1、Optimizing the nitrogen application rate for maize and wheat based on yield and environment on the Northern China Plain

Taking the wheat-maize rotation cropping system on the North China Plain as a case study, we quantified the variation of N application rates when targeting constraints on yield, economic performance, N uptake and N utilization, by conducting field experiments between 2011 and 2013.

2、Effects of nitrogen fertilizer rates and ratios of base and topdressing on wheat yield, soil nitrate content and nitrogen balance

In order to explore the optimal regime of nitrogen fertilizer application suitable for environment and economy, a field experiment on the different rate and ratio of base and topdressing of nitrogen fertilizer at the different growth periods of winter wheat was conducted.

3、Effects of topdressing with nitrogen fertilizer on wheat yield, and nitrogen uptake and utilization efficiency on the Loess Plateau

Abstract Studies from various countries show that topdressing with nitrogen fertilizer can effectively increase winter wheat grain yields. However, information on its effects on wheat yields on the Loess Plateau in China is scarce.

4、Requirement of nitrogen, phosphorus and potassium fertilizers for wheat cultivation under irrigation by municipal wastewater

This study was therefore designed to determine the optimum dose of the three major nutrients: nitrogen, phosphorus and potassium for wheat cultivation under irrigation by municipal wastewater.

Increased Dryland Winter Wheat Yields by Nitrogen Fertilizer Topdressing and its Relationship to Soil Moisture, Available N, P and K in Northwestern China

The findings also suggested that it is not necessary to analyze soil for ammonium-N, available P and K before topdressing N fertilizer. It is necessary to analyze 0–60 cm soil profile for nitrate-N and 40–100 cm depth for soil moisture before topdressing N fertilizer for winter wheat in dryland areas of northwestern China.

Nitrogen Fertilizer Management in Dryland Wheat Cropping Systems

Timely and efficient rates of nitrogen (N) application are vital for increasing wheat grain yield and protein content, and maintaining environmental sustainability.

Tailoring NPK fertilizer application to precipitation for dryland winter wheat in the Loess Plateau

The fertilizer sources were urea, superphosphate (12% P 2 O 5) or triple superphosphate (46% P 2 O 5), potassium sulphate (50% K 2 O) or potassium chloride (60% K 2 O). All the fertilizers were broadcast and incorporated into top 20 cm soil at sowing.

The effect of fertilizer placement on nitrogen uptake and yield of wheat and maize in Chinese loess soils

In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha −1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N.

Effects of nitrogen applications on soil nitrogen balance and nitrogen utilization of winter wheat in a rice–wheat rotation

For topdressing ratio, a number of studies have showed that topdressing applications increased grain yield, N fertilizer recovery and N efficiency compared to basal applications (Limaux et al., 1999, López-Bellido et al., 2005).

Full article: Excessive nitrogen application decreases grain yield and increases nitrogen loss in a wheat–soil system

The objectives of this present study were therefore to determine effects of N application rates on distribution of nitrogen derived from basal and topdressing 15 N in a soil–plant system, and to estimate optimal rate of N application to winter wheat in high-yielding fields for sustainable and environmentally friendly crop production practices.

Wheat, as one of the world's most important food crops, has critical nutrient demands during its growth. Nitrogen (N) and phosphorus (P) fertilizers are two essential inputs that play irreplaceable roles in wheat production. Their rational application not only boosts yields but also improves soil health and quality. Below is a detailed guide on the appropriate dosages and precautions for combining N and P fertilizers during wheat topdressing.

I. Role and Application of Nitrogen Fertilizer

1. Key Functions of Nitrogen Fertilizer

• Nitrogen is a vital nutrient for plant growth, supporting amino acid synthesis, cell division, and tissue development. During early growth stages, it promotes tillering, leaf expansion, and disease resistance.
• It aids protein synthesis, crucial for grain formation, as proteins constitute a major component of wheat seeds.
• Nitrogen regulates metabolic processes such as photosynthesis and respiration, influencing overall plant physiology.

2. Application Rates

• Dosage varies based on soil fertility and production goals. A typical recommendation is 5–10 kg of urea per mu (~0.067 hectare). This balances crop needs while minimizing excess fertilization risks.
• Use stratified application (base fertilizer followed by topdressing) to reduce soil compaction and nutrient loss.
• For high-yield fields or low-fertility soils, increase N slightly but avoid overapplication to prevent resource waste and environmental harm.

II. Role and Application of Phosphorus Fertilizer

1. Key Functions of Phosphorus Fertilizer

• Phosphorus drives energy transfer and transport within plants. It strengthens root development, enhancing water and nutrient uptake.
• It supports sugar and fat synthesis, improving grain quality and yield.
• Phosphorus improves soil structure, increasing water retention and aeration, which boosts soil productivity.

2. Application Rates

• A standard dose is 1–2 kg of superphosphate per mu, adjusted according to soil conditions.
• Apply using stratified methods to minimize soil compaction and runoff.
• On high-yield or poor-fertility fields, adjust P dosage cautiously to avoid waste or environmental issues.

III. Combined Application of Nitrogen and Phosphorus

1. Benefits of Combined Use

• Synergistic effects: N and P complement each other, promoting root growth, nutrient absorption, and soil health.
• Enhanced soil structure: Improved water retention, aeration, and microbial activity.
• Reduced loss: Minimizes leaching and gas emissions, lowering costs and environmental impact.

2. Precautions

• Balanced ratio: Maintain an approximate 1:1 N-to-P ratio to avoid nutrient imbalances.
• Avoid overapplication: Excess N causes excessive vegetative growth, while excess P leads to soil compaction or salinization.
• Quality matters: Use high-grade fertilizers to prevent contamination and ensure efficacy.
• Monitor crop response: Adjust dosages if plants exhibit stunted growth, yellowing, or nutrient deficiencies.
• Irrigation management: Pair fertilization with proper watering to prevent waterlogging or drought stress.
• Tailor to crops and practices: Adapt rates for crop types (e.g., wheat vs. other grains) and planting methods (direct seeding vs. transplanting).
• Integrated practices: Combine with organic fertilizers, crop rotation, and optimal plant density to maximize results.
• Climate and season: Adjust timing and dosage based on weather patterns and growth stages.
• Pest and disease control: Strengthen monitoring to mitigate risks from pests or diseases exacerbated by nutrient imbalances.
• Soil health: Regularly test pH, organic matter, and micronutrient levels to refine fertilization strategies.
• Economic efficiency: Optimize costs without compromising yield or sustainability.

Rational use of N and P fertilizers is vital for wheat productivity. By following scientific application methods and adaptive management, farmers can achieve high yields while promoting soil health and agricultural sustainability.