| Object:Cotton is the most important cash crop in xinjiang,but improper management of water and fertilizer is restricting the healthy development of cotton industry.Cotton transpiration not only regulates the farmland ecological environment,but also plays an important role in cotton growth.Effective fertilization can improve quality and increase yield,and water is the key factor affecting fertilizer absorption and utilization.Water and fertilizer regulation has both synergistic and antagonistic effects on cotton growth.At present,studies on the characteristics of cotton transpiration and fertilizer utilization based on water-fertilizer coupling effect need to be further enriched.Methods:For this reason,the bucket planting experiment of drip irrigation under plastic film was carried out during the growth period of cotton in 2019,and three irrigation levels were set,which were 360,420 and 480 mm and marked I1,I2 and I3,respectively.At the same time,three levels of nitrogen application were set,which were 210,280 and 350 kg·hm-22 and marked N1,N2 and N3,respectively.Results:This study revealed the response characteristics of cotton transpiration and nitrogen absorption and utilization to water-fertilizer coupling,established a multi-objective optimization equation for cotton production based on spatial analysis and proposed a scientific and efficient water and fertilizer management strategy.Conclusions:?1?During the cotton growth period which was full-bloom stage,full-boll stage and boll opening stage,The interaction of water and nitrogen had significant effects on net photosynthetic rate?Pn?,stomatal conductance?Gs?,transpiration rate?Tr?and intercellular CO2 concentration?Ci??P<0.01?.At the same irrigation level,Pn,Gs and Tr increased first and then decreased with the increase of nitrogen application level.And at the same nitrogen application level,Pn,Gs and Tr increased with the increase of irrigation level.The continuous monitoring results of stem flow rate?Mp?by stem flowmeter showed that,from 7:00to 19:00,the Mp of cotton showed a unimodal curve trend that first increased and then decreased with time,and from12:00 to 16:00 was the peak range of Mp during the day.?2?The interaction of water and nitrogen had a significant effect on the cumulative daily transpiration?Wt?of cotton?P<0.01?.At the same irrigation level,the Wt of cotton increased first and then decreased with the increase of nitrogen application level.And at the same nitrogen application level,the Wt of cotton increased with the increase of irrigation level.During the cotton growth period which was full-bloom stage,full-boll stage and boll opening stage,the Wt of cotton treated with I1N1 was the smallest,which was573.38,390.40 and 297.05 g·d-1,respectively.The plants treated with I3N2 had the highest Wt,which was922.68,803.22 and 646.23 g·d-1,respectively.From the flowering stage to the boll opening stage,Pn,Tr,Gs,and the Wt of cotton showed a decreasing trend.?3?In the 0-60 cm soil layer,the total nitrogen content and 15N abundance of the soil showed a decreasing trend,and enrichment phenomenon occurred in the 0-20 cm soil layer.From the flowering stage to the boll opening stage,the total nitrogen content,15N abundance and nitrogen derived from fertilizer?NDFF,representing the nitrogen uptake and regulation capacity of the organ?of cotton roots and boll showed an increasing trend,while total nitrogen content,15N abundance and NDFF of stem and leaf showed a decreasing trend.At the same growth period,the total nitrogen content,15N abundance and NDFF of each organ showed as follows:cotton boll>leaf>stem>root.The interaction of water and nitrogen had an extremely significant effect on the total nitrogen content of each organ?P<0.01?,but not on the abundance of 15N and NDFF?P>0.05?.?4?The interaction of water and nitrogen had an extremely significant effect on total nitrogen uptake,total soil nitrogen absorption and nitrogen utilization rate?NUE?of cotton?P<0.01?,but no significant effect on total urea nitrogen absorption and nitrogen partial productivity(NPFP)?P>0.05?,while single factor irrigation and nitrogen application had an extremely significant effect?P<0.01?.The Total nitrogen absorption of each cotton was between 2.19-3.32 g,the total absorption of urea nitrogen per cotton plant was between 0.34-0.61 g,the total soil nitrogen uptake per cotton plant was between 1.85-2.77 g,NUE was between 23.78-39.77%,and NPFP was between 13.92-27.08.The high level of irrigation and nitrogen application was not conducive to the absorption of nitrogen by cotton,and NUE decreased.?5?Leaf area index?LAI?,boll weight,biomass and yield of I3N2 reached the maximum values in all treatments.Cotton fiber quality was the best at I3 irrigation level,and water use efficiency?WUE?was higher at I2 irrigation levels than at I1 and I3 irrigation levels.The economic benefit of I3 irrigation was1.86-6.07 times that of I1 irrigation.When the irrigation range was 430.88-445.08 mm and the nitrogen application range was 269.18-295.76 kg·hm-2,WUE,NUE,yield and economic benefit can reach more than 90%of their maximum value at the same time. |
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