Effects Of Film Mulching On Microclimate And Water-heat Flux In Maize Farmland Under Full Drip Irrigation

Studying the effects of film mulching on the microclimate and water-heat flux of corn in the farmland is beneficial to quantitatively evaluate the effect of drip irrigation under the corn film on water-saving yield increase in Northeast China from the farmland scale,which is beneficial to ensure the water regulation during the growth period of maize.This study was conducted in the Heilongjiang Water Resources Science and Technology Experimental Research Center from 2017 to 2018.Measure soil temperature and humidity,canopy temperature,inter-row temperature and humidity,solar net radiation and soil heat flux,and calculate the latent heat flux and sensible heat flux of farmland using the Bowen ratio energy balance equation.The microclimate,water-heat flux and evapotranspiration of corn farmland with and without film treatment were systematically studied.The comparison provides a theoretical basis for the study of water-saving mechanism of coated drip irrigation maize in Northeast China.The main conclusions are as follows:?1?The film at the whole growth period increased the average ground temperature of0-80cm and the accumulated temperature of the soil.And as the depth of the soil layer increases,the temperature increase effect of the film gradually decreases.In addition to rainfall periods,film mulching significantly increases soil moisture.The film mulching increased the canopy temperature in the jointing stage,the filling stage and the maturity stage,while reducing the corn canopy temperature during the seedling stage and the tasseling stage.The effect of film mulching on the canopy temperature during the filling period was the most significant?P<0.05?.?2?The main meteorological factors affecting the corn canopy temperature regardless of filming or not were temperature and saturation differences.The baselines of the CWSI model for the mulching and non-mulching treatment were?T_c-T_a?_ll=2.934-1.788 VPD and?T_c-T_a?_ll=2.756-1.714 VPD,and the determination coefficients were all greater than 0.75.?3?The film changed the intra-day variation of each component of the water-heat balance,significantly reduced the latent heat flux on the daily scale,significantly increased the sensible heat flux?P<0.05?,and increased the soil heat flux during the daytime.During the whole growth period,the film reduces the net radiation and latent heat flux,while increasing the soil heat flux and sensible heat flux in addition to seedling,filling and maturity's Bowen ratio was significantly improved by 0.03?P<0.1?.The ratio of latent heat flux to net radiation in the whole growth period of the mulching and non-mulching treatment was 73.28%and74.99%,respectively,and the ratio of sensible heat flux to net radiation was25.68%and 24.13%respectively.?4?The results of the path analysis showed that the results of path analysis showed that the main meteorological factors affecting the instantaneous latent heat flux of corn were solar radiation and saturation difference.However,the film enhanced the influence of saturation difference on the instantaneous latent heat flux and reduced the influence of solar radiation on the instantaneous latent heat flux.The main meteorological factors affecting the daily heat flux of corn were saturation difference,solar radiation and relative humidity.But the film enhanced the effect of saturation and relative humidity on the latent heat flux and reduced the impact of solar radiation on the latent heat flux.?5?Compared with the non-mulching treatment,the transpiration rate of sunny corn the mulching treatments decreased by 13.46%.Cloudy days will weaken the effect of film mulching measures on the transpiration rate of corn during grain filling.The peak time of the mulching treatment of evapotranspiration lags behind the mulching treatment by about1 hour.Compared with the non-mulching treatment,the film treatment was significantly reduced by 20.36%?P<0.05?at the seedling stage respectively.The water consumption of the whole growth period crop decreased by 8.07%;In addition,the film made the corn concentrate more water consumption during the tasseling and filling stages,with an average increase of 2.82%compared with the non-film treatment.?6?The crop coefficient fitting model was established by using the post-emergence time?DAG?,atmospheric accumulated temperature?GDD?and leaf area of maize?LAI?.Compared with the non-mulching treatment,the crop coefficient?K_c?of each treatment period of the mulching treatment was smaller,the whole growth period crop coefficient decreased by an average of 0.10 and 9.26%.The model fitting results showed that the K_c?DAG?model is better than the K_c?GDD?model and K_c?LAI?model,regardless of filming,with the best fitting and estimation accuracy.It can be seen that the film-covering measures have changed the corn soil environment,reduced the net radiation of corn farmland,increased the soil heat flux,and affected the response relationship between meteorological factors and latent heat flux,thereby reducing the evapotranspiration of corn farmland and eventually changing the corn.The distribution pattern of water and heat flux in farmland.