When selecting between organic fertilizers and chemical fertilizers, multiple factors need to be considered, including soil conditions, crop requirements, fertilizer efficiency characteristics, and environmental impact. Below is a detailed comparison and selection advice for organic fertilizers and chemical fertilizers.

I. Composition and Sources

1. Organic Fertilizers:

   • Composition: Contain a large amount of organic matter (40%-60%), multiple trace elements, and beneficial microorganisms.
   • Sources: Derived from the fermentation of animal and plant residues (such as manure, straw).

2. Chemical Fertilizers:

   • Composition: Only contain single or a small number of inorganic nutrients (such as nitrogen, phosphorus, potassium), with fixed nutrient ratios.
   • Sources: Made through chemical synthesis or mineral processing.

II. Fertilizer Efficiency Characteristics

1. Organic Fertilizers:

   • Nutrients are released slowly, with long-lasting fertility (months to years).
   • Nutrient concentration is low, requiring large amounts of application (e.g., 500-700 kg/mu).

2. Chemical Fertilizers:

   • Dissolve quickly, with short but intense fertility (weeks to months).
   • High nutrient content, requiring less application (e.g., urea contains 46% nitrogen).

III. Impact on Soil

1. Organic Fertilizers:

   • Increase soil organic matter, promote microbial activity, improve aggregate structure, and alleviate compaction.
   • Enhance soil long-term fertility, supporting sustainable agricultural development.

2. Chemical Fertilizers:

   • Long-term single application can lead to soil acidification and compaction.
   • Overuse can reduce soil self-regulation capacity and inhibit microbial activity.

IV. Environment and Agricultural Product Quality

1. Organic Fertilizers:

   • Good compatibility with the environment, low pollution risk.
   • Enhance agricultural product flavor and nutrition (e.g., increase tomato sweetness by 50%).

2. Chemical Fertilizers:

   • Easy loss can cause water eutrophication or soil salinization.
   • Excessive use may reduce quality and increase harmful residue.

V. Selection Advice

1. Based on Soil Conditions:

   • When soil organic matter content is low and structure is poor, prioritize organic fertilizers to improve soil.
   • When soil nutrients are lacking, select chemical fertilizers for rapid nutrient supplement.

2. Based on Crop Requirements:

   • During the initial growth stage of crops, when rapid nutrient supplement is needed, chemical fertilizers can be chosen.
   • During the middle to late growth stages of crops, when soil improvement and quality enhancement are more important, organic fertilizers can be selected.

3. Mixed Use:

   • Organic and chemical fertilizers have their own advantages and disadvantages. Mixed use can balance fertilizer efficiency and environmental protection needs.
   • Mixed use can reduce chemical fertilizer usage by 30%-50% and improve fertilizer utilization efficiency.

In summary, the choice between organic fertilizers and chemical fertilizers should be based on specific circumstances. In agricultural production, soil conditions and crop requirements should be prioritized, with organic and chemical fertilizers reasonably combined to achieve optimal fertilizer efficiency and environmental benefits.