| This paper aimed for six kinds of legume crops in different levels of fertilization, which are experimented in bashing region, using field experiment and laboratory analysis and other methods to study leguminous crops' output, soil nitrogen content, nitrogenase activity, nitrogen fixation quantity, root distribution, economic benefits and so on, by comparison of legume crop cultivation in the area, Its main conclusions were as follows:1. In the first year ,when nitrogen application rate were 91.64kg/hm2,50.78 kg/hm2,35.65 kg/hm2,189.88 kg/hm2, the theoretical maximum economic yield of alfalfa, broad beans, peas and soy beans were 4203.74 kg/hm2,1859.97kg/hm2,2359.02kg/hm2, 3204.77kg/hm2. The outputs of one grain hereditary kidney beans and red kidney beans decreased with increased nitrogen application rate. After four years continuous cropping,the reduction order of average economic outputs of legumes was alfalfa, broad beans, red kidney, one grain hereditary kidney beans,peas,soybeans.2. The soil nitrogen contents after cultivation of leguminous crops had different changes. In the 1st year after planting leguminous crops soil nitrogen content changed little, about 1.00-1.2g/kg, In the 2nd year after planting alfalfa, broad beans, soybeans soil nitrogen were 1.40-1.8g/kg,significantly higher than the 1st year. Red kidney beans and peas soil nitrogen contents increased little in the 2nd year. In four years, soil nitrogen contents of alfalfa, broad beans, soybeans, peas, red kidney beans were increased enough to decline, while one grain hereditary kidney beans was a downward trend in year-on-year.3. In the fourth year, through surveying and evaluating nitrogenase activities of six legume crops in the flowering stage, we can conclude that the broad beans and alfalfa were, namely 20.6479 umolC2H4·min-1 District -1,20.1262 umolC2H4·min-1District -1, which are higher than red kidney beans and soybeans. The nitrogenase activities of six legume crops were no significant different. Nodule dry weight of broad beans was the highest, which was significant different from the other five legume crops. We compared nitrogenase activity and nodule dry weight, the results indicated that the difference of six leguminous crops in nitrogen fixation was not significant, descending order as follows: alfalfa>broad beans>one grain hereditary kidney beans > soybeans>red kidney beans>peas. The highest was alfalfa which reached 324kg/hm2, followed by broad bean, namely 252 kg/hm2, peas was 211 kg/hm2. 4. The net incomes of broad beans and alfalfa in three fertilizer levels were higher, between 25,000 -3.1 million / hm2. Peas and soybeans net income in three fertilizer levels were lower, red kidney beans reached 31,638 Yuan / hm2 in N8P6, for one grain hereditary kidney beans, the more fertilizer, the less net income. The productivity ratio of broad beans was between 5-6 Yuan / Yuan, expect which the other five legume crops productivity ratios were decreasing with increasing fertilizer, alfalfa in three fertilizer levels were higher than other five crops, namely, 157.66 Yuan / Yuan, 41.31 Yuan / Yuan, 17.15 Yuan / Yuan.5. In the fourth year, we measured and analyzed six legume crops'root distribution characteristics, the conclusion was that: average root dry weight of alfalfa was highest ,up to 3.7370g/1000cm3in0-20 depth, significant different from other legume crops, extremely significant different from red kidney beans, peas. No significant difference between other five crops. Legume crops roots were mainly distributed in 0-20cm soil layer, the root quantity decreased with increasing soil depth. It was a "T"-type distribution.Based on the above results and nitrogen fixation analysis by Wang Xiang-feng in the first year and second year, we can conclude that: alfalfa had a good prospect in the future as nitrogen-fixing legume resources, with higher nitrogen fixation, economic benefit, soil nitrogen content.
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