Abstract:

Revealing the dynamic changes of water and heat fluxes in straw-covered farmland ecosystems can provide a theoretical basis for the quantitative regulation of efficient water use by crops under agronomic mulching. Two treatments of straw mulching (S) and none mulching (N) were set up in the experiment. The dynamic changes of net radiation flux (R_n), latent heat flux (λET), sensible heat flux (H) and soil heat flux (G) of farmland energy flux elements under straw mulching in North China Plain and their responses to meteorological factors were studied by using Bowen ratio energy balance method and measured data. The results showed that the diurnal variation of R_n, λET and H in each growth period showed an obvious single-peak pattern. Compared with N treatment, S treatment mainly reduced the daily peak of R_n, λET and H in each growth period in both wheat and maize growing seasons. However, from the perspective of daily mean value, S treatment increased the proportion of λET in R_n in wheat growing season, and the proportion of λET in R_n in the total growth period of S treatment (68.8%) was slightly higher than that of N treatment (68.4%). The proportion of λET to R_n in the total growth period of S treatment (65.0%) was lower than that of N treatment (65.9%).The meteorological factor that had the greatest influence on instantaneous λET in wheat growing season and maize growing season was R_n, and the other factors had little influence. Each meteorological factor affects instantaneous λET through direct and indirect effects. The influence of R_n on instantaneous λET is mainly reflected in the direct effect, and the other factors are mainly reflected in the indirect effect.

Key words:

 , Straw mulching, Bowen ratio, Water and heat flux, Meteorological factors