Yongfeng XING, Yinping LI, Sixia FANG, Xianghua MU, Qingmei LU, Xinping LI*

1. Zhoukou Academy of Agricultural Sciences, Zhoukou 466001, China;

2. Agricultural Bureau of Wen'shang City, Wen’shang 272250, China

Wheat-maize rotation system is a typical planting pattern in Huanghuai wheat region[1].The perennial planting area of wheat is 900×104hm2, which accounts for 58.5%of the whole country’s area.Nitrogen is a necessary nutrient element for the growth and development of crops, nitrogen fertilizer application is an important part of crop production[2],therefore, appropriately applying nitrogen fertilizer can not only increase wheat and maize yield, but also be of great significance in developing highyield, high-efficiency and ecological agriculture, and improving farmers’cultivation techniques and economic income[3-4].

As a medium gluten wheat variety with fine quality, disease resistance and super high yield, Zhoumai 22 was bred by Zhoukou Academy of Agricultural Sciences in He’nan Province who used Zhoumai 12 -Wenmai No.6∥Zhoumai 13,it has the advantages of compact plant type,strong stress resistance, high temperature resistance at the later period,good yellowing and maturity,high yield and good quality, etc. Its accumulated popularized area reached more than 560×104hm2,so it has been one of the main popularized varieties in Huanghuai wheat region in recent 10 years.

To realize the successive high yield of Zhoumai 22 in the condition of wheat-maize integration, the regularity of nitrogen requirement of Zhoumai 22 was explored,so as to provide a theoretical basis and practical guidance for high-yield cultivation of Zhoumai 22.

Materials and Methods

Experimental materials

The experimental wheat variety was Zhoumai 22, and the maize variety was Jundan No.28.

Experimental methods

The experiment was carried out in Xihua Research Institute of Agricultural Sciences in Henan Province dur-ing 2011-2014; there were three levels of annual nitrogen application amount under wheat-maize doublecropping system, namely 300,450 and 600 kg/hm2, and three allocation proportions of nitrogen fertilizer between wheat and maize,namely 4∶6,5∶5 and 6∶4, thus there were totally nine treatments; the plot area was 30 m2which designed by split plot experiment(Table 1).

Table 1 Experimental design

Measuring items

With the growth and development of wheat, the samples were chosen from the field to measure every physiological index; in the mature period, the samples within 1 m line length were all taken for testing in the laboratory, and at the same time, the wheat of the whole plot was harvested to calculate its yield.

Data analysis

All data were treated preliminarily using Excel, and DPS was used for analyzing systematically.

Results and Analyses

Effects of nitrogen fertilizer on growing dynamics of Zhoumai 22 population

As seen in Fig.1, in the condition of the same basic seedlings, with the change of nitrogen fertilizer application amount,Zhoumai 22 population would change correspondingly; C8 population was the largest in wintering period,seedling establishment period and jointing stage, which was larger than C1 (the smallest population)by 58%,the differences among the treatments were prominent; in the mature period,the population size followed the following sequence: C8 ＞C7 ＞C6 ＞C5 ＞C9＞C4＞C3＞C2＞C1. These indicated that only appropriate application of nitrogen fertilizer was the basis ensuring the percentage of earbearing tiller,thereby obtaining the large population in the mature period.

Effects of nitrogen fertilizer on dry matter of wheat individual in different growth periods

During the whole growth period,nitrogen fertilizer is one of the important factors affecting the amount of dry matter of wheat population and individual. As shown in Fig.2, the larger the supply of annual nitrogen fertilizer,the larger the amount of dry matter of wheat population and individual, and vice versa. In different levels of nitrogen fertilizer, the differences on the average value of the amount of dry matter before jointing stage were larger,indicating that heavily applying nitrogen fertilizer before jointing stage made the differences on the growth conditions of wheat population and individual become larger, however, the survey results of heading stage and late filling stage showed that the differences on the amount of dry matter of wheat population and individual were consistent with the variation trend of the dosage of nitrogen fertilizer, moreover, the differences on the amount of dry matter of wheat population and individual were narrowed. These showed that in specific stages of growth and development of wheat,appropriate nitrogen fertilizer supply was a requirement to promote the full growth of wheat population.

Effects of nitrogen fertilizer on grain filling rate of Zhoumai 22

Based on the measuring results of grain filling rate from Fig.3 and Fig.4, it was shown that the grain filling rate of the 9 treatments basically followed the rule of slow-fast-slow, and the fastest grain filling rate mainly concentrated on May 14th-19th. With the increase of nitrogen application rate of the whole year, the grain filling rate presented the trend of increasing firstly and decreasing then, the grain filling rate of treatment 1 was larger,however, that of treatment 9 was smaller,and the grain filling rate of the above two showed the trend of increasing firstly and decreasing then with the increase of nitrogenous fertilizer distribution rate from maize to wheat and nitrogenous fertilizer application rate as well as the distribution ratio of Zhoumai 22 under the same nitrogen level with different distribution ratios. These indicated that appropriately applying fertilizer was beneficial to improving the filling intensity of kernels, but excessive nitrogen fertilizer was bad for grain filling.

Effects of nitrogen application on yield factors

There were obvious differences on yield factors among different treat-ments (Table 2), C8 treatment had the most spikes per hectare, namely 44 ×104, which was higher than C1 treatment (the least)by 30%;the size of kernels followed the following sequence:C8＞C7＞C6＞C5＞C9＞C4＞C3＞C2＞C1, the differences among different treatments were significant; the differences on 1 000-seed weight among different treatments were greater, in which that of C1 treatment was the lowest and lower than the other treatments by 5%-14.2%,indicating that appropriate nitrogen fertilizer supply was a material basis ensuring grain filling rate, there was a positive correlation between nitrogen fertilizer supply and yield factors within a certain range, when the amount of nitrogen fertilizer reached a certain degree(600 kg/hm2, 4 ∶6), yield factors would not increase with the increase of nitrogen fertilizer supply, these showed that only appropriate nitrogen fertilizer supply was the material basis for high yield.

Table 2 Effects of nitrogen fertilizer on yield traits of Zhoumai 22

Effects of nitrogen application on yield

Within the range of 0-600 kg/hm2of nitrogen application, the yield of Zhoumai 22 showed the trend of increasing firstly and decreasing then with the increase of nitrogen application, hereinto, the yield of C8 was the highest and higher than the other treatments by 3%-25%; within the nitrogen application of 0 -450 kg/hm2,the yield showed an increasing trend with the increase of nitrogenous fertilizer distribution rate from maize to wheat; under the nitrogen application of 450-600 kg/hm2, the yield showed the trend of increasing firstly and decreasing then with the increase of nitrogenous fertilizer distribution rate from maize to wheat; the total yield of wheat-maize integration all over the year showed the variation trend of increasing firstly and decreasing then within the range of 0-600 kg/hm2of nitrogen application,in which the yield of C8 was the highest, namely 16 886.8 kg/hm2.

Conclusions and Discussions

Effects of nitrogen fertilizer on the growth of winter wheat

Nitrogen fertilizer level affects crop growth and nutrient accumulation and transformation, there were a lot of studies, such as Huang Zhenglai et al.[5]pointed out that with the increase of nitrogenous fertilizer application, the accumulation of dry matter of wheat during the flowering period increased significantly. Lu Zenggen[6]held that nitrogen application rate had greater effect on the amount and ratio of nutrient transfor-mation before the flowering, and assimilation amount and contribution rate after the flowering, but there were differences among different varieties,and the author also specified that nitrogen application rate had significant effect on nitrogen absorption of winter wheat. Nitrogen is a nutrient element needed most by crops. Therefore, increasing nitrogenous fertilizer and available nitrogen content in soil plough horizon was beneficial to the nitrogen absorption of plants, thereby improving crop yield,but excessive nitrogen application would decrease crop yield[7].Some studies showed that the relationship between wheat grain yield and nitrogenous fertilizer application was quadratic curve;in a certain range, total nitrogen absorption amount of plants had potitive correlstion with nitrogen application rate[8].The result of this study was consistent with the above.

The aftereffect of nitrogen fertilizer apply for summer maize on winter wheat

The sources of crop nitrogen nutrition mainly include nitrogen fertilizer and soil, and soil nitrogen contains residual fertilizer nitrogen of previous crops and mineralized nitrogen of soil[9].Without nitrogen fertilizer,the nitrogen for crops is only from soil;because of excessive nitrogen fertilizer application for many years, there has been a large amount of residual nitrogen in the soil[10], therefore, there have been the phenomena of unobvious yield increase and low utilization rate of nitrogen fertilizer without applying nitrogen fertilizer in recent years[11-12];some other studies suggested that the use efficiency of nitrogen fertilizer from previous crops was low, because the immobilization of microorganism and the mineralization of organic nitrogen,fertilizer nitrogen and soil nitrogen continually exchanged, considerable amount of nitrogen was fixed as organic nitrogen and can not be absorbed and utilized directly by crops,causing the low recovery rate of residual nitrogen[13-15], and weakening the aftereffect of next season’s crops;this study results showed that the nitrogen fertilizer from preceding crops had certain aftereffect, but the effect was not obvious.

Conclusions

In meadow soil area, total yield of Zhoumai 22 all over the year showed increasing trend with the increase of nitrogenous fertilizer distribution rate from maize to wheat under the nitrogen application range of 0-450 kg/hm2,however, under the nitrogen application range of 450-600 kg/hm2, total yield showed the trend of increasing firstly and decreasing then. Annual amount of nitrogenous fertilizer of 600 kg/hm2and the distribution ratio of 5:5 in the condition of wheat-maize integration was beneficial to the high yield of the whole year’s crops (16 886.8 kg/hm2)andZhoumai22(7550kg/hm2).

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