residues of the different cover crop treatments.

	C	N	P
Treatment	(%)			C:N^§	C:P
100% oat	42.1^c	2.3^a	0.31	18.3^c	133
90% oat + 10% vetch	39.4^bc	3.0^b	0.32	13.1^b	124
70% oat + 30% vetch	39.1^b	3.1^b	0.31	12.6^b	126
50% oat + 50% vetch	38.9^b	3.3^b	0.31	11.8^ab	125
100% vetch	38.7^b	3.9^c	0.32	9.9^a	116
Weedy fallow	35.8^a	3.0^b	0.30	11.9^ab	121

^§Muzangwa et al. (2015). Oat is Avena sativa L. and vetch is Vicia dasycarpa L. Different letters within a column indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 3. Average annual carbon inputs as cover crop (winter 2009 and 2010) and maize biomass (summer 2009/2010 and 2010/2011), as affected by the different cover crop treatments.

	Annual carbon inputs (kg ha^−1)^&
Treatment	Cover crop	Maize^#	Total^$
100% oat	2520^b	4338^ab	6858^b
90% oat + 10% vetch	3046^bc	4400^bc	7445^b
70% oat + 30% vetch	3006^c	5084^c	8090^c
50% oat + 50% vetch	2577^b	4867^bc	7444^b
100% vetch	2689^b	5083^c	7772^bc
Weedy fallow	1290^a	3675^a	4965^a

^&Annual carbon inputs were calculated from average annual biomass input multiplied by carbon concentrations in Table 2. ^#Average carbon concentration in maize dry matter was 41%. Oat is Avena sativa L., vetch is Vicia dasycarpa L. and maize is Zea mays L.

^$ Total carbon input is the sum of the inputs from cover crops and maize.

Different letters within a column indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 4. P-values from the two-way analysis of variance on soil carbon (C) pools and enzyme activities, with cover crop treatment and depth as factors.

Property	Treatment	Depth	Treatment x depth
Total carbon	0.020	< 0.001	NS
POM	< 0.001	< 0.001	< 0.028
WSC	< 0.001	< 0.001	< 0.001
MBC	< 0.001	< 0.001	NS
β-glucosidase	< 0.001	< 0.001	< 0.001
Dehydrogenase	< 0.001	< 0.001	< 0.001
Urease	< 0.001	< 0.001	< 0.001
Aryl-sulphatase	< 0.001	< 0.001	< 0.001
Acid phosphomonoesterase	< 0.001	< 0.001	< 0.001
Alkaline phosphomonoesterase	< 0.001	< 0.001	< 0.001

POM = particulate organic matter; WSC = water soluble carbon; MBC = microbial biomass carbon;

NS = not significant.

Table 5. Total and microbial biomass carbon (C) under different cover crop treatments and depths.

	Total C (%)	Microbial biomass C (µg g^−1 soil)
Treatment
100% oat	0.99^ab	2057^b
90% oat +10% vetch	1.05^ab	2531^c
70% oat + 30% vetch	1.10^ab	2727^d
50% oat + 50% vetch	1.09^ab	2090^b
100% vetch	1.14^b	2074^b
Weedy fallow	0.96^a	1878^a
Depth (cm)
0–5	1.17	2308
5–20	0.94	2144

Oat is Avena sativa L. and vetch is Vicia dasycarpa L. Different letters within a column indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 6. Particulate organic matter (POM) and water soluble carbon (WSC) under different cover crop treatments and depth.

	POM (%)		WSC (mg g^−1 soil)
Cover crop treatment	0–5 cm	5–20 cm	0–5 cm	5–20 cm
100% oat	2.23^g	1.90^f	1.77^d	1.45^b
90% oat +10% vetch	1.95^f	1.39^cd	1.94^e	1.78^d
70% oat + 30% vetch	1.81^ef	1.35^c	2.21^f	1.95^e
50% oat + 50% vetch	1.59^de	1.24^c	1.89^e	1.63^c
100% vetch	1.36^cd	0.96^b	1.87^de	1.51^b
Weedy fallow	0.86^ab	0.64^a	1.63^c	1.28^a

Oat is Avena sativa L. and vetch is Vicia dasycarpa L. Different letters within both columns of the same parameter indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 7. Cover crop treatment and soil depth effects on β-glucosidase (μg PNP g⁻¹ soil h⁻¹) and dehydrogenase activity (μg TPF g⁻¹ soil h⁻¹).

	β-glucosidase		Urease
Cover crop treatment	0–5 cm	5–20 cm	0–5 cm	5–20 cm
100% oat	33.3^e	21.8^ab	1968^c	1968^c
90% oat +10% vetch	37.1^f	25.3^c	1970^e	1968^c
70% oat + 30% vetch	41.4^gh	25.7^c	1971^f	1969^d
50% oat + 50% vetch	40.1^g	24.0^bc	1972^g	1969^d
100% vetch	43.7^h	26.1^c	1972^g	1970^e
Weedy fallow	29.4^d	21.1^a	1967^b	1965^a

Oat is Avena sativa L. and vetch is Vicia dasycarpa L. Different letters within both columns of the same parameter indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 8. Cover crop treatment and soil depth effects on urease (μg urea g⁻¹ soil h⁻¹) and aryl-sulphatase activity (μg PNP g⁻¹ soil h⁻¹).

	Dehydrogenase		Aryl-sulphatase
Cover crop treatment	0–5 cm	5–20 cm	0–5 cm	5–20 cm
100% oat	1238^i	696^c	35.7^h	29.5^c
90% oat +10% vetch	1599^k	884^e	38.0^i	33.6^f
70% oat + 30% vetch	1636^l	922^f	38.9^j	34.6^g
50% oat + 50% vetch	1358^j	732^d	35.5^h	30.7^d
100% vetch	1205^h	661^b	34.2^fg	27.5^b
Weedy fallow	1137^g	540^a	31.7^e	26.2^a

Oat is Avena sativa L. and vetch is Vicia dasycarpa L. Different letters within both columns of the same parameter indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 9. Cover crop treatment and soil depth effects on acid and alkaline phosphatase activity (μg PNP g⁻¹ soil h⁻¹).

	Acid phosphomonoesterase		Alkaline phosphomonoesterase
Cover crop treatment	0–5 cm	5–20 cm	0–5 cm	5–20 cm
100% oat	34.4^f	33.7^cdef	35.3^f	28.4^c
90% oat +10% vetch	34.3^f	33.9^def	45.8^h	32.2^de
70% oat + 30% vetch	35.4^g	34.1^ef	48.9^i	34.0^ef
50% oat + 50% vetch	33.5^cde	32.5^b	34.2^f	26.6^c
100% vetch	34.1^ef	33.3^cd	37.1^g	30.9^d
Weedy fallow	33.2^c	30.8^a	19.5^b	17.6^a

Oat is Avena sativa L. and vetch is Vicia dasycarpa L. Different letters within both columns of the same parameter indicate differences at p = 0.05 according to a Tukey-Kramer test.

Table 10. Correlation coefficients (r) of soil carbon (C) pools and enzyme activity with carbon inputs.

	Cover C input	Maize C input	Total C input	Soil total C	MBC	POM	WSC	β - glucos	Dehydr	Ureas	Aryl sulphat	Acid phospho	Alkaline phospho
Cover C input
Maize C input	0.777
Total C input	0.952**	0.933**
Total soil C	0.690	0.944**	0.855*
MBC	0.761	0.489	0.674	0.420
POM	0.747	0.331	0.589	0.098	0.508
WSC	0.803*	0.767	0.834*	0.674	0.914*	0.445
β -glucos	0.747	0.970**	0.901*	0.994**	0.463	0.194	0.716
Dehydr	0.752	0.431	0.641	0.373	0.967**	0.525	0.864*	0.413
Urease	0.688	0.920**	0.843*	0.968**	0.381	0.133	0.641	0.964**	0.396
Aryl sulphat	0.890*	0.562	0.784	0.422	0.929**	0.767	0.878*	0.490	0.934**	0.433
Acid phospho	0.732	0.564	0.694	0.386	0.837*	0.642	0.838*	0.457	0.703	0.272	0.833*
Alkaline phospho-	0.958**	0.702	0.891*	0.610	0.909*	0.701	0.898*	0.667	0.870*	0.575	0.956**	0.857*

*Correlation is significant at p = 0.05 level; ** correlation is significant at p = 0.01 level. MBC = microbial biomass carbon; POM = particulate organic matter; WSC = water soluble carbon; β-glucos = β-glucosidase; Dehydr = dehydrogenase; Aryl sulphat = Aryl sulphatase; phospho = phosphomonoesterase. Maize is Zea mays L.

Figure 1. Microbial biomass carbon (MBC) response to water soluble carbon (WSC) at (a) 0–5 cm and (B) 5–20 cm soil depths.

Figure 2. Microbial biomass carbon (MBC) response to particulate organic matter (POM) at (A) 0–5 cm and (B) 5–20 cm soil depths.

Muzangwa LR, Chiduza C, Muchaonyerwa P 2015: Bicultures of oat (Avena sativa) and grazing vetch (Vicia dasycarpa) regulate residue decomposition, nitrogen and phosphorus dynamics, and weed suppression in Maize. Int. J. Agr. Biol., 17, 475–482.

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