| Reasonable fertilizer application method is an important technical measure to improve summermaize yield and reduce the waste of fertilizer resource. The fertilizer application method affects on theroot morphology, nutrient uptake, dry matter accumulation and yield of crop; meanwhile it affects on thedistribution characteristics of fertilizer nutrients in the soil. At present, these studies on applicationmethods of conventional fertilizer are more concerned, and some methods had relatively matureapplication in summer maize production. However, with the rapid development of slow/controlledrelease fertilizer, the application methods of conventional fertilizer may not be suitable for theslow/controlled release fertilizer because the slow/controlled release fertilizer has different nutrientrelease characteristics comparing with conventional fertilizers. Hence the study on application methodsof slow/controlled release fertilizer is more and more urgent.The effects on summer maize nutrient uptake and utilization of different application methods werestudied and discussed in this paper. The fertilization placements included the seed side5cm, seed side10cm, seed undersurface5cm, and seed undersurface10cm and the fertilization methods includedpoint fertilization and band fertilization.The effects of nutrient application placements on root growth,nutrient uptake and dry matter accumulation in early growth stage of summer maize were studied by potexperiments, the effects of different fertilizer application placements on root distribution and nutrientdiffusion range in the soil were researched by a root box experiment, the comprehensive effects onmaize yield,economic and environmental benefits of different fertilizer application methods wereevaluated by a field experiment. The main conclusions were as follows:(1) The effects of urea application placements on seed germination and growth of maize seedlingstage were significant. Relatively short distance application would significantly inhibit the maizeseedling growth. In all the treatments, the point application urea of the seed side10cm and the bandapplication urea of the seed side10cm were better than other treatments. The dry matter accumulation,nutrient uptake amount and root length of the band application urea were the largest in all the treatments.It should be paid attention to the distance and direction between urea and seed when urea was centralizedapplication, and did not apply urea below the seed, therefor, band application methods were relativelyreasonable and recommended.(2) The effects of coated urea application placements on the growth of maize seedling stage werenot as significant as normal urea, and the effect way and degree were closely related with nutrientreleased characteristics and application rate of the coated urea. Under the higher fertilizer dosageconditions, the point fertilization below seed may still inhibit the maize root growth. After10days ofgrowth, there were no significant differences on the seedling growth for different treatments due to thenutrient of coated urea released slowly; however, the dry matter accumulation, nutrient uptake amountand root length of the band application urea were the largest in all the treatments after30days ofseedling.(3) The application placements of phosphorus fertilizer significantly affected on the dry matter accumulation, nutrient uptake amount and root length, the point application of phosphorus fertilizercould induce maize root to form the obvious root ball in the phosphate fertilization position. Thedistance between the phosphate fertilizer and seeds was closer,the longer the root length,the greater theamount of dry matter accumulation and the more nutrient uptake. The application orientation ofphosphorus fertilizer, seed side and seed undersurface, had not significant influence on maize growth.(4) Different application methods of potassium fertilizer had little effects on the dry matteraccumulation in maize seedling stage, whereas it had effect on the potassium content of plant and rootdry weight. It was found that the maize root grew along the periphery of the fertilization point, and rootgave a wide berth for high concentrations of potassium fertilizer area. Therefore, it is not as close aspossible for point application of potassium fertilizer.(5) Under root box conditions, the effects of the application placements of controlled releasenitrogen fertilizer on maize root morphology, dry matter accumulation, nutrient uptake and transport ofnitrogen nutrients in the soil were significant.After45days of sowing, aboveground dry matteraccumulation amount and plant N uptake of the treatment which fertilizer placement is at seedundersurface10cm (BF)was significantly higher than the treatment which fertilizer placement is at seedside10cm(SF),but it was no significant difference when maize was mature.The results show thatnitrogen nutrient horizontal diffusion radius was6-10cm when the nutrient release ratio of thecontrolled release nitrogen fertilizer was highest, and the nitrogen nutrients moved down significantly.Summer maize roots were mainly distributed in the0-40cm soil layer, the root density decreasedgradually with the soil depth increasing. Maize root growth had evident fertiliertaxis. The root length inthe fertilization side of the SF treatment was obviously longer than the no fertilizer side, and also higherthan the root length on the same fertilization side of the BF treatment. In no fertilizer side, the rootlength of the BF treatment was significantly higher than the root length of the SF treatment. In the samesoil layer, the total length roots of the SF treatments were slightly lower than that of the BFtreatments.To the BF treatment, nutrition diffusion zone completely centralized in the dense regions ofroot system, which could provide sufficient nutrients to the maize growth.(6) The experiments results show, under the band fertilization conditions, urea application at twicecould increase maize yield compared with once application, and the yield of the slow release fertilizerhad no significant difference with that of urea application at twice.Under the conditions that slow releasefertilizer were point application,the yield of fertilizer use was reduced by20%was slightly lower thanthat of fertilizer use were100%,whereas the difference was not significant.Fertilizer applicationmethods influenced the nutrients uptake in different maize growth periods. The application effect ofpoint fertilization methods with10cm below the seed and with5cm beside the seed was better thanother fertilization methods, the maximum accumulation amount of nitrogen, phosphorus, potassium was217.8kg/hm2,29.3kg/hm2,191.8kg/hm2, respectively.The fertilizer application methods hadsignificant effect on the use efficiency of fertilizers, economic and environmental benefits. The recoveryrates of nitrogen, phosphorus, potassium fertilizer of once application urea treatment were lowest, whichwere9.5%,11.2%and22.6%, respectively; however, the highest recovery rate of nitrogen, phosphorus, potassium fertilizer were the treatment of fertilizer was point application at5cm beside seed (80%fertilizers use), which were35.8%,19.3%and54.8%, respectively. Under excluding the cost of laborconditions, urea application at twice had the highest economic profits, whereas there were no significantdifferences compared with the treatment of fertilizer was point application at5cm beside the seed. Theapplication of slow release fertilizer could reduce nitrate leaching, maintain nitrogen nutrients in theupper soil, and be conducive to the absorption and utilization of the next season crop.Overall, compared with conventional fertilizer, the slow/controlled release fertilizer should apply tothe closer placement of the seed, which could promote crop to uptake and use the fertilizer nutrients, andimprove the yield of summer maize.The application of slow/controlled release fertilizer below seedcould promote the nutrient diffusion region coupled the region whose root absorption capacity was larger,reduce the waste of fertilizers, and improve the yield.
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