**6. Conclusions**

rhizosphere pH values with TU Purple plots receiving PL and Whatley/Loretan and NCC-58 plots receiving Megabloom, having the lowest values, respectively. SOC was similar among amendments but was highest for TU Purple and J6/66 and ranged from 0.63 for Whatley/ Loretan to 1.07 for J6/66 (data not shown). Storage root yield was similar regardless of the amendment applied ranging from a low of 12.0, 10, 21.1 t/ha for control and plants receiving

> **ALKP (μg** *p***nitrophenol (per g**

**βNAG (μg** *p***nitrophenol (per g**

.

**βGLU (μg** *p***nitrophenol (per g**

**soil/h))**

**soil/h))**

**soil/h))**

Con 12.0 172.89a 2.21a 16.56 13.05 PL 19.7 287.71b 7.06b 31.39 45.86 FSH 18.1 329.99b 7.41b 23.14 48.25 NPK 21.1 308.66b 7.69b 29.40 49.47 Significance NS \* \*\* \*\*\* \*\*

ACP, acid phosphatase; ALKP, alkaline phosphatase; βGLU, β-glucosidase; βNAG, β-glucosaminidase.

Therefore, the addition of organic amendments increased both soil enzyme and microbial activity, which is consistent with the findings of others [59–61]. NPK-treated plots had higher enzyme activity compared to the controls and, the organic amendments as a nutrient source

In general, the addition of fertilizer and organic amendments had a significant impact on bacteria at every taxonomical level while TU Purple and Whatley/Loretan impacted the

TU Purple J6/66 NCC-58 Whatley/Loretan

**Table 8.** Main effect of fertilizer amendments on storage root yield soil enzyme activitya

did not adversely affect enzyme activity relative to NPK treated plots.

**Class Con BL NPK FSH** Actinobacteria 6.69b 6.60b 7.78ab 9.29a Chloroflexi 1.83a 1.55a 1.50a 0.59b Cytophagia 1.56a 1.36a 1.36a 0.75b Δproteobacteria 4.80a 4.34ab 4.43a 3.06b Rubrobacteria 1.82b 1.73b 2.26ab 3.03a Cultivars

α-Proteobacteria 3.62b 4.17b 3.50b 5.34a Gemmatimonadetes 3.10bc 3.44b 2.57c 4.34a

**Table 9.** Effect of fertilizer, organic amendments, and cultivars on class bacterial composition of sweetpotato

Means with same letters in rows are not significantly different Tukey's (0.05).

*Gemmatimonadetes* at every taxonomical level (**Table 9**).

NPK, respectively (**Table 8**).

**Root yield (t/ha)**

44 Organic Fertilizers - From Basic Concepts to Applied Outcomes

**ACP (μg** *p***nitrophenol (per g**

**soil/h))**

\*, \*\*, \*\*\*significant at 0.05, 0.01, 0.001 levels of probability.

**Fertilizer amendments**

a

rhizosphere.

The impact of organic amendments on biomass production varied based on the species that were grown as plant species exerted a stronger influence on biomass production than the organic amendments. Vitamin C content was enhanced by NPK fertilizers for Amaranth and Celosia and by Megabloom in Gboma, similar to what others reported [64]. Gboma also showed higher radical scavenging (DPPH) than the other species. DPPH values according to reference [65] showed that the normal values are 37.7–89.5 with Gboma and Longbean in range or surpassing these values. Overall, these results show that organic amendments ex‐ erted inconsistent influences on phytochemicals. Thus, based on yield and phytochemical content, these vegetables can potentially be produced successfully on these sandy loam soils in South Central Alabama using organic amendments, but more conclusive data through ad‐ ditional studies are required. For sweetpotato, the results show that bacteria associated with C and N cycling under aerobic conditions can dominate in their rhizosphere.
