| Health conditions of four types of cultivated alfalfa (Medicago sativa L.) grassland were evaluated in Linxi of Inner Mongolia in 2007 and 2008 from yield components and the morphological characteristics of root system, physiological and biochemical properties, soil properties, M. sativa cv. Aohan, M. sativa cv. Rangelander, M. sativa cv. Algonquin and M. sativa cv. Golden queen as materials. The results showed as below:(1) 39 indicators were selected to evaluate health conditions of cultivated alfalfa grassland, which were height, branches, leaf weight, leaf area, leaf area index, leaf angle, over-wintering rate, growth rate, yield, crown diameter, crown systolic, crown buds, total root length, total root surface area, nodules, root biomass, Ca, proline, MDA, CAT, Pn, Tr , WUE, Gs, chlorophyâ…¡, soil water content, soil pH, soil compaction, soil respiration, soil total nitrogen, soil total potassium, soil total phosphorus, soil organic nitrogen, soil organic carbon, soil organic, microbial biomass carbon, microbial biomass nitrogen, microbial quotient,Nbio/Norgand microbial amount.(2) Fuzzy comprehensive evaluation(FCE) and analytical hierarchy process(AHP) were integrated to evaluate health conditions of cultivated alfalfa grassland. The results showed that deferent health coefficients on cultivated grassland of Rangelander,Algonquin and Golden queen were 1.36, 1.34 and 1.16 respectively, which were better than cultivated grassland of native cultivar Aohan. The results from the method of ecological carrying capacity were similar to FCE.(3) Yield components of four alfalfa cultivars presented regularity with increasing years of growing. All the indicators reached the peak after growing for three or four years, then showed descending trend with growing years'increasing. The first two years were growing period. Yield components of the 5t h or 6t h year showed the descending trend, especially height, branches and leaf weight.(4) All the indicators of root system showed the tendency of increase with growing years'increasing. The percentage of root rot area of Algonquin,Golden queen, Rangelander and Aohan was respectively 7.09%, 8.11%, 8.45% and 15.49%. According to the grade criteria of root rot, the root system of Algonquin,Golden queen and Rangelander located at the level of slight injury, while Aohan located at the level of moderate injury.(5) The difference of nutrients content of four alfalfa cultivars with different growing years was not significant (P>0.05). The time that the maximum value of diurnal variation of Pn, Tr and WUE appeared was 11: 00 ~13:00, 9:00~11:00 and 15:00 respectively. Variation laws of physiological adaptive indicators were related to cultivars and growing years. Four alfalfa cultivars with three or four years'growing have good resistance to environmental stresses. In four alfalfa cultivars, Algonquin had strong resistance to environmental stresses with high praline content and CAT activity, low MDA content and electric conductivity. On the contrary Golden queen showed different variation laws and had weak resistance to environmental stresses. Aohan is between Algonquin and Golden queen.(6) The variation of soil water content showed a double peak curve with the maximum values at 15cm and 17cm respectively, the minimum value at 30cm. Soil compaction showed the trend of increase with the planting years'increasing. The difference of soil pH was generally not significant. Soil respiration rate had slight fluctuation with the maximum value at 4:00am. Soil nutrients show the ascend-drop trend with growing years'increasing and accumulated in the surface.(7) Microorganism biological indicators of four cultivated alfalfa grassland showed the single peak curve which were low at the first two growing years, then highest at the 3 th year, lastly dropped, such as protease and urease. The activity of soil invertase was not related to growing years and cultivars. On the grasslands of Aohan and Rangelander with six years'growing and the grasslands of Algonquin and Golden queen with four years'growing, microorganism lived in a favorable environment.
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