Effects Of Nitrogen Fertilizer Management On Yield And Nutrient Utilization Of Ratoon Sugarcane

In view of the problem of low nitrogen（N）utilization rate in sugarcane production in China,under the condition of returning sugarcane leaves to the field,taking no N treatment as the control（CK）,the effects of five N fertilizer rates(N₁:150 kg N hm^-2,N₂:225 kg N hm^-2,N₃:300 kg N hm^-2,N₄:kg N hm^-2and N₅:450 kg N hm^-2),and two kinds of N application times（F₁:3 times of N application,30%N fertilizer as basal fertilizer,30%N fertilizer as tillering fertilizer and 40%N fertilizer as elongation fertilizer,and F₂:2times of N application,30%N fertilizer as basal fertilizer and 70%N fertilizer as elongation fertilizer）on yield,quality and N、P、K、Ca、Mg nutrient uptake of ratoon sugarcane,soil N、P、K、Ca、Mg nutrient content and enzyme activity,and N fertilizer utilization were investigated using a field experiment,so as to obtain the N fertilizer management for ratoon sugarcane production.The results show as follows:（1）The application of N fertilizer was beneficial for increasing plant height,sugarcane diameter,fresh single stem weight,dry mass accumulation,and effective stem number of ratoon sugarcane.At N fertilizer rate of higher than 300 kg N hm^-2,the effective stem number in F₁was significantly higher than that in F₂.（2）At N fertilizer rates of 375 kg N hm^-2and 450 kg N hm^-2,the increase of ratoon sugarcane yield was significant,but the effect of N application times on ratoon sugarcane yield was not significant.And F₁N₃₇₅,F₁N₄₅₀,F₂N₃₇₅and F₂N₄₅₀had higher ratoon sugarcane yields.（3）With the increase of N fertilizer,the sucrose content increased firstly and then decreased,and F1 was beneficial for sucrose accumulation.At N₃₇₅and N₄₅₀,the sugar yield of ratoon sugarcane in F₁was significantly higher than that of F₂,and F₁N₃₇₅and F₁N₄₅₀treatments had higher sugar yield of ratoon sugarcane.（4）The contents and uptakes of N,P,and K in the leaves and stems of ratoon sugarcane increased with the increase of N fertilizer.Except N₁₅₀,the N fertilizer utilization rate showed a downward trend with the increase of N fertilizer.The N fertilizer utilization rates in F₁and F2 were 22-36%and20-32%,respectively.（5）The amount of nitrogen applied affected the soil nutrient content,and F₂N₄₅₀had the highest total N and alkali-hydrolyzed N contents.Therefore,the best N application mode was N fertilizer rate of 375 kg N hm^-2with 30%N fertilizer as basal fertilizer,30%N fertilizer as tillering fertilizer and 40%N fertilizer as elongation fertilizer for ratoon sugarcane production under the condition of returning sugarcane leaves to the field.