| Soil water deficit and oil nutrient deficient caused by long-term cultivation of alfalfa in the arid sandy area, this paper takes Ningxia alfalfa grassland in arid sandy area as the research object for the study, conducted grain crop rotation experiment from2012to2013. Study of10-old-years alfalfa (A) with different crop rotations many index dynamic changes of soil and crop during2012and2013, such as soil moisture, soil nutrient, soil microorganism, soil enzyme activity and WUE, physiological indicators and economic yield. Finally, analyse different crop roataion of ecological environmental and benefit. Aim to provide a theoretical reference for the rotation of grass and crops in arid sandy area of Ningxia. The main conclusions are as follows:1. Experiment has been carried out that different crops are rotated on the10-year-old alfalfa grassland in arid sandy area of Ningxia. Results indicate:Each rotation pattern for0-200cm soil moisture in the crop growth period were higher than CK, the rotation for0-200cm soil moisture content change is different, the main differencewas in0-120cm soil layers, the fluctuation was quite obvious, affected by precipitation, evaporation and crop consumption influence is very obvious,120～200cm soil moisture fluctuations relatively stable, the layer of soil moisture have some recovery with the extension of alfalfa growth years.The end of rotation, ACB and APM storage capacity of soil moisture was the highest, deep soil water compared to crop rotation before had some recovery. But ACC, ASS,ACS storage capacity of soil moisture was relatively low, compared with other rotations, deep soil moisture was low, but higher than the year after10years of growing alfalfa ground..2. Determination of soil water and corn xylem fluid δ18O by IsoSource software in critical reproductive period. The results show:The early growth of corn,0～20cm soil moisture for corn growth contribution rate was highest, up to38.3%, follow as20～40cm, was26.8%. Corn growth medium,60～100cm soil moisture for corn growth contribution rate was the highest,63.5%,100～120cm times; was24.1%. Com maturity to harvest,140-180cm soil moisture for corn growth contribution rate was the highest, up to67.1%,100～180cm times, was23.8%.3. Alfalfa ploughed after alfalfa grain rotation,0～60cm soil pH value was increased during two years, but less than alfalfa grassland. Soil organic matter and soil nitrogen content was decreased, but the nitrogen use efficiency was relatively high. The total phosphorus, available nitrogen content increases and decreases, the content of available phosphorus showed the trend increased and then decreased, the content of available potassium showed the trend of decreased first and then increased. Alfalfa crop tillage for soil nutrient consumed more obvious.4. The quantity of soil microorganisms in each rotation along with the growth of crops were first increased and then decreased in arid sandy area. Different rotation soil microbial quantity significant difference, the number of bacteria occupy absolute advantage, the number of fungi was the least. Grass-crop rotation increased the soil enzyme activity. Urease activity changed first increased and then decreased, the other enzyme activity increased regularity from June to October. Different alfalfa grass rotation activity of soil urease, phosphatase, invertase activity and catalase activity varied. Soil enzyme activity of crop rotation was higher than cropping patterns.5. After plowing alfalfa crops, effect of different crop rotations on indicators of physiological indicators, crop water use efficiency and yield was very obvious. High yield crop cropping, crop height, water use efficiency and yield were significantly reduced in the second year.6.10-year-old Alfalfaâ†'cornâ†'sorghum (ACS) is the best grass crop rotation patterns.0～200cm Soil water restoration is better after the rotation, its depth soil moisture, total yields, water use efficiency, nitrogen use efficiency and economic benefits are higher than others, which are in turn211.31mm,6085.91kg/hm2,8.03kg/hm2·mm-1,37.80kg/kg-hm-2,8110.4yuan/hm2. |
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