Effects Of Different Sugarcane Leaf Returning Patterns On Soil Nutrients And Sugarcane Yield And Quality

Sugarcane production usually produces rich straw resources.The application of sugarcane leaf returning technology not only improves the soil fertility,but also helps to reduce the environmental pollution caused by leaf burning,and thus to favor sugarcane green production.The common sugarcane leaf returning patterns include crushed leaf returning,whole leaf covering returning,and manure returning after leaf fed to animals,etc.Previous studies mainly focus on leaf returning patterns alone,and few researches have reported the effects of leaf returning combined with other management practices.Therefore,considering the climate characteristic of seasonal drought and the current situation of excessive fertilization in the sugarcane areas of Yunnan Province,this work conducted a tow-year field experiment from 2021 to 2023with different sugarcane leaf returning patterns(T1,control,no leaf returning and no mulching;T2,control,no leaf returning and with mulching;T3,whole leaf covering returning and no mulching;T4,crashed leaf returning and no mulching;T5,crashed leaf returning and with mulching;T6,crashed leaf returning,mulching and with 30%reduction in nitrogen fertilization),and the effects of different treatments on soil nutrients,sugarcane agronomic traits,nutrient uptake,quality and sugar yield were measured.The main research results are as follows:1.Sugarcane leaf returning treatments increased soil p H.Compared with the basic soil p H level,the soil p H value of treatments T3,T4,T5,T6 averagely increased by 0.4.In both seasons,treatment T6 had the highest level of soil alkali-hydrolyzed nitrogen content,significantly higher than that in T1 and T2.Compared with the control treatments,soil organic matter,phosphorus and potassium contents were increased under the four treatments with leaf returning,but there was no significant difference between them.Overall analysis showed that although there was no significant difference in soil physicochemical properties between leaf returning treatments and control treatments,sugarcane leaf returning treatments had a trend to improve soil fertility.2.From the perspective of population growth,sugarcane leaf returning treatments increased the number of seedlings,tillers and effective stems of sugarcane.At both harvest times,treatment T6 showed the highest effective stem number,6534and 5829 plant/666.7m~2respectively,significantly higher than T1 treatment.For the individual growth,leaf returning treatments increased stem and leaf dry matter accumulation and stem/leaf ratio.At 2022/23 harvest,T5 treatment had the highest aboveground dry matter accumulation,but T6 treatment had the highest stem/leaf ratio.In term of the final cane yield,in both seasons cane yield showed an increasing trend from treatment T1 to T6,and the highest cane yield was obtained in T6treatment,111.21 and 88.32 t/hm~2,respectively.These agronomic results showed that sugarcane leaf returning treatments promoted sugarcane plant growth,and treatment T6 had the best effect.3.The total amount of aboveground nutrient accumulation in sugarcane was in the order of nitrogen,potassium,calcium,phosphorus,magnesium,iron,manganese,zinc,and copper from high to low.Sugarcane leaf returning treatments promoted nutrient uptake of sugarcane plants,and the aboveground accumulation of nitrogen,phosphorus,potassium,magnesium,iron,copper and zinc in T5 and T6 treatments were significantly higher than those in control treatments T1 and T2.4.Compared with the control treatments,sugarcane leaf returning treatments improved stem sucrose content,Brix,gravity purity and juice yield,but reduced fiber content.The stem sucrose content of T6 treatment was the highest;it was 15.37%at harvest in 2021/22 season,4.83%and 4.51%(absolute value)higher than that of T1and T2,respectively;in 2022/23 season,it was 13.93%at harvest,3.35%and 2.51%(absolute value)higher than that of T1 and T2,respectively.Similarly,the final sucrose yield in sugarcane leaf returning treatments were higher than that in the two control treatments,and sucrose yield in T6 treatment was the highest,15.37 t/hm~2in2021/22 and 13.92 t/hm~2in 2022/23,respectively.In summary,in this study compared with no sugarcane leaf returning(control T1)and mulching alone(control T2)treatments,the four treatments of different sugarcane leaf returning patterns improved soil physiochemical properties,promoted sugarcane growth and nutrient uptake,increased cane yield,cane quality and sugar yield.Overall,treatment T6(crashed leaf returning,mulching and with 30%reduction in nitrogen fertilization)displayed the best effect.These results can provide some reference for further exploration of the efficient sugarcane leaf returning techonolgy in Yunnan sugarcane areas.