Research On Drip Irrigation Techniques For Developing Poplar Plantation

Aiming at achieving the drip irrigation techniques for developing poplar plantation, Aseries of researches were conducted on soil water movement mechanisms, soil water contentdynamics,irrigation schedule and appropriate irrigation quantity for2-year-old poplar plantionunder drip irrigationcondition in Daxing forest farm of Beijing in2012. the main researchresults are as follows:1)The emitterwith consistent rate of flow in4L·h^-1was adopted for irrigation experimentand results showed that the movementrangeof wet soil front and the shape of wet soil bodyafter varioustime lengths of drip irrigation treatments aresimilar to the distribution range andmorphological characteristicsof poplar root system, which indicate that the emitter with flowrate of4L·h^-1is suitable one for designing ground drip irrigation system for developing poplarplantation.2) According to the movement distance of wet soil front in horizontal direction atdifferent depth in soil resulted from varioustime lengths of drip irrigation treatments, theappropriate spacingbetweenemitters on drip tube suit be60～80cmto insure forming a wetsoilbody with semi-diameter of30～40cm under each erase and wet belt along drip tube in soillayer of0～40cm deep, since most roots of poplar trees distributed in soil layer of0～40cmdeep.3) During the continuous drip irrigation of6hours, the changing process of soilvolumetric water content（SVWC） at various testing locations appeared a tendency of fastincrease to slow increase and thenremaining stable, after drip irrigation of varioustime lengths,the SVWC appeared a tendency of fast decrease to slow decrease if the SVWC reached themaximal value when irrigation stopped, while the SVWC appeared slow decrease consistently if the SVWC reached the maximal value when drip irrigation stopped for6hours.4) When the spacing between emitters is60cm on drip tube, a wetbeltof60cm widecould be formed in soil layer of0～20cm deep in which the SVWC could be increased to thelever of over the field water capacity（FWC）after continuous drip irrigation of2.5～3hoursandthe SVWC could be remainedin the appropriate status for poplar root absorption in48hoursafter stopping irrigation.If sufficient irrigation is needed for whole root in soil layer of0～40cm deep, the continuous drip irrigation of6hours is required to form a wetbeltof60cm wide insoil layer of0～40cm deep and the SVWC could be remainedin the appropriate status forpoplar root absorption in48hours after stopping irrigation.5) For the2-year-old poplar plantation with drip irrigation system, the planed annualirrigation quantity should be368.8mm in growing season with efficient one-time-irrigationquantity of6.0～9.0mm and weekly irrigation frequency ofone to three times.6) For the2-year-old poplar plantation with drip irrigation system, the monthly growingperformance of poplar trees showed maximalheight increament in July, maximalDBHincreamentin June and maximal volumeincreamentin August, comparing their monthlyincreaments in each calendar month of growing season.7) For the2-year-old poplar plantation with drip irrigation system, The annual volumegrowth increased with increasing of irrigation quantity, but the optimal irrigation quantityshould be100%of the evapotranspiration quantity level for having the maximal marginalbenefit from volume growth in growing seasonconsidering the increased marginal costs andmarginal revenue resulting from increasing of irrigation quantity levels.