Effect Of Ammonium Polyphosphates (APP) With Different Degree Of Polymerization On The Growth Of Maize Seedling

In order to study the effect of ammonium polyphosphates?APP?with different degrees of polymerization as dressing by seeds on the growth of maize seedlings,four pot experiments with maize were conducted on latosol with industrial-grade monoammonium phosphate as the control.1)The effects of four APPs with different polymerization degrees?abbr.as APPY,APP1,APP2,and APP3?and the combination application of APP1 and MAP on seedling growth were compared.A total of 7 treatments of CK?non-phosphorus fertilizer?,MAP,APPY,APP1,APP2,APP3,APP1:MAP?1:1?were set up in the trial.2)The effect of APPY,APP3 rates on the growth of maize at different time periods were studied.Three treatments including CK?non-phosphorus fertilizer?,APPY and APP3 were arranged.3)The effect of APPY and APP1 as dressing by seeds on the growth of maize seedlings was studied.The application rates of APPY,APP1,MAP at the rate of 0.74 g P₂O₅per pot were compared.The effect of APP placement.?that is,the fertilizer is further down a certain cm position at a certain cm in the lateral direction of the seed?was studied.APPs were applied at 5 fertilization distances 2 cm,3 cm,4 cm,5 cm and 6 cm away from the seed.4)Comparison of 5 APPs with different degrees of polymerization?referred to as APP1,APP2,APP3,APP4,APP5 and each APP with a MAP ratio of 3:1,1:1,and P₂O₅mass ratio,respectively?on maize seedling growth was carried out.17 treatments including CK?without phosphate fertilizer addition?,MAP,APP1,APP2,APP3,APP4,APP5 and APP:MAP for each APP with ratio of 3:1,1:1 were arranged.The results showed as follows:1)APPs with different degree of polymerization had significant effect on the growth of maize seedlings,of which APPY and APP1 had similar effect,but were lower than MAP treatment,and APP3 had the worst fertilizer effect.APP1 combined with MAP significantly increased seedling biomass,nitrogen and phosphorus uptake and soil available phosphorus content.2)The APPs of two different polymerization degrees showed significant differences in seedling growth at different time.Among them,the differences in plant height,stem diameter,dry weight of above-ground and underground,and nitrogen and phosphorus uptake between APPY and APP3 treatments were significant.With the extension of time,there was a decreasing trend.Only the soil available phosphorus content showed a trend of decreasing first and then increasing.3)There were significant differences in APP effect among different APP application placement.Plant height,stem diameter,dry matter accumulation,and N and P uptake were all maximum at the application distance of 4 cm.The uptake of nitrogen and phosphorus by plants reached the highest.It showed that under the conditions of this experiment,the APP effect was the best when the three APPs were applied at a distance of 2 cm and 4 cm from the seeds.Considering the problem of salt damage,the APP fertilization distance of 4 cm is the best fertilization distance.There was no significant difference in fertilizer use efficiency between APPY,APP1 and MAP.4)When APPs were applied alone,the APP4 and APP5 treatments had similar effect,which was higher than that of MAP treatment.APP3 was the worst.After APP was combined with MAP?APP:MAP=3:1?,only APP3 effect was significantly improved,and other APP treatments had no significant difference,but after APP combined with MAP?APP:MAP=1:1?,the maize biomass,nitrogen and phosphorus uptake and soil available phosphorus content increased significantly,of which APP3 showed the best effect.When APP was applied as dressing by seeds,the application of APP,which has a uniform distribution of degree of polymerization,and a fraction of the oligomeric components,could promote the growth.In addition,combination application of MAP with APP with medium to high degrees of polymerization showed a positive effect on the growth of maize.