Responses Of Maize Canopy Structure And Function To Planting Density And Its Nitrogen Effect Of Xian Yu335

Reasonable planting density is an important way to achieve hight yield of crops.Increasing density will have adverse effect on the individual development and population formation of crops.In order to provide theoretical support for high yield in high planting density,we investigated the effect of planting density on structure and function of maize canopy and explored the way of constructing reasonable canopy populations under high planting density.In this experiment,two planting density of 37500plants/ha and 67500 plants/ha were set up with three kind of nitrogen fertilizer treatments of 300kg/ha,150kg/ha and 0kg/ha.The results are as follows:(1)Effects of planting density on canopy structureCompared with 37500 plants/ha treatment,the plant height and ear height of 67500 plants/ha were increased,and the stem 11~15(2~5above the ground)was significantly elongated.The length and width of leaves 1~8 significantly decreased,while,the width of leaves 9~12 decreased significantly and the length of the leaves was not obvious,which lead to the reducing of the leaf areas of per plant.The leaf areas index of the population increased.The leaf areas of per plant and LAI were decreasing faster than that of 37500 plants/ha after silking stage.(2)Effects of planting density on canopy light distributionCompared with 37500 plants/ha treatment,the total intercepted PAR of 67500 plants/ha population increased,while,the PAR at each leaf position was less than 37500 plants/ha.Leaf 1~8 light intercepted more than 37500 plants/ha,while,leaf 9~15 leaves of light intercepted less than 37500 plants/ha.The distributions of extinction coefficient at different leaf positions were consistent with the trend of intercepted light in the canopy.(3)Effects of planting density on canopy functionThe distributions of photosynthetic capacity in different leaf positions in the canopy were in the form of sigle-peak curve,among them,leaves 4~6>leaves 7~9>leaves 1~3> leaves 10~12>leaves 13~15.Compared with 37500 plants/ha treatment,the length of leaf function stage and net photosynetic rate of each leaf position in the canopy were decreased.The photosynthetic capacity of leaves1~9 were more than 37500 plants/ha,while,the leaves10~15 were less than 37500 plants/ha.(4)Effects of nirtrogen structure and function of canopyCompared with no application of nitrogen fertilizer,the internode length of stem 12~10(4~6 above the ground)were significantly elongated and leaf areas were significantly increased with the nitrogen fertilizer.The extinction coefficient(K)had been changed,the leaf functional stage had been prolonged and the amount of intercepted light was improved,but there were different effects on different leaf positions.Fertilizer application was influenced the light distribution in canopy through the regulation of canopy structure,and ultimately affect the material production and yield formation of maize population.The results showed that increasing the planting density to change the structure and function of maize population,can increase the light interception,dry matter production and yield in canopy,while,it had a negative effect on photosynthetic performance.Increasing the application of nitrogen fertilizer can partially alleviate the negative impact of increased density,improve photosynthetic performance and further enhance the level of production.