| Soil water content is one of the important factors limiting the development of agricultural crop production.From the perspective of improving crop photosynthesis and water production efficiency,reducing ineffective evapotranspiration water consumption,and providing an appropriate basis for water regulation during growth period,soil water content is considered as follows: In this experiment,four soil moisture ranges were established during the growing season of potted corn,which were T1(55%±5%FC),T2(65%±5%),T3(75%±5%FC)and T4(85%±5%FC),respectively.By measuring plant height,stem diameter,leaf area and leaf water content(LWC)growth indexes of summer maize during growth period,analyzing dry matter distribution and yield composition,studying photosynthetic physiological changes of photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs)and leaf water use efficiency(LWUE)at jointing stage,tasseling stage and filling stage,as well as nutrient accumulation in organs and residual distribution of soil nutrients in summer maize at harvest period,exploring the response mechanism of evapotranspiration(ET)to soil water content in summer maize,and seeking the water-fertilizer regulation mode of water-saving and highyield summer maize.The main conclusions are as follows:(1)The diurnal ET of summer maize showed unimodal variation trend and reached the peak at tasseling stage.ET size meets T4 > T3 > T2 > T1,which is compactly interrelated to soil water content,and the total ET of summer maize under different water treatments has a positive linear correlation with soil water content.ET in each growth stages increased gradually with the increase of soil water content,and tasseling stage was the period when summer maize consumed the most water.(2)Under the same soil fertility level,the growth and yield of summer maize were increased firstly and then decreased with the increase of soil water content(the change of cob+ glume and hundred grain weight was opposite).Combined with the whole growth period,the plant height and stem diameter of summer maize were positively correlated with soil water content in the whole growth period.With the increase of soil water content,leaf area,panicle length,panicle diameter,panicle grain number,grain yield and total dry matter above ground increased firstly and then decreased.The growth of summer maize during the growth period under different treatments showed a rapid increase at first and a stable trend and then a downward trend,and reached the maximum growth rate at the jointing stage.The increase of soil water content was beneficial to grain acquisition of summer maize,but too much water promoted the increase of bare tip length and the decrease of grain number per spike,leading to a significant decrease in yield.Therefore,the optimum water treatment range for dry matter transfer to grain is 75%±5%FC.The relationship between LWC and Pn,Tr and Gs in different growth stages was significantly conic.The most suitable soil water content for photosynthesis and transpiration was 78.09%～90.00%FC at jointing stage,sexting stage and filling stage.(3)The diurnal changes of Pn,Tr,Gs and LWUE of summer maize in different growth stages were significantly affected by different soil water content.At jointing stage,tasseling stage and filling stage,Pn increased first and then decreased with the increase of soil water content,which was T3 > T4 > T2 > T1.There was no significant difference between T3 and T4 treatments at jointing stage.The changes of Tr and Gs were similar.Tr and Gs were positively correlated with soil water content,and the sizes of Tr and Gs were in the order of T4 > T3 > T2 > T1 in the three growth stages.There was no significant difference between LWUE treatments at jointing stage,and LWUE increased first and then decreased with the increase of soil water content at tesseling stage and filling stage.The diurnal variation of Pn,Tr and Gs of summer maize during the measured growth period increased firstly and then decreased with a single peak(except Pn,Tr and T4 at tasseling stage and Pn,Tr and Gs at tasseling stage in T3 treatment).At jointing stage,LWUE decreased first,then increased and then decreased;at tasseling stage,LWUE showed a U-shaped change with large fluctuation in the morning and evening;at filling stage,LWUE showed a single-peak change with an increase first and then decreased(T2 increased after noon).With the development of growth period and the increase of soil water content,the peak time of Pn,Tr and Gs was delayed.Pn,Tr,Gs and LWUE at tasseling stage and grain filling stage increased compared with jointing stage,and all treatments tended to be stable and fluctuated near the peak value at grain filling stage,and photosynthesis and transpiration were the most stable.(4)Different water treatments had significant effects on the absorption and distribution of nitrogen,phosphorus,potassium and carbon in leaves and stems of summer maize.The absorption of N,P and K in leaves and stems of summer maize showed a parabolic relationship with soil moisture.The variation trends of soil nutrient contents under different water treatments were different at different depths.The higher the soil moisture content is,the depth of peak appears to be deepened in different degrees.With the increase of soil water content,the downward migration degree of nitrate nitrogen was significantly higher than that of other nutrient indexes.The accumulated residues of nitrogen,phosphorus and potassium in soil nutrients were at a high level in T4 treatment,but at a low level in T2 and T3 treatment,and appropriate soil water content was conducive to nutrient uptake by roots.Considering the effects of soil water content on ET,photosynthetic performance,growth and output,plant nutrient absorption and distribution,and soil nutrient distribution and residue,T3 treatment was superior to other treatments in growth,and the photosynthesis,plant nutrient absorption and soil nutrient utilization were the best,while achieving the highest yield with less ET.Therefore,Under the experimental conditions,70%-80%FC is the suitable water content for efficient utilization of water and fertilizer of summer maize. |
