| The maize/soybean intercropping system not only use of environmental resources, but also increase crop yields, and play important roles in Chinese traditional farming. Previous studies focused on the advantage of yield, water use, and nutrient, and other aspects of the maize/soybean intercropping system. However, the mechanism of the maize density regulation of nitrogen utilization and ―N min inhibitory effect‖ of soybean in the maize/soybean intercropping system, and technical research were still relatively weak. The potential did not make fully use of nitrogen utilization of planting models. The concurrent experiments had been done in the Qiliying test base of Chinese Academy of Agricultural Science, Xinxiang city, Henan province, and the experimental plot of Henan Institute of Science and Technology in 2012 and 2013. The object of studies was the maize/soybean intercropping system, by using the method of field experiment and pot experiment combination. Under the different densities of maize/soybean systems, the nitrogen utilization enhanced planting modes between maize and soybean, and the way to achieve nitrogen complementary use, and the density regulation mechanism of complementary use of nitrogen was researched. The main conclusions are as follows:(1) The soil inorganic nitrogen content was reduced by component, and the alleviation effect of "N min inhibitory" of interplanting soybean had significant improved in the intercropping system. the alleviation effect of "N min inhibitory" gradually increased with increasing maize density. The CI(%) value and Ca(%) value are greater than 0 in the intercropping systems, the interplanting soybean nodulation growth could be promoted, and nodule tumors and nitrogen fixation were inhibited. The trial results shown that the number of nodules and tumor weight(CI(%)) per plant could be increased by 11.3%~64.5% and 28.4%~105.3%,respectively in the intercropping system. The alleviation effect of "N min inhibitory" of soybean was enhanced by regulation maize densities in intercropping systems, it is one of the ways to achieve complementary and enhancing nitrogen utilization in maize/ soybean intercropping planting patterns.(2) With the interplanting maize density increasing, the proportion of fixed nitrogen atmosphere by soybean increased, so intercropping system to get more non-exogenous nitrogen, and the nitrogen transfer was promoted in the intercropping systems. In the treatment of high density of maize(PM1), the amount of nitrogen transfer reached peak, namely 6.8mg.pot-1, comparing with low density(PM3),the transfer amount increased by 58.1%. The amount of soybean nitrogen fixation in the treatment of PM1 was more 25.2% than that of PM3. These conclusions proved to achieve a nitrogen compensation use in the intercropping system via the nitrogen transfer from soybeans to maize, it also showed that nitrogen transfer from intercropping legume to cereal was one of the important mechanisms to compensative use of nitrogen in the intercropping system.(3) In the whole growth period, the maize root weight and length density of intercropping models were more than that of monoculture, and increases with the density increasing tendency. However, the soybean root weight density of intercropping models was lower than that of monoculture, and with the maize density increased, the soybean root weight density of intercropping models was seemed to that of monoculture; the soybean root length density of intercropping models was lower than that of monoculture in the early growth period, but the later growth period, the soybean root length density of intercropping models was more than that of monoculture. In the whole period, the maize root weight density of intercropping models were more than28.1% that of monoculture. For soil level of 20~40cm, the average density of treatment of FM3、FM2、FM1 were more than 5.8%~19.4%、19.8%~25.6%、5.9%~20.9% that of monoculture, respectively. The root weight density of intercropping system generally was lower than that of monoculture in the soybean whole growth period, and the root weight density closed to that of monoculture soybean with the maize density enhancing in the intercropping systems. However, the soybean root length density exhibited lower than that of monoculture in early period, and the soybean root length density exhibited lower than that of monoculture in post period. The root system growth of maize and soybean were improved by maize density regulation in intercropping system, at the same time, the competition between aboveground and underground of maize and soybean. The biological basement was laid to high nitrogen uptake and use in intercropping system between soybean and maize.(4)The amount of aboveground nitrogen accumulation was increased, and the soil inorganic nitrogen content was reduced when the soybean and maize harvest under intercropping system. In the whole growth period, the maize nitrogen accumulation of aboveground under intercropping system was significantly greater than that of monoculture, and with the density increasing, the value was increased. The amounts of FM1 was more than 25.4% ~ 36.8% that of FM3, and the values of FM1 was more than 14.9% ~ 26.6% that of FM2. However, the soybean nitrogen accumulation of aboveground under intercropping system was all lower than that of monoculture. The effect of maize density tended to be indiscriminative. The total aboveground nitrogen accumulation was greater than the sum of monoculture. The soil inorganic nitrogen levels were lower than that of monoculture when intercropping maize and soybean harvest; among the FM1, FM2, and FM3, the amount of soil inorganic nitrogen levels were lower than 20.3%, 15.3 %, 9.4%, that of monoculture respectively, during intercropping maize harvested. Among the FM1, FM2, and FM3, the amount of soil inorganic nitrogen levels were lower than 36.8%, 22.7 %, and 16.4% that of monoculture respectively, during intercropping soybean harvested. The results showed that intercropping system through the use of nitrogen to compensate increased accumulation of total nitrogen system, reducing residual soil nitrogen, to achieve a high absorption, to meet the requirement of sustainable agricultural development.(5) The Density effect increased the aboveground biomass and economic yield under intercropping system, the land equivalent ratio(LER) rose too. In the whole growth period, the aboveground biomass and economic yield of intercropping maize increased with the density increased, and was significantly higher than that of monoculture. However, in the whole growth period, the aboveground biomass and economic yield of intercropping soybean were less than that of monoculture. The maize density had little effect on the soybean aboveground biomass and economic yield in intercropping system. The total aboveground biomass and economic yield in intercropping system were more than the sum of maize pulsing soybean of monoculture planting. Among the density treatment of FM3、FM2、FM1, the LER increased with maize density increasing, the value were 1.218、1.251and1.278, respectively. The results showed that intercropping system increased the total biomass and economics yield, increased the land use efficiency, through density controlling.(6) The nitrogen uptake and utilization of intercropping system of soybean and maize had been effectively regulated by maize density, the alleviation effect of "N min inhibitory" had been enhanced, and the amount of nitrogen fixation and the amount of nitrogen transfer had been promoted. The experimental results showed that the maize density regulation effect was best under the maize density of 75,000 plants per hectare, namely the spacing was 25 cm. The findings confirmed that competition effect could be weakening, and effective use of nitrogen compensation was practical way, through component density regulation in the intercropping system of soybean and maize. The technology could be widely applied in the actual production. |
PDF Full Text Request