灌溉方式对杨树根系分布及硝态氮运移的影响

Effects of Different Irrigation Modes on Poplar Root Distribution and Nitrate Nitrogen Transport

为了在传统灌溉模式的基础上探寻一种更实用有效的替代方式,以欧美I-107杨为试材,通过大田试验研究了常规漫灌(FI)和畦灌(BI)两种灌溉方式下I-107杨在0—100cm土层的土壤含水量、水势、根系垂直分布特征及硝态氮运移的规律。结果表明,BI在0—40和60—100cm土层的含水量、水势均显著降低,且土层越深差异也越大,说明畦灌下的水分深层渗漏明显减弱;随着土层深度的增加,BI和FI下的根系生物量均逐层降低,大量根系集中在0—40cm土层,其中在0—20cm土层中,BI的根量比FI减少8.28%,但在20—80cm土层中根量却增加35.87%,并且在0—80cm土层中的总根重增加5.52%,同时消根系数β也大于FI。此外,BI使0—40cm土层的硝态氮含量显著升高,而60—100cm土层的硝态氮含量却明显降低。综合分析,畦灌有利于杨树根系的合理分布,扩大了根系对水分和养分的吸收空间,并能减少硝态氮的深层淋溶,这对于提高杨树潜在生产力、肥料利用率和保护地下水环境具有重要意义。

A field experiment with two treatments, i.e. FI （flood irrigation） and BI （border irrigation）, was designed and performed for the purpose of exploring a more effective irrigation mode based on traditional mode. The study was conducted to determine the effect of different irrigation modes on soil water content, soil water potential and vertical distribution characteristics of poplar root system and nitrate transport pattern in 0--100 cm soil layer. Results showed that BI decreased the soil water content and water potential in 0--40 and 60--100 cm layers with increased soil depth, indicating the weakened water deep seepage in the BI treat- ment. Root biomass decreased along with increased soil depth. Additionally, most of the roots concentrated in the 0--40 cm soil layer. Compared with the FI treatment, the BI treatment decreased root biomass in the 0--20 cm soil layer by 8.28%, whereas that in the 20--80 cm increased by 35.87%. Besides, the BI treat- ment increased the total root biomass in 0--80 cm soil layer by 5.52%, resulting in a higher extinction coefficient （13）. As a result from BI, additionally, the nitrate content in 0--40 cm soil layer significantly increased, whereas that in 60--100 cm significantly decreased. Hence, border irrigation benefited the poplar root distri- bution. In conclusion, the BI treatment encouraged reasonable poplar root distribution, benefited water and nutrient absorption, and reduced nitrate leaching, which are important for the increased fertilizer use effi- ciency, environment protection and potential productivity of poplar.