| Black soybean,the Chinese characteristic plant resource,has a profound developing potential and is widely cultivated in northeast,northwest and other regions of China.Black soybean is under extensive research owing to its rich nutrition,medicinal and hygienic value.As the necessary nutrition elements of plant growth and development,nitrogen and phosphorus directly limit crop growth and grain yield,therefore,reasonable ratio of nitrogen and phosphorus is the precondition of high yield.Small black soybean cultivar ?Lianjiatiao? was taken as the sample and the experiment was arranged into a randomized complete block design with two factors and four levels.The agronomic traits,yield,dry matter accumulation and transportation,the accumulation and distribution of nitrogen and phosphorus in plant and grain and the group canopy structure were discussed in this study and the main conclusions were as follows:1.Plant height,stem diameter,node numbers of main stem,branch numbers,main stem pods and branches pods of small black soybean increased gradually from 10 d after flowering.Yield and 100-grain weight of small black soybean under all the film mulching treatments were significantly higher than CK at the same stage when compared between different ratio of nitrogen and phosphorus.Meanwhile,the yield of N1P3(pure N 6 kg/667 m2 + pure P2O5 36 kg/667 m2)reached the highest 1890 kg/hm2.2.The accumulation of dry matter in seeds after flowering presented the “S” curves,and the accumulation of dry matter in above-ground organs after flowering in the above-ground organs increased firstly and then decreased.There was significant difference on the accumulation of dry matter in seeds and in above-ground organs under different ratio of nitrogen and phosphorus of small black soybean at the same stage.The distribution of dry matter in different organs of small black soybean changed along with the transition of the growth center from flowering to maturity.The distribution of dry matter in stems and leaves of small black soybean at the early flowering stage relatively high,while,at pod bearing period,the distribution of dry matter in stems and leaves relatively decreased,the distribution of dry matter in pods increased gradually.Meanwhile,assimilate in stems and leaves transported to pods in different degree with grain grouting,and the dry matter output in leaves on the main stems was the most.3.The accumulation of nitrogen and phosphorus in stems and leaves after flowering increased firstly and then decreased,while,the accumulation of nitrogen and phosphorus in pods always showed increasing trend from flowering to maturity.The accumulation of nitrogen and phosphorus in stems,leaves and pods under all the treatments were significantly higher than N0P0 at the same stage when compared between different ratio of nitrogen and phosphorus.Nitrogen and phosphorus in stems and leaves transported to pods in different degree with grain grouting from flowering to maturity.Moreover,the output and transportation amount of nitrogen in leaves were higher than which in stalks,while,the output and transportation amount of phosphorus had no obvious difference in leaves and stalks.There was significant difference on the transportation amount,move ratio and transportation ratio of nitrogen and phosphorus in the organs under different ratio of nitrogen and phosphorus of small black soybean at the same stage.4.Leaf area index(LAI),intercepted photosynthetically active radiation(IPAR)and photosynthetically active radiation interception rate(FIPAR)of small black soybean after flowering under different nitrogen levels increased firstly and then decreased gradually,while,transmitted photosynthetically active radiation(TPAR)decreased firstly and then increased gradually.There was significant difference on LAI,TPAR,IPAR,FIPAR under different amount of nitrogen of small black soybean at the same stage.Correlation analysis indicated that IPAR and FIPAR had very significant exponential positive association with LAI,while,there existed a very significant exponential negative correlation between TPAR and LAI.Furthermore,canopy hyperspectral reflectance under different amount of nitrogen of small black soybean remained consistent change trend at different stages.Hyperspectral curve had a peak and two valley obviously in visible region(350-700 nm),but the location of peak and valley changed little.The most differentia was found in the peak in visible region(550 nm)and near infrared region(760-1330 nm).Correlative analysis between canopy hyperspectral reflectance and LAI under different amount of nitrogen of small black soybean indicated that there was a significant negative association at about 390-700 nm,while,hyperspectral reflectance from about 750 nm to 1330 nm,1480 nm to 1780 nm and 1990 nm to 2400 nm had significant positive association with LAI.Moreover,correlation coefficients at about 700 nm to 750 nm fluctuated apparently,which varied from obvious negative association to obvious positive association.The optimal model to monitor LAI of small black soybean was exponential function model whose independent variable was RVI(760,560)and the regression equation was y = 0.6198e0.2614x(R2=0.6090).Comprehensive analysis showed that the most appropriate ratio of nitrogen and phosphorus of small black soybean by plastic film mulching in arid regions of northern Shaanxi was pure N 6 kg/667 m2,pure P2O5 36 kg/667 m2,which could effectively coordinate the relationship between ?source? and ?sink? and promote the accumulation and transportation of dry matter,nitrogen and phosphorus in leaves,stalks and pods.In addition,it was of great significance of small black soybean to remain larger leaf area index and solar energy use efficiency,extend the time of photosynthesis,improve the canopy light distribution of group and achieve high quality and high yield. |
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