The effect of crop rotation on soil health in the north-western Free State region, South Africa

Figures & data

Table 1: Plot design of trials on the farm Christinasrus for three consecutive seasons

Plot number	Rotational system	Crops planted
		Season 1 (2020/2021)	eason 2 (2021/2022)	Season 3 (2022/2023)
Replicate 1
Plot 1	MMS	Maize	Maize	Soybean
Plot 2	MS	Maize	Soybean	Maize
Plot 3	MM	Maize	Maize	Maize
Plot 4	MCS	Maize	Cover crop	Soybean
Plot 5	MCS	Cover crop	Soybean	Maize
Plot 6	MMS	Soybean	Maize	Maize
Plot 7	MS	Soybean	Maize	Soybean
Plot 8	MCS	Soybean	Cover crop	Maize
Plot 9	MMS	Maize	Soybean	Maize
Replicate 2
Plot 10	MCS	Maize	Cover crop	Soybean
Plot 11	MS	Soybean	Maize	Soybean
Plot 12	MCS	Cover crop	Soybean	Maize
Plot 13	MMS	Maize	Maize	Soybean
Plot 14	MCS	Soybean	Maize	Cover crop
Plot 15	MM	Maize	Maize	Maize
Plot 16	MMS	Maize	Soybean	Maize
Plot 17	MS	Maize	Soybean	Maize
Plot 18	MMS	Soybean	Maize	Maize
Replicate 3
Plot 19	MM	Maize	Maize	Maize
Plot 20	MMS	Soybean	Maize	Maize
Plot 21	MCS	Maize	Cover crop	Soybean
Plot 22	MS	Soybean	Maize	Soybean
Plot 23	MMS	Maize	Maize	Soybean
Plot 24	MMS	Maize	Soybean	Maize
Plot 25	MS	Maize	Soybean	Maize
Plot 26	MCS	Cover crop	Soybean	Maize
Plot 27	MCS	Soybean	Maize	Cover crop

Figure 1: Rainfall distribution over Christinasrus, Season 1 (2020/2021, Season 2 (2021/2022) and Season 3 (2022/2023), respectively

Table 2: Soil properties measured and integrated to obtain an overall soil health score using HSHT

Soil pH (H2O)
Physical properties	Volumetric stability
	Organic matter (OM)
Chemical properties	Total water extractable N (WEN)		Soil health score
	Inorganic N (NO3-N and NH4-N)
	Organic N (WEON)
	Total P
	Total K
Biological properties	Soil respiration CO2-C
	Water extractable organic C (WEOC)

Table 3: Mean measurements ± standard deviation of three replicates, ANOVA results of soil properties, and subsequent soil health score for each cropping system in each season

Soil properties		Cropping system		Season 1 (2020/2021)	Season 2 (2021/2022)	Season 3 (2022/2023)	Mean	ANOVA results
								Cropping system		Season		Cropping system × Season
								F	p-value	F	p-value	F	p-value
Soil pH (H2O)		MM		6.04 ± 0.10	7.13 ± 0.29	7.43 ± 0.15	6.87 ± 0.66	0.57	0.69	91.96	<0.001	0.80	0.61
		MMS2		6.16 ± 0.10	7.23 ± 0.10	7.83 ± 0.29	7.07 ± 0.78
		MMS1		5.95 ± 0.08	7.43 ± 0.60	7.53 ± 0.29	6.97 ± 0.84
		MS		5.97 ± 0.20	7.03 ± 0.55	7.70 ± 0.36	6.90 ± 0.83
		MCS		6.22 ± 0.27	6.93 ± 0.42	7.60 ± 0.10	6.92 ± 0.65
			Mean	6.07 ± 0.18	7.15 ± 0.43	7.62 ± 0.26
Physical properties	Volumetric aggregate stability:	All systems		2%	2%	2%	2%
	OM (%)	MM		0.50 ± 0.17	0.37 ± 0.12	0.37 ± 0.12	0.41 ± 0.14	0.63	0.65	6.36	0.005	0.67	0.72
		MMS2		0.47 ± 0.06	0.37 ± 0.06	0.40 ± 0.00	0.41 ± 0.06
		MMS1		0.43 ± 0.12	0.40 ± 0.00	0.33 ± 0.06	0.39 ± 0.08
		MS		0.40 ± 0.00	0.30 ± 0.10	0.37 ± 0.12	0.36 ± 0.09
		MCS		0.47 ± 0.06	0.27 ± 0.06	0.40 ± 0.10	0.38 ± 0.11
			Mean	0.45 ± 0.10	0.34 ± 0.08	0.37 ± 0.08
Chemical properties	WEN (mg kg^-1)	MM		11.83 ± 4.21	10.80 ± 0.44	10.53 ± 1.04	11.06 ± 2.26	0.73	0.58	0.75	0.48	0.84	0.58
		MMS2		11.80 ± 0.53	10.37 ± 0.37	13.87 ± 4.27	12.01 ± 2.60
		MMS1		12.70 ± 4.27	11.80 ± 0.87	9.63 ± 1.25	11.38 ± 2.65
		MS		10.23 ± 2.54	9.97 ± 0.87	10.80 ± 1.15	10.33 ± 1.51
		MCS		11.87 ± 3.67	10.67 ± 0.68	13.17 ± 2.18	11.90 ± 2.42
			Mean	11.69 ± 2.95	10.72 ± 0.85	11.60 ± 2.59
	Inorganic N (mg kg^-1)	MM		5.83 ± 1.78	5.26 ± 0.73	3.43 ± 0.25	4.84 ± 1.46	0.57	0.69	1.51	0.24	1.15	0.36
		MMS2		4.63 ± 0.81	5.77 ± 0.44	5.90 ± 4.11	5.43 ± 2.19
		MMS1		5.57 ± 1.63	5.96 ± 0.90	4.10 ± 0.36	5.21 ± 1.27
		MS		4.60 ± 0.79	5.38 ± 1.11	3.37 ± 0.45	4.45 ± 1.14
		MCS		5.47 ± 1.85	4.27 ± 0.80	5.50 ± 1.49	5.08 ± 1.39
			Mean	5.22 ± 1.33	5.33 ± 0.92	4.46 ± 1.99
	WEON (mg kg^-1)	MM		8.23 ± 2.16	5.43 ± 0.15	7.10 ± 0.92	6.92 ± 1.69	0.83	0.52	22.63	< 0.001	0.94	0.50
		MMS2		8.60 ± 0.92	4.57 ± 0.55	8.10 ± 0.44	7.09 ± 2.00
		MMS1		9.70 ± 2.38	5.80 ± 1.65	6.07 ± 1.16	7.19 ± 2.45
		MS		7.37 ± 1.75	4.03 ± 0.61	7.23 ± 1.31	6.21 ± 1.99
		MCS		8.77 ± 2.83	5.50 ± 0.26	7.63 ± 0.81	7.30 ± 2.06
			Mean	8.53 ± 1.95	5.10 ± 0.98	7.23 ± 1.08
Chemical properties (contd)	Total P (mg kg^-1)	MM		32.00 ± 8.54	35.37 ± 7.86	24.00 ± 7.81	30.46 ± 8.89	0.26	0.90	4.60	< 0.001	1.69	0.14
		MMS2		35.33 ± 2.08	33.71 ± 5.86	23.67 ± 6.66	30.90 ± 7.12
		MMS1		42.00 ± 5.57	31.52 ± 1.03	25.00 ± 3.61	32.84 ± 8.15
		MS		31.33 ± 5.69	31.00 ± 7.77	31.00 ± 8.54	31.11 ± 6.44
		MCS		28.33 ± 3.22	29.89 ± 4.34	32.00 ± 7.81	30.07 ± 5.01
			Mean	33.80 ± 6.89	32.30 ± 5.42	27.13 ± 7.07
	Total K (mg kg^-1)	MM		93.00 ± 34.77	80.71 ± 4.82	104.00 ± 29.46	92.57 ± 25.04	1.14	0.36	1.36	0.27	0.88	0.55
		MMS2		82.67 ± 30.75	83.37 ± 17.66	102.67 ± 30.73	89.57 ± 25.44
		MMS1		83.67 ± 25.33	75.24 ± 9.08	71.33 ± 12.86	76.75 ± 15.88
		MS		62.00 ± 7.55	87.69 ± 15.58	81.67 ± 20.82	77.12 ± 17.85
		MCS		85.00 ± 19.08	61.28 ± 9.67	90.33 ± 17.47	78.87 ± 19.24
			Mean	81.27 ± 23.94	77.66 ± 14.03	90.00 ± 25.54
Biological properties	Soil respiration (mg kg^-1 CO2-C)	MM		21.26 ± 1.75	16.67 ± 2.89	11.33 ± 1.53	16.42 ± 4.68	0.45	0.77	77.99	< 0.001	1.30	0.28
		MMS2		19.63 ± 3.63	13.67 ± 1.15	13.00 ± 0.00	15.43 ± 3.69
		MMS1		21.37 ± 3.80	13.33 ± 3.06	10.67 ± 0.58	15.12 ± 5.41
		MS		21.28 ± 0.24	14.33 ± 2.31	11.00 ± 1.00	15.54 ± 4.71
		MCS		22.24 ± 2.91	12.00 ± 1.00	12.33 ± 1.53	15.52 ± 5.32
			Mean	21.16 ± 2.52	14.00 ± 2.48	11.67 ± 1.29
	WEOC (mg kg^-1)	MM		84.33 ± 17.50	56.00 ± 9.85	87.00 ± 17.52	75.78 ± 19.97	0.03	0.99	31.79	< 0.001	1.26	0.30
		MMS2		86.33 ± 9.87	50.00 ± 4.00	89.33 ± 13.58	75.22 ± 20.83
		MMS1		98.33 ± 16.07	58.33 ± 5.51	68.67 ± 15.95	75.11 ± 21.43
		MS		80.33 ± 15.31	56.00 ± 9.64	87.00 ± 14.80	74.44 ± 18.34
		MCS		89.33 ± 16.86	46.33 ± 4.73	86.00 ± 9.64	73.89 ± 23.00
			Mean	87.73 ± 14.42	53.33 ± 7.63	83.60 ± 14.56
Overall soil health		MM		4.64 ± 0.51	3.33 ± 0.49	3.60 ± 0.26	3.86 ± 0.71	0.17	0.95	48.14	< 0.001	1.27	0.30
		MMS2		4.55 ± 0.63	2.83 ± 0.15	3.90 ± 0.26	3.76 ± 0.83
		MMS1		5.07 ± 0.93	3.07 ± 0.45	3.07 ± 0.45	3.74 ± 1.15
		MS		4.47 ± 0.46	2.97 ± 0.06	3.57 ± 0.46	3.67 ± 0.73
		MCS		4.89 ± 0.91	2.70 ± 0.00	3.77 ± 0.31	3.78 ± 1.06
			Mean	4.72 ± 0.65	2.98 ± 0.34	3.58 ± 0.42

Figure 2: Seasonal trend for total P and microbial respiration (CO₂-C), measured as Mg kkg⁻¹, over the duration of the study

Figure 3: Seasonal trend for WEON and WEOC, measured as mg kg⁻¹, over the duration of the study

Figure 4: Haney soil health scores in each cropping system for Season 1 (2020/2021), Season 2 (2021/2022) and Season 3 (2022/2023). MMS = Maize–Maize–Soybean, MS = Maize–Soybean, MCS = Maize–Cover crop–Soybean. The MMS system was split into MMS1 and MMS2 to distinguish between maize Season 1 (MMS1) and maize Season 2 (MMS2)