| Deep relaxation can improve the soil environment,regulate the distribution of spatial structure of roots,alleviate the "crowding effect" of roots caused by dense planting,and then regulate the normal growth and increase yield of plants under high density.In order to explore the mechanism of increasing densification and yield and controlling the mechanism of deep loosening of maize in Inner Mongolia Plain Irrigation Area,this study was conducted in the three plains irrigation areas of Hetao,Temochuan and Xiliaohe of Inner Mongolia.In 15 cm and deep pine 35 cm two cultivation methods,5 planting densities were set(45,000 plants/hm2,60,000 plants/hm2,75,000 plants/hm2,90,000plants/hm2,and 105,000 plants/hm2)from the root structure.In terms of characteristics,canopy morphology,photosynthetic physiology,yield,and yield composition,systematically analyzed the changing rules of various indicators of tightness tolerance and their mutual relations with the increase in planting density under shallow and deep tillage patterns.As well as the similarities and differences between regions,the differences in the tightness and different mechanisms of the deep loosening response of different corn varieties were revealed.For the Inner Mongolia Plain Irrigation Area,the selection of corn varieties with strong density and deep-seated measures to provide the theoretical basis for increasing the density and yield.The main findings are as follows:(1)Difference mechanism of different densimeter corn varieties:After the increase of planting density,the competition of maize roots intensified,and the morphological characteristics of the aboveground plants changed significantly.After spinning,the leaf SPAD value and LAI began to decline.The higher the planting density was,the faster the decline rate was,and the more dense-resistant varieties had a slower rate of decline than the less dense varieties.After the densification,the yield increased significantly,but it began to decrease after reaching a certain density.The highest density(82,800-96,200 plants/hm2)of the varieties with strong density was significantly higher than that of the weaker plants(81,600-88,900 plants/hm2).(2)Deep loosening control mechanism of different densities of corn varieties:Deep loose can effectively improve the soil environment,promote root growth,and ensure the growth and development of aboveground plants.From spinning to milk-cooking,the amplitude of SPAD decreased from 6.8-10.1 to 6.3-8.9 in leaves with strong compaction,and the range of SPAD decreased from 7.6-10.9 to 7.1-10.1 in varieties with weak compactness;The decreasing range of the LAI of the denser species changed from0.36-1.19 to 0.30-0.98,and the decreasing range of LAI of the less dense species changed from 0.45-1.32 to 0.43-1.23.Deep loose effectively delayed the senescence of the plants at the later stage,and had better effects on the varieties with strong denseness.The results oflinear fitting showed that the varieties with high density could increase the density by 7.7thousand plants/hm2 and increase yield by 1.37 t/ hm2 through the deep pine planting control;the plants with weak density could increase the planting density by 6.0 thousand plants/ hm2 and increase yield by 1.06 t/ hm2.(3)The mechanism of inter-regional differences in the effect of deepening,densifying,and increasing production of different types of tightness:The morphological characteristics,root characteristics,canopy physiological characteristics and yield and composition of maize shoots were significantly different in different ecological regions.The differences of the response to the deep loosening were mainly determined by the days after flowering with a temperature difference of <10°C,the number of days of sunshine after flowering <8 h,the average temperature after anthesis,and the available phosphorus content in the soil.The deep loosening effect of strong-tight varieties is more stable between regions. |
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