Practice and Exploration of Reducing Chemical Fertilizer Use in Bulk Vegetables

Practice and Exploration of Reducing Chemical Fertilizer Use in Vegetables

Authors: Liu Chunhua, Liu Zufeng

Abstract: Vegetables are crops with high fertilizer requirements. Due to their high yield, they take away a lot of nutrients from the soil, so fertilization is necessary to maintain the balance of soil nutrients. In response to the problems of declining cultivated land quality and low production-input efficiency of farmers caused by long-term excessive fertilization, experiments on different fertilization schemes and dosages were carried out on 7 kinds of vegetables in mountainous and plain areas, achieving the effects of moderate chemical fertilizer reduction, increased vegetable yield and increased farmers' income, providing a reference basis for the rational fertilization of vegetables.

Keywords: Vegetables; Chemical Fertilizer Reduction; Fertilization Recommendations

In 2017, under the guidance of Hubei Academy of Agricultural Sciences, Hubei Yishizhuang Agricultural Science and Technology Co., Ltd. carried out fertilization experiments and demonstrations on crops such as tomatoes, peppers, Chinese cabbages, radishes, cabbage balls, lettuces and baby cabbages in Changyang, Dangyang, Yicheng, Zhongxiang and other places. Through the comparison of different formulas and dosages, the effect of reducing pure nutrients by 2.2 - 25 kg per 667 m² of fertilization and reducing chemical fertilizers by 5.8 - 41%, but increasing the yield by 1.4 - 30.7% was obtained (see the following table).

The analysis of the results of the seven experiments comprehensively shows that: the combination of bio - organic fertilizer and special fertilizer is the best, with a yield increase of 4.3 - 30.7% compared with conventional fertilization; the combination of organic fertilizer and special fertilizer ranks second, with a yield increase of 3.5 - 19.3% compared with conventional fertilization; the organic - inorganic vegetable fertilizer ranks third, with a yield increase of 2.7 - 13.7% compared with conventional fertilization; the special vegetable fertilizer ranks fourth, with a yield increase of 1.2 - 19.3% compared with conventional fertilization; the yield of conventional fertilization is the lowest (see the following table).

I. Current Situation of Vegetable Fertilization

1.Prevalence of Blind Fertilization
As can be seen from the table, farmers' customary fertilization generally has a high dosage. Usually, the amount of fertilizer applied per 667 m² is 150 - 250 kg, which is quite different from the growth needs of vegetables. An additional 5 - 25 kg of pure nutrients per 667 m² has no effect. Instead, it causes waste of resources, low economic benefits, and excessive phosphorus enrichment affects the soil ecology. For rational fertilization in vegetable production, a 10 - 20% reduction in fertilizer can lead to no yield reduction or even an increase in yield.

2.Habit of Pursuing High Content and Ignoring Rational Formulation
Regardless of whether it is in mountainous or plain areas, farmers blindly pursue compound fertilizers with equal NPK ratios of 45%, 48%, 51%, or even 54%, believing that the higher the content, the better the effect. In fact, the demand for NPK in crop growth is not an equal relationship [1]. Different crops have specific requirements. Rational formulation based on the fertilizer - demand characteristics of each crop, and using special fertilizers for crop production has the best effect. Medium - concentration fertilizers can completely replace high - concentration fertilizers with equal nutrients, relatively increasing farmers' income.

3.Underestimating the Role of Organic Fertilizers
With the continuous reduction of farmyard manure resources, most farmers continuously grow crops with chemical fertilizers and maintain yields by continuously increasing the dosage. They have insufficient understanding of commercial organic fertilizers. Unlike nitrogen fertilizers, which have an immediate and intuitive effect, they fail to see the role of increasing the application of organic fertilizers in improving the soil, multiplying beneficial soil organisms, and improving fertilizer utilization [2]. Applying only organic fertilizers requires too much investment from farmers, and applying only chemical fertilizers damages the soil ecology. Only by using organic fertilizers and chemical fertilizers in combination can the yield be continuously increased, chemical fertilizers be reduced, and a virtuous cycle of the soil ecology be promoted.

4.Ignoring the Supplementation of Medium and Trace Elements
Crop growth requires a variety of nutrient elements, which are irreplaceable and indispensable. These elements are taken away from the soil by plant harvest and must be artificially applied to supply crop growth and maintain soil nutrient balance. Different crops have different demands for medium and trace elements [3]. Special fertilizers for each crop incorporate sensitive elements according to their nutritional characteristics, which have a special yield - increasing effect. Therefore, the promotion of special fertilizers is advocated.

II. Changing Traditional Fertilization Concepts

Continuous vegetable cultivation has led to a serious imbalance in soil nutrients, 加剧了酸化，hindered biodiversity, and made pests and diseases occur frequently. Some plots can no longer be continuously cultivated. The key to treatment is to increase soil organic matter. By increasing the application of organic fertilizers, plant nutrients can be provided, crop growth and development can be promoted, soil structure can be improved, the water - and fertilizer - retaining capacity of the soil can be enhanced, the activities of soil microorganisms can be promoted, the energy and nutrients required by soil microorganisms can be supplied, the soil temperature can be increased, and soil pollution can be eliminated [4]. Increasing the organic matter content in low - yield fields can fertilize the soil and improve the soil fertility level. For high - yield fields, due to the continuous decomposition of organic matter, continuous supplementation is also required. Humus can form complexes or chelates with phosphorus, iron, and aluminum ions, avoiding the precipitation of insoluble phosphates and increasing the amount of available nutrients. Continuous use can gradually restore soil fertility. At the same time, vigorously promote the combined use of organic fertilizers and special fertilizers, replace high - concentration compound fertilizers with special fertilizers, supplement medium and trace elements, achieve a reasonable reduction in chemical fertilizers, restore and enhance soil fertility, and reduce costs and increase efficiency for farmers.

III. Vegetable Fertilization Countermeasures and Suggestions

Reducing chemical fertilizers in vegetable cultivation is a systematic project. It is impossible to do without chemical fertilizers, and blind reduction is also not feasible. The reduction of chemical fertilizers can only be achieved by reducing the excessive amount due to unreasonable formulation, the excessive amount applied due to blind fertilization, and the amount of soil nutrients utilized by the transformation of organic fertilizers [5], so as to achieve no yield reduction or even yield increase while reducing fertilizers. The core of vegetable fertilization is to formulate a formula according to the growth needs of crops, so as to supplement what is lacking and use the right amount according to the deficiency. Based on practical tests, three schemes are recommended for each type of vegetable [6], for reference only.

1. Fertilization Suggestions

(1) Radish: Nitrogen application rate is 15 - 18 kg/667m², total nutrients NPK 30 - 35kg/667m²

A. 50kg of 15% bio - organic fertilizer + 70 - 80kg of 35% special vegetable fertilizer

B. 50kg of 6% organic fertilizer + 80 - 90kg of 35% special vegetable fertilizer

C. 100 - 115kg of 30% organic - inorganic special vegetable fertilizer

(2) Chinese Cabbage: Nitrogen application rate is 17 - 19 kg/667m², total nutrients NPK 35 - 40kg/667m²

A. 50kg of 15% bio - organic fertilizer (9 - 2 - 4:25) + 80 - 90kg of 35% special vegetable fertilizer (18 - 5 - 12)

B. 50kg of 6% organic fertilizer (1 - 1 - 4:45) + 90 - 100kg of 35% special vegetable fertilizer (18 - 5 - 12)

C. 110 - 120kg of 30% organic - inorganic special vegetable fertilizer (16 - 5 - 9:15)

(3) Cabbage Ball: Nitrogen application rate is 16 - 18kg/667m², total nutrients NPK 28 - 32kg/667m²

A. 50kg of 15% bio - organic fertilizer (9 - 2 - 4) + 70 - 80kg of 35% special vegetable fertilizer

B. 50kg of 6% organic fertilizer + 90 - 100kg of 35% special vegetable fertilizer (18 - 5 - 12)

C. 100 - 120kg of 30% organic - inorganic special vegetable fertilizer (16 - 5 - 9)

(4) Pepper: Nitrogen application rate: 18 - 21kg/667m², total nutrients NPK 50 - 55kg/667m²

A. 50kg of 15% bio - organic fertilizer + 100 - 110kg of 40% sulfur - potassium - type special fertilizer (30% of compound fertilizer as top - dressing)

B. 50kg of 6% organic fertilizer + 110 - 120kg of 40% sulfur - potassium - type special fertilizer (16 - 8 - 16) (30% of compound fertilizer as top - dressing)

C. 50kg of 6% organic fertilizer + 120 - 130kg of 40% sulfur - potassium - type special fertilizer (15 - 5 - 20) (30% of compound fertilizer as top - dressing)

(5) Tomato: Nitrogen application rate 25 - 28kg/667m², total nutrients NPK 55 - 60kg/667m²

A. 50kg of 15% bio - organic fertilizer + 120 - 140kg of 40% sulfur - potassium - type special fertilizer (30% of compound fertilizer as top - dressing)

B. 100kg of 6% organic fertilizer + 130 - 150kg of 40% sulfur - potassium - type special fertilizer (16 - 8 - 16) (30% of compound fertilizer as top - dressing)

C. 100kg of 6% organic fertilizer + 130 - 150kg of 40% sulfur - potassium - type special fertilizer (15 - 5 - 20) (30% of compound fertilizer as top - dressing)

(6) Lettuce: Nitrogen application rate 22 - 25kg/667m², total nutrients NPK 35 - 40kg/667m²

A. 50kg of 15% bio - organic fertilizer + 90 - 100kg of 35% vegetable fertilizer

B. 80kg of 6% organic fertilizer with bacteria + 100 - 110kg of 35% vegetable fertilizer

C. 150kg of 30% organic - inorganic vegetable fertilizer

(7) Baby Cabbage: Nitrogen application 22 - 25kg/667m², total nutrients NPK 35 - 40kg/667m²

A. 50kg of 15% bio - organic fertilizer + 90 - 100kg of 35% vegetable fertilizer

B. 50 - 80kg of 6% organic fertilizer + 90 - 100kg of 35% vegetable fertilizer

C. 130 - 140kg of 30% organic - inorganic vegetable fertilizer

2. Promote Water - Soluble Fertilizers Containing Humic Acid

In recent years, the rapid development of protected vegetable cultivation and alpine rain - shelter cultivation, along with the continuous improvement of irrigation facilities, has laid a foundation for more accurate and scientific fertilization. The application of water - soluble fertilizers is an important measure to reduce chemical fertilizers and improve fertilizer utilization efficiency.
Water - soluble fertilizers containing humic acid are highly efficient water - soluble fertilizers that combine organic and inorganic components. They can not only meet the crop's demand for nitrogen, phosphorus, and potassium but also timely supplement the organic carbon nutrients required by crops [7]. They are completely water - soluble with no residue, suitable for various drip - irrigation and sprinkler - irrigation equipment, without clogging the nozzles, and have a quick - dissolving and fast - acting effect. They contain rich organic matter components, which can improve the soil's water - and fertilizer - retaining capacity, increase the soil's granular structure, and improve soil compaction.

(1) Fertilization Schemes for Tomatoes and Peppers in Protected Vegetables

Scheme 1: 3 - 5 days after transplanting, root - apply twice with diammonium phosphate (2.5 kg/667m²) + potassium fulvate (3 kg/667m²) dissolved in 3000 kg of water, with an interval of 5 - 7 days. 10 - 15 days later, root - apply once with 20 - 20 - 20 (3 kg/667m²) + potassium fulvate (3 kg/667m²) dissolved in 2500 kg of water. 7 days later, flush - apply with high - calcium and magnesium (2.5 kg) once. One week later, root - apply twice with 20 - 20 - 20 (3 kg/667m²) + potassium fulvate (3 kg/667m²) dissolved in 3000 kg of water, with an interval of 10 days. Before flower bud differentiation, root - apply or foliar - spray 9 - 45 - 15 (2.5 kg/667m² for root - application or 500 g/667m² for foliar - spraying) twice, with an interval of 3 - 5 days. During the fruit - swelling period, flush - apply 10 - 6 - 42 (5 kg/667m²) + potassium fulvate (3 kg/667m²) 5 - 6 times, with an interval of one week.
Scheme 2: 3 - 5 days after transplanting, root - apply twice with F12 (17 - 17 - 17) 3 kg/667m² dissolved in 3 tons of water, with an interval of one week. 15 days later, root - apply three times with F12 (17 - 17 - 17) 5 kg/667m² dissolved in water. Add 3 kg/667m² of high - calcium and magnesium when applying fertilizer for the second time. Before flower bud differentiation, root - apply or foliar - spray 9 - 45 - 15 (2.5 kg/667m² for root - application or 500 g/667m² for foliar - spraying) twice, with an interval of 3 - 5 days. During the fruit - swelling period, root - apply 4 - 5 times with F12 (15 - 8 - 30) 5 kg/667m² dissolved in 3 tons of water, with an interval of one week.

(2) Vegetables with Appropriate Irrigation Conditions

Water - soluble fertilizers containing humic acid are suitable for drip - irrigation, sprinkler - irrigation, soil - watering, and foliar - fertilization.

Drip - irrigation and Sprinkler - irrigation: Focus on the principle of applying small amounts multiple times, with a dosage of 5 - 10 kg/667m². Dilute it 350 - 1000 times, for a total of 2 - 3 times.

Soil - watering: When watering or irrigating the soil, mix it into the irrigation water in advance, with a dosage of 5 - 10 kg per 667m².

Foliar - fertilization: Dilute it about 800 - 1000 times. Spray it once every 7 - 10 days during each growth stage of the crop, for a total of 2 - 3 times.

3. Gradually Treat Soil Acidification

To treat soil acidification, start with increasing the application of organic fertilizers. Apply more farmyard manure and plant green manure. Use commercial organic fertilizers to increase soil organic matter, regulate soil physical and chemical properties, and intermittently apply lime and calcium carbonate powder [8]. Generally, apply 75 - 100 kg of lime per 667m², with an interval of 1 - 2 years. Apply about 100 kg of calcium carbonate powder per 667m², which can be used continuously. Excessive application will affect soil biological activities. Gradually achieve the reduction of chemical fertilizers and overcome soil acidification.
References:

[1] Ma Guorui. 200 Questions on the Efficient Application of Chemical Fertilizers. Beijing: China Agriculture Press, 1998.

[2] Zhao Yitao. Soil and Fertilizer Science. Beijing: China Chemical Industry Press, 2009.

[3] Zhang Zhenxian. Vegetable Cultivation. Beijing: China Agriculture Press, 2003.

[4] Qin Fu. 200 Questions on Improving the Efficiency of Chemical Fertilizer Use. Beijing: China Agriculture Press, 1998.

[5] Wang Xiaoxue. Rational Fertilization for Vegetables. Beijing: China Agriculture Press, 1997.

[6] Huang Deming. Formula Fertilization for Vegetables. Beijing: China Agriculture Press, 2001.

[7] Gao Xiangzhao. A Practical Manual of Fertilizers. Beijing: China Agriculture Press, 2002.

[8] Shen Qirong. General Theory of Soil and Fertilizer Science. Beijing: Higher Education Press, 2001.