Study On The Growth And Development Characteristics And Water And Nutrient Requirements Of Disease-free Sugarcane Original Seedlings

Sugarcane is a large asexually propagated crop.Long-term planting can easily lead to the accumulation of multiple diseases,resulting in variety degradation and reduced production.The promotion of planting disease-free sugarcane healthy seedlings in sugarcane production plays an important role in eliminating sugarcane diseases,preventing variety degradation,purifying and rejuvenating,and promoting sugarcane production and sugar increase.The promotion of disease-free sugarcane healthy seedlings is inseparable from the large-scale breeding of disease-free seedlings,in which the planting and water and nutrient management process of the disease-free original seedlings during the breeding process are particularly critical for the quality and efficiency of the breeding of the virus-free seedlings.Therefore,this research conducted a two-year field experiment to determine and analyze the biomass accumulation,water and nutrient requirements during different growth and development stages of disease-free sugarcane original seedlings in the field,and clarified that the disease-free sugarcane original seedlings growth and biomass accumulation characteristics,as well as the water demand and profit and loss status of the different growth stages of the disease-free sugarcane original seedlings,the main nutrient absorption and accumulation characteristics,provide a scientific reference for the field breeding and water nutrient management of the disease-free sugarcane original seedlings in accordance with.The specific results are as follows:1.Through the measurement of the biomass of the disease-free sugarcane original seedlings in different growth periods,it is found that the total number of days for the growth and development cycle of the disease-free sugarcane original seedlings is 175-200 days,and the number of harvested stems is about 15 knots.During the stem elongation growth period,the growth rate of cane stems is the fastest from mid-August to late October,and the biomass maintains rapid growth.It grows at a growth rate of about 4 stem nodes per month,and the average daily bioaccumulation remains above 2.8 g.Months later,with the decrease of temperature,the biomass accumulation of disease-free sugarcane original seedlings slowed down,and the growth rate of its stem nodes slowed down to about 2 stem nodes per month.By the end of December,when the disease-free healthy seed stems are harvested,their fresh weight is 1810-1900 g/plant,the plant height is about 170-175 cm,and the single stem weight is about 0.95 kg.On the whole,disease-free sugarcane original seedlings per unit area can obtain 1.27-1.35 million effective buds per hectare,and planting 52500effective buds per hectare has a reproduction efficiency of 24.2-25.8 times.2.Using the Penman-Monteith comprehensive method combined with the single crop coefficient method to investigate and analyze the water requirements of the disease-free sugarcane original seedlings,it is shown that the total water demand of the disease-free sugarcane original seedlings during the growth period is about 643.0mm-659.6 mm.Among them,the water demand is the largest from the seedling stage to the middle stage of the stem elongation and growth,accounting for about 60%of the whole growth period.During the growth period（July-December）of disease-free sugarcane original seedlings,the effective rainfall is less,only 200.3 mm-241.9 mm,and it is concentrated in the early July to September and October,accounting for more than 90%of the rainfall during the whole growth period,resulting in a continuous water deficit in the disease-free sugarcane original seedlings（except in mid-July 2019and early August 2020）,with a total deficit of 427.4 mm-473.4 mm.Therefore,continuous irrigation is needed to improve the survival rate,quality and breeding efficiency of disease-free seed stems.3.Through the analysis of the nitrogen,phosphorus,potassium,calcium and magnesium elements in the various organs of the disease-free sugarcane original seedlings at different growth stages,it was found that during the growth and development of disease-free sugarcane original seedlings,the tillering stage is the highest daily absorption rate of potassium and nitrogen,which are 207.0 mg/plant·d and 152.8 mg/plant·d,respectively,which is the period of maximum nutrient absorption efficiency.It is necessary to ensure sufficient nutrient supply to lay the foundation for the formation of effective stems.It is clear that the elements nitrogen,phosphorus,potassium,calcium and magnesium account for 33.8%,20.5%,22.0%,14.6%and 12.4%in the seedling stage and the tillering stage,respectively.The growth period of stem elongation to 11 stem nodes（mid-August to late October）was54.7%,59.2%,60.0%,50.4%and 55.3%,respectively.The 12 to 15 stem nodes（early November to late December）account for 11.5%,11.6%,9.8%,20.5%and 16.7%of the nutrient requirements,respectively.The required quantity of each element N 1.86kg,P₂O₅0.59 kg,K₂O 2.27 kg,Ca O 1.21 kg and Mg O 0.16 kg can be calculated according to the target output for precise fertilization.