Abstract

Maize (Zea mays L.) is one of the valuable food crops in China as well serves as a model organism for biological research worldwide. The experiment was conducted in the maize experimental base of Shanxi agricultural in Shanxi Province, China. Organic fertilizer was the main plot, 0 and 1.5 t/ha (Chicken mature Organic fertilizer). Five treatments were set up ① Control CK (0g sludge + 0g chicken manure) ② Organic fertilizer H0 level (sludge + chicken manure 0g) ③ H1 level of organic fertilizer (sludge + organic fertilizer 60 g/kg) ④ H2 level of organic fertilizer (sludge + organic fertilizer 120 g/kg) ⑤ Organic fertilizer H3 level (sludge + organic fertilizer 180 g/kg), 4 replicates. The results indicated that the effects of municipal sludge, and different amounts of chicken manure at the first seedling stage compared to CK treatment (without municipal sludge, and chicken manure), Plant height, root length, above/blow ground dry weight, of all treatments increased first, and then decreased, and reached the maximum values in H1 treatment, respectively, and contents of total Cu and total Zn in calcareous brown soil of maize at the first seedling stage were 24.8-40.2 mg/Kg and 54.7-149.4 mg/Kg applied quantitative municipal sludge, and the highest amount of chicken manure increased respectively. At the second seedling stage compared to CK, the Zn content was significantly increased, respectively. The contents of total Cu and total Zn in calcareous brown soil of maize at the second seedling stage ranged from 27.0 to 42.9mg/kg, and from 55.1 to 164.5mg/kg, respectively. In third seedling stage compared to CK, the Cu content in H3 treatment was not significantly increased, and the other treatments were significantly increased. The contents of total Cu, and total Zn in calcine brown soil of maize at the third seedling stage ranged from 24.4 to 36.3mg/kg, and from 52.3 to 172.6mg/Kg, respectively. The grain starch content at maturity stage was the highest at H2 and the lowest at CK. The effects of CK on soluble sugar, sucrose and starch contents of mature grains were not significant. There was a H2, and H3 significant interaction between the content of sucrose, and starch in the mature stage. The grain protein content and grain protein yield of H2 combined to H3 were the highest, and significantly higher than those of other treatments. The overall trend of Cu transport coefficient increased and while Zn transport coefficient decreased with the increase of chicken manure application, respectively. The grain protein content and grain protein yield of H2 combined to H3 were the highest, and significantly higher than those of other treatments. Effects on soil heavy metal content where compared to CK and H0 treatments, the total Cu, total Zn, available Cu, and available Zn in calcareous brown soil of maize at the first, second and third cropping stages increased significantly with the increase of chicken manure application rate, but it was far lower than the national secondary soil standard.

1. Introduction

Maize (Zea mays L.) is a crop grown worldwide and used for human consumption and as animal feed. However, the growth and yield of maize can be severely limited by drought, high salinity, and low temperature. To adapt to abiotic stresses, plants must modulate various physiological and metabolic responses, such as stomata closure, repression of cell growth and photosynthesis, and activation of respiration ¹. Maize grows well in various agro ecologies, and is incomparable to any other crop due to its capability to adapt in diverse environments. It has emerged as a crop of universal importance owing to its multiple uses both as a human food and livestock feed. It serves as an important component for countless industrial products. Furthermore, maize serves as a model organism for biological research worldwide. Globally, about 1016.73 million metric tons of maize is produced every year and it is the highest among major staple cereals ². It is estimated that over 30% of irrigated land used for crop production is adversely affected by high soil salinity, which causes salt stress in plants ³. In this way, salinity has a major impact on world food production, lowering yields of important crop plants such as wheat, soybean and maize. High concentrations of salt cause ion imbalance and osmotic stress in plants, disrupting ion and water homeostasis in plant cells. Drastic changes in ion and water homeostasis in plant cells leads to macromolecular damage; plant cell death, and growth arrest ⁴. Currently, the most common method of salt removal is leaching through the root zone carrying ions deeper into the soil ⁵. This method does not remove salt contaminants from the soil, but moves them deeper into soils and nearer to ground water. Phytoremediation has the potential to remove these contaminants quickly at a lower cost. Salinity affects 954.8 million ha of land worldwide ⁶. The expected to increase in most arid and semiarid regions because of the excessive use of ground water and increased evapotranspiration ⁷. In maize the vitamin Thiamin (vitamin B1) present which is water soluble B-vitamin required in the human diet for normal metabolic activity. This vitamin serve as coenzymes in numerous metabolic reactions that produce energy ⁸. Maize insufficiency can lead to vita deficiency disorders, various fruits and vegetables, including sweet potato, which are considered moderate to good sources of these compounds, which contributes to their quality and nutritional value. Information on fruit and vegetable nutritional value and composition requires appropriate analytical methodologies for B-vitamin quantification. However, the separation and quantification of low tissue concentration B-vitamins, like thiamine and riboflavin, in complex matrices such as fruits and vegetables can have significant analytical challenges ⁹. Moreover, the application of organic fertilizer can increase soil field water capacity while increasing soil organic matter content ¹⁰. Livestock and poultry manure resources are abundant in China with the transformation of livestock, and poultry breeding methods, large-scale, and intensification have been developed greatly ¹¹. According to statistics, the increases the production of livestock and poultry manure the emission of livestock, and poultry manure in China was 690 million tons in 1980 ¹². The average annual emission of livestock, and poultry manure from 2011 to 2015 was about 2.335 billion tons ¹³. In 2016, livestock and poultry waste in China reached nearly 38 billion Tons ¹⁴. According to relevant statistics, the annual average emission of livestock and poultry manure pollution in China reaches 3.8 billion tons ¹⁵. However, the utilization rate of livestock manure resource is still less than 60%. It was found that the nutrient return rate of livestock manure was less than 45% from 1980 to 2010 ¹⁶. Livestock manure plays a very important role in the improvement of farmland soil fertility. It is an important resource for agricultural production. It contains various nutrient elements needed by plants, beneficial microorganisms and a large amount of organic matter, which can improve soil physical and chemical properties ^{17, 18}. Agricultural use of livestock manure is recognized as an economical, practical and environmentally friendly method of disposing of livestock manure ¹⁹. Moreover, the contents of NPK in chicken manure are relatively high, about 1.63%, 1.54%, and 0.85% respectively ²⁰. Therefore, as one of the main raw materials of organic fertilizer, chicken manure is widely used in agricultural production. The aim of present study was to examine the effects of reduced control CK "H0" level (sludge + chicken manure 0g) "H1" (sludge + organic fertilizer 60 g/kg) "H2" (Sludge + Organic fertilizer 120 g/kg) "H3" (Sludge + Organic fertilizer 180 g/kg) (1) Protein content soluble sugar, sucrose, starch; and (2). The would provide a novel view for achieving the balance between H3 was beneficial to increase the content of gluten in grains, obtain higher protein content, and protein yield in grains, and increase the content of dry gluten in grains.

2. Materials and Methods

The experiment was conducted in the maize experimental base of Shanxi agricultural in Shanxi Province, China (E112°34 'E, N37°25' N). The pond was planted in a pool 2 m deep, separated by concrete walls with a thickness of 20 cm, and an insulation layer of 10 cm added to the outer walls.

The experiment had a split-split-plot design with three replications. Organic fertilizer is the main plot, 0 and 1.5 t/ha (Chicken mature Organic fertilizer). Five treatments were set up. ① Control CK (0g sludge + 0g chicken manure) ② Organic fertilizer "H0" level (sludge + chicken manure 0g) ③ "H1" level of organic fertilizer (sludge + organic fertilizer 60 g/kg). ④ "H2" level of organic fertilizer (sludge + organic fertilizer 120 g/kg). ⑤ Organic fertilizer "H3" level (sludge + organic fertilizer 180 g/kg), 4 replicates. After thorough mixing, maize was sown in each pot, and then distilled water was poured according to 70% of the field capacity of calcareous brown soil, and the maize was placed in the sunshine greenhouse for 3 seedling periods. They were kept free from insects, pests, and diseases using pesticides as needed. During whole growing season, weed was well controlled by hands.

Mineral nutrients (Ca², K⁺.Na^+.Cl^-, SO₄². NO^-) were analysis by wet digestion ²¹. Furthermore; digested samples were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) ²¹. For quality control blanks and standard reference material (NIST 1567, wheat flour) were used, and after every 10 samples repetition was carried to minimize the errors.

Out of 12 cultivars two cultivar i.e. Above ground of crop, and Underground were selected and analyzed for future studies. Plants were harvested at the end of the experiment. Manually shoot and roots were separated and meanwhile fresh weight was recorded and then plant material was dried at 80 °C for 24 h in hot air oven to record dry weight and stored in a desiccator (-20 °C or -80 °C) for further analysis.

The bromophenol blue water solution and isopropanol lactic acid mixture, and the settling values were determined by shock. The landing value was measured using the Landing Numerical Measurer (FN-IV). The Micro dough LAB, a micro powder instrument was produced by a [Swedish company Botone (SCB)] and it was measured the fluidity of bread. The wet gluten content and gluten index were measured using the Gluten Index Meter (MJZ-II) Mian Jin zhi–2 gluten index analyzer china) quality analyzer. For Quality analysis dough mixed from 200g flour was divided into small dough weighted based on 0.25g flour calculated as by using the following formula ²².

The dry gluten was obtained by drying the wet gluten in an oven (TD5G, Hunan Xiang Li Scientific instruments com., Lt China) to constant weight at 100°C for 24h using the air oven drying method. The dried gluten was left cool for 1 h before taking its weight as the dry gluten content. The percentage of dry gluten obtund was calculated using following formula.

The different data were subjected to analysis of variance (ANOVA) as split-plot design using DPS and SAS 9.0. Graphics were constructed using Microsoft Excel 2010. Mean values were calculated and significance of the difference between treatments was tested by LSD (least significant difference) method at the significance level of P=0.05.

3. Results

The effects of municipal sludge, and different amounts of chicken manure on plant height, root length, above ground dry weight, and below ground dry weight of maize at the first seedling stage (Table 1). Compared to CK treatment (without municipal sludge, and chicken manure), H0, H1, H2, and H3 treatments increased plant height by 33.2%, 142.1%, 101.9%, and 97.1%, root length by 163.6%, 198.2%, 108.6% and 106.5%, respectively. The above ground dry weight increased by 142.2%, 604.4%, 384.4%, and 377.8%, and the underground dry weight increased by 170.3%, 316.2%, 151.4% and 124.3%, respectively. Plant height, root length, above ground dry weight, and underground dry weight increased significantly in all treatments except H0 treatment (which only applied municipal sludge). Compared to H0 treatment, plant height increased by 82.4%, 51.6%, and 47.3%, root length increased by 13.1%, decreased by 20.9%, and 21.6%, shoot dry weight increased by 190.8%, 100.0%, and 97.2%, respectively, in H1, H2, and H3 treatments. Underground dry weight increased by 54.0%, decreased by 7.0%, and 17.0%, respectively. Plant height, and shoot dry weight increased in all treatments, but the increasing amount decreased continuously. The increase of shoot dry weight in H2, and H3 treatments were non-significant. In H1 treatment, root length, and dry weight of underground parts were increased, and the dry weight of underground parts was significantly different. The root length and underground dry weight of H2 and H3 treatments decreased, and the root length was significantly different. Plant height, root length, above ground dry weight, and below ground dry weight of all treatments increased first, and then decreased, and reached the maximum values in H1 treatment (applying quantitative municipal sludge, and 60g/kg chicken manure), respectively. Compared to H0, it increased by 82.4%, 190.8%, 13.1% and 54%, respectively.

The Cu content range above, and below ground was 2.89-8.99 mg/kg, and 8.77-25.74 mg/kg, respectively, (Figure 1A). The Cu content in the upper, and underground parts of maize at the first crop seedling stage increased first and then decreased, and reached the maximum value in H0 and H1 treatments, which were 8.99mg/kg and 25.74mg/kg, respectively. Compared to CK, the Cu content in shoots and bellows were significantly increased in all treatments, and the highest Cu content in shoots, and bellows were increased by 211.1%, and 193.5% in H0 and H1 treatments, respectively. Compared to H0 treatment, shoot H1, H2 and H3 treatment were decreased by 16.8%, 21.6%, and 23.2%, respectively, and H3 treatment was decreased significantly. H1 and H2 treatment were increased by 85.8%, and 11.3%, respectively, while H3 treatment was decreased by 22.9%, among which H1, and H3 changed significantly, H2 did not change, significantly. The Cu content in underground part of maize was higher than that in above ground part in all treatments at seedling stage (Figure 1B). From the changing trend of Cu content, the application of municipal sludge, and low amount of chicken manure had a great difference on Cu content in the upper, and underground parts of maize at seedling stage, and the influence on underground part was greater than that on the above part. With the increase of chicken manure application, the Cu content in underground part of H1 treatment increased rapidly, and decreased significantly until H3 treatment. These indicated that the application of municipal sludge, and high quantity of chicken manure could reduce the content of Cu in the underground part of maize seedlings. Compared to the underground part, the change range of Cn content in H1 treatment was relatively small, the change range of H2 and H3 treatment were higher than that in the underground part, but compared to H0, the Cu content in H3 treatment was significant, and the difference of the reduction range was minimum. These indicated that the application of municipal sludge and low and medium amounts of chicken manure promoted the Cu absorption and accumulation in the root of maize at seedling stage, and reduced the Cu absorption accumulation in the shoot. The application of municipal sludge, and high quantity of chicken manure could significantly reduce the Cu content in the upper ground, and underground parts of maize at seedling stage.

In the second crop, the contents of Zn in the above, and below ground were noted 20.09-66.66 mg/kg and 29.26-80.91 mg/Kg, respectively (Figure 2A). The Zn content in the upper, and underground parts of maize field at the second crop seedling stage increased first, and then decreased, which was consistent with the change trend of the first crop, and reached the maximum in H0 treatment, which were 66.66mg/kg and 80.91mg/kg, respectively. Compared to CK, the Zn content in the above, and underground parts was significantly increased. The H0 treatment with the largest Zn content in the above and underground parts increased by 231.8% and 176.5%, and the H1 treatment increased by 174.7% and 139.6%, respectively. Compared to H0 treatment, the Zn content of H1, H2 and H3 treatment in the shoot was reduced by 17.2%, 35.3%, and 42.1%, respectively. H1, H2 and H3 treatment in the subsurface were reduced by 12.7%, 38.0% and 44.5%, respectively. In conclusion, according to the change trend of Zn content in the upper, and underground parts of maize at the second crop stage, the single application of municipal sludge still significantly increased the Zn content in the above, and underground parts of maize (Figure 2B). Compared to H0 applied with municipal sludge alone, the Zn content in the upper, and underground parts of maize at the second crop stage was significantly reduced by applying municipal sludge, and different amounts of chicken manure. However, compared to the underground part, the Zn content of the above-ground part was significantly reduced by the application of urban sludge, and low quantity chicken manure, and the Zn content of the above-ground part was slightly reduced by the application of urban sludge, and medium high quantity chicken manure.

In the third crop, the Cu content range of above and below ground was 1.70-8.89 mg/kg, and 6.42-44.96 mg/kg, respectively, (Figure 3A). The Cu content in the upper part of maize at the third seedling stage was still smaller than that in the underground part, indicating that heavy metal Cu was more likely to accumulate in the root of maize at the third seedling stage compared to the above shoot. the Cu content in the upper, and underground parts of maize at the third crop seedling stage increased first, and then decreased, and reached the maximum in H1, and H0 treatments, which were 8.89mg/kg, and 44.96mg/kg, respectively. Compared to CK, the Cu content in H3 treatment was not significantly increased, and the other treatments were significantly increased. The highest Cu content in H1 treatment, and H0 treatment increased by 422.9%, 600.3%, respectively, and the H1 treatment increased by 266.7%. Compared to H0 treatment, shoot H1 treatment increased by 9.1%, H2 and H3 treatment decreased by 2.7% and 16.0%, respectively, with no significant changes. The treatment of H1, H2, and H3 in underground area were decreased by 47.6%, 53.3% and 70.5%, respectively. These indicated that the application of municipal sludge and chicken manure could significantly reduce the Cu content in the lower part of maize the third crop stage, and the reduction range increased to the increase of the application rate of chicken manure. There was no significant effect on Cu content in the upper part of maize at the third crop stage, but with the increase of chicken manure application, the reduction range increased. It still indicated that the effects of municipal sludge, and chicken manure on Cu uptake, and accumulation in the roots of maize at the third crop stage were greater than those in the shoot. In the third crop, the contents of Zn in the above and below ground were 17.96-62.23 mg/Kg and 26.45-87.61 mg/Kg, respectively (Figure 3B). Zn content in the upper and underground parts of maize field at the third crop seedling stage increased first, and then decreased, and reached the maximum in H0 treatment, which were 62.23mg/kg and 87.61mg/kg, respectively. CK Compared to Zn content in the above, and underground parts was significantly increased. The H0 treatment with the largest Zn content in the above, and underground parts increased by 246.5% and 231.2%, and the H1 treatment increased by 216.0%, and 175.8%, respectively. Compared to H0 treatment, the Zn content in shoot H1, H2, and H3 treatment was decreased by 8.8%, 16.1%, and 39.2%, respectively. The Zn content in shoot H1, and H2 treatment was not significantly decreased, while that in shoot H3 treatment was significantly decreased. The underground H1, H2 and H3 treatments were decreased by 16.7%, 28.1%, and 32.4%, respectively. The H1 treatment did not decrease significantly, while H2, and H3 treatment decreased significantly According to the change trend of Zn content in the upper, and underground parts of maize at the third crop stage, the single application of municipal sludge still significantly increased the Zn content in the above and underground parts of maize. Compared to fertilization of the urban sludge H0, into the city sludge and different amount of chicken manure were reduced the upper third crop seedling maize, and underground part zinc content, among them, the applied into urban sludge and high chicken manure can significantly reduce the amount of maize upper zinc content in seedling stage, into the city sludge, high amount of chicken manure could significantly reduce maize lower zinc content in seedling stage.

The contents of total Cu and total Zn in calcareous brown soil of maize at the first seedling stage were 24.8-40.2 mg/Kg and 54.7-149.4 mg/Kg, respectively (Figure 4). Compared to CK, the total Cu, and Zn in H0 treatment increased by 12.1% and 58.7%, respectively. Compared to the H0 treatment that only applied municipal sludge, the total Cu and Zn in H3 treatment that was applied quantitative municipal sludge, and the highest amount of chicken manure increased by 44.6%, and 72.1%, respectively. The contents of total Cu and total Zn in calcareous brown soil of maize at the second seedling stage ranged from 27.0 to 42.9 mg/kg, and from 55.1 to 164.5mg/kg, respectively. Compared to CK, the total Cu and Zn in H0 treatment increased by 8.5%, and 62.6%, respectively. Compared to H0 treatment, the total Cu and Zn in H3 treatment with the highest amount of chicken manure increased by 46.4% and 83.6%, respectively. The contents of total Cu, and total Zn in calcine brown soil of maize at the third seedling stage ranged from 24.4 to 36.3mg/kg, and from 52.3 to 172.6mg/Kg, respectively. Compared with CK, the total Cu and Zn in H0 treatment increased by 13.5%, and 65.0%, respectively. Compared with H0 treatment, the total Cu and Zn in H3 trea-tment with the highest amount of chicken manure increased by 31.0% and 100%, respectively.

According to the Cu content in the lime brown soil of maize at the third seedling stage, the Cu content of each treatment in the second crop was higher than that in the first crop, and the Cu content of the other four treatments in the third crop was lower than that in the first and second crops, except that the H0 treatment was equal to that in the first crop (Figure 5). These indicated that increasing the number of stubble, the accumulation of Cu in calcareous brown soil of maize seedling stage was decreased, and some Cu was transferred to the crops through biological enrichment and migration. From the perspective of Zn content, compared with that of the first crop, except H2 treatment, Zn content of the other treatments in the second crop was higher than that of the first crop, especially H3 treatment was 10.1% higher than that of the first crop. In the third crop, Zn content in CK and H0 treatments was slightly lower than that in the first and second crops, H1 and H3 treatments were higher than that in the first and second crops, and H2 treatment was slightly lower than that in the first, and second crops. In general, with the increase of cropping stubble number, the accumulation of Zn in calcareous brown soil of maize seedling stage had an increasing trend. Compared to CK, the Cu and Zn contents in calcareous brown soil treated by WD, WZ and WG without removing heavy metal municipal sludge increased by 11.3%, 17.2%, 25.0% and 35.4%, 43.1% and 51.7%, respectively. Cu and Zn in calcareous brown soil increased by 5.5%, 7.8%, 11.7% and 22.5%, 21.7%, 29.1% in LD, LZ and LG treatments, respectively (Figure 6). Except for LD treatment of Cu, the differences of other treatments were significant. The Cu and Zn contents in calcareous brown soil with low, medium and high amounts of municipal sludge were reduced by 5.3%, 8.0%, 10.6% and 10.2%, 14.7%, 14.9%, respectively, compared to those without heavy metal removal. Cu and Zn contents in calcareous brown soil showed an increasing trend with the increase of the application rate of municipal sludge of the two treatments, and the increasing amount was constantly increasing (Figure 6). Compared to the municipal sludge treatment without heavy metal removal, the increase of Cu and Zn content in calcareous brown soil in the municipal sludge treatment with heavy metal removal was smaller. The variation range of Zn content in the two treatments were greater than that of Cu, respectively. It was indicated that the application of municipal sludge without heavy metal removal, and removal both increased the Cu, and Zn contents in calcareous brown soil to different degrees, but the promotion effect of municipal sludge with heavy metal removal on Cu and Zn in calcareous brown soil was less than that of municipal sludge without heavy metal removal. Moreover, the effect of different amounts of municipal sludge on Zn content in calcareous brown soil was greater than that on Cu content.

The change of Zn/Cu ratio in plant parts and its relative to the heavy metal content ratio in soil can represent the difference of Cu and Zn enrichment and transport in plants. According to (Figure 7), although Zn/Cu in soil and underground part of maize at the three cropping stages showed an increasing trend with the increase of chicken manure application rate, the increase range was small. The Zn/Cu values of the first, second and third crop soil CK treatments (no sludge and no chicken manure) were 2.2, 2.0 and 2.1, respectively, and the Zn/Cu values of the H0 treatment (no sludge and no chicken manure) were 3.13, 3.06 and 3.12, respectively. The Zn/Cu of H3 treatment (the treatment with the largest amount of chicken manure) were 3.7, 3.8 and 4.8, respectively. The Zn/Cu values of CK treatment (without sludge and chicken manure) were 2.1, 3.7 and 4.1, respectively; those of H0 treatment (without sludge and chicken manure) were 3.0, 2.4 and 1.9, respectively; those of H3 treatment (the treatment with the largest amount of chicken manure) were 4.2, 5.1 and 4.5, respectively.

In the upper part of corn field at the first, second and third crop stages decreased with the increase of chicken manure application rate, and the decrease was larger. The Zn/Cu in the upper part of maize at the first, second and third crop stages were 11.3, 10.4 and 10.6, respectively, and the Zn/Cu in the H0 treatment were 7.8, 10.1 and 7.6, respectively. The Zn/Cu in H3 treatment were 6.6, 5.4 and 5.5, respectively. Except for the second, and third stubble of H3 treatment, the Zn/Cu in the overshoot of each treatment was significantly higher than that in the subsurface and soil. These indicated that the Cu absorption and transport ability of maize at seedling stage was stronger than that of Zn. The increase of chicken manure application rate relatively promoted the Cu absorption, and transport of maize at seedling stage, and reduced the difference of Cu and Zn absorption and transport of maize at seedling stage.

The Calcium Ca²⁺ concentration was decreased in both genotypes in above ground of crop and Underground of crop as compared to CK 2.96±0.04 and 3.14±0.06 treated with H1 mM 2.75±0.043 and 2.85±0.03 spray, H2 mM 2.85±0.04 and 2.94±0.04 spray, HO mM 2.62±0.04 and 2.65±0.04, H3 mM 2.15±0.04 and 1.83±0.03 and H0+H4 mM 2.42±0.17 and 2.38±0.13. The Potassium K⁺ concentration was decreased H0 100 mM 14.54±2.06, and 12.54±2.06, H0 + H1 mM 16.54±2.65 and 14.54±2.07, and H0+H2 mM 18.06±2.04 and 16.42±2.00 as compared to H1 mM 37.46±2.04 and 49.97±2.02 and H2 Mm 36.42±1.82 and 32.46±2.04 (Figure 8). Sodium Na⁺ concentration were increased in H0 100 mM 47.87±2.11, and 41.87±2.11, H0+H1 mM 37.76±2.00 and 41.27±2.00 and H0+H2 mM 50.04±2.01 and 43.02±2.00. The chloride Cl^- concentration was increased in H0 100 mM 91.93±2.13 and 85.23±2.11, N0+H1 mM 53.36±2.03 and 48.96±2.02, and H0+H3 mM 71.98±2.09 and 62.52±2.28 as compared to CK 23.65±2.14 and 25.65±2.76. In SO₄^2- concentration was decreased in H0 100 mM 8.20±0.95 and 7.95±0.42, H0 + H1 mM 10.37±0.93, and 5.22±0.53, and H0+H2 mM 15.95±0.54 and 10.83±0.44 as compared to CK 14.43±0.75 and 16.45±0.23 (Figure 4). In NO₃^- concentration was decreased in H0 100 mM 14.3±0.95 and 8.20±0.78, H0+H3 mM 5.57±0.72 and 1.16±0.73.

4. Discussion

Urban sludge and chicken manure contain nutrient elements and organic materials needed for crop growth and development, which can promote their growth and development when applied into soil. However, they also contain substances harmful to crops, resulting in crop growth and development retardation ²³. Maize, and soybean grew best when the ratio of sludge compost application was 10% and 5%, respectively, and the heavy metal content in grain was within the range of national food hygiene standards. The biomass of three maize varieties increased significantly after sludge application ²⁴. Used sludge as fertilizer to plant maize in the plot experiment, and the growth potential and yield of maize were significantly better than the control and fertilizer treatment ²⁵. Conducted a positioning experiment of winter wheat-summer maize rotation for 3 years, and the results showed that three kinds of sludge fertilizers had obvious effect on crop yield, which was equivalent to equal nutrient fertilizer ²⁶. The combined application of organic fertilizer and nitrogen fertilizer could increase the yield of spring wheat. The combined application of chicken manure and fertilizer at 4:6 could increase the yield of maize. The germination and growth of flax seeds were seriously inhibited when the amount of sludge was more than 25% ²⁷. Inhibited the emergence rate and root length of maize in different degrees after the application of sludge ²⁸. The increase of chicken manure dosage, the dry weight of wheat straw, and grain increased firs, and then decreased. The experimental study showed that with the application of municipal sludge, and different amounts of chicken manure to maize at seedling stage in potted plants, the plant height and shoot dry weight of each stubble were promoted, but the increasing amount was decreased continuously (Table 1). The root length of the second and third stubble was inhibited, especially the root length of the high quantity chicken manure treatment was significantly lower than that of the blank and municipal sludge treatment. This indicates that the roots of maize at seedling stage are more affected by the amount of urban sludge and chicken manure than the shoots, and the harmful substances will first exert inhibitory effect on the roots of maize at seedling stage. In the process of agricultural fertilization, the application amount of chicken manure should be controlled according to the growth status of the roots to ensure the healthy growth of crops. It also indicated that the effects of chicken manure and municipal sludge on maize growth at seedling stage decreased with the increase of the number of stubble, which may be related to the gradual migration and accumulation of some nutrient elements into the crop.

Urban sludge and chicken manure contain a certain amount of heavy metals, which will affect the content of heavy metals in the soil ²⁹. The contents of heavy metals Cu, Zn, Pb and Cd in wheat grains treated with sludge compound fertilizer were increased, but they were all within the scope of national food hygiene standards. Application of sludge treatment significantly increased the content of heavy metals in wheat and maize grains ³⁰, studies on millet, maize and cabbage show that when the application rate of sludge reaches 240 T /hm2, the content of heavy metals in edible parts of plants does not exceed the standard ³¹. The pot experiment of calcareous soil that the change of heavy metal content in maize and rape crops at seedling stage was basically consistent with the change trend of heavy metal in soil, and both showed an upward trend with the increase of urban sludge application rate. The contents of Cu, Zn, Pb, Cr, Cd and As in the above ground part of maize in the first crop seedling stage were lower than those in the underground part, and the contents of Cu, Zn, Pb, Cr and As in the upper part of the second crop rape plot were higher than those in the underground part. Other studies have shown ³². The chicken manure can reduce Zn content but increase Cu content in root of Chinese cabbage. Characteristics and safe agricultural utilization of municipal sludge in part of Shanxi Province in this study, quantitative municipal sludge, and different amounts of chicken manure were applied to three crops of potted maize. Compared to those without urban sludge, and chicken manure, the single application of municipal sludge significantly increased the Cu, and Zn contents in the upper and underground parts of maize in each crop stage, which was consistent with the above research results. Compared to the single application of municipal sludge, the application of municipal sludge and high amount of chicken manure could significantly reduce the Cu content in the lower part of maize, and the medium and high amount of chicken manure could significantly reduce the Zn content in the underground part of corn field at each seedling stage. The influence law of Cu, and Zn contents in shoot was not obvious. The main reason is that organic substances in chicken manure, and municipal sludge have a certain effects on the absorption, and accumulation of Cu and Zn. The specific influencing mechanism needs further experimental study.

The enrichment coefficient can reflect the absorption of heavy metals from the soil and their accumulation in the plant body, and the migration coefficient can reflect the migration of heavy metals from the roots to the shoot of the plant. Studies have shown that soil humus contains a variety of functional groups, which can fix heavy metals through adsorption, chelation, and complexion reactions, thereby reducing the availability of heavy metals to plants ^{33, 34}. Found that Zn is more easily absorbed by plants from soil and accumulated in plants, while Cu is easy to form organically bound states due to the strong affinity of soil organic matter for it, which reduces its bio availability. Organic matter promoted strong competitive adsorption on soil colloidal surface ³⁵. Thereby improving the desorption and dissolution capacity of Cu ions, promoting the migration of Cu ions to the rhizosphere, and increasing the bioavailability of Cu ^{36, 37, 38}. The Cu enrichment coefficient of Chinese cabbage in soil increased with the increase of chicken manure application, but the Zn enrichment coefficient was just the opposite. The transport coefficients of Cu and Zn in Chinese cabbage decreased with the increase of chicken manure application, and the effect on Zn was greater than that on Cu. The results of this study showed that compared with the single application of municipal sludge, the Cu and Zn enrichment coefficients of maize at each stubble seedling stage under the application of municipal sludge and low, medium and high amount of chicken manure decreased with the increase of chicken manure application rate, but the reduction of Zn enrichment coefficient was greater than that of Cu. The transport coefficient of Cu increased with the increase of chicken manure application rate, while the transport coefficient of Zn decreased with the increase of chicken manure application rate.

5. Conclusion

This study concludes that the response of Maize (Zea mays L.) Protein Starch Content, Municipal sludge and Different Chicken Manure on Calcareous Brown Soil Seedling stage, where Plant height, root length, above ground dry weight, and below ground dry weight reached the maximum values in H1 treatment (applying quantitative municipal sludge, and 60g/kg chicken manure), respectively. The grain starch content, grain protein content and grain protein yield at maturity stage was the highest at H2 and the lowest at CK. The effects of CK on soluble sugar, sucrose and starch contents of mature grains were not significant. There was treatments H2, and H3 significant interaction between the content of sucrose, and starch in the mature stage. Our findings indicated that the increase of chicken manure application rate relatively promoted the Cu absorption, and transport of maize at seedling stage, and reduced the difference of Cu and Zn absorption and transport of maize at seedling stage.

Acknowledgements

The authors are thankful to Research Funding Program for Returned Students in Shanxi Province (2013 - Focus 7) Key Scientific and Technological Projects of Shanxi Province (20130313007-3) for financial support of this study.

References