Crop rotation and organic matter application restore soil health and productivity of degraded highland crop farms in northwest Ethiopia

Figures & data

Figure 1. Location map of the study sites in Gusha Shinkurta rural village, Guagusa Shikudad district, Amhara region, northwest Ethiopian highlands (Democh was station testing site, while Buahit, Cherta, Enter and Zoble were on-farm testing sites).

Table 1. Three phases of crop rotations used for the experiment in three consecutive years from 2013 to 2015

R	1st rotation phase (2013)	2nd rotation phase (2014)	3rd rotation phase (2015)
R1	Bread wheat …. … . … . … . … . … . … .	Clover … . … . … . … . … . … . … . … . … .	Potato
R2	Clover … . … . … . … . … . … . … . … . … .	Bread wheat US lupine … . … .	Potato
R3	Potato … . … . … . … . … . … . … . … . … …	Clover … . … . … . … . … . … . … . … . … .	Bread wheat
R4	Bread wheat US lupine … . … … .	Potato US lupine … . … . … . … … .	Bread wheat
R5	Lupine … . … . … . … . … . … . … . … . … .	Potato US lupine … . … . … . … . … .	Bread Wheat

R, rotation; US, under sowing; years 2013, 2014, and 2015 represented 1^st, 2^nd, and 3^rd consecutive rotation phases, respectively; crop rotation in different years was done on the same fixed plots, for instance, in the first rotation (R1), plots occupied with bread wheat in 2013 were occupied with clover and potato in 2014 and 2015, respectively.

Table 2. Physicochemical properties of the experimental soils before starting the experiment in 2013 in Awi highlands, northwest Ethiopia

Soil properties	On-station	On-farms	Mean	Category
Bulk density (g cm^−3)	1.36	1.37	1.37	Compacted@
pH (H2O)	5.36	5.15	5.19	Moderately acidic#
CEC (cmol(+) kg^−1)	16.10	15.52	15.64	Moderate*
Organic carbon (%)	1.30	1.25	1.26	Low*
Total nitrogen (%)	0.13	0.11	0.12	Low*
Available P (ppm)	9. 54	8.64	9.09	Low*
Exc. K (cmol(+) kg^−1)	0.68	0.67	0.68	Low*
Particle distribution
Sand (%)	27.00	29.50	29.00
Silt (%)	35.00	34.25	34.40
Clay (%)	38.00	36.25	36.60
Textural class	Clay loam	Clay loam	Clay loam

CEC = cation exchange capacity; P = phosphorus; K = potassium; ppm = part per million; pH = potential of hydrogen; @Blake and Hartge (1986), Panda (2010), and Landon (1991).

Table 3. Average soil properties over sites combination after three-year interventions of crop rotation and manure application in 2015 in Awi highlands, northwest Ethiopia

Treatment		Soil properties
a) Rotation (R)		BD	pH	CEC	SOC	TN	AP	EK
R1		1.16	5.92	23.24^a	2.06^a	0.23^a	15.40^a	0.87^a
R2		1.19	5.87	22.89^a	2.02^a	0.21^b	15.36^a	0.85^ab
R3		1.20	5.83	21.68^bc	1.82^b	0.20^bc	14.34^b	0.79^bc
R4		1.23	5.75	21.24^c	1.72^b	0.18^d	13.94^b	0.74 ^c
R5		1.21	5.80	21.50^bc	1.77^b	0.19 ^cd	14.19^b	0.78 ^c
P-value		ns	ns	*	*	*	*	*
SE±		0.02	0.07	0.43	0.04	0.01	0.29	0.02
b) Manure (M)
M1		1.29^a	5.54^c	19.66^c	1.52^d	0.14^d	12.40^c	0.73 ^c
M2		1.23^b	5.78^b	21.49^b	1.82^c	0.17 ^c	14.53^b	0.77^bc
M3		1.18^b	5.94^ab	22.43^b	1.99^b	0.23^b	14.96^b	0.81^b
M4		1.10^c	6.08^a	24.87^a	2.19^a	0.26^a	16.70^a	0.91^a
P-value		**	**	**	**	**	**	**
SE±		0.02	0.06	0.38	0.03	0.01	0.26	0.02
c) Interaction
R	M
R1	M1	1.25^abcdf	5.61^efghi	20.77^hij	1.59^ghi	0.16^gh	13.43^gh	0.79^efghi
	M2	1.19^cdfeg	5.81^bcdefgh	22.49^cdefgh	2.04^c	0.20^ef	14.98^cdef	0.83^cdefgh
	M3	1.15^feghi	6.07^abc	23.61^bcdef	2.22^abc	0.25^bc	16.04^abc	0.89^bcd
	M4	1.06^i	6.20^a	26.09^a	2.38^a	0.30^a	17.16^a	0.98^a
R2	M1	1.28^abcd	5.56^fghi	20.37^ij	1.55^ghi	0.15^hi	13.23^gh	0.77^fghijk
	M2	1.21^bcdfeg	5.80^bcdefgh	22.36^defghi	2.16^bc	0.18^fg	15.99^abcd	0.81^defgh
	M3	1.18^degh	6.00^abcd	23.31^cdefg	2.04^c	0.24 ^cd	15.25^bcde	0.86^bcde
	M4	1.08^hi	6.11^ab	25.53^ab	2.33^ab	0.27^b	16.98^a	0.94^ab
R3	M1	1.29^abc	5.51^hi	19.17^j	1.52^ghi	0.15^hi	12.22^hi	0.71^ijk
	M2	1.23^abcdfe	5.79^bcdefgh	20.89^hij	1.67^fg	0.17^gh	13.90^ef	0.75^ghijk
	M3	1.18^degh	5.90^abcde	22.14^efghi	1.94^de	0.22^de	14.59^defg	0.78^efghij
	M4	1.10^ghi	6.10^ab	24.52^abc	2.13^c	0.26^bc	16.64^ab	0.90^abc
R4	M1	1.32^a	5.46^i	18.91^j	1.44^i	0.13^i	11.37^h	0.69 ^k
	M2	1.27^abcd	5.72^defghi	20.83^hij	1.58^ghi	0.15^hi	13.76^fg	0.70^jk
	M3	1.20^bcdfeg	5.84^bcdefg	21.28^ghi	1.83^ef	0.20^ef	14.35^efg	0.74^hijk
	M4	1.14^efghi	5.99^abcd	23.93^bcde	2.04^cd	0.24 ^cd	16.26^abc	0.84^cdef
R5	M1	1.30^ab	5.54^ghi	19.06^j	1.48^hi	0.13^i	11.73^i	0.69 ^k
	M2	1.24^abcdfe	5.76^cdefghi	20.86^hij	1.65^fgh	0.16^gh	14.00^efg	0.74^hijk
	M3	1.19^cdfeg	5.87^bcdef	21.81^fghi	1.90^de	0.22^de	14.55^efg	0.77^fghijk
	M4	1.11^ghi	6.02^abcd	24.27^abcd	2.06^cd	0.25^bc	16.46^ab	0.90^abc
P-value		**	*	**	**	**	**	**
SE±		0.04	0.13	0.86	0.07	0.01	0.57	0.03
CV (%)		6.62	4.48	7.78	7.94	7.75	7.82	8.64

BD = bulk density (g cm⁻³); pH (H2O) = potential of hydrogen in water suspension; CEC = cation exchange capacity (cmol(+) kg⁻¹); OC = organic carbon (%); TN = total nitrogen (%); AP = available phosphorous (ppm); EK = exchangeable potasium (cmol(+) kg⁻¹); R1 = bread wheat–clover–potato; R2 = clover–bread wheat undersowing lupine–potato; R3 = potato–clover–bread wheat; R4 = bread wheat undersowing lupine–potato undersowing lupine–bread wheat; R5 = lupine–potato undersowing lupine–bread wheat; ⁺In the first and second cropping seasons, crop residues of wheat and potato after harvesting were incorporated into the soil, while the biomass of clover and lupine was chopped and incorporated into the soil at their 50% flowering; M1 = control at 0tha⁻¹ manure; M2 = 2.5tha⁻¹ sesbania green manure (SGM); M3 = 5tha⁻¹ fresh cattle manure (FCM); M4 = 2.5tha⁻¹ SGM + 5tha⁻¹ FCM; P = probability; **highly significant at P < 0.01; *sgnificant at P < 0.05; ns = not significant at P ≥ 0.05; SE = standard error; CV = coefficient of variation; means in a column followed with the same letter are not significantly different at P ≥ 0.05.

Table 4. Average percentile changes of soil properties over sites combination after three-year interventions of crop rotation and manure application in 2015 compared to the initial before starting the experiments in 2013 in Awi highlands, northwest Ethiopia

Treatment		Mean percentile changes of soil properties
a) Rotation (R)		BD	pH	CEC	SOC	TN	AP	EK
R1+		−15.15^a	12.60^a	48.59^a	63.29^a	89.58^a	69.44^a	28.31^a
R2+		−13.32^ab	11.55^ab	46.37^a	60.32^ab	75.00^ab	69.00^a	24.26^ab
R3+		−12.41^ab	10.74^ab	38.62^b	44.05^ab	66.67^ab	57.73^b	15.44^bc
R4+		−10.04^b	9.36^b	35.79^b	36.71^b	50.00^b	53.30^b	9.19^c
R5+		−11.68^ab	10.22^ab	37.47^b	40.67^ab	58.33^ab	56.05^b	13.97^bc
P-value		*	*	*	*	*	*	*
SE±		0.21	0.12	0.80	0.97	1.32	1.19	0.39
b) Manure (M)
M1		−5.99^c	5.25^c	25.68^b	20.32^c	20.00^b	36.37^b	7.35^c
M2		−10.36^bc	9.81^b	37.38^b	44.44^bc	43.33^b	59.80^ab	12.65^bc
M3		−13.87^b	12.85^a	43.41^ab	57.62^ab	88.33^a	64.53^ab	18.82^b
M4		−19.85^a	15.67^a	59.00^a	73.65^a	120.00^a	83.72^a	34.12^a
P-value		**	**	**	**	**	**	**
SE±		0.19	0.11	0.72	0.87	1.18	1.07	0.35
c) Interaction
R	M
R1+	M1	−8.76^efgh	6.65^fghij	32.80^ab	26.19^cde	33.33^ef	47.74^abc	16.18^cdefgh
	M2	−13.14^abcdefgh	10.46^bcdefghi	43.80^ab	61.90^abcd	66.67^bcdef	64.80^abc	22.06^bcdefg
	M3	−16.06^abcdef	15.40^abcd	50.96^ab	76.19^ab	108.33^abc	76.46^abc	30.88^abcd
	M4	−22.63^a	17.87^a	66.82^a	88.89^a	150.00^a	88.78^a	44.12^a
R2+	M1	−6.57^fgh	5.70^ghij	30.24^ab	23.02^de	25.00^ef	45.54^abc	13.24^defgh
	M2	−11.68^bcdefgh	10.27^bcdefghi	42.97^ab	71.43^abc	50.00^cdef	75.91^abc	19.12^bcdefgh
	M3	−13.87^abcdefg	14.07^abcde	49.04^ab	61.90^abcd	100.00^abcd	67.77^abc	26.47^abcde
	M4	−21.17^ab	16.16^ab	63.24^a	84.92^a	125.00^ab	86.80^ab	38.24^ab
R3+	M1	−5.84^gh	4.75^ij	22.57^b	20.63^de	25.00^ef	34.43^abc	4.41^fgh
	M2	−10.22^cdefgh	10.08^cdefghi	33.57^ab	32.54^bcde	41.67^def	52.92^abc	10.29^efgh
	M3	−13.87^abcdefg	12.17^abcdef	41.56^ab	53.97^abcde	83.33^bcde	60.51^abc	14.71^defgh
	M4	−19.71^abc	15.97^abc	56.78^ab	69.05^abc	116.67^ab	83.06^abc	32.35^abcd
R4+	M1	−3.65^h	3.80^j	20.91^b	14.29^e	8.33^f	25.08^c	1.47^h
	M2	−7.30^efgh	8.75^efghij	33.18^ab	25.40^cde	25.00^ef	51.38^abc	2.94^gh
	M3	−12.41^bcdefgh	11.03^bcdefgh	36.06^ab	45.24^abcde	66.67^bcdef	57.87^abc	8.82^efgh
	M4	−16.79^abcde	13.88^abcde	53.01^ab	61.90^abcd	100.00^abcd	78.88^abc	23.53^bcdef
R5+	M1	−5.11^gh	5.32^hij	21.87^b	17.46^de	8.33^f	29.04^bc	1.47^h
	M2	−9.49^defgh	9.51^defghij	33.38^ab	30.95^bcde	33.33^ef	54.02^abc	8.82^efgh
	M3	−13.14^abcdefgh	11.60^bcdefg	39.45^ab	50.79^abcde	83.33^bcde	60.07^abc	13.24^defgh
	M4	−18.98^abcd	14.45^abcde	55.18^ab	63.49^abcd	108.33^abc	81.08^abc	32.35^abcd
P-value		**	**	**	**	**	**	**
SE±		0.41	0.24	1.61	1.95	2.63	2.39	0.79
CV (%)		6.62	4.48	7.78	7.94	7.75	7.82	8.64

BD = bulk density (g cm⁻³); pH (H2O) = potential of hydrogen in water suspension; CEC = cation exchange capacity (cmol(+) kg⁻¹); OC = organic carbon (%); TN = total nitrogen (%); AP = available phosphorous (ppm); EK = exchangeable potasium (cmol(+) kg⁻¹); R1 = bread wheat–clover–potato; R2 = clover–bread wheat undersowing lupine–potato; R3 = potato–clover–bread wheat; R4 = bread wheat undersowing lupine–potato undersowing lupine–bread wheat; R5 = lupine–potato undersowing lupine–bread wheat; ⁺In the first and second cropping seasons, crop residues of wheat and potato after harvesting were incorporated into the soil, while the biomass of clover and lupine was chopped and incorporated into the soil at their 50% flowering; M1 = control at 0 tha⁻¹ manure; M2 = 2.5 tha⁻¹ sesbania green manure (SGM); M3 = 5 tha⁻¹ fresh cattle manure (FCM); M4 = 2.5 tha⁻¹ SGM + 5tha⁻¹ FCM; P = probability; **highly significant at P < 0.01; *sgnificant at P < 0.05; ns = not significant at P ≥ 0.05; SE = standard error; CV = coefficient of variation; means in a column followed with the same letter are not significantly different at P ≥ 0.05.

Figure 2. Average grain productivity of bread wheat over sites combination as influenced by interaction of crop rotation and manure application in three rotation phases (2013–2015) in northwest Ethiopian highlands (bars followed with the same letters are not significantly different at P ≥ 0.05).

Figure 3. Average grain productivity of bread wheat over sites combination as influenced by crop rotation in three consecutive rotation phases (2013–2015) in northwest Ethiopian highlands (bars followed with the same letters are not significantly different at P ≥ 0.05).

Figure 4. Average grain productivity of bread wheat over sites combination as influenced by manure application in three consecutive rotation phases (2013–2015) in northwest Ethiopian highlands (bars followed with the same letters are not significantly different at P ≥ 0.05).

Figure 5. Average tuber productivity of potato over sites combination as influenced by interaction of crop rotation and manure application for three rotation phases (2013–2015) in northwest Ethiopian highlands (bars followed with the same letters are not significantly different at P ≥ 0.05).

Figure 6. Average tuber productivity of potato over sites combination as influenced by crop rotation in three consecutive rotation phases (2013–2015) in northwest Ethiopian highlands (bars followed with the same letters are not significantly different at P ≥ 0.05).

Figure 7. Average tuber productivity of potato over sites combination as influenced by manure application in three consecutive rotation phases (2013–2015) in northwest Ethiopian highlands (bars followed with the same letters are not significantly different at P ≥ 0.05).

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