# Spectrophotometric Determination of Biopolymers in Alabama Benchmark Soils
## 4 Discussion
This can be explained by the fact that Sumter clay contains kaolinite, which has a lower cation binding capacity than montmorillonite (smectite) found in Houston and Vaiden clay soils [59; 60]. Soil cellulose, AB lignin, and ACE protein showed a positive correlation with total nitrogen and potentially mineralizable nitrogen. Cellulose and lignin also showed a strong positive correlation with SOM and TN, whereas ACE protein did not strongly correlate. In agricultural ecosystems, SOM and TN indicate soil quality, soil health, fertility, and potential agricultural productivity [61]. The results provided also showed a significant correlation between SOM and TN, suggesting soil cellulose and AB lignin are critical components of stable SOM and soil fertility. In addition to proteins, other organic N-containing compounds in the soil include amino acids, peptides, nucleic acids, or nucleotides that constitute total soil N [62]. Although soil protein is considered potentially mineralizable organic nitrogen [5], ACE protein did not show a significant relationship with potentially mineralizable nitrogen. While soils under legume cover crops benefit from potentially mineralizable nitrogen, those under non-legume cover crops do not [34]. Autoclaved citrate extractable (ACE) protein strongly and positively correlated with extractable acidity, while SC and AB lignin were weakly, but positively correlated with extractable acidity (Table 3); however, previous studies demonstrated significant correlations with SOM in high-pH soils [63]. Simple linear regression analysis showed that ACE protein can explain 69.5% of the variation in soil acidity [F (1,8) = 15.9, \(p\) = 0.005]. Although the role of ACE protein in regulating soil acidity has not been extensively studied, it has been suggested that its mechanisms in regulating soil acidity involve proton exchange between the soil and organic matter buffer systems [64]. The negative correlation between soil protein and pH is a demonstration that relatively low pH may benefit protein accumulations in soils. Soil pH greatly affects the composition of soil microbial communities involved in organic matter decomposition [65]. Soil protein is part of the soil buffering system which regulates soil pH. However, soil pH is controlled by various buffering systems (both organic and inorganic) whose effects may overlap [66]. This may explain in part the weak correlation with ACE protein. The strong positive correlation between pH and soil cellulose is an indication that the decomposition of cellulose may be slower in alkaline soils. Lignin and cellulose were higher in clay soils with high pH and lower in acidic soils. Clay soils have smaller particles with larger surface areas to adsorb lignin and cellulose, thus protecting them from microbial decomposition [67]. Soil electrical conductivity (EC) is a metric of the soluble salt content in soils, and it is an important soil health indicator due to its effects on soil microbial activity and crop production. Very low soil EC is an indication of insufficient nutrients, while very high EC may cause reverse osmosis, leading to removal of water from the plant root system [68]. The EC obtained for the soils used ranged from 0.02 to 1.93 dS/m. The optimal EC values for plant growth are usually between 0.8 and 1.8 dS/m and should not exceed 2.5; however, the threshold depends on the crop species [69; 70]. Although soil cellulose, AB lignin, and ACE protein correlated positively with soil EC, the relationships were not significant. This is because soil EC is affected by such factors as soil moisture, unalterable soil minerals, climate, soil texture, and land use (planting, irrigation, and chemical fertilizer application) [71]. Soil cellulose and ACE protein showed a stronger relationship with EC than AB lignin, indicating its high contributions to enhancing SOM to impact soil structure with soil EC. The relationships between soil cellulose, AB lignin, ACE protein, and soil chemical properties depend on soil pH.