Effects Of Different Mulch Models And Nitrogen Fertilization Rate On The Microorganisms In Rootzone And Bulksoil Of Wheat And Corn In Arid And Semi-Arid Region Of The Northwest

The results of the studies about the number and orgnization of soil microorganisms at different growth stages of the wheat and corn rootzone and bulk soil under the different mulch models and nitrogen fertilization rate in arid and semi-arid region of the northwest china could provide important information of developing high quality, high yield and high efficiency agriculture , and has important theory and practical meanings to instruct this area's grain-production. The estimation offers to various kinds of mulch mode and nitrogen ecosystem effect is important scientific value to optimum mulch mode and nitrogen through the change of soil microorganisms. In this paper, soil microorganisms in different growth stage of the wheat and corn rootzone and bulk soil under the different mulch mode and nitrogen in arid and semi-arid region of the northwest are studied systematically by normal microorganisms separate methods, particularly for the nitrogen-fixing bacteria and silicate bacteria. The results are as the following:1. Study on soil microorganisms in the wheat fallow period. In order to conducted The effects of mulching measures and nitrogen fertilization during the growth stage on the quantity of soil microorganisms during the fallow period. Soil samples were collected on the 52nd day after the wheat harvest from the plots of different treatments under 3 mulching models (conventional, plastic film mulching, straw mulching) and 3 nitrogen fertilization rates (N₀, N₁₂₀, N₂₄₀), and the quantity of different microflora were analyzed. The results indicate that:â‘ In comparison with the conventional cultivation model, the plastic film mulching and straw mulching models significantly increased soil bacteria, fungi, nitrogen-fixing bacteria and silicate bacteria in winter wheat fallow field.â‘¡Contrary to the nitrogen-fixing bacteria, the application of N fertilizer can increase the quantity of other tested soil microorganisms.â‘¢The quantity of every kind of soil microorganisms at the wheat fallow period in rootzone were higher than that of the bulk soil, the difference of the quantity of actinomycetes, nitrogen-fixing bacterium and silicate bacterium between rootzone and the bulk soil got to remarkable level(P<0.05) . 2. Study on soil microflora in the wheat and corn field. Soil samples were collected on the 52nd day after the wheat harvest from the plots of different treatments under 4 mulching models (conventional, plastic film mulching, straw mulching and ridge-furrow mulched by plastic film) and 3 nitrogen fertilization rates (N₀, N₁₂₀, N₂₄₀), and the quantity of different microflora were analyzed. The results indicate that:â‘ Film mulching(including plastic film mulching and ridge-furrow mulched by plastic film) is advantageous to increase the quantity of the soil bacteria, actinomycetes in rootzone and bulk soil of the wheat and the corn, the quantity of the fungi in rootzone and bulk soil of the wheat were increase, while the quantity of the soil fungi in rootzone and bulk of the corn under straw mulching is about 2 times than that of control.â‘¡With the increase of nitrogen, the quantity of soil microorganisms has the tendency to increase, except the fungi in rootzone and bulk soil of the wheat and the actinomycetes in the bulk of the corn.â‘¢The order of the quantity of bacteria in the rootzone at the wheat's three growth stages is: heading stage>maturing stage >jointing stage; But the quantity of bacteria in the bulk soil and fungi in rootzone and bulk soil of the wheat has the tendency to decrease.â‘£The orders of the quantity of bacterium and fungi in rootzone and bulk soil of the corn are: heading stage >jointing stage.3. The nitrogen-fixing bacteria's characteristics in the rootzone and bulk soil at the different growth stages of the wheat and corn under the 4 mulch models and 3 nitrogen fertilization rates were studied. The results indicate that:â‘ Film mulching(including plastic film mulching and ridge-furrow mulched by plastic film) has` the advantageous to increase the quantity of the nitrogen-fixing bacteria in rootzone and bulk of the wheat and corn, the quantity of the nitrogen-fixing bacteria in rootzone of the wheat and corn under plastic film mulching is about 2 times than that of control.â‘¡With the increase of nitrogen, the quantity of nitrogen-fixing bacteria in rootzone and bulk soil of the wheat and corn has the tendency to increase.â‘¢the quantity of nitrogen-fixing bacteria in the rootzone and bulk soil of the wheat has the tendency to decrease. The order of the quantity of nitrogen-fixing bacteria in rootzone of the corn is: heading stage >jointing stage, the nitrogen-fixing bacteria in the bulk of the corn are contrary to it.â‘£The effects of the roots on the nitrogen-fixing bacteria in the wheat and corn gets to a very remarkable level(P<0.01) .4. The silicate bacteria in the rootzone and bulk soil at the different growth stages of the wheat and corn under the 4 mulch modes and 3 nitrogen fertilization rates were studied. The results indicate that:â‘ Except the quantity of the silicate bacterium in the rootzone of wheat, the film mulching(including plastic film mulching and ridge-furrow mulched by plastic film) is advantageous to increase the quantity of the silicate bacteria of the 2 crops being tested; Straw mulching is advantageous to increase the quantity of the silicate bacteria in the rootzone of wheat.â‘¡With the increase of nitrogen, the quantity of silicate bacteria in rootzone and bulk soil of the wheat and corn has the tendency to increase, the quantity of silicate bacteria in rootzone of the wheat under the high(N₂₄₀) and middle(N₁₂₀) nitrogen is about 3 times than that of none(N₀) nitrogen.â‘¢The orders of the quantity of silicate bacteria in rootzone and bulk soil of the wheat are: jointing stage>heading stage>maturing stage; In rootzone and bulk soil of the corns'has the tendency to increase.â‘£The quantity of silicate bacteria of the wheat and corn in rootzone is higher than that of the bulk soil, the difference of the quantity of wheat's silicate bacteria between rootzone and the bulk soil gets to a very remarkable level(P<0.01).