Effects Of Phosphorus Supply Levels And Methods On Cotton Phosphorus Efficiency

In order to investigate the difference of response between different cotton cultivars to phosphorus supply intensity and phosphorus supply mode,improve the efficiency of cotton utilization and reduce the large application of phosphate fertilizer.In this study,the nutrient absorption and root morphological changes of different cotton cultivars were studied by hydroponic test of different phosphorus supply levels and root box test of local phosphorus supply,and the law of cotton dry matter and phosphorus absorption and utilization under different phosphorus supply levels and modes was mastered,which provided important scientific basis for improving the phosphorus efficiency of cotton.Using two different cotton cultivars(XLZ13 and XLZ19)as materials,the difference of different cotton cultivars under seven phosphorus supply intensity was compared by hydroponic test.Then,the root box test was used to set up phosphorus homogenization supply and phosphorus partial supply,and the response difference of two cotton cultivars roots to local phosphorus supply(20～40 cm)was studied by Root box stratification.The main results obtained are as follows:(1)Hydroponic test:With the increase of phosphorus supply intensity,the dry matter quantity,phosphorus content(no whole plant),nitrogen,phosphorus and potassium absorption and total root length,root surface area,root volume and average diameter of root system of the two cotton cultivars organs and the whole plant showed the tendency of increasing first and then decreasing.The phosphorus utilization efficiency and phosphorus physiological utilization efficiency of two cotton cultivars decreased with the increase of phosphorus supply intensity,and the utilization efficiency of phosphorus began to stabilize from P1.0 treatment.The dry matter quality,nitrogen and potassium uptake and root parameters of XLZ13 and XLZ19 reached the maximum under P0.8 and P0.5,respectively,while the root,stem and leaf phosphorus content of the two were respectively reached.The phosphorus uptake of the whole plant and the whole plant were the highest under the condition of P1.5.Under each phosphorus supply level,XLZ19 index data is generally better than XLZ13.In summary,two cotton cultivars compared to XLZ19 than XLZ13 can be more suitable for low phosphorus and high phosphorus environment.(2)Root box test:Local phosphorus application can increase the content of available phosphorus in rhizosphere soil of soil 0～20 cm,20～40 cm and 40～60 cm,increase the dry matter quantity,phosphorus content,phosphorus absorption and phosphorus utilization efficiency of cotton organs,and also significantly change the root morphology of cotton.There are variety differences in the response of cotton to local phosphorus supply,and the indexes of phosphorus-efficient variety XLZ19 are higher than those of phosphorus-inefficient variety XLZ13.The results of the principal component analysis showed that phosphorus supply could affect the plasticity of cotton root system,while cotton cultivar could modify basic structure of root system.Partial least squares regressive analysis showed that the total root length,fine(0～0.4 mm)root length in middle layer(20～40 cm),root surface and root volume played important role in aboveground phosphorus uptake.The fine(0～0.4 mm)root length in middle layer(20～40 cm)made greater contribution to phosphorus uptake of cotton in soil,i.e,the increase of 10%of fine(0-0.4 min)root length in middle layer(20～40 cm)could improve 2.33%of the aboveground phosphorus uptake.The high phosphorus efficiency cotton cultivar has higher environmental adaptability in the local phosphorus supply.For efficient and inefficient cultivars,the local phosphorus supply should be adopted to optimize root distribution and growth,and to improve cotton’s ability to obtain heterogeneous phosphorus nutrients so as to exert the maximum biological potential of cotton,improve nutrient utilization,reduce fertilizer dosage,and protect ecological environment.Through the above results,the following conclusions can be drawn:Cotton growth data in different phosphorus supply intensity and mode will occur different reactions.Phosphorus high efficiency cultivar cotton can adapt to low phosphorus and high phosphorus environment better than phosphorus inefficiency.Therefore,in agricultural production,it is necessary to select phosphorus-efficient cotton varieties,apply appropriate amount of phosphate fertilizer and adopt local phosphorus supply method to increase cotton phosphorus efficiency and increase yield,thereby increasing farmers’ income.