Biomass production, weed suppression, nitrogen and phosphorus uptake in white oat (Avena sativa L.) and grazing vetch (Vicia dasycarpa L.) cover crop bicultures under an irrigated no-till system

Figures & data

Table 1 : Mean monthly temperatures, rainfall and irrigation at the University of Fort Hare Research Farm from May to September in the 2009 and 2010 seasons

	Temperature (°C)				Rainfall (mm)				Irrigation (mm)
Month	2009	2010	30-year mean	CV (%)	2009	2010	30-year mean	CV (%)	2009	2010
May	16.3	17.2	15.73	6.2	14.9	5.6	20.7	114	20	15
June	13.6	13.2	12.99	6.2	20.5	48.3	21.4	98	40	30
July	13.5	14.23	12.97	8	53	16.8	17.8	105	15	45
August	15	16.17	14.31	7..3	15	12	32.1	109	45	50
September	16	17.49	16.05	5.8	25.3	9.1	34.2	95	0	10
Total					129	92			120	150

Table 2 : Effect of cover crop treatments and season on cover crop growth rates (CCGRs). Means followed by different letters in the same column differ significantly at p < 0.05

	2009 season		2010 season
Treatment	Slope	R ^2	Slope	R ^2
100% oat	68.5	0.96	55.4^c	0.93
90% oat + 10% vetch	65.0	0.96	84.3^ab	0.97
70% oat + 30% vetch	64.1	0.95	93.7^a	0.95
50% oat + 50% vetch	65.9	0.91	76.3^b	0.94
100% vetch	70.9	0.92	61.6^c	0.96
LSD0.05 (Interaction)	14.07
LSD0.05 (Season)	6.29
LSD0.05 (Treatment)^1	9.95
^1 Treatment LSD0.05 used for the mean separation of the CCGRs

Figure 1:  Effect of cover crop treatments on final cover crop dry matter at termination in the 2009 and 2010 winter seasons

Table 3 : Effect of cover crop treatments on weed dry matter (kg DM ha⁻¹) at various sampling times during the 2009 winter season. Means followed by different letters in the same column differ significantly at p < 0.05

Cover crop treatment	33 DAS	47 DAS	61 DAS	77 DAS	105 DAS	128 DAS
100% oat	98^c	321^b	682^b	810^b	917^c	961^c
90% oat + 10% vetch	150^bc	340^b	769^b	819^b	1 093^b	1 109^bc
70% oat + 30% vetch	176^bc	360^b	735^b	782^b	1 056^b	1 195^bc
50% oat + 50% vetch	236^b	355^b	743^b	847^b	1 121^b	1 213^bc
100% vetch	250^b	266^b	670^b	820^b	1 094^b	1 419^b
Weedy fallow	747^a	1 614^a	2 620^a	3 084^a	3 431^a	3 916^a
Significance	***	***	***	***	***	***
LSD0.05	136	244	408	502	130	406
CV (%)	27.2	24.8	21.5	23.1	4.9	13.6

Table 4 : Effect of cover crop treatments on weed dry matter (kg DM ha^-1) at various sampling times during the 2010 winter season. Means followed by different letters in the same column differ significantly at p < 0.05

Cover crop treatment	59 DAS	84 DAS	101 DAS	117 DAS	132 DAS
100% oat	455^b	633^b	699^b	317^b	303^c
90% oat + 10% vetch	321^c	496^c	357^c	234^b	221^b
70% oat + 30% vetch	382^bc	400^c	294^c	218^b	213^b
50% oat + 50% vetch	310^cd	418^c	318^c	226^b	226^b
100% vetch	188^d	395^c	299^c	252^b	202^b
Weedy fallow	2 010^a	2 156^a	2 591^a	2 955^a	3 292^a
Significance	***	***	***	***	***
LSD0.05	124	132	174	161	205
CV (%)	11.2	9.7	12.6	12.6	15.2

Figure 2:  Effect of cover crop treatments on weed species counts at cover crop termination in the 2009 and 2010 winter seasons

Figure 3:  Effect of cover crop treatments on nitrogen uptake at cover crop termination in the 2009 and 2010 winter seasons

Figure 4:  Effect of cover crop treatments on phosphorus uptake at cover crop termination in the 2009 and 2010 winter seasons