Fig.1 Characteristics of changes in soil microbial biomass C and N under different optimal water and fertilizer management
Note: Different capital letters indicate significant difference between different water and fertilizer control treatments in the same growth period (p <0.05); Different lowercase letters indicate significant difference between different growth periods under the same water and fertilizer control treatment (p <0.05)
2.2 Effect of different water and fertilize optimal management on soil enzyme activity change characteristics
Under the same optimal management of water and fertilizer, the activities of soil urease, sucrase, acid phosphatase, and catalase showed significant differences at different growth periods (p<0.05), which increased first and then decreased with the prolongation of the growth period of Panax notoginseng, and the activities ranged from large to small in flowering period, fruiting period, seedling period and rooting period. Tab.2 shows that the activities of urease, sucrase, acid phosphatase and catalase are 2.86~9.52 mg.kg -1.d.-1, 17.12~68.79 mg.kg-1.d.-1, 2.14~8.2 mg.kg -1.d.-1 and 5.1~9.42 mg.kg-1.h-1, respectively. Under the same optimal management of water and fertilizer, the active of urease, sucrase, acid phosphatase, and catalase increased by 30.81% and 46.08%, 31.94% and 44.43%, 34.08% and 59.01%, 12.44%, and 37.86% respectively from flowering period to flowering period. The soil enzyme activities of W3F4 were higher than those of other treatments. The rooting period of urease and catalase activities of W3F4 were 2.14 and 1.67 times of CK, respectively. The flowering period of sucrase and acid phosphatase activities were 1.83 and 2.53 times CK. The soil water content decreased firstly and then increased and then decreased with the prolongation of the growth period. The maximum value appeared in the flowering period , and the minimum value in the seedling period. The difference between the flowering and seedling period of W3F4 was the largest, 4.3%, and that of W2F3 was the smallest, 1.72%.
Under different water and fertilizer optimal management, soil urease, sucrase, acid phosphatase, and catalase activities in the same growth period showed significant differences (p<0.05). Soil urease, sucrase, acid phosphatase, and catalase activities increased with the increase of irrigation amount and fertilizer application amount. Soil urease, sucrase, acid phosphatase, and catalase activities W3F4 at the flowering period were the largest, increasing by 44.26%, 61.51%, 42.56 and 32.25% respectively as compared with the minimum value W1F1; Under the same water and fertilizer optimal management, the soil enzyme activities increased with the increase of fertilizer application amount, and the activities of urease, sucrase, acid phosphatase and catalase in W3F4 were the highest, which were 1.95, 1.69, 2.32 and 1.47 times of CK, respectively.