Cotton-wheat double cropping system is a main planting system in cotton cropping zones in China, but less research has been done in soil nutrient competition while more in light competition of up ground part of composite population in the symbiotic period of wheat-cotton.

In Huang huai cotton strict,for 2 kind of planting patterns of cotton wheat double cropping that were 3∶2 model and 3∶1 model,shading degrees resulting from the planting patterns in cotton wheat double cropping symbiotic period affected C metabolism and N metabolism,soluble protein content,POD activity and MDA accumulation of cotton seedling leaf.

Theory and practice of redevelopment in mature oilfield-taking Block Xinhai 27 of Haiwaihe oilfield as an example;