2.1 Effects of different water and fertilizer optimal management on soil microbial biomass carbon and nitrogen change characteristics
Under the same optimal management of water and fertilizer, the difference in soil microbial biomass C and N content was significant with different growth periods (p<0.05), and the changing trend was increased first and then decreased with time, and the order was flowering, fruiting, seedling and rooting period from big to small. As shown in Fig. 1, the carbon content of soil microbial biomass ranged from 0.49~1.05 g.kg-1, increased by 14.37% and 39.59% respectively from rooting period to flowering period, and the difference between the flowering period and rooting period of W3F4 was the largest, 0.26 g.kg-1; the difference between the flowering period and rooting period of W1F3 was the smallest, 0.11 g.kg-1; the difference between the flowering period and rooting period of CK was 0.25 g.kg-1, which was second only to that of W3F4 and ranked the second among all treatments. The soil microbial biomass nitrogen content ranged from 14.98 to 66.21 mg.kg-1, increasing by 26.55% and 43.86% respectively from rooting period to flowering period. The difference between the flowering period of W3F4 and the rooting period was the largest, 20.67 mg.kg-1, while the difference between the flowering period of W2F1 and the rooting period was 9.23 mg.kg-1, the smallest difference for all treatments. The CK flowering period increased by 10.88 mg.kg-1compared with the rooting period, ranking 12th among all treatments. Therefore, the soil microbial biomass C and N content of W3F4 changed most in the four growth periods.
Soil microbial biomass C and N content in the same growth period had significant differences with different water and fertilizer optimal management (p<0.05), and the soil microbial biomass C and N content increased with the increase of irrigation amount and fertilizer application amount. It could be seen from Fig. 1 that the soil microbial biomass C and N content of W3F4 in all growth periods was greater than that of other treatments. The soil microbial biomass C W3F4 at the flowering period increased by 0.41 g.kg-1, compared with the minimum value W1F1, and increased by 39.38% compared with CK at the same period. During the seedling period, W3F4 increased by 0.29 g.kg-1,compared with the minimum value of W1F1, and W3F4 at the seedling period was 1.9 times that of CK. The soil microbial biomass nitrogen at the flowering period was the maximum, and W3F4 increased by 39.52 mg.kg-1 compared with the minimum value of W1F1, and increased by 55.08% compared with CK at the same time. However, during the rooting period W3F4 increased by 29.63 mg.kg-1 compared with the minimum value of W1F1, and W3F4 during the rooting period was 2.36 times as much as CK. In the same growth period, CK was greater than that of W1F1, and the difference in the rooting period was the largest, 3.86 mg. kg-1, and the ratio of CK to that of W1F1 was the largest, 20.51% in the rooting period.