The selection of organic fertilizers suitable for specific crops should be comprehensively judged based on the nutritional requirements of the crops, soil conditions, the characteristics of the organic fertilizers themselves, and planting goals (such as yield, quality, and ecological safety). The following are specific selection methods and practical suggestions:

1、 Core principle: Match the "nutritional needs" and "growth characteristics" of crops

There are significant differences in the types, proportions, and demand periods of nutrients among different crops. The selection of organic fertilizers requires a clear understanding of the crops "fertilizer profile":

1. Classified by crop type:

Leafy vegetable crops (lettuce, spinach, cabbage, etc.)

Core requirement: Quickly supplement nitrogen, promote fresh and plump leaves, moderate demand for phosphorus and potassium.

Suitable for organic fertilizers: high nitrogen composted poultry manure (chicken manure, duck manure) or compost (straw+poultry manure mixed composted). This type of organic fertilizer has a high nitrogen content (about 1.6% total nitrogen in chicken manure and about 1.1% in duck manure), and the release rate after decomposition is moderate, which can meet the short-term rapid growth needs of leafy vegetables.

Attention: Avoid using immature poultry manure (which can easily burn seedlings), and use a small amount of humic acid fertilizer to regulate the soil and prevent overgrowth.

Fruit and vegetable/berry crops (tomatoes, peppers, strawberries, watermelons, etc.)

Core requirements: Phosphorus is needed during the flowering period to promote flowering and fruit setting, potassium is needed during the fruit expansion period to promote fruit enlargement and enhance sweetness, and sensitivity to trace elements such as calcium and magnesium (lack of easily cracked fruits and navel rot).

Suitable for organic fertilizers: decomposed sheep manure, rabbit manure (with high phosphorus and potassium content, sheep manure total phosphorus is about 0.45%, total potassium is about 0.5%)+bone meal/fish protein organic fertilizer (supplementing phosphorus and calcium). Sheep manure has a mild thermal nature, is not easy to burn roots, and is rich in humus, which can enhance the flavor of the fruit; During the fruit expansion period, it can be combined with decomposed plant ash (which has a high potassium content and does not affect the taste of the fruit).

Root and stem crops (potatoes, radishes, yams, sweet potatoes, etc.)

Core requirements: High potassium promotes root/tuber enlargement, moderate phosphorus is needed to promote root development, and excessive nitrogen should be avoided (which can easily lead to excessive stem and leaf elongation and small underground parts).

Suitable for organic fertilizers: composted cow manure, pig manure (with low nitrogen content, cow manure total nitrogen is about 0.3%, high carbon nitrogen ratio)+straw compost (rich in cellulose, improves soil permeability, and facilitates root and stem enlargement). Can be paired with a small amount of gypsum (calcium supplement) to reduce root and stem deformities.

Fruit trees (apples, citrus, grapes, etc.)

Core requirements: Long term need for balanced nutrients (nitrogen, phosphorus, potassium+trace elements), emphasis on improving soil organic matter (maintaining tree vigor and fruit quality), and avoiding short-term excessive nitrogen (causing excessive branch growth and fruit discoloration).

Suitable for organic fertilizers: decomposed sheep manure, rabbit manure (long-term slow-release)+humic acid organic fertilizer (improves soil aggregate structure)+cake fertilizer (such as soybean cake, rapeseed cake, rich in amino acids after decomposition, enhances fruit sweetness). In autumn, sheep manure and straw compost are mainly used as the base fertilizer (to supplement carbon sources), while mature fish protein fertilizer (to supplement phosphorus and promote flowering) is used as the topdressing during the flowering period.

Medicinal plants (ginseng, wolfberry, Panax notoginseng, etc.)

Core requirements: Avoid residual fertilizers, use pure organic fertilizers (free of heavy metals and antibiotics), and pay attention to soil microecological balance (affecting the accumulation of effective ingredients).

Suitable for organic fertilizers: decomposed plant ash (pH adjusted)+earthworm castings (rich in probiotics and humic acid, high safety)+Chinese medicine residue compost (homologous nutrition, may enhance medicinal ingredients). Avoid using poultry manure (which may contain antibiotics) and prioritize organic certified fertilizers.

2. Divided by crop growth stage:

Seedling stage: requires a small amount of fertilizer but is sensitive, suitable for high maturity and mild organic fertilizers (such as earthworm castings and decomposed pig manure), to avoid high concentration organic fertilizers (such as undiluted cake fertilizers) causing seedling burning.

Flowering/fruiting period: It requires concentrated phosphorus and potassium, and is suitable for organic fertilizers with high phosphorus and potassium content (such as bone meal and decomposed sheep manure). It can be sprayed on the leaves with liquid organic fertilizers (such as fish protein liquid fertilizer) to quickly supplement nutrients.

After harvesting: It is necessary to supplement soil organic matter, restore soil fertility, and use organic fertilizers with high crude fiber content (such as straw compost and sawdust fertilizer) to slowly release nutrients and reserve fertility for the next season.

2、 Key basis: Select fertilizer according to soil conditions

The selection of organic fertilizer should be based on both soil remediation and adaptation to avoid a "mismatch between fertilizer and soil" that may compromise its effectiveness

The principle of action of suitable types of organic fertilizers for soil problems

Acidic soil (pH<5.5), plant ash, and calcareous organic fertilizers (such as shell powder compost). Alkaline organic fertilizers can neutralize acidity and raise pH to the suitable range for crops (most crops are suitable for pH 6.0-7.5)

Humic acid organic fertilizer and decomposed sawdust fertilizer (slightly acidic) in alkaline soil (pH>8.0) can reduce alkalinity, release organic acids during sawdust decomposition, and improve soil compaction

Sandy soil (poor fertilizer retention) with decomposed cow manure and pig manure (high clay content, strong fertilizer retention) increases soil colloids and enhances water and fertilizer retention capacity (cow manure has an organic matter content of about 15-20% and a long shelf life)

Viscous soil (with poor air permeability) forms pores after fiber decomposition of straw compost and mushroom residue fertilizer (containing coarse fibers), improving air permeability (straw compost can reduce soil bulk density by 10-15%)

Continuous cropping of soil (imbalanced microbial community) with organic fertilizers containing probiotics (such as EM decomposed compost) to supplement beneficial bacteria, inhibit soil borne diseases (such as Fusarium), and restore soil microecology

3、 Examining the Quality and Characteristics of Organic Fertilizer

There are significant differences in the quality of organic fertilizers of the same type, and they need to be screened through the following indicators:

1. Maturity level: must be "completely matured"

The hazards of immature organic fertilizers (such as fresh poultry manure and raw cake fertilizers): During the decomposition process, ammonia gas is released to burn roots, breed bacteria/insect eggs, consume soil oxygen, and cause root hypoxia.

Maturity judgment: the color is dark brown/black, without pungent odor (with a light earthy smell), loose texture, hands are not sticky, and pH is neutral to slightly acidic (6.5-7.5).

2. Nutrient content and proportion

View product testing report: Focus on the total content of total nitrogen, total phosphorus, total potassium (N+P ₂ O ₅+K ₂ O) (high-quality organic fertilizer ≥ 5%), organic matter content (≥ 30%), carbon nitrogen ratio (C/N) (ideal value of 15-25, too high will decompose slowly, too low will easily lead to nitrogen loss).

For example, organic fertilizers with lower C/N ratios (15-20) are selected for leafy vegetables (such as chicken manure compost), and organic fertilizers with higher C/N ratios (20-25) are selected for fruit tree base fertilizers (such as straw+cow manure compost).

3. Safety: Avoid "invisible pollution"

Testing for heavy metals (lead, cadmium, mercury, etc.), antibiotics, pesticide residues: When planting fruits, vegetables, and medicinal materials, products that meet the standards of "Organic Fertilizers" (NY525-2021) must be selected, and heavy metal limits must meet the standard (such as lead ≤ 50mg/kg).

Source safety: Prioritize the use of manure from large-scale breeding farms (with strict control), and avoid organic fertilizers made from industrial waste and sludge (which may contain unknown pollutants).

4、 Combining planting mode and cost

Greenhouse planting: It is necessary to control the salt content of organic fertilizers (to avoid secondary soil salinization), prioritize low salt organic fertilizers (such as earthworm castings and decomposed mushroom residue), and use less poultry manure (with higher salt content).