Effect of Long-term Application of Chemical Fertilizer on the Quality of Summer Maize

The study on the effect of fertilization on the quality of maize grain was conducted based on continue application of fertilizer for 26 and 36 years in gleyic cambisols. The amounts of protein, starch, fat and amino acid were determined and the amino acid was analyzed by cluster analysis. The results showed: Long-term fertilization 26 years showed that N2K and N2P processing protein content as high as 9.01, 9.01%, lowest comparing CK treatment is 5.52%; all fertilizer treatments reduced the summer maize starch content, including N2PK deal with relatively high starch content is 57.55%; N2K processing crude fat content as high as 5.95%; N2P processing total amino acids and essential amino acid content is the highest, 8.13 and 3.22%, respectively. Long-term fertilization 36 years (2013) summer maize grain each nutrition indicators in line with 26 years change rule.


INTRODUCTION
Compared to the long-term fertilization experiment with routine test, has for a long time and climate advantages, provided data to solve many theoretical and practical problems has an important role (Zhao and Zhang, 2002).Maize is an important food crop and its nutritional quality refers to the nutrient components in the grain and the nutritional value of human and livestock.Its main quality traits include protein, amino acid, fat, starch four aspects.Maize quality except for variety, environment and cultivation techniques factors (Ma et al., 2007;Wu et al., 2008) and harvest time also have great relationship; corn harvest time is generally in the largest output, the quality of the best period (Herrmann et al., 2005).Some studies have indicated that summer maize delayed harvest and yield increase meanwhile significantly affected the quality of corn grain (Meng et al., 2007;Wen et al., 2007;Zhang et al., 2010).Liu et al. (2010) indicated that the effect of different fertilization levels on the lysine content of maize was not significant.Shen et al. (2008) show that the regulation affects of nitrogen fertilizer on maize plant material production capacity is more obvious; nitrogen fertilizer had greater control of nitrogen fertilizer and corn on corn plant material production capacity and is mainly influenced by grain number per spike.Chen and Zhao (2006) showed that spring maize grain amylose, amylopectin, the total starch accumulation in the filling period showed an upward trend, conform to the law of "S" curve.Within a certain range, the content of starch increased with the increase of nitrogen application rate.Feng et al. (2006) of waxy corn in autumn sowing date tests found, there was no significant change of pure corn seeding time found during grain filling the changing trends of main quality components, but had a great influence on the content of main quality components.In general, there is a lot of research on the effects of fertilization on the quality of maize, however, the effect of long-term fertilization on the quality of summer maize in the fluvo-squic soil is not reported (Oikeh et al., 1998;Belay et al., 2002;Montemurro et al., 2002;Huang et al., 2010).Therefore, this study use began in 1978 the Laiyang non calcareous fluvo aquic soil, long-term fertilization, respectively, to study the effect of 2003 and 2013 nitrogen fertilizer and the combined application of phosphorus and potassium on grain quality of summer maize, aimed at for rational fertilization in maize, the production of high quality corn provides a theoretical basis.---------------------------------------------------------------------------- The experiment began in the autumn of 1978, total 12 processing, 3 repeat, randomized block arrangement design, 36 cells, each cell area 33.3 m 2 , cell with 1.0 m glass plate separated, no leakage and independent irrigation.This thesis selects 6 of them to analyze the process.Respectively non fertilization control treatment (CK), single application low (N 1 ), high amount of nitrogen fertilizer (N 2 ), high nitrogen and phosphorus fertilizer (N 2 P), potassium fertilizer treatment (N 2 K), combined application of N, P and K (N 2 PK).The urea was used for N fertilizer, the application of P 2 O 5 and KCL for the P and K fertilizer, the P and K was used as basic fertilizer, as a kind of nitrogen fertilizer and wheat rose, fertilizer and Maize Jointing, heading fertilizer, other management measures are the same.There were six treatments in this study (Table 1).

Experiment method:
The summer maize grain samples were protected by paper bags in the field and samples in 2003 and 2013 were used in this study.In each plot, 30 samples were random collected and kept 25% samples on average.All the samples were sieved to 0.25 mm.The content of protein of the wheat was investigated by Kjeldahl determination.The starch was determined by anthranone-H 2 SO 4 and fat was tested by residue method, but automatic amino-acid analyzer analyzed the amino acid.All the data were analyzed by SPSS 19.0.

Effect of long-term fertilization on the starch of summer maize grain:
The starch content of all fertilizer treatments than CK treatment are falling, fertilization affected maize grain starch content.26 years long-term experiment, comparing CK treatment compared to other fertilization starch content as high as 62.15%; N 2 PK with higher 57.55%;N 1 and N 2 treatment at the same level, for low starch content processing, fell more than 26% compared with CK treatment.36 years long-term experiment, besides comparing CK treatment, N 2 PK processing content as high as 58.58%;N 2 deal with lowest amount is 50.35%;NP with two processing N 2 PK, N 2 P starch content increased significantly; each processing starch content decreased: CK> N 2 PK> N 2 P> N 1 > N 2 K> N 2 (Table 2).26 years with 36 years of the test results show that with the increase of N application, maize grain starch content showed a trend of decrease, illustrate the N fertilizer in maize grain starch content decreased and with the increasing of application rate of N amount, drop increases accordingly; N 2 PK processing compared with N 2 K, N 2 P processing, content increase rate is higher, that single P fertilizer or K fertilizer to improve the maize starch content effect is not obvious, N 2 PK with can significantly improve the maize starch content.

Effect of long-term fertilization on the fat of summer maize grain:
The starch content of all fertilizer treatments than CK treatment were increased, fertilizing influence crude fat content of maize kernels.26 years long-term experiment shows that N 2 K processing content up to 5.75%, compared with the CK treatment increased by 1.54%; N 2 P processing second-highest is 5.09%; N 2 treatment adipose content is higher than N 1 , both differ by 0.52%.A long-term experiment, 36 years N 2 K processing crude fat content as high as 4.95%, the order from high to low is: between the groups: N 2 K> N 2 PK> N 2 P >N 1 > N 2 > CK (Table 3).Illustrate the high amount of N fertilizer fertilizer can raise the content of the maize grain crude fat and K fertilizer, P fertilizer promote synthesis and accumulation of fat.
Effect of long-term fertilization on the amino acid of summer maize grain: 26 years long-term fertilization experiment, compared with CK treatment, all fertilizer treatments were significantly improve amino acid and essential amino acid content in maize grains, with N 2 P treatment, among them the highest total amino acid and essential amino acid content, 8.13, 3.22%, respectively, compared with the CK treatment increased by 64.57, 65.13% (Table 4).That illustrate the impact of P fertilizer for amino acid, can promote the accumulation of amino acid; compared with N 1 and N 2 , N 2 to deal with a high content of amino acids, that high amount of n fertilizer can raise the content of the maize grain amino acid; N 2 K treatment just below N 2 P amino acid content; the fertilizer processing amino acids in the order: N 2 P> N 2 K> N 2 > N 2 PK> N 1 > CK.
Clustering analysis based on Q clustering of SPSS clustering in 6 processes into three categories (Fig. 2).It can be seen that, from 1 to 3 kind of amino acid content is lower, N 2 , N 2 PK and N 2 K similarity of amino  3 All data are repeated three times average; "*" must nutrition amino acids for human body acid content is higher, together for the first class; N 2 P treatment separately for class 2; CK, N 1 processing results similar to class 3. 2013 and 2003 compared to produce change, N 2 , N 1 treatment for second categories, CK treatment alone is divided into third categories.
In Table 5, 36 years long-term fertilization experiment, compared with CK treatment, all fertilizer treatments can raise the content of the maize grain amino acids, of which N 2 P deal with highest total amino acid content of 6.37%, which increased by 28.95% over CK, essential amino acid content is as high as 2.54%, increased by 30.26% than CK control treatments, this illustrates of P fertilizer influence on amino acids, can promote the accumulation of amino acids; N 2 K treatment just below N 2 P, N 2 PK processing amino acid content than 26 years, the rest of the process change law is consistent, through long-term fertilization, N 2 PK with treatment on the influence of amino acids gradually increase.The results showed that the factors influencing the summer maize protein content of the main is N, followed by P element, the last is the K factor.For six processing (36 years) clustering analysis, the generated clustering analysis tree diagram into three categories (Fig. 3).As you can see, from 1 to 3 kind of amino acid content is lower, N 2 P, N 2 K and N 2 PK similarity of amino acid content is higher, together for the first class; N 1 , N 2 , processing into 2 classes; CK treatment alone together for class 3.

DISCUSSION
Show that it has been reported in nitrogen fertilizer can significantly improve the summer maize grain protein content, within a certain range protein content increased with the increase of amount of N application (Yang et al., 2009;Li et al., 2004).Jin et al. (2004) studies have shown that summer maize grain protein content increased with N application rate increased.Grain protein content is very significant positive correlation with N application rate, consistent with the test results.Which shows that nitrogen fertilizer on summer maize grain protein content in the enhancement effect is relatively stable; N 2 P treatment significantly increased the amino acid and essential amino acids, which shows on the basis of high nitrogen with P fertilizer can significantly improve the content of amino acids in maize kernels, Zhang et al. (2004) study applied P effect on protein content and grain amino acid content is not obvious, do not agree with the test results.May be because the varieties tested, fertilizer and soil environment.Wang and Ju (2012) and Yi et al. (2008) thinks that potassium can promote grain protein synthesis and can improve the summer maize grain protein content and amino acid content, with the same experimental results.Huang et al. (2004) research thinks, with the increase of n application maize grain crude fat content increased.Shi and Zhang (1994) suggested appropriate use of potash fertilizer can improve the fat content, but excessive K fertilizer can produce inhibition.Genter et al. (1956) and Wang et al. (2006) reported that P of fat did not make any difference, are the same as the experimental research results.

CONCLUSION
The test results show that the application of inorganic fertilizer can significantly improve the quality of summer maize kernels, especially on the basis of applying high amount of N fertilizer with P fertilizer and a moderate amount of increasing K fertilizer application could obviously increase the summer maize grain quality.plan in national key technology for agriculture (2013BAD07B06-03); Scientific Research Innovation Team in Colleges and Universities of Shandong Province.

Fig. 1 :
Fig. 1: Protein contents of maize grain in different fertilization treatments

Fig. 2 :
Fig. 2: Long-term fertilization experiment of maize grain amino acid composition of hierarchical cluster analysis results (26 years)Table 5: 36 years (2013) Effect of different fertilizing on the content of amino acid (%)

Fig. 3 :
Fig. 3: Long-term fertilization experiment of maize grain amino acid composition of hierarchical cluster analysis results (36 years)

Table 3 :
Crude fat contents of maize grain in different fertilization treatments