| Heilongjiang Province is an important food production base in China,but the total amount of water resources is relatively scarce.Facing the increase of agricultural water consumption and the intensification of drought trend year by year,it is of great significance to develop water-saving agriculture in this area to ensure food security in China.In this paper,the author conducted a watersaving irrigation experiment on sprinkler-irrigated Maize at Zhaozhou Irrigation Experiment Station in Western Heilongjiang Province.Using CROPWAT model as a research tool,this paper studied the variation law of maize water consumption,effective rainfall and irrigation water requirement in different years and growing periods in the semi-arid region of Western Heilongjiang Province,analyzed the coupling degree between crop water demand and effective rainfall in different hydrological years,and worked out the corresponding sprinkler irrigation system;13C stable isotope mass spectrometry was used to study water consumption and water use efficiency(WUE)of leaves and yields of maize,and to further explore the effects of different irrigation schemes on WUE of Maize in black soil region of cold region;Using 15N-labeled urea as jointing fertilizer at jointing stage of maize,the absorption and utilization of topdressing nitrogen and its distribution in aboveground organs of Maize at maturity stage under different irrigation schemes were studied,and the residual and final loss rate of topdressing nitrogen in soil after harvest of maize were also studied.The main results of the experimental study are as follows:(1)Under different irrigation schemes,the daily water consumption intensity of maize reached its peak value at jointing stage,and the peak value ranged from 4.21 mm/d to 5.89 mm/d.WUEi ranged from 7.56 to 29.84 μmol/mmol,WUEn ranged from 73.15 to 168.69 μmol/mmol and WUEy ranged from 2.90 to 3.74 kg/m3.The dry year,the normal year and the wet year were selected as 2004,2010 and 1992 respectively,the net irrigation quotas in dry and normal years are 170.2 mm and 79.9 mm respectively,and the irrigation times are 3 and 1 times under sprinkler irrigation conditions,respectively.In order to ensure stable and high yield of maize,supplementary irrigation must be carried out at the stage of tasseling and filling.(2)The carbon isotope resolution(ΔLB),mature leaf carbon isotope resolution(ΔLC)and fruit carbon isotope resolution(ΔF)were 0.451%~0.505%,0.505%~0.598%,0.396%~0.526% at jointing stage,respectively.The response of ΔL to irrigation quota and irrigation times was better than fruit ΔF.Under different irrigation schemes,maize ΔL was negatively correlated with WUEi and WUEn,and the correlation between L and WUEn was better than that between ΔL and WUEi,and maize ΔF was negatively correlated with WUEy and Y.(3)Under the condition of constant irrigation quota,the dry matter of the above-ground parts of maize decreased gradually with the decrease of irrigation times.Under different irrigation treatments,the accumulation of nitrogen and 15 N in maize grains at mature stage accounted for 45.50%~68.80% and 47.88%~74.40% of the total accumulation,respectively.The total accumulation of nitrogen in maize shoots at mature stage was 8.14%~13.21% from jointing nitrogen.Among them,the accumulation of 15 N in maize grains at mature stage was the most,accounting for 47.95~74.4%,and the proportion of nitrogen from topdressing was about 4.80%~9.83% of the total nitrogen accumulated in Maize grains.(4)After harvest,8.81%~24.89% of topdressing nitrogen remained in soil,of which 83.25%~95.55% of 15 N remained in 0~60 cm soil layer,and the 15 N remained below 60 cm only accounted for 4.45%~16.75%.Nitrogen fertilizer application had little effect on the nitrogen level in the soil below 40 cm,but had no impact on the nitrogen level in the soil below 60 cm.Under the condition of constant irrigation quota,excessive single irrigation will result in the leaching loss of nitrogen in soil,so increasing irrigation times and reducing single irrigation can effectively reduce the loss of nitrogen fertilizer,increase the residual rate of fertilizer nitrogen,and maintain the balance of soil nitrogen to a certain extent.In conclusion,the irrigation scheme that meets the requirements of water saving and high yield of maize is 800 m3/hm2 in the whole growth period,which is irrigated three times at seedling stage,jointing stage and tasseling stage respectively.Under this scheme,maize WUEy is 3.65 kg/m3 and its yield is 14712 kg/hm2;It is feasible to use ΔL and ΔF to indicate the water use efficiency of Maize at different levels.13 C in leaves and grains of Maize at maturity stage can be used as an important index to quantify the water use efficiency of crop leaves and yield levels;The distribution proportion of 15 N in the above-ground parts of maize was in the order of grain,leaf,stem,spike axis and bract leaf.Shortage of water during male-pumping and Grain-filling stages will lead to a significant decrease in the total absorption of 15 N in plants,inhibit the absorption of fertilizer nitrogen by maize,reduce the absorption of nitrogen fertilizer,and increase the leaching loss of nitrogen fertilizer and reduce the utilization rate of fertilizer by excessive single irrigation. |
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