Abstract: A rain-proof pool culture experiment was conducted to study the effects of nitrogen (N) application rate and post-anthesis soil moisture content on the flag leaf senescence and kernel weight of wheat. The results indicated that in all N fertilization treatments, the flag leaf SPAD value, soluble protein content, SOD and CAT activities, and photosynthetic rate decreased in the order of 60%-70% >80%-90%>40%-50% post-anthesis soil moisture content, while the MDA content decreased in reverse order, suggesting that over high or low post-anthesis soil moisture content could cause the early senescence of flag leaves, impact grain filling, and decrease kernel weight. Under the same post-anthesis soil moisture content, the SPAD value, soluble protein content, SOD and CAT activity, and photosynthetic rate increased, while the MDA content decreased with increasing N application rate, indicating that increased N fertilization could postpone the senescence of wheat flag leaves. However, over N application was not favorable to the increase of kernel weight, especially under the condition of post-anthesis soil moisture deficiency. It was concluded that appropriate N application and post-anthesis soil moisture content control could postpone the plant senescence and increase the kernel weight of wheat.

Key words: yield difference, soybean-wheat cropping, nitrogen fertilizer management method, rice-wheat cropping