When we look at onion production, we know that healthy plant growth is closely linked to balanced nutrition. Nitrogen supports vegetative growth and leaf development, while sulphur contributes to protein and amino acid formation and has particular importance in onion quality.
For us, managing these nutrients together is an important part of a well-planned onion nutrition programme. Ammonium sulphate can provide both nutrients in one fertiliser, making it a useful option where soil and crop requirements indicate a need for additional nitrogen and sulphur.
Our Ammonium Sulphate contains 20.5% ammoniacal nitrogen and 23% sulphate sulphur. The product is intended for soil application during vegetative growth and early flowering and fruiting stages and is listed for vegetables and horticultural crops.
What Does Ammonium Sulphate Provide
When we use ammonium sulphate, we are supplying two important nutrients together.
Nitrogen supports the formation of proteins, enzymes and chlorophyll and contributes to vegetative growth.
Sulphur is required for the synthesis of amino acids, vitamins and enzymes. Together, these nutrients can support the plant’s nutritional needs during active growth.
We should, however, remember that the exact requirement depends on the crop, soil, weather and existing nutrient availability. Fertiliser application should therefore be based on the overall crop nutrition programme rather than on a single nutrient.
1. Supporting Healthy Onion Vegetative Growth
We begin with the vegetative stage because onion plants need to establish healthy leaves before moving into bulb development.
Nitrogen is particularly important during this phase because leaf growth determines the plant’s ability to build the canopy required for photosynthesis. Adequate sulphur also supports important metabolic processes within the plant.
Our Ammonium Sulphate provides a readily available source of both nitrogen and sulphur, and the company recommends its application during vegetative growth at 50 kg/acre.
2. Supporting the Transition Towards Bulb Development
As the onion crop develops, the focus gradually shifts from leaf production towards bulb formation and enlargement.
We need to maintain sufficient nutrition during this transition without treating nitrogen as the only requirement. A balanced nutrient programme should account for the crop’s changing needs and the availability of other essential nutrients.
Our crop-specific onion programme includes PROM and SSP at sowing, followed by Bio-NPK, Bio-ZSB, Power Gold/Tej and Bio-Zyme during the vegetative stage, and Bio-Potash and Power Gold/Tej during tuber formation.
This gives us an important reminder: ammonium sulphate can be considered as one nutrient source where appropriate, but it should fit into the wider onion nutrition programme rather than replace it.
3. Balancing Nitrogen and Sulphur
We often focus heavily on nitrogen because of its visible effect on plant growth. However, nitrogen and sulphur are closely connected through protein synthesis.
When sulphur availability is inadequate, the plant’s ability to use nitrogen efficiently can also be affected. Maintaining a suitable balance between the two nutrients is therefore important for overall crop nutrition.
With 20.5% ammoniacal nitrogen and 23% sulphate sulphur, our Ammonium Sulphate provides both nutrients in a single product.
This can simplify nutrient planning where both nitrogen and sulphur are required, subject to soil-test results and agronomic recommendations.
4. Supporting Bulb Development Through Balanced Nutrition
For us, good bulb development begins well before the bulb starts to enlarge. The crop first needs a healthy root system and sufficient leaf growth to support the later stages of development.
This means we need to look at the complete nutrition programme, including phosphorus, potassium, secondary nutrients and micronutrients alongside nitrogen and sulphur.
Our onion recommendations reflect this stage-based approach. PROM and SSP are used at sowing, biological and micronutrient products are introduced during vegetative growth, and Bio-Potash is included during bulb-development stages.
The objective is not simply to apply more fertiliser, but to provide appropriate nutrients as the crop progresses through each stage.
5. Integrating Ammonium Sulphate into Onion Nutrition
We believe fertiliser management works best when it is planned around crop growth and soil conditions.
A practical approach can include:
- At sowing: Establish the crop with appropriate phosphorus and organic nutrient sources according to soil and crop requirements.
- During vegetative growth: Support leaf and plant development with balanced nutrition, including nitrogen where required.
- Before bulb formation: Review the crop’s nutrient status and ensure balanced availability of the major and secondary nutrients.
- During bulb development: Maintain appropriate potassium and other nutrient availability while avoiding unnecessary nutrient application.
- Throughout the crop cycle: Monitor the crop and follow product-specific dosage and application recommendations.
Our crop platform lists onion as one of its covered crops and provides stage-wise recommendations for its fertiliser portfolio.
A Balanced Approach to Better Onion Growth
For us, successful onion nutrition is about maintaining balance from early growth through bulb development.
Nitrogen helps support vegetative growth, while sulphur contributes to protein, amino acid and enzyme synthesis. Ammonium sulphate brings both nutrients together, providing 20.5% ammoniacal nitrogen and 23% sulphate sulphur in a single fertiliser.
Our wider onion programme combines organic, biological and mineral fertilisers at different crop stages. This integrated approach helps us look beyond a single product and focus on the nutritional needs of the crop as a whole.
With soil assessment, stage-based fertiliser management and balanced nutrition, we can support healthy onion growth and create a stronger nutritional foundation for bulb development and overall crop performance.
