The Study On The Photosynthetic Characteristics And Yield Formation Mechanism In Jujube/Wheat (Cotton) Agroforestry Systems

In order to analyze the photosynthetic characteristics,crop yield formation of intercropping crops and the microclimate changes of the intercropping system in the jujube/cotton and jujube/wheat intercropping systems.There are three intercropping modes,which is planting 4 rows of cotton and 2 rows of cotton between two rows of jujube,and planting 10 rows of wheat between two rows of jujube.Different distance from jujube were 90cm?D1?,110cm?D2?and 130cm?D3?.The plant height,leaf area index,dry matter accumulation,net photosynthetic rate,stomatal conductance,intercellular CO₂ concentration,transpiration rate,chlorophyll content?SPAD value?,yield and yield composition of cotton and wheat in sole and intercropping systems were measured.In addition,the change of air temperature,relative humidity and wind speed in jujube/cotton and jujube/wheat intercropping systems were measured.By studying the photosynthetic characteristics and yield formation of intercropping crops in jujube/cotton and jujube/wheat intercropping systems,the article revealed the competitive mechanism of photosynthetic characteristics above ground in jujube/cotton and jujube/wheat intercropping systems.For layouting reasonable intercropping mode and improving intercropping yield provide a theoretical basis.Main conclusions were as follows:In jujube/cotton intercropping system1.There was no significant difference in chlorophyll content between sole cotton and intercropping cotton in jujube/cotton intercropping system.In the early stage of cotton growth,there was no significant difference in net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO₂concentration between sole cotton and intercropping cotton.With the elapse of growth stage,intercropping significantly reduced the photosynthesis of intercropped cotton in cotton flower and boll stage.The net photosynthetic rate,stomata conductance and transpiration rate of monoculture cotton were significantly higher than that of intercropping cotton,intercellular CO₂ concentration was significantly lower than intercropping cotton.Intercropping had no obvious influence on the photosynthetic characteristics of cotton in the cotton wadding stages.However,there was no significant difference in the photosynthetic characteristics of cotton between different intercropping models.2.There was no significant difference in plant height,leaf area index and dry matter accumulation between sole cotton and intercropping cotton in the early stages of cotton growth period.With the elapse of growth stage,plant height,leaf area index and dry matter accumulation decreased significantly in intercropping system.The plant height,leaf area index and dry matter accumulation showed some differences in different intercropping patterns,plant height,the leaf area index,dry matter accumulation of Int-2 cotton was significantly higher than Int4.3.Intercropping significantly reduces the yield of cotton.Compared with sole cotton,cotton yield decreased by 41.98%and 48.72%in Int-4 and Int-2 intercropping mode,but LER in intercropping mode is greater than 1,LER value of Int-4 intercropping mode is 1.12,LER value of Int-2 intercropping mode is1.045.In addition,the number of harvested plants and the number of rings decreased in the Intercropping cotton field,while the number of rings and single boll weight had no significant changes.4.Compared with sole cotton,the average temperature in Int-4 and Int-2 systems decreased by1.285?and 0.815?,respectively.The intercropping mode can produce humidification effect,the average relative humidity of Int-4 and Int-2 intercropping system were 50.65%and 49.50%.There were4.47 and 3.32 percentage points higher than the control?46.18%?.Windbreak effect analysis shows that the windbreak efficiency of Int-4 and Int-2 intercropping system reached 27.53%and 24.51%,respectively.In jujube/wheat intercropping system1.There was no effect on the chlorophyll content of wheat during the early stages of wheat growth period,intercropping significantly reduced the chlorophyll content of wheat in the late stage of wheat growth.There was no significant difference in the chlorophyll content of wheat with different spacing from the tree.Compared with sole wheat,there were no significant changes in net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO₂ concentration of intercropping wheat at the jointing,heading period.There were significant differences in photosynthetic characteristics between the D1 and the D0 treatment at the flowering stage and filling stage.Comparison of photosynthetic characteristics of different tree spacing trees,the closer from jujube trees the more affected by the shade of the jujube tree.There were significant differences in net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO₂ concentration between D1 and D3 treatment at grain filling stage.2.In jujube/wheat intercropping system,plant height,leaf area index and dry matter accumulation in wheat were affected by intercropped jujube trees.Especially after the heading stage,intercropping significantly reduced wheat plant height,LAI and dry matter accumulation.The closer from the jujube trees,the lower the plant height,LAI and dry matter accumulation of intercropping wheat.3.Jujube significantly reduces the yield of wheat in jujube/wheat intercropping system.Compared with sole wheat,yields of intercropping wheat from different tree rows decreased,and the closer from the jujube,the lower yield of wheat.The yields of sole wheat D0 were 47.00%,35.17%and 23.23%higher than those of D1,D2 and D3,respectively.However,the LER value of intercropping system was 1.395,this shows that land use efficiency is significantly higher than that of sole wheat.In addition,intercropped jujube affects the number of spikes,grains per spike and 1000-grain weight of wheat.With the distance from the jujube tree to wheat become shorter,the spike number of wheat,grains per spike and grain weight were lower.4.Compared with sole wheat,the average temperature in intercropping systems decreased by1.085?respectively.The average relative humidity of intercropping system was 49.21%,which was 9.43percentage points higher than the control?39.78%?.Windbreak effect analysis shows,the windbreak efficiency of jujube/wheat intercropping system reached 32.49%,respectively.Conclusion:In jujube/crop intercropping system,the photosynthetic characteristics,agronomic characters and yield of crops were affected by the shading of jujube trees,but jujube/wheat intercropping is more favorable to land utilization.In addition,because the average tree height of jujube is shorter in northern Xinjiang,therefore,the planting density of crops can be increased appropriately,and the higher yield can be obtained.Jujube/crop intercropping has good farmland microclimate effect,in contrast,the small climate change of farmland in jujube/wheat intercropping model is more obvious.