| With the continuous development of national economic construction and increasing population, the grain security problem of nation always is a foundation stone that influences the national security and stability. The intercropping mode has many advantages that are increasing utilization rate of solar energy, improving the ventilation and transmittance condition and giving full play to the boundary line. As a measure for increasing agricultural output, it was thought highly of again. Hetao irrigation district is a important commodity grain reserve base of country. It locates in northwest and has plentiful solar heat resource, which makes it become the ideal place for intercropping mode. However, Hetao irrigation district belongs to the salinization of arid and semi-arid district. In order to guarantee the economic development of the lower reaches of Yellow river, the Hetao irrigation district would face the mandatory requirement of saving 20% water. Therefore, There are so many problems in the salinity area with intercropping. The water use efficiency is low. The transport law of salt is not clear. The compensation effect of water between two crops has not been quantified. The shade impact of high stalk crops on dwarf crops is not clear. The root distribution and water absorption law with non-sufficient irrigation is not yet clear. Aiming at these problems, this paper adopted the technology of root separation and water control in stages. Study the intercropping advantages with influence of underground factors and the soil salt movement mechanism. The shade impact of high stalk crops on dwarf crops and the water use efficiency with non-sufficient irrigation were studied. This paper explored the dry matter transferring and filling characteristics of intercropping wheat. The characteristics of intercropping root distribution and water absorption law were also studied. Finally, it studied the yield components and the water sensitivity. The main results of this paper are as follows:1. The yield advantage of wheat-maize intercropping system in Hetao irrigation district is 27.67%. The 20.44% of them derived from compensation action of underground part. The 7.23% of them derived from aboveground part. The 10.01% of intercropping yield advantage resulted from superposition of soil space by intercropping root. And the compensation effect of water and nutrient between wheat belt and maize belt is 10.43%. The yield advantage of wheat-sunflower intercropping system in Hetao irrigation district is 33.33%. The 28.17% of them derived from compensation action of underground part. The 5.16%of them derived from aboveground part. The 18.52% of intercropping yield advantage resulted from superposition of soil space by intercropping root. And the compensation effect of water and nutrient between wheat belt and sunflower belt is 9.65%.The intercropping would not make the saline-alkali land produce secondary salinization in Hetao irrigation district. On the contrary, it could control the salinity slightly.2. The research showed that slight controlling water by stages dose not produce significant effect on shading under intercropping model, the shading effect of intercropping mode was bad for the growing and the formation of production of dwarf crop. Due to the shading effect of high crop after 0-20 days of flowering, flag leaf net photosynthetic rate of wheat decrease 5.76%-7.38%, the stomatal conductance of wheat decrease 8.04%～9.26%, and transpiration rate of wheat decrease 8.19%-9.88%. The intercellular CO2 concentration increase 5.20%-5.22%. The above factors led to the photosynthesis degradation of wheat flag leaf. But the leaf area index of intercropping wheat canopy increase18.09%-19.97%. The increase of light interception amount and the enhancement of photosynthesis of bottom leaf partly compensated the photosynthesis decrease of intercropping wheat. The decrease degree was lower than the decrease of PAR significantly. Moreover, the border effect made the intercropping wheat more store 6.09%-8.15% assimilate before flowering. Although the photosynthesis decreased after flowering, the border effect delayed senescence and increased the photosynthetic time. With the much translocation of assimilate before flowering, the grain yield of intercropping wheat increase 3.05%-6.10%.3. The degree of crop root mixture of wheat-maize intercropping mainly experienced three processes which was "non-mixture-larger extent mixture-largest extent mixture". The maximum depth of wheat root with deficit irrigation is 10cm deeper than the maximum depth of sufficient irrigation. The final average distribution depth of root is 8cm deeper than it. The maximum lateral spreading distance of maize with deficit irrigation is 30cm. The maximum lateral spreading distance of maize with sufficient irrigation has surpassed the border wheat. The maximum depth of root is 15 cm deeper than the maximum depth of sufficient irrigation. The final average distribution depth of root is 12.1cm deeper than sufficient irrigation. The root mass density showed the law that it would decrease with the increase of crop row distance. The deficit irrigation made the root mass density of intercropping wheat decrease by 12% in 0-30cm soil layer. It also made the root mass density of intercropping maize decrease by 13% in 0-30cm soil layer. The average soil water content between border wheat and border maize with deficit irrigation was 5 days earlier than the sufficient irrigation. The average soil water content change of intercrop belt in the whole sampling date was:between belt>wheat belt>maize belt.4. The dry matter translocation yield of wheat stem and leaf intercropped with sunflowers or intercropped with maize were 1.08-1.86 times and 1.12-2.17 times, respectively, under the same irrigation treatment. The dry matter translocation yield of glume and cob from the maize model was 1-1.19 times that of the sunflower model. The wheat, intercropped with maize, reached a peak grain fill rate after 25-30 d of flowering. It was 1.26-2.85 d faster than the control treatment. The wheat, intercropped with sunflowers, reached a peak grain fill rate was 1.8-2.44 d faster than the control treatment. The maximum grain fill rate of both treatments and the average grain fill rate were all higher than the control treatment. Furthermore, they reduced the time needed for maximum grain fill rate. The lower irrigation,298-328 mm, were found to be conducive to extend the active filling stage of the wheat which was intercropped with maize. The higher irrigation, 358-388 mm, was found to be conducive to extend the active filling stage of the wheat which was intercropped with sunflowers.5. The irrigation amount by more 15mm, the effective tiller number increased 5.4%～15.07% in wheat tillering stage with intercropping, and with the aggravation of the water stress, the grains per spike,1000-grain weight and yield showed that first increase and then decrease trend in wheat milk stage with intercropping. Decrease the irrigation amount properly in wheat tillering stage and jointing stage and increase the irrigation amount in wheat milk stage and maize grouting silking stage were beneficial to increase the maize yield sharply with intercropping in water-deficient district, with the increase of total irrigation amount, the grains per spike increasing by the speed of 1.27grain/mm-2.47grain/mm, and the yield in "S" rate curve increased gradually of 62.24kg/mm,94.9g3k/mm,29.73kg/mm. With the increase of total irrigation amount, the seed number of intercropping sunflower showed that first increase and then decrease trend, the change of 100-seed-weight and yield as shown in N-shape and M-shape curve. For the water sensitivity index of intercropping crops with different irrigation treatments, it showed that the water sensitivity index of wheat was highest. The water sensitivity index of sunflower was lowest and the maize was middle. The harvest index of intercropping wheat with water stress was increased generally. The harvest index of intercropping maize increased with the increase of total irrigation amount. But the harvest index of intercropping sunflower decreased with the water stress. |
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