Coupling Effect Of Long-term Water And Nitrogen Fertilizer On The Stand Volume Of Populus Tomentosa And Chemical Properties Of Soil

In order to study the coupling effect of water and nitrogen fertilizer on the soil chemical properties and stand volume of Populus tomentosa, a field experiment was conducted in the base of Weixian County continuously for6years from2007to2012. The main conclusions were:(1) Soil pH declined significantly with increasing soil water content and declined significantly with increasing nitrogen application rate. Soil total N content declined significantly with increasing soil water content and increased significantly with increasing nitrogen application rate in0-20cm soil layers. Available P content declined significantly at first and then increased slightly with increasing soil water content, declined significantly with increasing nitrogen application rate in0-20cm soil layers. Available K. content declined significantly at first and then almost constant with increasing soil water content, declined significantly with increasing nitrogen application rate in0-20cm soil layers.(2) After6years’management of irrigation and nitrogen application, soil pH in0-20cm decreased significantly, from8.62in2007dropped to7.08in2012. Soil total N content in0-20cm decreased significantly, from0.58g·kg-1in2007dropped to0.21g·kg-1in2012.(3) Stand volume of four Populus tomentosa clones were with the order of S86>B331>BT17>1316, at229.041m3·hm-2,186.786m3·hm-2,170.729m3·hm-2and112.185m3·hm-2, separately. S86improved stand volume by158.696m3·hm-2compared with1316under the same water-fertilizer condition.(4) Stand volume increased significantly with increasing soil water content and increased significantly with increasing nitrogen application rate. The coupling of water and nitrogen had significant influence on stand volume. Stand volume can be improved at most109.509m3·hm-2with the coupling of water and nitrogen, which means92.2%of the volume.(5) In this study, economic benefit of water-nitrogen coupling is very significant. The maximum profit to S86was102011yuan·hm-2at the treatment W3N3, increased profit by195.15%compared with the control treatment W1N0. The maximum profit to B331was63574yuan·hm-2at the treatment W3N3, increased profit by194.47%compared with W1N0. The maximum profit to BT17was61726yuan·hm-2at the treatment W3N3, increased profit by454.39%compared with W1N0. The maximum profit to1316was13405yuan·hm-2at the treatment W3N1, increased profit by190.86%compared with W1N0.