| In recent years,soil sanding and soil erosion have become serious problems in northeastern farming-pasture zone,the uneven spatial and temporal distribution of precipitation further restricts forage growth and reduces forage biomass.Optimizing irrigation strategy and adjusting crop structure are effective ways to enhance water use efficiency and forage biomass.The Gramineae-legume intercropping used to be considered as a productive and efficient complex system,which could not only increase the biomass per unit area,but also improve the resource utilization efficiency.In this research,three planting patterns(Medicago sativa monoculture,MA;Sorghum sudanense monoculture,MS;Medicago sativa/Sorghum sudanense intercropping,I)and two irrigation treatments(irrigation treatment,I;no irrigation treatment,N)were set up in a sandy loam farmland to investigate the intercropping effect between above-and below-ground parts of Medicago sativa/Sorghum sudanense intercropping system under different moisture conditions and the effect on forage quality in Chang-ling County,Jilin Province.This study aimed to clarify the effects of irrigation treatment and intercropping pattern on above-ground biomass,nutritional quality and soil water use.The main results were as below.(1)The analysis of land use advantages in the intercropping system of alfalfa at flowering stage and Sudan grass at heading stage showed that the land equivalent ratio of intercropping system was higher than 1.0 in the year 2020 and 2021,which was advantageous for the production.Specifically,in the first year of establishment,Medicago sativa had weaker interspecific competitive ability,the above-ground biomass of intercropped Medicago sativa reduced and that of intercropped Sorghum sudanense increased.And irrigation treatment significantly increased the above-ground biomass of two forage species in intercropping system.In the second year of establishment,at the first crop of Sorghum sudanense,the interspecific competitive ability of Medicago sativa was greater than that of Sorghum sudanense,the aboveground biomass of intercropped Medicago sativa increased and that of intercropped Sorghum sudanense decreased.And irrigation treatment reduced the interspecific competition pressure of Sorghum sudanens.At the second crop of Sorghum sudanense,the interspecific competitive ability of two forage species was comparable,the above-ground biomass of intercropped Medicago sativa and Sorghum sudanense decreased compared to monoculture.(2)The analysis of plant traits in the intercropping systems of Medicago sativa at flowering stage and Sorghum sudanense at heading stage showed that intercropping affected the plant morphology of Medicago sativa,and the plant traits of Sorghum sudanense were different between two years.Specifically,compared to monoculture,intercropping increased plant height of Medicago sativa,decreased its stem diameter.In the first year of establishment,intercropping increased the plant height,dry weight of single plant and stem-leaf ratio of Sorghum sudanense,and in the second year of establishment,intercropping decreased the plant height and dry weight of single plant of Sorghum sudanense.Irrigation treatment differentially increased the plant height and number of branches of intercropped Medicago sativa,increased the plant height,stem diameter and number of tillers of intercropped Sorghum sudanense.(3)The analysis of leaf photosynthetic characteristics parameters and chlorophyll content in the intercropping systems of Medicago sativa at flowering stage and Sorghum sudanense at heading stage showed that intercropping was beneficial to photosynthesis in Sorghum sudanense.Specifically,intercropped Sorghum sudanense increased stomatal conductance,transpiration rate,increased net photosynthetic rate,and increased chlorophyll content,indicating that Sorghum sudanense increased biomass by forming more photosynthetic products.The irrigation significantly increased transpiration rate of intercropped Sorghum sudanense;while Medicago sativa captured less light energy due to shading effect of Sorghum sudanense,and net photosynthetic rate decreased,while relative chlorophyll content increased,indicating that Medicago sativa used this to enhance light energy capture ability and adapt to low light environment.Under no irrigation treatment,the instantaneous water use efficiency of leaves of intercropped Medicago sativa and Sorghum sudanense was increased than irrigation treatment.When subjected to water stress,Medicago sativa to avoid excessive transpiration of the plants,while Sorghum sudanense reduced net photosynthetic rate by non-stomatal factors.(4)The analysis of crude protein(CP)content,neutral detergent fiber(NDF)content,and acid detergent fiber(ADF)content of forage grasses in the intercropping systems of Medicago sativa at flowering stage and Sorghum sudanense at heading stage showed that intercropping improved the nutritional quality of forage grasses.Specifically,intercropping increased CP content of Medicago sativa,reduced NDF and ADF content of Medicago sativa and Sorghum sudanense.Compared to no irrigation treatment,irrigation treatment decreased CP content of Medicago sativa,increased NDF and ADF content of Sorghum sudanense.(5)The analysis of soil moisture content in intercropping system of Medicago sativa at flowering stage and Sorghum sudanense at heading stage showed that there was water competition and complementarity in the intercropping system.Specifically,in the soil depth range of 40-60 cm,under irrigation treatment,soil moisture of intercropped Sorghum sudanense field was transferred to Medicago sativa field.Under the no irrigation treatment,there was competition between Sorghum sudanense and Medicago sativa for soil water.In the first year of establishment,when interspecific competitive ability of Sorghum sudanense was greater,Medicago sativa tended to access soil water below 60 cm.In the second year of establishment,when interspecific competitive ability of Medicago sativa was greater and it accessed soil water from Sorghum sudanense field.In summary,Medicago sativa/Sorghum sudanense intercropping had advantages for the production,not only increased system biomass,economic benefits and improved forage nutritional quality,but also increased light,heat and water utilization.Compared to no irrigation treatment,irrigation further improved the biomass of the intercropping system,increased the plant height,stem diameter,and the number of branches(tillers)of intercropped Medicago sativa and Sorghum sudanense,enhanced the transpiration rate of Sorghum sudanense and Medicago sativa,reduced interspecific competition for soil water,and increased the net economic benefit per unit area.The results of this experiment showed that irrigation and Medicago sativa/Sorghum sudanense intercropping were feasible and advantageous,provided a theoretical basis for the development of the forage industry in northeastern farming-pasture zone. |
PDF Full Text Request