| The straw mulching experiment was carried out in Spring-wheat field in Lijiabu, Dingxi county, the typical area of semiarid region, in order to study the change of soil temperature, soil moisture, soil nutrient and quantity of soil microbe after the field was covered by straw mulch. Results from the research showed that straw mulching could improve conditions of soil moisture, nutrient, air, temperature and heat and soil microbe. And its ecological effect on spring-wheat field were apparently improved.(1) Straw mulching had apparent effects on adjustment to soil temperature and on the absorption and heat conduction of sun radiation .The effects of not only increasing of soil temperature when the air temperature was low but also decreasing of soil temperature when the air temperature was high were very apparent, particularly, in the top soil layer. Straw mulching could increase the temperature of 0~ 10cm, 10-15cm by 0.5~1.5"C,0.5~1.0'C, individually'. The soil temperature in the depth of 20cm have no apparent change in the period of low air temperature (5,AprilXbut in the period of high air temperature (15 4uly),it could decrease the temperature of Ocm,5cm,10cm by 2~10"C,0.2~1.0'C, 0.5~0.8"C, individually, and the temperature of the layer between 15cm to 20cm have no apparent change, The soil layer effected apparently by straw mulching were 0~5cm and 5~10cm.thus.the soil layer effected by straw mulching could be divided into three layers .such as 0~ 1 Ocm, the easily effected layer, 10~ 15cm ,the transitional layer, and 15~ 20cm,the almost stable layer. In the whole growth stage of spring wheat, the effect of straw mulching increasing soil temperature happened in the earlier stage, but decreasing soil temperature in the middle and later stage of itIn the whole growth stage of spring-wheat, the accumulated temperature which more than 0 'C of the layer(0-1 Ocm) were decreased 3.72"C,33.99'C,153.44'C with the addition of straw mulching quantity. Effects of increasing soil temperature in earlier growth stage of spring wheat and decreasing of soil temperature in middle and later stage were very useful for the emerging, development and growth of spring-wheat And it could mitigate the harm which come with the violent change of air temperature.(2)Effects of water storage and water conservation which caused by straw mulching were very apparent in the soil layer which the depth of Ocm to 40cm, and the effects were increased with the increase of straw mulch. As compared to ck, die water storage of the treatment which covered straw 3000kg/hm2 had no apparent change, but that of 6000kg/hm and 9000kg/ hm2 were apparently increased. So the conclusion was drawn that straw mulching have an effect on water storage. But it was not obvious when the straw mulch was too little.In the whole growth stage of spring wheat, the water consumption of the treatment of 6000kg/ hm2 was the biggest one. and mat of straw mulching 9000kg/ hm2 was the smallest one but lower than that of ck ,the one of 3000 kg/ hm2 was the middle one of the treatments. The water consumption was 304.92mm, 290.58 mm, 284.29 mm, 271.64 mm, individually, and the corresponding water use efficiency was 8.070 kg/ hrrrlmm, 7.335 kg/ hitrlmm, 6.690 kg/ hrrr.mm, 8.085 kg/ hnrlmm.as compared to ck, the improve of water use efficiency was 9.61 %, 20.60%, 20.93%. It showed mat when the quantity of straw mulch was proper, it could effectively improve the conditions of soil water and soiltemperature .So it could promote the growth of spring wheat(3)As to the soil layer which the depth of 0cm to 40cm, with the growing of spring wheat, the nutrient in the top soil layer were increased, and the change ranges were increased with the increase of straw mulching, but the changes of total N, total P were not obvious, but the content of organic matter and available K changed obviously, as compared to ck, the organic matter of the layer 0~10cm increased by 0.19 g/kg,0.16 g/kg,0.62g/kg)individually, the available K increased by 0.10mg/kg,0.92 mg/kg,1.36 mg/kg, individual... |
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