Abstract:

To clear under the condition of slow release nitrogen fertilizer applying different content of maize development rule of the diurnal change of photosynthetic characteristics and growth,the light response curve was to fit,so as to farming-pastoral zone of spring maize cultivation and nitrogen utilization to provide theoretical basis.This study took Guangde 5 as the research object,and based on the long-term positioning experiment in 2018,the leaves ear position in spinning—tasseling stage of maize were mesured and analyzed under six nitrogen gradient of N 0(N0,CK), 120(N8), 180(N12), 240(N16), 300(N20),360(N24) kg/ha in 2019 and 2020. SPAD value, intercellular carbon dioxide concentration, stomatal conductivity, diurnal variation of net photosynthetic rate, transpiration rate, light response curve and dry matter accumulation rule.The results showed that with the increase of nitrogen fertilizer application, the changes of SPAD value, net photosynthetic rate, transpiration rate and stomatal conduction degree day of maize increased first and then decreased,and N16 treatment was the highest,and intercellular carbon dioxide concentration was the lowest.The changes of net photosynthetic rate,transpiration rate and stomatal conduction degree day showed unimodal curve.The light response curve fitting analysis showed that the maximum net photosynthetic rate of N16 treatment was the highest.In 2019 and 2020,N16 treatments were 37.48%,29.51%,31.85%,18.17%,37.32% and 80.04%,59.73%,50.30%,6.42%,62.51% higher than N0,N8,N12,N20 and N24 treatments,respectively.Dry matter mass accumulation in whole plant and ear were positively correlated with maximum net photosynthetic rate,apparent quantum efficiency and SPAD value.Comprehensive analysis showed that the most suitable nitrogen fertilizer application rate in western Inner Mongolia was 240 kg/ha.

Key words: Maize, Diurnal variation of photosynthesis, Nitrogen gradient, Light response curves, Spinning—Tasseling stage, Mass of dry matter