3.2 Effect mechanism of water and fertilizer optimal management
on soil enzyme activity of Panax notoginseng
Soil enzymes were key components for catalytic decomposition of soil
nutrient conversion, and their activity in soil could be used as a
measure of soil health index(Ashraf et al.,2020;Kotroczo et al.,2014).
this study found significant differences in soil urease, sucrase, acid
phosphatase, and catalase activities at different growth periods under
optimal management of that same water and fertilizer (p<0.05),
and the increasing and then decreasing trends were observed with the
prolongation of growth period of Panax notoginseng, which ranged from
large to small in flowering period, fruiting period, seedling period and
rooting period. This was consistent with the findings of Peibing et al.
that soil enzyme activities had obvious seasonal variation
characteristics, with the soil sucrase activity in summer >
autumn > spring > winter, and urease activity
in summer > spring > autumn >
winter. The results showed that the two soil enzyme activities were the
highest in summer and the lowest in winter similar (Pei et al.,2018).
Zhu et al. believed that soil enzyme activities had obvious seasonal
variation characteristics, with the peak values of soil catalase,
phosphatase, and urease of reed community appearing in the exuberant
growth period, and the trough value appearing in the germination period
and the leaf developing period (Zhu et al.,2017). In this study, the
flowering period of Panax notoginseng was in summer and it grew
vigorously, while the root increasing period was in winter, which was
the germination period. Therefore, the flowering period of soil enzyme
activity of Panax notoginseng was the largest, and the root increasing
period was the smallest. The reason was that summer was the rainy
season, with plenty of rainfall. The soil temperature and humidity were
suitable for the growth and reproduction of microorganisms, and the
enzyme activity in the soil was increased by the increase of microbial
activity. This study found that under different water and fertilizer
optimal management, soil urease, sucrase, acid phosphatase, and catalase
showed significant differences in the same growth period
(p<0.05). The contents of soil urease, sucrase, acid
phosphatase, and catalase increased with the increase of irrigation
amount and fertilizer application amount, and the treatment of soil
urease, sucrase, acid phosphatase, and catalase W3F4 at the flowering
period was the largest.
This study found a significant correlation between soil microbial
biomass C and N and soil enzyme activities (p<0.05), a very
significant positive correlation between soil acid phosphatase and
catalase and soil microbial biomass C and N (P<0.01), and a
significant positive correlation between urease and sucrase and soil
microbial biomass C and N (P<0.05). This was similar to the
finding by Eivazi, F. et al. that the activities of soil urease,
sucrase, and alkaline phosphatase had a very significant positive
correlation with the soil microbial biomass of carbon, nitrogen, and
phosphorus (Eivazi et al.,1996). Yang et al. found a highly significant
positive correlation between soil microbial biomass C, N, and P and soil
urease, sucrase, and alkaline phosphatase activities(Yang et al.,2015).
The study also reveals that soil invertase, acid phosphatase, and
catalase were the main factors affecting the regulation of microbial
biomass c and n, while urease was an important factor affecting
microbial biomass C and N.