营养元素对连作大豆减产的控制功能

通过实验室和田间微区试验方法 ,连续三年研究结果表明 :连作大豆在受到有害生物危害和大豆残茬腐解物中间产物的毒害抑制时 ,其根系的吸收和运输营养物质及固氮能力均减弱或部分丧失。此时 ,增加营养元素在土壤中浓度 ,可达到胁迫吸收的功效 ,弥补损失。连作大豆增施氮肥 ,可比不施氮最高增产 97.7% ;施磷比不施磷最高可增产 89% ;施钾与不施钾比 ,最高增产可达 2 6 %。施用微量元素 ,亦能提高产量 ,与对照相比 ,施锌增产16 .9% ,施锰增产 13.2 % ,施硼增产 1.4 % ,施钼增产 4 .6 % ,施镁增产 14 .6 %。

Analysis of Phosphorus Nutrition Efficiency of Soybean Genotypes with Different Phosphorus Efficiency at Blooming Stage under Low Phosphorus Stress

[Objective] This study aimed to investigate the phosphorus nutrition effi- ciency of different soybean genotypes at blooming stage under low phosphorus stress. [Method] By using four ＂low phosphorus efficiency＂ soybean genotypes （D03, D05, D17 and D18） and four ＂high phosphorus efficiency＂ soybean genotypes （D31, D34, D37 and D38） as experimental materials, soil culture experiment was conduct- ed with two treatments of high phosphorus （＋P） and low phosphorus （-P）, to analyze the relationship between phosphorus content, phosphorus uptake, phosphorus use efficiency and phosphorus efficiency of soybean genotypes with different phos- phorus efficiency. [Result] Under low phosphorus conditions, four soybean genotypes with high phosphorus efficiency showed significant advantage in phosphorus uptake at seedling stage, to be specific, D34 showed relatively high phosphorus absorption capacity but no advantage in adaptability of phosphorus use efficiency, while only D37 showed relatively high phosphorus absorption capacity and phosphorus use ca- pacity. Correlation analysis and path analysis showed that the level of phosphorus efficiency of soybean at blooming stage under （-P） and （＋P） treatments was mainly determined by phosphorus absorption capacity, and that under （-P） treatment was significantly greater than （＋P） treatment. Phosphorus uptake and phosphorus use ef- ficiency under （-P） and （＋P） treatments both showed great direct effects on phos- phorus efficiency, and phosphorus uptake made greater contribution; however, the indirect effects were relatively low, Under low phosphorus stress, the mechanisms for various soybean genotypes with high phosphorus efficiency to adapt to low phospho- rus stress were different, and phosphorus absorption efficiency （phosphorus uptake） was the main variation source of the phosphorus efficiency of various soybean genotypes at blooming stage. [Conclusion] This study revealed the contribution made by phosphorus absorption efficiency and phosphorus use efficiency to phosphorus efficiency of soybean.

Growth and nitrogen status of cotton(Gossypium hirsutum L.)under salt stress revealed using^(15)N-labeled fertilizer

Salt stress is a vital factor limiting nitrogen uptake and cotton growth in arid regions.The mechanisms underlying salt stress tolerance in cotton plants under high soil salinity have not been fully elucidated.Therefore,the aim of this study was to examine the proportion and mechanism of cotton nitrogen uptake under salt stress using the^(15)N isotope labeling technique.Cotton plants were grown in four undisturbed saline soils(1,3,6 and 9 dS m^(-1)),and the experiment was designed using the ENVIRO-GRO(E-G)model.The results showed that the dry matter of roots,stems and leaves of the cotton parts in slightly saline soil(C2,3 dS m^(-1))was not significant compared with the non-saline soil(C1,1 dS m^(-1)).The cotton fruit grown in low-salinity soil(C2,3 dS m^(-1))had significantly higher dry matter than that grown in the other treatments,implying that cotton plants grown in 3 dS m^(-1)soil have the best nitrogen uptake and salt tolerance.Cotton plants grown in weakly(C3,6 dS m^(-1))and moderately(C4,9 dS m^(-1))saline soils exhibited premature senescence.The distribution of total nitrogen and nitrate content in cotton was the best explanatory variable of total^(15)N recovery,of which cotton^(15)N recovery was between 26.1%and 47.2%,and soil^(15)N recovery was between 7.7%and 14.9%.Our findings provide guidance for further exploitation and utilization of saline soil resources and sustainable development of the agricultural soil ecosystem in arid regions.