Impact of biochar and organic fertilizers on sweet potato yield, quality, ascorbic acid, β-carotene, sugars, and phenols contents

Figures & data

Figure 1. Overall average of sweet potato root weight of plants grown under six soil management practices (Cow = cow manure, SS = sewage sludge, Control = no-mulch native soil, Bio = biochar, Vermi = vermicompost, and CM = chicken manure). Each bare is an average of 6 replicates ± standard error. Values in each treatment accompanied by the same letter(s) are not significantly different (p≥ 0.05) using Duncan’s multiple range test (SAS Institute Inc 2016).

Table 1. Average number of sweet potato roots categorized according to the USDA standard grades of plants grown under each soil treatment.

Soil Treatment	U.S. Extra No.1	U. S. No.1	U.S. No.1 Petite	U.S.Commercials	U. S. No.2	Culls	Number of Roots Plot^−1
Bio	6	12	25	12	55	87	197 b
CM	22	2	23	7	61	54	169 c
Cow	30	1	47	25	89	44	236 a
Control	48	5	27	16	65	48	209 b 201 b
SS	31	8	27	13	65	57
Vermi	23	11	25	10	85	52	206 b

Bio = biochar, CM = chicken manure Cow = cow manure, Control = no-mulch native soil, SS = sewage sludge, Vermi = vermicompost. Each value in the table is an average of 6 replicates ± standard error. Values in the number of roots column accompanied by the same letter are not significantly different (p≥ 0.05) using Duncan’s multiple range test (SAS Institute Inc 2016).

Figure 2. Overall sweet potatoes average root weight of each USDA standard grade, regardless of soil treatment. Each bare is an average of three replicates ± standard error. Values in each grade accompanied by the same letter(s) are not significantly different (p≥ 0.05) using Duncan’s multiple range test (SAS Institute Inc 2016).

Figure 3. Overall sweet potatoes average root weight of each USDA standard grade, regardless of soil treatment. Each bare is an average of three replicates ± standard error. Values in each grade accompanied by the same letter(s) are not significantly different (p ≥ 0.05) using Duncan’s multiple range test (SAS Institute Inc 2016).

Figure 4. Overall sweet potato root standard USDA grades of plants grown under field conditions regardless of soil treatments. Each bare is an average of three replicates ± standard error. Values in each grade accompanied by the same letter(s) are not significantly different (p ≥ 0.05) using Duncan’s multiple range test (SAS Institute Inc 2016).

Figure 5. Concentrations of ascorbic acid (a) and β-carotene (b) ± std. error in sweet potato roots of plants grown under six soil management practices (chicken manure, CM; cow manure cow, vermicompost vermi, biochar bio, sewage sludge SS, and no mulch control treatment. Statistical comparisons were performed among six treatments. Bars associated with the same letter(s) are not significantly different (p ≥ 0.05) using Duncan’s multiple range test.

Figure 6. Concentrations of total phenols (a) and soluble sugars ± std. error (b) in sweet potato roots of plants grown under sex soil management practices (chicken manure, CM; cow manure cow, vermicompost vermi, biochar bio, sewage sludge SS, and no mulch NM control. Statistical comparisons were performed among six treatments. Bars associated with the same letter(s) are not significantly different (p ≥ 0.05) using Duncan’s multiple range test.

SAS Institute Inc. 2016. SAS/STAT Guide, version 9.4. Campus drive. Cary, NC, USA: SAS Institute Inc.; p. 27513.

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