Effects Of Combining Slow-Release Fertilizer And Normal Urea In Reducting Nitrogen Application Rate On Spring Maize Growth And Benefits In The Loess Plateau

Loess Plateau is one of the most important grain-based areas in China,and spring maize is the main food crops in this region.Aimed to the excessive and inefficient application of nitrogen fertilizer（N）and lower benefit in the planting of spring maize in Loess Plateau,a two-year field experiments were conducted in the southern of the Loess Plateau to investigate the effects of a mixture of conventional urea（U）and slow-release fertilizer（C）and N application rates on soil moisture,soil nutrients,spring maize growth and benefits with semi-film flat covering in a randomized complete block design.The experiment included five treatments:（a）no N application,CK;（b）the conventional fertilization mode with N application rate of 225 kg·hm^-2（100%U）;（c）the combination of C and U with N application rate of 225 kg·hm^-2（100%CU）;（d）the combination of C and U with N application rate of 180 kg·hm^-2（80%CU）;（e）the combination of C and U with N application rate of 135 kg·hm^-2（60%CU）.The above three treatments had the same C:U ratio of 7:3.The main results are as follows:（1）The two-meter soil water storage showed a trend of high-low-high during the whole growth period of spring maize in two years.The application of nitrogen fertilizer increased the soil moisture consumption,especially the water consumption in the depth under 40cm,which was more obvious in the filling periods of spring maize,but it was not obviously different between slow-release fertilizer treatments and conventional fertilizer mode in soil water content,soil water storage and water consumption at different growth stages.（2）The soil ammonium nitrogen,nitrate nitrogen,and total nitrogen in 0¹00 cm soil layer gradually decreased with the increasing soil depth during the filling period and mature period.The combination of slow-release fertilizer and urea significantly increased the nitrate nitrogen content in the 0⁴0 cm soil layer during mature period,organic matter content in 0²0 cm soil layer had no significant difference between 80%CU and 100%U,but 60%CU decreased organic matter content.The difference of ammonium nitrogen in different fertilization treatments was not significant.（3）Compared with conventional mode,the combination of slow-release fertilizer and urea did not cause the decrease of SPAD value in filling period,plant height and grain nitrogen content in mature period.Compared with 100%U,leaf area index at filling period,dry matter and plant nitrogen accumulation at mature period of 80%CU were not significantly different,but it`s dry weight of maize kernels and grain filling rate increased.Moreover,leaf area index,grain filling rate at grain filling period,dry matter content and nitrogen accumulation at mature period in 60%CU decreased（4）The highest grain yields(12068 kg·hm^-22 and 13214 kg·hm^-2)were achieved in the treatment of 80%CU,increased by 4.68%and 4.63%in comparison with the treatments of100%U in two years.And 80%CU obtained the highest net revenue among all treatments,with a 2-year average of 1,1222 CYN·hm^-2,which was 189 CYN·hm^-2 higher than 100%U.Moreover,water use efficiency and precipitation use efficiency of 80%CU were the highest in all treatments.And the N agronomic efficiency（NAE）,N using efficiency（NUE）and partial factor productivity of applied（NPFP）in 80%CU and 60%CU were significantly improved compared with 100%CU,but no significant difference was found in 100%CU.Besides,80%CU has no significant difference in grain quality compared with conventional fertilization mode.The results demonstrated that moderate amount(180 kg·hm^-2)of application of the combination of slow-release fertilizer and normal urea is recommended for greater net revenue and nitrogen use efficiencies in Loess Plateau.