Abstract:Super absorbent polymers (SAP) can absorb water up to a few hundred or even a few thousand times of their own mass. Their special physical structures, unique chemical compositions, and characteristics of high water absorption capacity allow super absorbent polymers to be widely used in agriculture, forestry and other industries to relieve drought and reserve water for farmland, afforestation and crop yield improvement. However, the ways of super absorbent polymers applied is an important factor to evaluate．In order to explore the effect of SAP application ways on microecological environment in rhizophere soil of Platycladus orientalis, a pot experiment including five treatments, i.e. CK (neither fertilizer nor SAP was applied), U (urea was applied alone), S (SAP was applied alone), SUM (SAP was mixed with urea) and SUG (gel was made of SAP and urea) was performed. The experiment was to evaluate the effect of different ways of SAP application on enzyme activity and microbial functional diversity in rhizosphere soil as well as growth of Platycladus orientalis. Results indicated that in comparison to U treatment, the SUG treatment significantly increased total amino acids, total organic acids and total sugar in the root exudates. The activity of catalase enzyme, urease enzyme, polyphonic oxidase enzyme and invertase enzyme was also improved by SUG treatment, showing the urease enzyme activity was increased by 29.53%, 14.88%, 27.81% and 7.82% compared to the treatments of CK, U, S and SUM, respectively. At the same time, the values of AWCD and indexes of Shannon and McIntosh were significantly higher in the SUG treatment than in the other treatments, while the Simpson index was decreased by the SUG treatment, indicative of 28.78%, 30.22%, 26.91% and 8.39% increases in Shannon index over the treatments of CK, U, S and SUM. Additionally, the SUG treatment obviously promoted the growth of ground diameter and plant height, and had significant differences with other treatments. However, in S and SUM treatments, less effect on soil enzyme activity and microbial diversity was observed than in SUG treatment, which indicated that the gel way could significantly improve the drought adaptability of Platycladus orientalis compared with the ways of SAP application alone and mixture of SAP and urea. As a result, the gel was beneficial to improve the microecological environment of rhizosphere soil, enhance the ability of drought resistance and promote growth of Platycladus orientalis.
