| This reearch was conducted in maize-soybean strip mixed cropping system which is r-ising in Southwest China,and used Chuandan418 as materil which is the main maizevariet-y in Sichuan. Seven wide-narrow row spacing treatments were set up in both two strip wid-th (1.6m strip width:"20+140","30+130","40+120","50+110","60+100","70+90","80+80" );2.0m strip width:("20+180","30+170","40+160","50+150","60+140","70+130" and"100 +100").In order to research how maize response to different microenvironment when wide-narrow spacing was changed,probe the mechanism of yield increased in suitable wide-narrow row spacing,clear the lowest patience value of narro-w row width for maize, provide theoretical support to complete maize-soybean strip mixed cropping system, included microenvironment inside canopy, agronomic traits, dry matter accumulation, photo synthetic characteristics were investigated. The main conclusions were as follows:1. Effects of wide-narrow row spacing on microenvironment inside canopyThe light transmittance in wide row gradually reduced in both two strip width when the narrow row width increased,the decreasing extent showed as bottom>central>top;And the light transmittance in narrow row increased in both two strip width when the narrow row width increased,the increasing extent showed as central>bottom>top. Wide row air temperature decreased with increasing narrow row spacing under 1.6m strip width,narrow row air temperature firstly decreased and then increased with the increase of narrow row spacing; Wide and narrow row air temperature increased with the increasing narrow spacing at first and then decreased under 2.0m strip width. Variation of air humidity and air temperature under both the bandwidth were contrary. The air CO2 concentrations of wide and narrow rows were decreased with increasing of narrow space under 1.6m width; But under 2.0 m strip width, it was increased with the increasing narrow row spacing at first and then decreased.2. Effects of wide-narrow row spacing on agronomic traits and dry matter accumulation of maizeMaize agronomic traits and dry matter accumulation significantly enhanced and improved when narrow row spacing increased from 20cm to 40cm in both two strip width, showed as higher plant height,stem diameter increased,spike high coefficient decreased,ear upper internodes length increased.Meanwhile,maize dry matter accumulation rate and the growth period of dry matter accumulation increased significantly. In the process, narrow row spacing increased from 40cm to equidistant row, maize agronomic traits and dry matter accumulation exhibits little variation and the indexes achieved the optimal when the narrow row spacing was 50 cm.3. Effects of wide-narrow row spacing on photosynthetic characteristics of maizeThe maximum LAI and SPAD at silking stage gradually increased when the narrow increased from 20cm to 50cm in both two strip width.and maximum LAI and SPAD got the highest value when the narrow row width was 50cm.At the same time, LAI and SPAD decreased slowly in later growth when the narrow row width was 50cm, LAI and SPAD still had a high value at filling stage so that ensured enough photosynthetic time and area. The photosynthetic rate within maize canopy had following distribution features:wide row>narrow row; top>central>bottom.Each part of the photosynthetic rate in wide row were inversely proportional to the narrow row width and had exponential relationship with light transmittance in both two strip width; It was proportional in narrow row and had logarithmic relationship with light transmittance. The average photosynthetic rate of all parts were up to a maximum value when narrow row width was about 50cm, and with the advance of growth period,the strengths of narrow row spacing treatments about less than 40cm tended to be more significant.4. Effects of wide-narrow row spacing on on yield of maizeThe maize yield increased significantly when the narrow row spacing increased from 20cm to 40cm in both two strip width and reached the maximum value when the narrow row spacing was about 50cm. The maize yield of "50+110" treatment reached 6826.74 kg·hm-2 in 1.6 meters strip width, the yield was 39.1 percent higher than that "20+ 140"treatment and 6.7 percent higher than equal row spacing; The maize yield of 50+150"treatment reached 9709.72 kg·hm-2 in 2.0m strip width, the yield increased 10.9 percent compared with "20+180" treatment and there was no significant difference compared with equal row spacing. Yield had different trends when narrow row width contonue increasing from 50cm. In 1.6 meters strip width,the yield gradually decreased,but the tendency of the yield with changing distanc was not obvious and yields were roughly in line with"50+150" treatment in 2.0 m strip width.Combine to the special background of maize-soybean strip mixed cropping syestem in this research,in order to minimize the hidden stress of maize to soybean, this paper finally concluded that both more reasonable under the width of narrow row should be controlled between 40cm and 50cm.5. The relationship between photosynthetic characteristics and yieldIn the wide-narrow planting patterns, especially middle leaves’ photosynthetic rate of narrow lines and high photosynthetic ability in filling stage were two main factors which restrict the yield. The correlation analysis of maize yield and the photosynthetic rate of each part show that the photosynthetic rate and yield of central leaves had the most significant correlation; the influence of upper and lower leaves on yield was significantly lower than central leaves. The photosynthetic rate of upper and lower leaves was not significant negative correlation with yield; The photosynthetic rate of upper and lower leaves was not significant positive correlated to yield. So, the grain filling stage is a critical period yield formation. The correlation between the photosynthetic rate and yield characterized by filling stage> milk stage> silking stage, we could see that filling stage was the key to the grain yield formation period. |
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