Effects Of Ridging And Furrow Combined Practices On Soil Water Content And Temperature, Microclimate And Population Characteristics Of Proso Millet

Proso millet?Panicum miliaceum L.?is mainly and widely planted in Loess Plateau areas,because its growing season fits the rainy season in these areas and the its obvious advantages of great resistances to drought,high temperature and poor soil conditions,presenting significant roles in this region.However,the productivity of proso millet in these regions is still restrained by the poor conditions and cultivation techniques,and relative researches are still insufficient.Therefore,it is very important to find effective cultivation techniques to improve the growth and grain yields of proso millet in these regions.A field experiment was conducted in Yulin Modern Agriculture Demonstration Garden of Yulin,Shaanxi in the three growing seasons from 2014 to 2016.Employing a randomized complete block design,the experiment had three replications.Yumi 2,a proso millet variety,was used as the test material.In the experiment,a flat plot without any mulch was considered as the control?CK?and six ridging and mulching combined practices were considered as the different treatments:?a?NM,ridging without any mulching;?b?JM,ridging with furrows biodegradable film mulched;?c?YM,ridging with furrows liquid film mulched;?d?DM,ridging with both hills and furrows plastic film mulched;?e?BU,ridging with only hills plastic film mulched and furrows not mulched;?f?JG,ridging with furrows straw mulched.In treatments b to f,hills were completely mulched with plastic film.Effects of different ridging and furrow combined practices on soil water content and temperature,microclimate and population characteristics were analyzed,and the mechanism of yield formation of proso millet in ridging and furrow combined practices were discussed in this study,based on soil and microclimate conditions,population characteristics,physiological metabolism and dry matter accumulation of proso millet in different treatments.The main results showed as follow:?1?Compared with CK,all the ridging treatments could effectively improve the soil moistures by increasing 3.2%-13.3%and 4.0%-18.4%of soil water content in 0-200 cm soil in 2014 and 2015,respectively,and the benefit intensified with the extensions of the corresponding mulched areas.DM,JM and JG provided better soil water conditions than other treatments,while the increased effect of NM was relatively slight.DM and JM could effectively increase the soil temperatures,while JG could obviously decrease the soil temperature during the growing season in the experimental years.Compared with the CK,YM,BU and NM showed negligible effect on soil temperature.Soil water contents in jointing and filling periods had strong positive correlations?P<0.001?with dry matter accumulation in jointing and filling periods,respectively.The mean soil water content throughout the growing season had strong positive correlations?P<0.001?with yield.The mean temperature of 0-25 soil in filling period had strong positive correlations?P=0.001?with dry matter accumulation in filling period.It had great significance to improve soil water content and increase soil temperature in filling period for yield improvement of proso millet.DM provided better effects on soil water and temperature than other treatments in both 2014 and 2015?drought years?,and JM followed.?2?Ridging and mulching combined practices drove the formation of relative cool and humid microclimate to improve the microclimate for proso millet production by decreasing the canopy and air temperature and increasing the relative humidity.Proso millet was very sensitive to water and temperature in flowering periods.Ridging and mulching combined practices could drive the formation of relative cool and humid microclimate by decreasing0.7?-2.0?and 0.6?-1.7?of canopy temperature after anthesis,reducing 0.4?-2.4?and 0?-1.9?of air temperature within the canopy in anthesis and increasing 0.1%-6.5%and 0-3.4%of relative air humidity within the canopy in 2015 and 2016,respectively.Compared with other treatments,DM provided better effects.Ridging and mulching combined practices also improved the distribution of photosynthetically active radiation?PAR?within the canopy and increased the radiation use efficiency.It was different with 2014 and 2015?drought years?that the radiation interception by canopy was not the highest in DM in 2016?wet year?.Compared with CK,the practices also enhanced the radiation use efficiency by 1.7%-41.5%,15.1%-64.6%and 0.6%-27.1%after heading in 2014-2016,respectively.Ridging and mulching combined practices could improve microclimate of proso millet;DM provided better effects than other treatments in drought year,but its superiority in wet year decreased.?3?Ridging and mulching combined practices could significantly increase the plant height,leaf SPAD value and leaf area index?LAI?,and effectively decrease radiation extinction coefficient?K value?in later period in drought years,and effectively decrease the accumulation of MAD and O₂^-·.Throughout the growing season in 2014-2016,the mean LAI was increased by14.4%-39.8%,19.9%-65.2%and 14.9%-35.1%,and the LAI after anthesis was increased by21.8%-59.2%,22.1%-77.9%and 21.0%-44.5%,compared with CK;the mean leaf SPAD value was increased by 3.3%-16.8%,2.2%-13.4%and 2.4%-9.4%,and the leaf SPAD value after anthesis was increased by 2.7%-20.9%,2.0%-17.4%and 2.6%-9.9%,respectively.Strong positive correlations?P<0.01?exhibited between dry matter accumulation and leaf SPAD value after anthesis.Positive correlations?P<0.05?exhibited between dry matter accumulation and LAI after anthesis.Maintaining higher LAI and leaf SPAD value after anthesis provided important prerequisite for positive dry matter accumulation after anthesis.Ridging and mulching combined practices could compose favorable population characteristics for proso millet production;DM provided better effects than other treatments in drought year,but its superiority in wet year decreased.?4?Ridging and mulching combined practices could increase dry matter accumulation before and after anthesis,and enhance yield?except JG in 2014?and its compositions of proso millet,but the superiority decreased in wet year?2016?than drought years?2014 and 2015?.Ridging and mulching combined practices drove the improvement of the dry matter accumulation of individual plant by 1.4%-73.7%,19.5%-94.3%and 14.8%-58.9%in2014-2016,respectively;Ridging and mulching combined practices drove the improvement of the dry matter accumulation before anthesis by 2.2%-72.8%,13.4%-88.0%and25.2%-70.5%,and the enhancement of the dry matter accumulation after anthesis by4.8%-99.6%,80.4%-142.5%and 3.7%-83%in 2014-2016,respectively.They also enhanced the grain yields by 3.7%-31.3%?except JG in 2014?,6.8%-35.3%and 6.8%-16.4%,compared with CK,in 2014-2016.Increasing the dry matter accumulation before and after anthesis,and grain weight and number were the important approaches to yield improvement.Higher LAI,lower recession of leaf area and lower contents of MDA and O₂^-·after anthesis were also important reasons of achieving favorable yield in ridging and mulching combined practices.Compared with CK and other practices,DM achieved better dry matter accumulation and the best harvests for three consecutive years,however,the improvement of yield was decreased in 2016?wet year?.Possible reasons were that DM provided better soil conditions and microclimate for proso millet production,and composed better population characteristics than CK and other treatments,while its superiority in wet year decreased.Therefore,DM was recommended for proso millet production in Loess Plateau areas in drought years.?5?Based on the correlations among LAI,TPAR and IPAR with spectral variables,regression formulae of LAI,the mean TPAR?TPARm?and IPAR were developed preliminarily in this study.The regression formula,y=0.387 x^0.869(x=R₇₅₀/R₄₇₀),was more suitable for monitoring the LAI within the proso millet canopy from heading to maturity.The regression formulae,y=-0.711x+1.259(x=R₁₀₆₅/R₁₂₀₀),y=1.318 x-0.749(x=R₁₂₇₅/R₁₀₆₅),y=-1.987 x+0.591[x=(R₁₀₆₅-R₁₂₀₀)/(R₁₀₆₅+R₁₂₀₀)]and y=-2.110 x+0.543[x=(R₁₀₆₅-R₁₂₇₅)/(R₁₀₆₅+R₁₂₇₅)]were more suitable for monitoring TPARm within the proso millet canopy from heading to maturity.The regression formulae,y=-0.0985 x²-0.2693 x+0.9914(x=R₆₇₅/R₅₅₀)and y=-0.5092 x²-0.7638 x+0.6346[x=(R₆₇₅-R₅₅₀)/(R₆₇₅₊R₅₅₀)]were more suitable for monitoring the IPAR within the proso millet canopy from heading to maturity.These preliminary models of monitoring LAI,TPARm and IPAR could also provide useful information of growth monitoring and yield estimation of proso millet in ridging and mulching combined practices in Loess Plateau areas,for combining the regression formulae with the close correlations among LAI,TPAR,IPAR with yield and other traits.The regression formula of LAI could help to monitor soil water contents in filling period and estimate the dry matter accumulation in heading stage,and the regression formulae of TPARm help to estimate the dry matter accumulation from flowering to maturity and grain yield of proso millet based on ridging and mulching combined practices in Loess Plateau areas.