Effects Of Sowing Date, Plant Density, Fertilizer On Sink-Source Relationship Of Summer Maize (Zea Mays L.)

In order to reveal the characteristic of source and sink, source-sink relationship, the effect of source and sink on grain yield, find out the restrictive factors of grain yield, a study was conducted with several kinds of hybrids in different filed management practices under limited light and heat condition. It can provide a theoretical support for high grain yield cultivation of summer maize in Hebei province. The results were as follows:1. Total leaves area, leaf area duration, dry matter production capacity and supply capacity of source decreased gradually with the delayed sowing date. High value duration of total leaves area were long , leaves senescence were slow after spinning, net assimilation rate and population growth rate were high under early sowing. So it was a main method of early sowing to increase population total leaves area, dry matter production capacity, supply capacity of source, prolong the leaves function period. The grain number and grain weight of single plant decreased gradually with the delayed sowing date, and the effective sink content decreased. The 1000-grain weight, total grain number and effective sink content of early sowing (6/10) increased 14%~27%, 14%~22% and 25%~36% than the late sowing(6/25), respectively. Therefore, the sink-source ratio decreased gradually with delayed sowing date. The early sowing promoted harmonious development of source and sink, decreased kernel abortion, increased sources and sinks quantity, and delayed senescence of leaves. Source was lack in late growth stage, so source was the major restrictive factor under early sowing condition. The late sowing was lack of sink, but relative large of source. So sink was the main factor limiting yield under the late sowing.2. The population total leaves area, leaf source duration and dry matter production capacity increased with the increase of plant density. The population total leaves area decreased rapidly from 30th day after spinning under high plant density treatment (90 000 plant per hm2). The supply capacity of source showed a fluctuation of an initial rise and a drop later with the increase of plant density. The net assimilation rate deceased with the increase of plant density, but the population growth rate increased. It was a basis of obtaining high yield for high density population by reducing the leaves senescence speed from 30th day after spinning and increasing the dry matter production capacity and prolonging the function period of the leaves. The grains number of single plant and grain weight decreased, the effective sink content showed a fluctuation of an initial rise and a drop later with the increase of plant density. While the ear number, grain number and the maximum potential sink content per unit area increased. The population sink of high density treatment (90 000 plant per hm2) was higher 16%～103%, 4%～87% and 8%～73% than the other treatments. The sink-source ratio deceased gradually with the increase of plant density. It showed sink was the main restrictive factor of yield under the condition of high density. So it was a guarantee of obtaining high yield for high density population by improving grain of single plant, decreasing the kernel abortion and increasing grain weight.3. Nitrogen fertilizer can increase population total leaves area, leaves source duration, the dry matter production capacity, supply capacity of source, net assimilation rate and population growth rate under different fertilizer treatments. of Population total leaves area of nitrogen application was higher 1%~12% than those no nitrogen application. Grain number and grain weight were higher under nitrogen application; maximum potential sink content and effective sink content were also relatively higher. Grain-leaf ratio, grain weight, production capacity of source, stem and sheath dry matter translocation were low with nitrogen application; however, dry matter translocation efficiency after spinning and the economic coefficient were high. Both source quantity and sink content increased with nitrogen application, but the increasing range of source was higher than that of sink. Therefore, sink was the main factor limiting yield. Both source and sink were the restrictive factors of yield with no nitrogen application.4. The source of summer maize was higher under the early sowing, high plant density and nitrogen application, but the effect of sowing date and plant density on source were larger than fertilizer application. Effective grain number, grain weight of single plant and effective sink content were higher under early sowing and nitrogen application; effective grain number and grain weight of single plant were low under high density, while grain number and effective sink content per area were higher. Early sowing, increasing plant density and nitrogen application were the main practice to obtain large total leaves area and increase population effect grain number, delay leaves senescence and grain weight were the key to obtain high grain yield under limited light and heat resources of Hebei province.