Objectives The aims of this study were to explore the effects of root pruning on microbial characteristics in the rhizosphere soil and growth of Populus euramericana cv. ‘Neva’, and provide a theoretical foundation for high-yield cultivation of Populus euramericana cv. ‘Neva’.
Methods A field experiment was conducted, in which the root systems of five-year-old poplar were manually pruned with a sharp spade at six, eight and ten times of DBH (diameter at breast height) distance along both sides (east-west direction) or four sides (south-east-north and west direction) prior to buds break, named 6-2, 8-2, 10-2, 6-4, 8-4 and 10-4 treatment, respectively. The experiment began in April of 2014 and the rhizosphere soil was collected in October of 2016 to evaluate effects of different root pruning treatments on root exudates contents, physicochemical properties, and microbial functional diversity in rhizosphere soil and volume growth of poplar.
Results In comparison with the CK (un-pruned), the pruning at eight times on two sides significantly increased the total organic acids and total amino acids contents in the root exudates, with the increased rates of 44.6% and 26.0%, respectively. The pruning at ten times on four sides and eight times on four sides also showed significant increase effect, whereas the pruning at the six times on both two sides and four sides showed adverse effect. In treatment of running at eight times on two sides, the rhizosphere soil available P, organic C and active organic C contents were significantly higher than those in other treatments, and were 15.8%, 39.6% and 35.8% higher than those in the CK; the available N, readily available K contents and pH value were lowest and obviously lower than those in other treatments, and were 11.6%, 26.0% and 0.67 lower than those in the CK, respectively; the values of AWCD and indexes of Shannon and McIntosh were significantly higher than those in other treatments, and were 46.6%, 27.8% and 44.1% higher than those in the CK; the Simpson index of eight times on two sides was lowest and was significantly different with other treatments, and were 22.8% lower than the CK; the average growth rate was 58.2%, and was about 43.6%, 64.4%, 84.8%, 25.8%, 42.2% and 17.1% higher than in the CK, pruning at six times on both two and four sides, eight times on four sides, ten times on both two and four sides, respectively. Pruning at both ten and eight times on four sides also performed significantly better than the CK, whereas pruning at six times on both two and four sides showed significantly averse effect, compared with the CK.
Conclusions Root pruning at distance of eight times of the DBH along both sides could improve the available nutrient and organic acids contents in the root exudates, improve microbial functional diversity, and promote the growth of Populus euramericana cv. ‘Neva’. Its effect is significantly superior to other positions.
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