Effect Of The Nitrogen On Growth Of Root System And The Nitrogen Utilization Of Drip-irrigated Cotton In Different Soil Textures

This study used two factors randomized block experiment in field and gets 0 ~ 60 cm depth of drip irrigation in different soils textures.And with the help of UV determination of nitrate content and flow injection analyzer,explore the rules and correlation analysis of soil nitrate nitrogen and cotton yield;We use the utilization rate of the fertilizer experiment,and the nitrogen utilization rate and yield of cotton;through CI-600 minirhizotron experiment proved the difference of root distribution in different soil texturesby cotton root length density and root surface area index.At the end of the study,we summarized the relationship between distribution of root parameters and the yield of cotton,and provide a theoretical basis for different drip irrigation in quantitative fertilizationultimately.The main results were as follows:1.Effect of soil textures on the characteristic of root distribution and cotton yield.The objective of this field experiment was to study the effect of soil texture and N fertilizer on the characteristics of root length density and root surface area.Using the method of minirhizotron technique in the field randomized block experiment,we studied the vertical distribution characteristics of different soil cotton root length density and surface area under drip irrigation and its effect on cotton yield.The results showed that:(i)to the root of different soil textures,fertilization and irrigation can significantly reduce the cotton root length density and surface area,the cotton root length density and surface area had a significant negative correlation with the increasing of fertigation;(ii)the cotton root length density showed that sand soil > clay soil > loam soil before flowering stage and sand soil > loam soil > clay soil after flowering stage,The cotton length density in deep sand soil decreased significantly higher than that in other soil textures;to sand?loam and clay soils,the coarse root surface area showed N2(N 360 kg· hm-2)>N3(N 480 kg·hm-2)>N1(N 240 kg·hm-2)>CK(no nitrogen treatment);(iii)the correlation analysis between root distribution parameters and cotton yield showed that the root length density,root surface area had a significant influence on cotton yield.Decreasing the root length density and root surface area index is conducive to improve cotton yield.2.Effect of nitrogen fertilizer and soil texture on the nitrogen utilization and yield of drip-i rrigated cotton productionThe objective of this field experiment was to study the effect of soil texture and N fertilizer on the N utilization and yield of drip-irrigated cotton.The experiment used a randomized complete block design.The results showed that regardless of soil texture,the total N content of the cotton decreased in the order N2(340 kg N·hm-2)>N1(240 kg N·hm-2)>N3(480 kg N·hm-2)>CK(unfertilized control).In all soil textures,the total N content in different cotton organs before the bolling stage decreased in the order leaves > buds> stems.After bolling,the total N content decreased in the order leaves >bolls > stems.In the N2 treatment,there was no difference in boll number between loam and clay soil when irrigation amounts were the same.There was no significant difference in single boll mass either between sandy and clay soil in the N2 treatment or between loam and clay soil in the N3 treatment.The effects of the other treatments on single boll mass were extremely significant.Cotton yield was greatest when 256.00,287.34,and 369.25 kg·N hm-2 was applied to sand,loam,andclay soilrespectively.We suggest that these N application rates can be used for sand and loam soil.The N application rate to clay soil should be <369.25 kg·N hm-2.A combination of inorganic and organic fertilizer is best in clay soil.These fertilizer recommendations will optimize fertilizer use for maximum cotton yield.3.Effect of soil texture on the distribution of nitrate nitrogen in the soil profilesThe methods of column simulation in greenhouse was used to study the effect of soil texture on the distribution of NO3–N in the 0 ~ 60 cm soil depth and cotton yield under drip irrigation.The results showed that when irrigation amounts were the same,N application ratesof 256.00 kg/hm2 to sand soil and 287.34 kg/hm2 to loam resulted in the greatest cotton production.Compared with the unfertilized control(CK),these fertilizer amounts increased cotton yieldby 43.87% in the sand soil and by 44.92% in the loam.Soil NO3 –N was mainly distributed in the 30 ~ 40 cm depth under these N application rates.This was conducive to the absorption of N by the cotton root system,thus allowing soil N absorption efficiency to be properlyregulated and production to be increased.The resultsalso showed that when fertilizer rates were the same,soil NO3–N was distributed more uniformly in the loam soil than in the sandy soil.Soil NO3–Nwas mainly distributed in the 20 ~ 40 cm soil depth ofthe loam soil.This improved the N utilization rate and increased cotton yield by an average of6.16% compared with the sand soil.Soil NO3 –N contents in both the sand soiland loam soil changed with the curve of “decrease-increase-decrease”across the growing season.At the second peak,soil NO3-Ncontent in the 60 cm depth with N application rate of340 kg/hm2 was 15.98% greater in the sand soil than in the loam soil.At the end of the growth period,the sand soil had greater N content than the loamsoil and therefore had greater risk for N loss due to leaching.