Regulation Mechanism Of Plant Growth Regulator On Stem Quality And Yield Formation Of Spring Maize In Cold Region Under Different Plant Densities And N Fertilizer Levels

Lodging is one of the most important limiting factors to further increase yield. There were several lodging happened of large areas in China.This study was conducted in Heilongjiang province which belongs to cold spring maize belt, Zhengdan958and Xianyu335were materials, the objectives of the study were:effect of plant growth regulator (PGR) on maize stem quality, lodging and yield under different plant densities and nitrogen fertilizer levels; to establish maize biomechanics lodging model; The main results were as follows:(1) With the increase of plant density, the canopy structure and photosynthesis became deteriorated; lodging rate was increased. The number of ears per unit ground area increased linearly with plant density, but number of kernels per ear and kernel weight showed decreased, the yield showed a peak at intermediate plant density of75000plant ha’1. There was a significant interaction between plant density and cultivar. Plant growth regulator30%Hex-ethyl-aqua improved canopy structure and photosynthesis, increased3internode strength of breaking-resistance and decreased lodging rate at higher plant density.30%Hex-ethyl-aqua also regulated carbon translocation rate of leaf and stem. Application of PGR increased the yield of two maize by increasing thousand-kernel weight (TKW) and kernels per ear.(2) In the study of nitrogen application, the canopy structure weakened and the length of basal3rd were increased with the increase of nitrogen application. The ratio of carbon and nitrogen in internode and strength of breaking-resistance were decreased with the increase of nitrogen application. Medium application of nitrogen (180kg hm"2) could improve the structure of canopy and increase yield. Under the180kg hm’2nitrogen level,30%Hex-ethyl-aqua improved canopy structure and photosynthesis, increased3rd internode strength of breaking-resistance and yield. There were not significant interactions between30%Hex-ethyl-aqua, plant density and cultivar on yield and components.(3) The multiple linear regression model between lodging and plant height, ear height and the strength of breaking-resistance of2nd to5th internode was deduced, y=24.40112+0.31213xi+0.23863x2+0.15592x3-0.37010X4-0.12414x5-0.01177Xe. Analysis of mechanics and plant morphology under the wind force, and to preliminary built biomechanic equation of maize lodging index (MLI). This MLI can evaluate lodging risk of plant and reflect the differences of HK, hybrids and cultivation ways on lodging. And this can provide theoretical basis for selection reasonable cultivars and cultivation ways under field production.(4) Application of a novel plant growth regulator DHEAP solution through spraying leaves at early jointing stage (V7). Plant height was decreased, ear height and basal internodes length were significantly shortened, internodes diameter were increased, and there were an obvious dose effect relationships. The strength of breaking-resistant of2nd and3rd internodes was improved so that increasing the ability of resistant lodging and decreased lodging rate. The yield was increased by3%-8%under the treatment of600mL hm-2. In a word, our results demonstrate that application of30%Hex-ethyl-aqua under the medium nitrogen (180kg hm-2) and medium plant density condition is the optimum cultivation practice in maize of cold region due to the best yield, plant morphology, population structure and lodging resistance force. Overall, this research provided theoretical basis for the establishment of the high-yield cultivation and the prediction of maize lodging.