Biochar In PH Nitrate Leeching And Vegetable Growth Biology Essay

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The hypothesis tested out in this study was that Biochar will increase the growth of plants, increase nitrate retention, and maintain a pH level of 6.5 to 7.0 when added as % of the mass of soil. 5 pots were used, with the control as regular soil, one with fertilizer, and 3 with 10%, 30%, and 50% each. Chive was grown from seed for a period of 9 weeks, from November 15th to January 10th. A 17-30 gram sample of each soil was taken each week, placed in a boat dish, and water was poured onto it. A test tab to measure nitrate level and another test tab to measure the pH was used to collect the data.

Biochar decreased the amount of nitrate leached; however the amount of Biochar did not influence the retention process significantly. Also, it decreased the soil pH to a range of 6.5 to 7.

It is concluded that Biochar has enhancing impacts on nutrient retention and soil pH, although it is not significant. Also, it yields a notably larger plant than regular fertilizers.

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Intro

Gardening has always been a prominent hobby and pastime for a vast number of people. For these avid horticulturalists and gardeners, a fertile, well-growing soil is ideal. A recent botanical finding, a carbon-rich charcoal substance named Biochar, has emerged to be a satisfying addition to regular soils to enhance its fertility. Biochar has been inspired by Terra preta, a Brazilian soil that was created when Native Americans incorporated charcoal into their soils. Made of charcoal, this revolutionary amendment has been used in traditional agriculture as well as gardening in modern days, with accumulating evidence to prove its singularity among soil enhancements.

There are two major soil benefits of Biochar: high nutrient affinity and high persistence of Biochar. In this study the former was tested by observing the retention of nutrients that are essential to plant growth and soil pH, which has a significant impact on nutrient availability. Biochar is able to retain nutrients due to its porous nature and high surface area. Different pore-size classification system makes it hard to compare Biochar porosity to that of soil, and pore sizes of Biochar depend upon the parent material, production method, and conditions. However, activated Biochar is 95% composed of micropores (<2 x 10-3 um). They account for nutrient retention by trapping nutrient-containing water in them, which limits the mobility of soil water through the soil. By trapping a considerable volume of this water, the nutrients dissolved in it will remain close to the soil surface and plants will gain greater accessibility to these nutrients. In addition, Biochar has low surface oxidation and is hydrophobic, allowing them to absorb organic particles like nutrients in hydrophobic molecules such as nitrogen.

There are sixteen essential nutrients for plant growth. Of those, the mineral nutrients are divided into macronutrients and micronutrients. Nitrogen belongs to the primary macronutrient group, along with phosphorus and potassium. These three are consumed in large amounts by plants for their growth and survival. Nitrogen can be found in multiple "fixed" forms such as ammonium (NH4+) and nitrate (NO3-), where the nitrogen is incorporated into compounds. Nitrogen is essential to plant life for it is a basic constituent of proteins. Enzyme systems reduce nitrate into nitrite and then ammonium, which produces amino-nitrogen that combines with an organic acid created from carbohydrate metabolism to produce amino acids. In the process nitrate assimilation, nitrite reductase enzymes reduces nitrate into nitrite during the catalysis of nitrite reduction. Then, nitrite breaks down again to ammonia by nitrite reductase. This ammonia is incorporated into glutamine during the glutamine synthetase process. Then along with 2-oxoglutalate, which is a product from various synthase that rise from the calvin cycle of photosynthesis, it forms 2 molecules of glutamate in the process glutamate synthase. Glutamate (proteinogenic amino acid) is one of the amino acids that can be found in proteins

http://www.isb.vt.edu/news/images/sep0401-2.jpg

Nitrogen assimilation in plants. Abbreviations: 2-OG, 2-oxoglutarate. Several key enzymes are also indicated by abbreviations: GS, glutamine synthetase; GOGAT, glutamate synthase; NIA, nitrate reductase. [Image from Ref. 4 Copyright Proceedings of the National Academy of Sciences, USA.].

In fertilizers, nitrogen is incorporated in ammonium nitrogen (NH4+) and is quickly converted to nitrate when added to soil. Because nitrate is negatively charged, and because soil particles are mostly negatively charged, it can stay in the soil and move with water. Thus nitrate has the potential to leach out with excessive rain. This characteristic was used to measure retention of nitrogen. By measuring the amount of nitrate available in the soil water, the ability of Biochar to keep and supply nitrogen to the plant could be estimated. The lower the concentration of nitrate indicated higher retention capability.

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Soil pH, the measure of acidity or alkalinity of soil, is another soil property and is closely linked to the availability of nutrients. In order for nutrients to be consumed by plants, it must be dissolved in the soil solution first. Numerous studies prove that Biochar increases pH in acidic soils. This is due to the concentration of alkaline metal oxides such as Ca2+ Mg 2+ and K+ that exist in the Biochar and a decrease in the concentration of soluble soil Al3+.

Soil pH also impacts plant growth if it is too acidic. Beneficial microorganisms such as bacteria that decompose soil organic matter are hindered in their activity. Thisresults in the accumulation of organic matter in the soil, and the nutrients in the matter, particularly nitrogen, cannot be released into the soil and thus cannot be used by the plant. For example, autotrophic nitrifying bacteria are favored by less acidic soil conditions. Thus Biochar is able to maintain the ideal, slightly acidic pH range for plants.

Data

Week 1 11/5

Nitrate

pH

Height

Mass

Control

10

8

n/a

5.2

Fertilizer

0

8

n/a

4.4

10%

2

7

n/a

5.7

30%

2

8

n/a

4.9

50%

0

8

n/a

5.7

Week 2 11/22

Nitrate

pH

Height

Mass

Control

10

8

n/a

25.3

Fertilizer

2

7.5

1.41 cm

21.4

10%

2

7

n/a

22.5

30%

0

8

n/a

24.5

50%

0

8

n/a

20.9

Week3 11/29

Nitrate

pH

Height

Mass

Control

2

7.5

1.84

24.2

Fertilizer

10

7

1.54

24.1

10%

2

7

2.35

20.1

30%

0

7.5

2.12

22.1

50%

0

7

1.00

22.5

Week4 12/6

Nitrate

pH

Height

Mass

Control

10

6.5

2.01

26.71

Fertilizer

2

6.5

2.00

25.22

10%

0

7.0

2.89

24.18

30%

0

7

2.68

22.26

50%

0

7.5

1.06

20.39

Week 5 12/13

Nitrate

pH

Height

Mass

Control

2

6.0

2.83

25.8

Fertilizer

10

6.0

2.46

31.6

10%

0

7.0

3.83

29.8

30%

0

6.5

3.36

25.69

50%

0

6.5

1.34

31.5

Week 6 12/20

Nitrate

pH

Height

Mass

Control

2

6.5

3.42

25.6

Fertilizer

2

6.5

2.91

24.7

10%

0

6.5

4.83

28.1

30%

0

7.0

4.92

24.8

50%

0

7.0

2.61

26.3

Week7 12/27

Nitrate

pH

Height

Mass

Control

2

6.0

5.36

26.1

Fertilizer

10

6.5

4.18

23.6

10%

2

7.0

6.85

20.6

30%

0

7.0

6.52

27.4

50%

0

6.5

4.81

24.5

Week 8 1/3/11

Nitrate

pH

Height

Mass

Control

10

6.0

10.09

24.53

Fertilizer

2

6.0

7.21

23.64

10%

2

7.0

7.24

26.89

30%

0

7.0

11.72

24.29

50%

0

7.5

6.35

21.28

Week 9 1/10/11

Nitrate

pH

Height

Mass

Control

2

6.5

19.32

18.52

Fertilizer

0

6.0

7.42

19.65

10%

0

7.0

10.11

19.83

30%

0

7.0

22.53

18.99

50%

0

7.0

7.54

17.72

Data work up

The pH starts about 7-9 and decreases to 6-7 and becomes more stable by end of December/beginning of January.pH of the control is slightly lower, staying from 6 to 6.5, while Biochar plants range from 6.5 to 7.5.

All the plants in each pot begin with slow growth but rapidly increases later, especially for 30% and control, although 30% remains higher throughout the trial. 50% and fertilizer are the slowest in growth, not surpassing 10 cm. 10% experiences moderate growth.

50% and 30% remain low for the vast majority of the trial, staying at 0. 10% also stays low, shifting from 2 to 0. However the control and fertilizer shift back and forth from 10 to 2 and remain as the two highest pots with nitrate leeching.

Average height

Control: 4.99 cm

Fertilizer: 3.24 cm

10%: 4.23 cm

30%: 5.98 cm

50%: 2.75 cm

Average leeching

Control: 5.6 ppm

Fertilizer: 4.2 ppm

10%: 1.1 ppm

30%: .22 ppm

50%: 0 ppm

Discussion

There was no significant change in pH, although Biochar ones had higher pH (0.5 to 1). 50% had the least amount of leaching with the no nitrate leeched out, followed by 30% (0.22 ppm) and then 10% (1.1ppm). 30% grew the most, with average growth of 5.98 cm during the period of growth. Larger amount of Biochar means a more porous soil, which results in a greater amount of retention. This accounts for such a low amount of leeching as the amount of Biochar increases.

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The small amount of height growth in 50% may be because 50% of Biochar may mean that there is a lack of soil in the composition and too much charcoal, which hinders plant growth. This may be why the control grew more than 50%; it has the necessary nutrients. Biochar has high retention rate but it doesn't have much nutrient content in itself. Thus there must be enough soil for plants to actually obtain nutrient in. It is shown that 30% is the adequate amount of Biochar to be added without severely reducing soil available to plants and showing noticeable improvements. The high growth of 30% also can be attributed to the high retention of nitrogen, which allows them to be used for protein production. The Biochar composition did not affect much pH, which may be because the control soil wasn't made specifically acidic. It was normal soil, and Biochar's effect may not have been portrayed fully because of it. Thus the ineffective result shouldn't indicate directly to Biochar but the conditions set up by the experiment.

When data was compared with the fertilizer, it had much more leeching than Biochar and its pH was a little more acidic if not about the same. This indicates that doesn't have a significant impact in bringing the pH up in alkalinity, as with the control. However, it maintained a pH of 6.5 to 7.0, which is the ideal pH for plant growth. In terms of pH, there's no reason why Biochar should be preferred over regular fertilizers. The fertilizer had 536% more leeching and average height growth of Biochar-enhanced plants was 33% higher than that of fertilizers. This shows that Biochar is a better soil amendment than regular fertilizers.

Errors may have been created due to the limited range of nitrate concentration and pH levels. These were not specific enough, so a more scrupulous measurement wasn't available. This affects the magnitude of difference in the data results. Instead of 2 or 10, there could've been intermediate concentrations of nitrates that could be found. So instead of finding that 50% didn't have any leeching, we can see that very little leeched out, which would be more reliable. Also, not have such a weird looking graph.

Also, due to the fact that the plants were grown in winter, which is not a fruitful season, the growth of chives could have been inhibited and the best, most accurate results may not have been produced. Further investigation using acidic soil in spring or summer will provide more accurate results by giving a better setting to produce a more significant result.

Conclusion

There was a slight increase in pH (.5-1), for Biochar-amended soils, although the improvement wasn't significant and wasn't better for the soil when compared to control and fertilizer. 50% had the least amount of leeching, with average of 0 ppm of nitrate leeched out to water, compared to 30% grew the most with average of 5.98 cm growth, compared to 2.75cm for 50%, 4.23cm for 10%, 5.6 cm for control, and 3.24 cm for fertilizer. 30% of Biochar by mass was proven to be the most adequate amount to add.