| Fertilization of planted tobacco soils is the key to improving tobacco quality and physical and chemical properties of planted tobacco soils.However,the irrational application of potassium fertilizer leads to low long-term potassium content in tobacco,and conventional potassium fertilizer is unable to meet the potassium nutrient requirements of tobacco in late growth.In this study,we conducted a tobacco field trial using a new slow-release potassium fertilizer to investigate the effects of nutrient release on tobacco yield,quality,nutrient uptake and utilization,as well as the physicochemical properties of tobacco planting soils,to provide a basis for the application of slow-release potassium fertilizer to tobacco.The field trial was conducted on two different soils(light and heavy loam)with four treatments:no fertilizer treatment(T1),conventional fertilizer treatment(T2),conventional fertilizer +conditioner treatment(T3),and conventional fertilizer + conditioner + slow-release potassium fertilizer treatment(T4)at the trial site in the light loam(Xinlong Village),and five treatments at the trial site in the heavy loam(Fuchuan Village): no fertilizer treatment(T1),conventional(T2),conventional fertilizer + conditioner(T3),conventional fertilizer +slow-release potash(T4),and conventional fertilizer + conditioner + slow-release potash(T5).The main study results were as follows.(1)The new slow-release potassium fertilizer significantly promoted root growth in the middle and early stages of tobacco.The application of slow-release potassium fertilizer significantly improved the morphological indices of root length,root diameter,root projection area,and root diameter of the tobacco root system in the middle and early stages of fertilization compared with the conventional fertilization treatment.As shown by the morphological indicators of the tobacco root system in the early stage of fertility(40 d),the largest root diameter of 1.95 mm was achieved in the trial site of light loamy soil(Fuchuan village)with conventional fertilization + slow-release potassium + conditioner treatment(T5),which was 39.29% higher than that of the conventional fertilization treatment and40.29% higher than that of the no fertilization treatment(T1).The total root length reached6128.70 cm,which was 92.24% higher than that of the no-fertilizer treatment and 39.42%higher than that of the conventional fertilizer treatment.From the above results,it is clear that the additional application of slow-release potassium fertilizer can promote root development to a certain extent during the growth of tobacco in the early stage.(2)The new slow-release potassium fertilizer had significant effects on agronomic traits in the middle and early stages of tobacco growth.Plant height,stem circumference,nodal distance and leaf length were significantly better in the treatment with the new slow-release potassium fertilizer than in the other treatments.The combination of the conditioner and the slow-release potassium fertilizer had the best effect on the mid-growth agronomic traits.In particular,the conventional fertilizer + conditioner + slow-release potassium(T5)treatment significantly improved the plant height,stem circumference,pitch,leaf length,and leaf width of tobacco at the mid-growth stage(60 d)at the Fuchuan trial site.The maximum pitch reached 5.22 cm,which was 43.80% higher than the non-fertilizer treatment and 6.5% higher than the conventional fertilizer treatment(T2).The maximum leaf length reached 85.60 cm,which was 25.70% higher than the non-fertilizer treatment and 3.26% higher than the conventional fertilizer treatment(T2).It can be seen that the application of the new slowrelease potassium fertilizer made up for the deficiency of potassium fertilizer in the conventional fertilizer application in the early stage of tobacco growth,resulting in the improvement of agronomic traits in the early stage of tobacco growth.(3)The new slow-release potassium fertilizer had a significant effect on the nutrient uptake of tobacco.The experimental results showed that the application of the new slowrelease potassium fertilizer was beneficial to increase the nitrogen,phosphorus and potassium content in tobacco during the whole reproductive period.The nitrogen content of tobacco plants at the late growth stage(110 d)was higher in the lower and middle leaves of the conventional fertilizer + slow-release potassium treatment(T4),which increased by206.25% and 316.67%,respectively,compared with the non-fertilizer treatment,and by68.97% and 63.33%,respectively,compared with the conventional fertilizer treatment(T2);the nitrogen content of the lower and middle leaves of the conventional fertilizer + slowrelease potassium + conditioner treatment(T5)was higher than that of the non-fertilizer treatment(T1).The nitrogen content of the lower and middle leaves of the treatment(T5)increased by 131.25% and 208.33% compared with the no fertilizer treatment(T1)and by27.59% and 23.33% compared with the conventional fertilizer treatment(T2).These results showed that the application of the new slow-release potassium fertilizer promoted the potassium uptake of tobacco plants by increasing the soil potassium supply throughout the reproductive period.(4)The new slow-release potassium fertilizer had a significant effect on the nutrient content of planted tobacco soils.The results showed that the treatment with additional slowrelease potassium fertilizer continued to release potassium into the soil throughout the tobacco growing period,increasing the soil fast-acting potassium content throughout the growing period and improving the soil pH at the later stage of tobacco growth,thus providing a high-quality soil environment for tobacco growth. |
