Research Of Green Manure Of Vicia Faba L.(Faba Bean) On Nitrogen Transformation And Nitrogen Utilization Of Spring Maize In Purple Soil

Purple soil is one of major soils for grain production in China. But seen from the results of the second national soil survey, nitrogen content of pueple soil is generally low. Moreover, reclamation rate and multiple crop index of purple soil are increased in recent years, which accelerated the loss of nitrogen, and then it made the nitrogen element becoming the limiting nutrient of agricultural production in purple soil. But green manure is a kind of high quality organic fertilizer, it has good effect to improve soil nitrogen nutrition. In this paper, faba bean was chosen as the materials of green manure, because it is commonly planted in purple soil now and was used as green manure for a long time. Two types of patterns of green manure were used, including green manure mulching and green manure incorporation. Three indoor heated aerobic incubation experiments were used to study the effects of green manure of faba bean on the soil nitrogen mineralization, soil nitrogen nitrification and the quantity of nitrogen-transforming microbes which revealed the process of improving nitrogen fertility of purple soil by utilizing green manure of faba bean. And a pot experiment was used to study the effects of nitrogen fertilizer reduced and combined with green manure of faba bean on nitrogen uptake and utilization of spring maize. It explicated application value of green manure of faba bean in agriculture production. In a word, the aims of this paper were to improve nitrogen fertility in purple soil and explore the application value of green manure of faba bean in agriculture production. The main conclusions are as follows:（1） Green manure of faba bean mulching or incorporation could promote the increase of the contents of ammonium nitrogen（NH₄⁺-N）, soil mineral nitrogen and soil net nitrogen mineralization in purple soil, and they all had a tendency to increase with the increase of application rates of green manure in a certain range. The contents of NH₄⁺-N, soil mineral nitrogen and soil net nitrogen mineralization in all treatments with showed similar trends with the increase of application rates of green manure of faba bean. They fluctuated strongly in the 0-21 d and fluctuated slowly after 21 d. In terms of the maximum peak values, the above three were characterized by FY1.8 > FG3.0,FY3.0 > FG1.8 > FY0.6 > FG0.6. The content of nitrate nitrogen（NO3--N） in all treatments with the application of green manure of faba bean decreased firstly and then increased rapidly and increased slowly with the increase of the time. The NO3--N content in the treatments with green manure mulching appeared minimum value and maximum value in 7th d and 63 th d respectively. The NO3--N content in the treatments with green manure incorporation appeared minimum value and maximum value in 5th d and 56 th d or 63 th d respectively. In terms of the maximum value s, The NO3--N content were characterized by FG3.0,FG1.8 > FY3.0, FY0.6, FY1.8 > FG0.6. Green manure mulching or incorporation increased soil total nitrogen and organic matter content. With the same application amount of green manure, soil total nitrogen and organic matter content in the treatments of green manure incorporation were significantly higher than those of the treatments of green manure mulching.（2） Soil nitrification rate in all treatments showed the change of "S" shape with the increase of the time, which could be divided into slow phase in 1-7 d, rapidly ascending stage in 7-28 d and stationary phase in 28-63 d. Soil nitrification rate showed those of the treatments with green manure mulching was higher than those of the treatments with green manure incorporation in 1-14 d. Green manure mulching or incorporation obviously improved soil nitrification rate in 21-63 d and soil nitrification rate had a tendency to increase with the increase of culture time after 35 d. Soil nitrification rate in all treatments with the application of green manure of faba bean were more than 90% in 28-63 d. Green manure of faba bean mulching or incorporation significantly increased ammonia oxidation potential and soil nitr ification intensity in purple soil, and they both increased with the increase of the application amount of green manure. But when the application amount of green manure was more than 1.8%, the nitrification intensity no longer increased significantly. With the same application amount of green manure, soil ammonia oxidation potential and soil nitrification intensity of treatments with green manure incorporation were greater than those of the treatments with green manure mulching.（3） Green manure of faba bean mulching or incorporation all promoted the increase of the numbers of soil aerobic nitrogen- fixing bacteria, soil ammonifying bacteria, soil nitrifying bacteria, soil denitrifying bacteria. The amounts of aerobic nitrogen- fixing bacteria and nitrifying bacteria had a tendency to increase with the increase of culture time, while the amounts of ammonifying bacteria and denitrifying bacteria had a tendency to decrease with the increase of culture time. The amount of aerobic nitrogen- fixing bacteria increased with the increase of the application amounts of green manure, while ammonifying bacteria, nitrifying bacteria and denitrifying bacteria changing with the amount of green manure is not obvious. With the same application amount of green manure, soil aerobic nitrogen- fixing bacteria and soil ammonifying bacteria of the treatments with green manure incorporation were greater than those of the treatments with green manure mulching.（4） Nitrogen fertilizer 15% reduced and combined with green manure of faba bean mulching or incorporation could all promoted dry matter accumulation and nitrogen accumulation and grain yield in the maturity of spring maize.Effects of nitrogen fertilizer 15% reduced and combined with green manure of faba bean mulching on dry matter and nitrogen accumulation were significantly better than those of nitrogen fertilizer 15% reduced and combined with green manure of faba bean incorporation, but there was no significant difference in grain yield between the above two. N itrogen fertilizer 30% reduced and combined with green manure of faba bean incorporation could also significantly promoted dry matter accumulation in the maturity of spring maize. 40.18⁹2.21% nitrogen sources in spring maize grain came from nitrogen transferred of vegetative organs. N itrogen transferred contribution ratio of leaf and srem-sheath is rather larger, namely 17.99⁵0.62% and 11.32²8.00% respectively. However, nitrogen transferred contribution ratio of bract and cob is a little smaller, namely 0.41¹4.49% and 4.44⁹.80% respectively. In the view of total nitrogen transferred in the aboveground of spring maize, compared with 100% nitrogen application, nitrogen fertilizer reduced 15% and 30% and combined with green manure of faba bean mulching or incorporation all contributed to the increase of nitrogen amounts transferred, and the effects of the treatments with green manure incorporation were better than those of the treatments with green manure mulching. In addition, nitrogen fertilizer 30% reduced and combined with green manure of faba bean mulching or incorporation both contributed to the increase of nitrogen transferred contribution ratio.