| Purpose of this experiment was to investigate the effects of different spacing between maize and soybean rows on nitrogen fixation and final grain yield of soybean with different nodulation characteristics.To explore the effects of soybean varieties and row spacing on soybean nodule growth and nodulation,nitrogenase activity biomass accumulation,grain-filling parameters and yield.We carried out a field experiment with two-factors randomized complete block design,and deployed five row spacing between maize and soybean(A1: monoculture of soybean,marked as SS,A2: 30 cm,marked as IS30,A3:45 cm,marked as IS45,A4: 60 cm,marked as IS60,A5:75 cm,marked as IS75)and three soybean varieties(B1: weak-nodulation Gongxuan No.1,B2:medium-nodulation Guixia No.3;B3:strong-nodulation Nandou No.25).The main results showed as follows:1.B1 under monoculture and B2 under IS60 have the highest pods per-plant.IS45 and IS60 were more conducive to the increase of pods per-plant;the number of monoculture were lower than that of IS60.The maximum values under the intercropping were noticed in B1(2016,2017)and B2(2016)under IS60.B2 had the highest pods per-plant.The differences between the varieties showed as B3>B1>B2.Under the intercropping,the yield of IS60 was the highest,and the difference was not significant compared with monoculture.At the same line spacing,the yield showed B3>B2>B1.In 2016,the yield of IS60 B3 was 9.33% and 9.92% higher than that of the B2 and B1,respectively.In 2017,it was 1.54% and 2.68% higher respectively.2.B1 had higher effective grout duration and 100-grain weight at maximum grouting rate under IS60,and the highest number of days was reached at IS30.B2 had the highest effective grouting duration under IS60,and IS30 had the highest average rate.B3 had the largest initial grouting value,the maximum grouting rate and the lowest effective grouting duration under monoculture,and the least number of days when IS60 reached the maximum grouting rate.IS75 and IS60 had the highest 100-grain weight reaching the maximum grain filling rate.3.The dry matter accumulation of soybean increased first and then decreased,and the growth accelerated after R3 stage.The highest values for monoculture and intercropping were observed at R4 and R5 respectively.In 2016,there were B1> B2> B3,and B2> B3> B1 in 2017.The maximum value of IS60 was higher than that of monoculture at R5 stage.B3 had the most significant advantages under the IS60 at R5 stage.4.The unit mass nitrogenase activity and single plant nitrogenase activity of soybean root nodules increased first and then decreased with the advancement of the growing period.Monoculture was better than intercropping,and IS60 was the highest and IS30 was the lowest.The differences between the varieties showed as B3>B1>B2.Unit-mass nitrogenase activity in R2 in 2017 was higher than the maximum in R3 in 2016.It indicated that R2 stage was the period when soybean root nodule had the highest activity of nitrogenase activity per unit mass.The maximum value of nitrogenase activity per plant under monoculture and intercropping was the R4 and R5 respectively.5.The regular pattern of nodule number and fresh weight in the growth period was consistent,first increased and then decreased.The maximum value of monoculture and intercropping appeared at R4 and R5 respectively.And The maximum value of R5 intercropping is higher than the maximum of R4 monocultur.Under the intercropping,IS60 was better and IS30 was the lowest.The differences between the varieties showed as B3>B1>B2.6.At V5 stage,the rhizobia began to infest but the area of infection was small.After maize harvest,the infection area of rhizobia and number of bacteria both increased at R2 stage.On contrary to intercropping,in monoculture the area of infection was larger and number of bacteria were less,under IS60,B3 had the highest number of bacteria.At R5 stage,the bacteria began to break down,and nodules began to dote,but the advantage of intercropping was obvious.The differences between the varieties showed as B3>B1>B2. |
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