Effects of irrigation and fertilizers management on nitrate reductase activities in Mollisols under facility eggplant field

In order to investigate the effects of reducing irrigation and chemical fertilizers on soil nitrate reductase activities and nitrate content in a facility vegetable field in Mollisols region, in a long-term experiment of Mollisols vegetable field with three treatments: regular irrigation and chemical fertilizers(WF), 80% regular chemical fertilizers + regular irrigation(W80%F), regular chemical fertilizers + 80% regular irrigation(80%WF), we analyzed the changes of soil nitrate reductase activities and nitrate content in eggplant field after reducing irrigation and chemical fertilizers.The results showed that: both reducing irrigation and chemical fertilizers significantly affected soil nitrate reductase activities.Compared to WF, W80%F increased the soil nitrate reductase activities in 0~20 cm and 40~60 cm soil depth by 22.0% and 33.2% respectively, while 80%WF decreased the activities by 5.37% and 23.7% respectively.Soil nitrate reductase activities decreased firstly and then increased with the extension of eggplant growth period.Soil nitrate reductase activities in W80%F and 80%WF at seedling stage and initial fruit stage were significantly higher than that in WF(P < 0.05).Soil nitrate contents in all three treatments decreased with increasing soil depth and exhibited an order of WF>W80% F>80% WF in the same soil depth.Compared with WF, W80%F reduced nitrate contents by 7.91%~31.6% during the whole eggplant growth period; 80%WF increased soil nitrate contents in seedling stage and seedling pulling stage by 9.49% and 13.5% respectively, but significantly reduced the soil nitrate contents in initial and full fruit stage by 69.6% and 54.2% respectively.The correlation analysis between nitrate reductase activity and soil nitrate content showed a significant positive correlation in 40~60 cm soil depth, but no significant correlation in 0~20 cm and 20~40 cm soil depth, indicating that the nitrate reductase activities in deeper soil reflect the changes of soil nitrate content.