Photosynthetic Eco-physiological Charateristics Of Dense Planting Maize Under Drip Irrigation With Optimized Water And Nitrogen Management

Is it feasible to achieve high corn yield by increasing planting density under the condition of water and nitrogen reduction?In response to the unclear problem of the photosynthetic physiological characteristics of different density maize,the field experiment was carried out in the Oasis Irrigation District of Hexi,and the effects of different irrigation amount and nitrogen application rate on the yield formation and photosynthetic physiology of densely planted maize were studied.It provides a theoretical basis for reasonable density and nitrogen reduction and water-saving and drought-resistant cultivation of maize in dryland.The main conclusions are as follows:（1）The application of nitrogen treatment and the reduction of 20%irrigation level can significantly weaken the decline of photosynthesis rate,transpiration rate,chlorophyll,leaf water potential and leaf area index of maize leaves caused by high-density planting.In the whole fertility cycle,the corn leaf area index of high and medium density treatment increased by 3.0%and 5.3%respectively compared with low density treatment under high nitrogen application.If the same nitrogen application,the photosynthetic rate,chlorophyll content and leaf area index of normal irrigation are increased by 6%,4.8%and 15.7%respectively compared with the 20%irrigation level;if it is in the same irrigation Under the model,the photosynthesis rate and chlorophyll content of the nitrogen treatment were increased by 34.1%and 49.6%,respectively,and the leaf area index of the whole growth period of the nitrogen application was increased by 14%.（2）As the density density of corn planting increases,the inter-canopal transmittance decreases,the population CO₂ concentration and atmospheric relative humidity increase.The rational combination of water and nitrogen reduction can weaken the trend of ecological indicators such as light transmittance between corn canopies,CO₂ concentration between populations and relative humidity of the atmosphere.The CO₂ concentration in the population showed that D₃ increased by an average of 3.2%in the CO₂ concentration in the D₁ corn population.The relative humidity of the atmosphere is expressed as the average relative humidity of D₃ in the canopy of the D₁ corn is increased by 3.2%in the mid-fertility period.In the middle stage of maize growth,the CO₂ concentration in the W₁ treated corn group increased by 6.7%and 4.2%in D₂ and D₃,respectively,compared with W₂.Compared with N1treatment,N₀ increased the average growth of D₂ and D₃ corn in the middle growth stage by 6.7%and 4.1%.Compared with different irrigation levels,W₁ increased the average relative humidity of corn in the canopy of W₂ treatment by 7.7%.Under horizontal conditions,N₀ was treated with N1 and N₂,which increased the relative humidity of the corn canopy in the mid-term growth period of D₁,D₂ and D₃ corn by4.2%,5.1%and 5.7%.（3）With the increase of planting density,corn grain yield showed a downward trend,and reasonable water and nitrogen operation could reduce the negative impact of grain density on grain yield and biomass yield.The grain yield of D₂ treatment was4.8%higher than that of D₃,and the grain yield of D₂ treatment was 10.5%higher than that of D₁.Compared with different irrigations,W1 treated grain yield was 7.6%higher than W₂.Compared with N₀,the grain yield of N₂ and N1 treatment increased by 45.1%and 43.1%compared with different nitrogen application rates.