Application effects of humic acid fertilizer on “Tieguanyin” tea plants

CHEN Xue-tao, KONG Qing-bo, Zhang Qing, Zhang Ming-qing, LI Juan
(Institute of Soil and Fertilizer, Fujian Academy of Agriculture Science, Fujian Province)

Abstract: Effects of different fertilizer amount and fertilizer application frequency on tea leaves output, one-hundred-bud weight, budding density and soil physical and chemical properties by applying organic fertilizer of humic acid in tea garden were studied. The results showed that the tea leaves output increased with the increase of the applying dosage of humic acid fertilizer, the increased range was 4.32%-12.62%. In addition, applying humic acid fertilizer could increase budding density and one-hundred-bud weight of tea plant, and improve the soil PH value 4.50%-14.19%. Basing on the results, it is suggested that, application amount of humic acid fertilizer was 40kg/667m2 (600kg/ha) in single application.

Key words: Humic acid fertilizer; Tea plant; Effect

The world famous “Hometown of Chinese Oolong Tea” – Anxi, where has tea plantation of 40,000 hm2, annual tea output of 60,000 tons and total annual output value relates to tea plantation reaches up to 9.5 billion RMB. It is also the cradle of famous Tieguanyin, Huangjingui tea and has the China biggest tea wholesale market.

Due to a high economic profit of tea plantation, there is a common phenomenon that the tea farmers treat soil with excessive chemical fertilization, which caused serious soil acidification and hardening problems. The humic acid fertilizer, with multi-kinds active components, it’s a good soil conditioner and can enhance the water retention, nutrient uptake efficiency and promote the plant growth. This study will research how effect comes with tea plantation treated with humic acid fertilizer and the appropriate humic acid dosage to be applied.

1.Material and Methods

1.1 The testing situation

The test was taken place in Anxi, Fujian province, subtropical mild and humid climate, annual average temperature 18-21 ℃ with abundant rainfall, latosol soil with nutrient conditions: organic matter 6.5g/kg, alkali-hydrolyzable nitrogen 41.91 mg/kg, rapid available phosphorus 56.94 mg/kg, rapid available potassium 74.00mg/kg, PH value 4.4. The tea trees are 6 years age old. Humic acid fertilizer specification: humic dry basis: 50%, organic matter: 60%, K2O: 10%, PH: 8-10.

1.2 Testing treatment

The test is set with 9 treating methods:

(1) Chemical fertilizer (CF);
(2) Chemical fertilizer + humic acid fertilizer 5kg/667m2  (CF+T5);
(3) Chemical fertilizer + humic acid fertilizer 10kg/667m2  (CF+T10);
(4) Chemical fertilizer + humic acid fertilizer 20kg/667m2  (CF+T20);
(5) Chemical fertilizer + humic acid fertilizer 40kg/667m2  (CF+T40);
(6) Chemical fertilizer + humic acid fertilizer 80kg/667m2  (CF+T80);
(7) Chemical fertilizer + humic acid fertilizer 20kg/667m2, divided into 3 applications (CF+T20-3);
(8) Chemical fertilizer + humic acid fertilizer 40kg/667m2, divided into 3 applications (CF+T40-3);
(9) Chemical fertilizer + humic acid fertilizer 80kg/667m2, divided into 3 applications (CF+T80-3);

Each treatment is applied on 3 different random areas, each area is 30 m2

The Chemical fertilizer (NPK) is composed by urea 61kg/667m2, calcium superphosphate 100kg/667m2, and potassium sulfate 28kg/667m2. Fertilizing method: base dressing at the end of March, first top dressing after the spring tea harvest, second top dressing after summer tea harvest.

Chemical fertilizer applying ratio of each fertilizing stage: Base dressing 40% + first top dressing 30% + second top dressing 30%

For humic acid fertilizers which divided into 3 applications in treatment 7,8 and 9, the ratio is: Base dressing 50% + first top dressing 25% + second top dressing 25%

1.3 Sample collection and measurement

One-hundred-bud weight: random pick 100 tea bud with 3 leaves, weigh in total
Bud density: the bud number in area of 30cm x 30cm
Output: the tea weight by manual harvest
Nutrients: sampling 5 points covered in the soil depth of 0-20cms by ordinary tests

2. Results and analysis

2.1 The humic acid fertilizer effects on tea leaves output (Table 1).

The tea leaves output increased along with the applied humic acid fertilizer amount. The output has apparent increase of 9.56% and 10% respectively while applied humic acid fertilizer 40kg and 80kg. The humic acid fertilizer divided into 3 applications have a better but not apparent output than a single application. Take the labor cost into consideration, it is suggested to adopt the treatment method by 40 kg in a single application.

Table 1 the humic acid fertilizer effects on tea leaves output

Note: the output is calculated by measuring every 667m2

2.2, The humic acid fertilizer effects on tea bud density (Table 2).

It can be learned from table 2 that the tea trees applied with humic acid fertilizer get higher bud density than those applied chemical fertilizers only. The average bud density of 3 seasons increased 3.35-7.53%. The density increase along with the applied humic acid amount but didn’t reach an apparent level.

Table 2 the humic acid fertilizer effects on tea bud density

Note: the output is calculated by measuring every 667m2

2.3 The humic acid fertilizer effects on one-hundred-bud weight (Table 3)

The tea trees applied with humic acid fertilizer got different increase of one-hundred-bud weight, which ranges from 4.18%-11.96, and the highest value lies on the group with the highest amount of humic acid fertilizer divided into 3 applications. It has an apparent increase compared with the chemical fertilizer which demonstrated the humic acid fertilizer can increase the tea leaves thickness and improve the tea quality.

Table 3 The humic acid fertilizer effects on one-hundred-bud weight

2.4 The humic acid fertilizer effects on tea plantation soil nutrients

Due to the tea plantation had applied chemical fertilizers in a large amount year by year, it lead to the soil nutrients unbalance and had a low soil PH value, this could affect the tea tree roots growth and cause a low output and low quality of tea leaves. The humic acid fertilizer which is rich in organic matter, could improve the soil structure and adjust the PH value. It can be seen from Table 4 that the PH value increased apparently along with the applied humic acid fertilizer amount. The PH of the group applied 80 kg increased 14.19% comparing to applied chemical fertilizers only. The humic acid fertilizer with the feature of absorption can stabilize NPK nutrients and decrease the nutrients loss.

Table 4, The humic acid fertilizer effects on tea plantation soil nutrients

3. Conclusion

The humic acid fertilizer make Tieguanyin tea trees have apparent increase of tea leaves output, tea bud density, one-hundred-bud weight and soil PH value. The soil organic matter, nitrogen, phosphorous and potassium nutrients index are better but didn’t reach an apparent level than the group applied common chemical fertilizers only, this might be associated with the reason that the application is in a short time.The organic fertilizer acts slower than the chemical chemical fertilizers but it keeps longer effect. It is suggested to track the soil structure and physical properties regularly to have a long term study about humic acid fertilizer effect on soil.Take the labor cost into consideration, the suggested dosage of humic acid fertilizer on tea plantation is 40 kg/667m2 (600kg/ha) in a single application.