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In order to understand the soil nitrate nitrogen concentration in the dynamic changes of time and space in wheat-maize interplanting system, this article through typical wheat-maize interplanting long-term experiment in Hexi Oasis Irrigation Area to study the effect of the soil nitrate nitrogen concentration in the dynamic changes of time and space at different growth stages in 0-200cm soil profie under the non-N N0 (0 kg.hm-2), low nitrogen N1 (210kg.hm-2), medium nitrogen N2 (420kg.hm-2), high nitrogen N3 (630kg.hm-2) of the local conventional irrigation W3 (5550m3.hm-2) and the irrigation amount of W1 (3150m3.hm-2), W2 (4350m3.hm-2), W3 (5550m3.hm-2), W4 (6759m3.hm-2) of the local conventional nitrogen N2 (420kg.hm-2) . The results showed as following:Under the condtion of different Nitrogen application rate and same irrigation rate for W3 (5550m3.hm-2), wheat-maize intercropping soil NO3--N content and distribution with the increase in nitrogen application rate increased, and in different growth stages of different crops in different soil depth and bring a certain degree of regularity there. Growth stages from the point of view, with the exception of N0 differences in the growth stage smaller, N1, N3, N2 showed a high level for the flag leaf stage and trefoil Stage, and other characteristics of the smaller growth period, among them, flag leaf stage is the highest, trefoil Stage times ; in 0-200cm soil depth: 0-60cm soil NO3--N content of more obvious changes in each growth stage; 60-200cm differences in changes in soil content of less than small; and with the growth stage over the peak nitrate concentration showed obvious downward trend of migration; bring in different crops,wheat pre-sowing to flag leaf stage with the nitrate content of maize than wheat belt, filling stage to maize post-harvest with the NO3--N content of maize than wheat belt.Under the condtion of different Nitrogen application rate and same irrigation rate for W3 (5550m3.hm-2), the overall representation of wheat and maize total yield showed as N3> N2> N1> N0, in which N0 （not N）is the minimum, N3 is the highest. Wheat yield showed N1 for the highest,and followed by the increase of nitrogen application rate to reduce the wheat yield, that is, N1> N2> N3> N0, in which improves 58 percent, 99 percent and 112 percent for compared N1, N2, N3 with N0. Maize yield with the nitrogen application rate increased, N1, N2, N3 compared with N0 increased 428 percent, 577 percent, 710 percent, increase in nitrogen application rate on maize yield than wheat to significantly.Effects of wheat-maize intercropping yield under the condtion of different Nitrogen application rate and same irrigation rate for W3 (5550m3.hm-2), wheat,maize and total yield has showed a similar law, in which W2 (4350m3.hm-2) the highest, W1 (3150m3.hm-2) a minimum, W4 (6750m3.hm-2) more than W3 (5550m3.hm-2), that is, W2> W4> W3> W1, yield is not as irrigation rate the increase has been higher, but showing a first peak and then gradually started to reduce production.Under the condtion of different Nitrogen application rate and same irrigation rate for W3 (5550m3.hm-2) ,total yield of wheat-maize intercropping and soil nitrite nitrogen showed with the increase of nitrogen application rate and increased,however, N2 of the maximum yield in different nitrogen rate is still lower than W3. Combination of nitrate content of soil in front of changes under the conventional nitrogen application rate for the N2 (420kg.hm-2) condition and the premise of the recommendation in Hexi Oasis Irrigation, optimal effectiveness of the economical and environmental of the irrigation rate is W2 (4350m3.hm-2), than the local conventional irrigation W3 (5550 m3.hm-2) to reduce the 1200 m3.hm-2, while maize and wheat yield increased 3482.2 kg.hm-2. Rational combination of irrigation and fertilizer is to achieve high yield of water-saving and reduce environmental pollution.
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