Sweet potato response to low-input agriculture and varying environments of KwaZulu-Natal, South Africa: implications for food security strategies

Figures & data

Table 1. Experimental site description for Deepdale, Richards Bay and Umbumbulu.

	Deepdale	Richards Bay	Umbumbulu
Geographical location	28°01'S; 28°99'E	28°19'S; 32°06E	29°98'S; 30°70'E
Altitude (m a.s.l.)^a	998	30	632
Bio-resource group/agro-ecological zone	Coast hinterland thornveld	Moist coast forest, thorn and palmveld	Moist coast hinterland and ngongoni veld
Annual rainfall (mm)	7500–850	820–1423	800–1160
Average temperature (°C)	18.4	22	17.9
Frost occurrence	Moderate	None	Light and occasional
Soil texture class^b	Clay	Sand	Clay
Clay content (%)	53	<5	>60
Soil type^b	Jonkersberg form (Jb)	Inhoek form (Ik)	Hutton form (Hu)
Field capacity (%)	45.2	10.9	45.1
Permanent wilting point (%)	34.7	6.2	34.5
Saturation (%)	50	47.1	51
Previous crop	Fallow (3 years)	Fallow (1 year)	Fallow (2 years)

^aMetres above sea level.

^bSoil Classification, a Taxonomic System for South Africa 1991.

Figure 1. Stomatal conductance (mmol m⁻² s⁻¹) of sweet potato cultivar grown in different locations (A: Deepdale, B: Richards Bay and C: Umbumbulu) of KwaZulu-Natal. Different lines on graph represent different cultivars, that is A40, A45 and 199062.1.

Figure 2. Climatic conditions observed in the different experimental locations during the first (2012/13) growing season (maximum and minimum temperature readings on left axis and evapotranspiration and rainfall readings on right axis).

Figure 3. Climatic conditions observed in the different experimental locations during the second (2013/14) growing season (maximum and minimum temperature readings on left axis and evapotranspiration and rainfall readings on right axis).

Figure 4. Chlorophyll content index of sweet potato cultivar grown in different locations (A: Deepdale, B: Richards Bay and C: Umbumbulu) of KwaZulu-Natal. Different lines on graph represent different cultivars, that is A40, A45 and 199062.1.

Table 2. Yield components of cultivars grown in three different locations of KwaZulu-Natal, South Africa, during 2012/13.

	Deepdale			Umbumbulu			Richards Bay
Cultivars	Biomass (t ha^−1)	Storage root (t ha^−1)	Harvest index (%)	Biomass (t ha^−1)	Storage root (t ha^−1)	Harvest index (%)	Biomass (t ha^−1)	Storage root (t ha^−1)	Harvest index (%)
A40	19.1a	37.5a	34.0a	25.9a	29.7a	46.7a	5.7b	7.4c	48.0a
A45	25.7a	45.3a	35.4a	25.6a	38.3a	38.9a	3.8b	2.4c	60.0a
199062.1	18.7a	43.1a	30.1a	9.2b	20.2b	30.9a	4.3b	6.3c	41.1a
Location mean	21.2a	42.0a	33.2a	20.2a	29.4b	38.8a	4.6b	5.4c	49.7a
LSD(P= .05)	7.33	9.38	13.70	7.33	9.38	13.70	7.33	9.38	13.70

Values in the same column sharing the same letter are not significantly different at LSD_{(P = .05)}. Significant differences for location mean are presented on specified rows.

Table 3. Yield components of cultivars grown in three different locations of KwaZulu-Natal, South Africa, during the second growing season.

	Deepdale			Umbumbulu			Richards Bay
Cultivars	Biomass (t ha^−1)	Storage root (t ha^−1)	Harvest index (%)	Biomass (t ha^−1)	Storage root (t ha^−1)	Harvest index (%)	Biomass (t ha^−1)	Storage root (t ha^−1)	Harvest index (%)
A40	45.4b	6.9d	14.9c	68.7a	31.0a	45.2b	12.8d	5.8d	44.6b
A45	50.5b	15.3c	29.7bc	52.7b	24.1b	45.8b	8.9d	5.9d	38.7b
199062.1	45.8b	18.5c	40.8b	44.6c	28.9a	65.1a	6.7d	3.1d	46.4b
Location mean	47.2b	13.6b	29.7b	55.4a	28.0a	52.0a	9.5c	5.2c	43.3a
LSD(P= .05)	7.55	4.29	9.82	7.55	4.29	9.82	7.55	4.29	9.82

Values in the same column sharing the same letter are not significantly different at LSD_{(P = .05)}. Significant differences for location mean are presented on specified rows.

Figure 5. Vine length of sweet potato cultivar grown in different locations (A: Deepdale, B: Richards Bay and C: Umbumbulu) of KwaZulu-Natal. Different lines on graph represent different cultivars, that is A40, A45 and 199062.1.

Figure 6. Number of leaves of sweet potato cultivars grown in different locations (A: Deepdale, B: Richards Bay and C: Umbumbulu) of KwaZulu-Natal. Different lines on graph represent different cultivars, that is A40, A45 and 199062.1.

Figure 7. Number of branches of sweet potato cultivars grown in different locations (A: Deepdale, B: Richards Bay and C: Umbumbulu) of KwaZulu-Natal. Different lines on graph represent different cultivars that is A40, A45 and 199062.1.

Table 4. Soil analysis results from the three experimental locations.

	Experimental locations
	Deepdale		Richards Bay		Umbumbulu
Soil nutrient parameters	First season	Second season	First season	Second season	First season	Second season
Nitrogen (%)	0.4	0.33	0.1	0.08	0.3	0.02
Soil pH (KCl)	4.8	4.48	4.2	5.0	4.2	4.25
Phosphorus (mg/L)	5.0	10	6.0	30	1.0	8.0
Potassium(mg/L)	349.0	265	18.0	29	62.0	72.0
Magnesium (mg/L)	420.0	543.0	0.0	69	247.0	341.0
Calcium (mg/L)	1398.0	1956.0	103.0	355.0	1071.0	1226.0
Manganese (mg/L)	20.0	62.0	4.0	10.0	13.0	80.0
Copper (mg/L)	4.2	5.0	0.5	0.6	8.4	10.2
Zinc (mg/L)	2.2	3.5	0.6	2.1	1.2	1.4
Exchange acidity (cmole/L)	0.1	0.19	0.3	0.07	0.3	0.36
Total cations (cmole/L)	11.4	15.1	0.9	2.48	7.8	9.47
Acid saturation (%)	1.0	1.0	37.0	3.0	4.0	4.0
Organic carbon (%)	4.4	4.4	<0.5	1.1	3.4	3.3
Clay (%)	49.0	50.0	6.0	11.0	58.0	55.0

Table 5. Fertilized and non-fertilized storage root yield from three different locations of KwaZulu-Natal during the second growing season

	Deepdale		Richards Bay		Umbumbulu
Cultivars	Fertilized storage roots (t ha^−1)	Non-fertilized storage roots (t ha^−1)	Fertilized storage roots (t ha^−1)	Non-fertilized storage roots (t ha^−1)	Fertilized storage roots (t ha^−1)	Non-fertilized storage roots (t ha^−1)
A40	8.9e	6.9e	19.7c	5.8ef	14.2d	31.0a
A45	2.3c	15.3d	18.5c	5.9ef	13.3d	24.1b
199062.1	4.8b	18.5c	20.5c	3.1f	16.7cd	28.9a
Location mean	5.3d	13.6c	19.6b	5.2d	14.7c	28.0a
LSD(P= .05) Fertilizer	2.25

Values in the same column sharing the same letter are not significantly different at LSD_{(P = .05)}. Significant differences for location mean are presented on specified rows.