Effects Of Plant Density And Film Mulch On Mazie Water-using And Root Growth In The Rainfed Farming Land Of Northeast China

Maize is one of the main crops in rai-fed areas of northeast China.The study effects of film mulch and planting density on water consumption,yield and root growth of maize are significant for stable and high yield of maize and improvement of rainwater utilization efficiency in northeast rainfed areas.Based on field experiments,we established a water balance model based on the water balance equation to simulate and analyze the effects of filming mulch and planting density on water consumption of maize in different precipitation years.At the same time,principal component analysis,principal component regression and maximum information index methods were used to analyze the effects of film and planting density on maize root growth and the response of maize yield to maize root growth.Firstly,the standard precipitation index(SPI)was used to analysis the trend of precipition of past 55 years.The results indicate that there is a abviously increasing trend of annual precipitation in past 55 years,that rainfall in maize growing period occupies almost 79.3% of annual precipitation and that in recent decade,the frequency of extreme precipitation year including extreme dry year and extreme wet year is more than past decades.Secondly,based on field experiments,the farmland water balance model was established based on the farmland water balance equation and the dual crop coefficient method.Using the experimental data in 2016 and genetic algorithm calibrated the important parameters of the model and those parameters was verified by experimental data in2017.The results show that the model can better descripe soil moisture changes.Using validated models and historical meteorological data,the water consumption of mazie in extreme drought,moderate drought,normal,moderately moist and extremely wet years were calculated.The results showed that compared with bare land,the mulch increased maize transpiration by about 20% to 32% and reduced the evaporation by 51.8% to 60%.Overall,the mulch significantly reduced maize water consumption by about 11.1%.The mulch treatments also increased the basic maize crop coefficient by 0.03~0.075 and reduced the average evaporation coefficient by 0.188 of maize,compared with bare land treatments.In addition,the maize transpiration increased with the increased of planting density,and the maize evaporation increased with the increased of planting density under the film-covering conditions but decreased under bare land conditions.In different precipitation years,the effects of film mulch and planting density on water consumption of maize showed that in extreme drought years and moderate drought years,the planting density had no significant effect on the evaporation of maize,but the evaporation of maize decreased with the increased of planting density in other years.Lastly,the experimental data of maize root growth,field temperature,and water storage in 2016 under the mulch and planting density were compared by mthods of principal component analysis,principal component regression,and maximum information index.The results show that different color film mulch,and planting density have a significant effect on soil water storage,temperature,and root growth.For soil moisture,the mulch significantly increased the soil water storage by 7.2~12.3 mm,and the density had little effect on soil water storage.For the soil temperature,the transparent plastic film and black film mulch significantly increased the soil temperature during the seedling stage by 3.1℃ and 1.3℃,respectively,in which the transparent plastic film had a better temperature effect than the black plastic film.For the root growth,the mulch mainly increased the root length,root length density,root surface density and root diameter of the maize.Density treatments had a significant effect on root length,root surface area,root volume,and root diameter.Additionaly,transparent film mulch increased root length,root length density and root diameter by 17%,21.4% and 11.6% at heading-filling growth stage,respectively,compared with non-mulch treatment.With the increased in planting density,those maize root indicators significant decreased.