HuaTAN，Chenglin ZOU，Debo ZHENG，Aihua HUANG，Runxiu MO，Xinxing WEl，Yongsheng WU，Weiping JlANG，hui WEl，Kaijian HUANGMaize Research Institute，Guangxi Academic of Agriculture Science，Nanning 530227，China

Effect of Fertilizing Level and Planting Densities on Yield and Nitrogen Utilization in Maize

HuaTAN，Chenglin ZOU，Debo ZHENG，Aihua HUANG，Runxiu MO，Xinxing WEl，Yongsheng WU，Weiping JlANG，hui WEl，Kaijian HUANG
Maize Research Institute，Guangxi Academic of Agriculture Science，Nanning 530227，China

Elite maize hybrid Guidan0810 was selected as material，and the effects of fertilizing level and planting densities on yield and nitrogen utilization were discussed in the study.In field experiments as per double-cropping system，4 main plots （fertilization levels）and 6 subplots （planting densities）were set in a split plot design.The results suggested that yield had close relationship with fertilization levels and planting densities.Different fertilization levels and planting densities significantly affected yield.With the increase of nitrogen fertilization，nitrogen use efficiency，nitrogen agronomic efficiency and nitrogen physiological efficiency declined.Under the same fertilization level，nitrogen use efficiency，nitrogen agronomic efficiency and nitrogen physiological efficiency grew a little with the increase of planting density，so nitrogen efficiency could be improved by regulating planting density.The results also showed that A2 （including N 225.0 kg/hm2，P2O575.0 kg/hm2，K2O 187.5 kg/hm2）matching to B3（52 500 plants/hm2）or B4（60 000 plants/hm2）was a better design，which could obtain a higher yield in the range of 7 913.2-8 207.8 kg/hm2，respectively.

Maize hybrid；Fertilizing level；Planting density；Effects

M aize is the largest grain plant in China，concerning crop safety［1］.Since the 1960s，maize has always played a key role in resolving subsistence problem，guaranteeing crop and forage safety，developing national economy，and relieving energy crisis［2］.As breeding technology advances of maize，the update of new maize species significantly promotes maize production and the cultivation technology of new species has drawn much more attention in terms of exploiting species potential and increasing maize yield in recent years.Therefore，it is of significance to explore the effects of fertilizer quantity and planting density on yield and nitrogen use for maize species.

Density is an important factor affecting maize yield［3］，as well as a factor deciding physiological trait.For example，environmental factors，such as fertilizer，water，sunshine and temperature，would be adjusted by changing density［4］and it can be concluded that density is key for accomplishing a high maize yield［5］with high quality.What’s more，a rational density would coordinate yield components well［6-7］.Therefore，it is necessary to balance nutrient demands and supply by adjusting group structure and fully exploit yield potential to improve benefits by maximizing local eco-condition.

It is notable that a rational density and scientific fertilization are crucial for increasing crop yield［10］.In order to get a high maize yield，it is necessary to make use of a rational density and appropriate fertilizer quantity［11］.Fertilization would considerably increase accumulated dry matter to enhance the number of kernels per spike and hundred-kernel weight for further growth of the maize yield［12］.With fertilization at a specific quantity，maize yield is increasing upon planting density，but declines at a certain extent［13-14］.Given a denser density，excessive photo-synthate would be consumed by nitrogen metabolism，so that leaf ages faster and maize yield would be limited［15-16］.It can be concluded that scientific adjustment of water and fertilizer，rational group structure and full use of local eco-condition are crucial for achieving a high yield of maize［17-18］.

In southern ecotope，researches available are few on the effects of different densities on yield and the effect of nitrogen use.The research explored the effects of different densities on yield and nitrogen use with Guidan No. 0810，a new hybrid maize species，as test materials in order to seek a highyielding cultivation technology characterized by optimizing fertilization，saving costs，using suitable planting density，rational group structure and improving sunshine and temperatures，which provides references for highyielding optimized cultivation of maize.

Materials and Methods

Test materials

The test was conducted in a subcentral test base of Nanning，National Maize Improvement Center，at 107° 19′E and 22°12′N，with an elevation of 105 m in spring and autumn in 2012. The test material is Guidan No.0810，a hybrid maize，and test soils are sandy loams，containing organic matter of 1.96%，total N of 0.196%，total P of 0.058%，total K of 0.396%，available nitrogen of 53.5 mg/kg，available P（P2O5）of 17.9 mg/kg and available K（K2O）of 125.0 mg/kg，with pH value of 7.5.The preceding crop was sown with a maize tractor.

Test design

The test was carried out as per split block design.Specifically，the primary treatment mainly involved fertilization，including treatment A1 with pure N of 321.0 kg/hm2，P2O5of 107.0 kg/hm2，and K2O of 268.0 kg/hm2，treatment A2 with pure N of 225.0 kg/hm2，P2O5of 75.0 kg/hm2，and K2O of 187.5 kg/hm2，treatment A3 with pure N of 160.5 kg/hm2，P2O5of 53.5 kg/hm2，and K2O of 134.0 kg/hm2，and treatment A4 which was a control group without fertilizers.Sub-treatment referred to density，including treatment B1 with 37 500 plants/hm2，treatment B2 with 45 000 plants/hm2，treatment B3 with 52 500 plants/hm2，treatment B4 with 60 000 plants/hm2，treatment B5 with 67 500 plants/hm2and treatment B6 with 75 000 plants/hm2.

Test methods

The test was conducted as per randomized block design，with three repetitions.Specifically，the test included four lines，with line length of 5 m and line distance of 0.7 m.Furthermore，plant distance was designed as per densities，and fertilizers were urea containing 46.0%N，calcium magnesium phosphate fertilizer containing 18.0%P5O2，and potassium chloride containing 60%K2O.In addition，the fertilizer prices were as follows:N at 5.87 yuan/kg，P2O5at 4.12 yuan/kg，K2O at 8.0 yuan/kg，and maize price was 2.3 yuan/kg.It is notable that all P fertilizer，20%N fertilizer，and 20%K fertilizer were taken as base fertilizer，20%N fertilizer and 60%K fertilizer were as additional fertilizer，and rest N and K fertilizers were applied when the 11thleaf spread.The farmlands were managed as local method and maize of the middle two lines was harvested and dried until water content reduced to 14%.

Data collection and calculation

During ripening period，10 plants were measured in terms of characters in sequence in different test regions and 5 plants were collected from different regions，followed by kill-out at 105℃and drying at 80℃to obtain a constant weight in order to compute biological yield.Finally，the materials were ground to measure total N of the plant.

After harvest，10 ear samples were collected randomly from every test region to observe the characters and total N was measured.The dried samples were ground and digested with concentrated H2SO4-H2O2，followed by measurement as per kjeldah method.

Nitrogen use rate=（T he absorbed N quantity by plants in N fertilized test areas-T he absorbed N quantity in test area without fertilization）/T he quantity of applied N fertilizer×100%；

Agronomic efficiency=（The yield in N fertilized test areas-Yield in control group）/The quantity of applied N fertilizer×100%；

Nitrogen physiological efficiency=（The yield in N fertilized test areas-Yield in control group）/（The absorbed N quantity by plants in N fertilized test areas-The absorbed N quantity in test area without fertilization）.

The averages of the two seasons were analyzed with Excel 2007 and SAS 9.0.

Results and Analysis

Effects of fertilizations and planting densities on maize yield

As shown in Table 1，maize yield reached significant differences，with different fertilizations （A），and with the same fertilization，but varied planting densities （B）；the yield showed insignificant differences in the treatments involving fertilization and planting density（A×B）.These indicated that both of fertilization and planting density have dramatic effects on maize yield.

Comparisons of primary treatments（fertilization）on maize yield

According to analysis of variance，maize yields in treatments A1（6 894.6 kg/hm2），A2（7 484.2 kg/hm2），and A3（6 949.5 kg/hm2）were significantly higher compared with A4 （4 551.9 kg/hm2），which indicated fertilization plays a key role for maize yield.The statistics suggested that maize yield of treatment A2 was considerably higher compared with treatments A1 and A3，and the yields of A1 and A3 showed little differences，which incorporated that the fertilization of treatment A2 performed better compared with treatments A1 and A3（Table 2）.

Comparisons of sub-treatments（planting density）on maize yield

As shown in Table 2，the effects of planting densities tended to be volatile on maize yield.For example，maize yields were as follows:B3（7 013.8 kg/hm2）＞B4（6 780.0 kg/hm2）＞B5（6563.3 kg/hm2）＞B2（6 433.8 kg/hm2）＞B6（6 290.0 kg/hm2）＞B1（5 739.4 kg/hm2）；the yield of B3 was of significant differences with the yields of B2，B6 and B1；yield differences among treatments B3，B4 and B5 were not so significant，which was also true among treatments B2，B4，B5 and B6；the yields of B2，B3，B4，B5 and B6 reached significant differences with treatment B1.When planting density grew from B1 （37 500 plants/hm2）toB3 （52 500 plants/hm2），maize yield increased from 5 739.4 to 7 013.8 kg/hm2，and when planting density grew from 52 500 to 75 000 plants/hm2，maize yield started declining from 7 013.8 to 6 290.0 kg/hm2.It can be concluded that a rational planting density is a beneficial factor for a high yield of maize and B2 of 52 500 plants/hm2proves the optimal density.

Table 1 Variance analysis of yield

Table 2 Average yields of treatments with different fertilizations and densities

Comparisons of different planting densities on maize yield with fertilization fixed

According to variance analysis of the treatment with the same fertilization but different densities，yields of B2，B3，B4 and B5 showed little differences with fertilization A1.Specifically，maize yield of treatment B3 performed significantly better compared with treatments B1 and B6；yield differences among B1，B2，B5 and B6 showed insignificant.With fertilization A2，maize yields of B3，B4 and B5 performed better compared with B1 and maize yields among B1，B2 and B6 showed insignificant differences. With fertilization A3，maize yields of B3 and B4 were significantly better compared with B1，maize yields of B2，B4，B5 and B6 reached insignificant differences，and maize yields of B1，B2，B5 and B6 were of insignificant differences.With A4，maize yields with different densities differed，with little differences（Table 3）.It can be concluded that B3 density performed the best， followed by B4.

Table 3 The effects of fertilization and planting density on maize yield and benefits

Effects of fertilization and planting density on maize yield and benefit

As shown in Table 3，with fertilization A3，maize yields tended to be volatile in the range of 6 135.2-7 609.1 kg/hm2as per different densities（B），as follows:B3＞B4＞B5＞B2＞B6＞B1，and the yields increased in 1 813.4-3 035.7 kg/hm2compared with treatment A4.With fertilizer investment costs deducted，net profits kept in the range of 198.40 yuan/hm2（deficit）to 2 513.40 yuan/hm2（benefits）and input-output ratio referred to that net profits was in the range of 0.06 yuan/hm2（deficit）to 0.56 profits with one yuan fertilizer cost.In general，net profits and input-output ratios were as follows:B3﹥B4﹥B2﹥B5﹥B1﹥B6；with fertilizer A2，maize yields in treatment B maintained in 6 402.1-8 207.8 kg/hm2，and from high to low were B3＞B4＞B5＞B6＞B2＞B1，which increased by 2 242.6-3 534.6 kg/hm2. With fertilizer cost deducted，net profit was in the range of 2 032.21-5 233.86 yuan/hm2，and input-output ratio in 0.65-1.67.What’s more，both of net profit and input-output ratio from high to low were B3＞B4＞B5＞B2＞B6＞B1. With fertilization of A3，maize yields of treatment B kept in the range of 6 260.8-7 665.2 kg/hm2，and from high to low were B3＞B4＞B5＞B2＞B6＞B1，increasing by 1 743.630 919 kg/hm2compared with treatment A4；with different densities，the increased yields were B3＞B4＞B2＞B5＞B1＞B6. With fertilizer cost deducted，net profits tended to be volatile in 1 775.78-4 876.92 yuan/hm2，and input-output ratio was in 0.80-2.18；both of net profits and input-output ratio were B3＞B4＞B2＞B5＞B1＞B6.

It can be concluded with different fertilizer quantities，net profit and inputoutput ratio both kept decreasing upon fertilizer quantity and a high net profit and input-output ratio can be reached by adjusting planting density given a fixed fertilizer quantity.

Effects of fertilization and planting density on maize biological yield and nitrogen use

Fertilizer quantity and planting density have varying effects on maize biological yield and the use of nitrogen（Table 4）.Specifically，in treatment A1，biological yields were in the range of 15 150.9-19 015.1 kg/hm2with different planting densities，the absorbed N quantity in the range of 183.0-218.9 kg/hm2and the use rate of nitrogen was in 21.0%-28.9%.It can be concluded that the fertilization of pure N per kg would obtain maize yield of 9.5-5.6 kg and physiological efficiency of crops was 23.0-32.7 kg in transforming absorbed nitrogen to economic yield.With fertilization A2，biological yields kept in the range of 14 922.0-19 415.5 kg/hm2，the absorbed pure N was in 172.9-209.7 kg/hm2，the use rate of nitrogen was in 25.5%-37.2%，agronomic efficiency was in 16.2-10.0 kg，and physiological efficiency of N maintained 43.5-33.7 kg under influence of different planting densities. With fertilization A3，biological yields kept in 14 727.4-17 839.7 kg/hm2，the absorbed N was in 158.3-192.8 kg/hm2，the use rate of nitrogen was in 26.9%-41.4%，agronomic efficiency was in 19.3-10.9 kg，and physiological efficiency of N maintained 25.3-50.2 kg under influence of different planting densities.It can be concluded from analysis and comparisons that as N quantity grew，the use rate，agronomic efficiency，and physiological efficiency of nitrogen all grew，and it is effective to make full use of nitrogen by adjusting planting density.However，it is notable that excessive high content of N actually increases the possibility of inorganic nitrogen into soils.

Effects of fertilization and planting density on maize and yield components

As shown in Table 5，plant height and ear height reached extremely significant differences with varying fertilizer quantities or the same fertilizer quantity but different densities；the effects from interplay of fertilizer quantity and planting density（A×B）differed little on plant and ear heights.Furthermore，for fertilizations A1 and A2，plant and ear heights differed insignificantly，which kept considerably higher compared with fertilizations A3 and A4；plant and ear heights of fertilization A3 performed higher compared with A4；among different fertilizer quantities（A）or with the same fertilizer quantity，but different densities（B），stem diameter showed little differences.These all incorporated that both of fertilization and density have dramatic effects on plant and ear heights，but little effects on stem diameter.

Table 4 Effects of fertilization and planting density on biological yield and nitrogen use rate of maize

With varied fertilizer quantities（A）or with the same fertilizer but different densities（B），ear length，ear diameter，hundred-kernel weight and the number of kernel reached extremely significant differences and the interplay of fertilization and density（A×B）has positive effects on ear length，ear diameter，hundred-kernel weight and the number of ear，with insignificant differences. For fertilizations A1，A2 and A3，ear length，ear diameter，and the number of ear differed insignificantly，but all performed better compared with A4；hundred-kernel weights in the fertilization treatments A1，A2 and A3 were significantly higher compared with treatment A4，and hundred-weight showed insignificant differences between A1 and A3 and A2 and A3.It can be concluded that maize bald-top rate showed insignificant differences among treatments with different fertilizer quantities （A）and different planting densities （B）with a fixed fertilizer quantity，which suggested that baldtop rate was less influenced.

Conclusions and Discussions

The research indicated that among treatments with different fertilizer quantities，maize yield in A2 reached 7 484.2 kg/hm2that was considerably higher compared with A1 of 6 894.6 kg/hm2and A3 of 6 949.5 kg/hm2.With the same fertilizer quantity，the effects of planting density（B）tended to be volatile on maize yield. For example，maize yield increased from 5 739.4 kg/hm2of B1 to 7 013.8 kg/hm2of B3 upon planting density. However，as the density grew，maize yield continued growth to75000 plants/hm2，followed by decreasing. These incorporated the effects of fertilizer quantity and planting density on maize yield，whose effects were much significant on ear length，the number of kernel，and hundred-kernel weight，which coincided with researches available［10-11，14］.The research also showed that fertilization in A2 performed better compared with A1 and A3，and planting density of B3 was much suitable.

The use rate of nitrogen reflects the recycling rate of N fertilizers in soils by crops；agronomic efficiency of nitrogen the increased number of kernel contributed by N fertilizer per unit；physiological efficiency of nitrogen is the increased yield of kernel of groundpart crops by absorbing nitrogen per unit fertilizer.These are indices indicating the use rate of N fertilizer from different perspectives，and the differences of yield are a result of nitrogen absorption and physiological utilization efficiency.

According to the research，in treatment A1，the use rate of nitrogen was in the range of 21.0%-28.9%；maize yield was of 9.5-5.6 kg；nitrogen physiological efficiency of crops transforming absorbed nitrogen to economic yield was in the range of 23.0%-32.7%.In treatment A2，the use rate of nitrogen was in the range of25.5%-37.2%；maize yield was of 16.2-10.0 kg；nitrogen physiological efficiency of crops transforming absorbed nitrogen to economic yield was in the range of 43.5%-33.7%.In treatment A3，the use rate of nitrogen was in the range of 26.9%-41.4%；maize yield was of 19.3-10.9 kg；nitrogen physiological efficiency of crops transforming absorbed nitrogen to economic yield was in the range of 25.3%-50.2%.These demonstrated that with increasing of N fertilizer，nitrogen use rate，nitrogen agronomic efficiency and physiological efficiency all kept declining，and with the same fertilizer quantity，the three factors all improved as density grew，which are in consistent with researches available［7-8］.The research indicated that with a fixed fertilizer quantity，the role played by nitrogen can be fully exploited by adjusting planting density.

The research conducted a test on a double cropping system，and it is proved that maize yield can be as high as 7 913.2-8 207.8 kg/hm2with pure N of 225.0 kg/hm2，P2O5of 75.0 kg/hm2，K2O of 187.5 kg/hm2，and planting density of 52 500 （B3）-60 000（B4）plants/hm2.

Still，the research just explored the effects of fertilization and planting density on yield and nitrogen use，and further attention should be paid to the effects of fertilization and planting density on nutrients of kernel，as well as nitrogen movements.

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Responsible editor:Xiaoxue WANG

Responsible proofreader:Xiaoyan WU

施肥水平與種植密度對玉米產(chǎn)量和氮素利用的效應(yīng)

譚 華，鄒成林，鄭德波，黃愛花，莫潤秀，韋新興，吳永升，蔣維萍，韋 慧，黃開健 （廣西農(nóng)業(yè)科學(xué)院玉米研究所，廣西南寧 530227）

為探討不同施肥水平與種植密度對玉米產(chǎn)量及氮素利用的作用效應(yīng)，以玉米雜交種‘桂單 0810’為材料，裂區(qū)設(shè)計，設(shè)置4個施肥水平和6個種植密度，進(jìn)行一年兩季田間試驗。結(jié)果表明：不同施肥水平與不同種植密度對玉米產(chǎn)量都有顯著的作用效應(yīng)；隨著施肥水平提高，氮素利用率、氮素農(nóng)學(xué)效率、氮素生理效率均有所降低，同一施肥水平隨密度增加，氮素利用率、氮素農(nóng)學(xué)效率、氮素生理效率均有所提高，通過調(diào)節(jié)種植密度可以較好發(fā)揮氮素的作用效率；以（A2）施純N 225.0 kg/hm2、P2O575.0 kg/hm2、K2O 187.5 kg/hm2與種植密度在 （B3）52 500株/hm2至 （B4）60 000株/hm2玉米產(chǎn)量可達(dá)7913.2～8207.8 kg/hm2是一種較優(yōu)的密、肥配合選擇。

玉米雜交種；施肥水平；種植密度；效應(yīng)

現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系廣西創(chuàng)新團(tuán)隊建設(shè)專項（nycytxgxcxtd-07-B）；國家支撐計劃子課題“廣西玉米抗旱關(guān)鍵技術(shù)集成與示范”（2012BAD40B04-2）。

譚華（1959-），男，廣西貴港人，研究員，主要從事玉米遺傳育種及高產(chǎn)優(yōu)化栽培技術(shù)研究，E-mail：tanhua19881206@126.com。*通訊作者，研究員，主要從事玉米遺傳育種及科研管理，E-mail：hkjian@gxass.net。

2015-01-03

2015-02-13

Supported by Gyangxi Innovation Team of Modern Agriculture Industry Technology System （nycytxgxcxtd-07-B）；Sub-topic of National Science and Technology Support Program（2012BAD40B04-2）

.E-mail:hkjian@gxass.net

January 3，2015Accepted:February 13，2015