Sulphur Fertilizer and Crop Yield
Sulphur is critical to the development of healthy, nutritious crops but it also contributes to the efficiency of other nutrients.
Sulphur and The Law of Limiting Factors
Imagine you are filling a bucket with water but one of its slats is broken! The water level can only go as high as the lowest slat before it begins to overflow. Imagine these slats are nutrients available for crop uptake.
Fertilizers contribute to plant growth like bucket slats help to hold in water. If a nutrient is lacking, the plant can only utilize a portion of the other nutrients. Proper sulphur levels are critical to the efficiency of other nutrients being applied. Ironically, by apply one of the lowest cost nutrients (sulphur), farmers can improve the effectiveness of their costliest nutrients.
Impacts on crop yield and quality
Both the yield and quality of crops grown on sulphur-deficient soils are reduced unless sulphur is included in the fertilizer treatment. Sulphur fertilizer can increase crop yields and quality and result in significant economic returns to producers. TSI conducted numerous field experiments in India which demonstrated the positive impact on yield.
The following table summarizes these research findings:
Average crop responses to sulphur application under field conditions
| Crop | Studies averaged* |
Mean application rate, kg S/ha |
Response to S kg grain/kg S |
|---|---|---|---|
| Wheat | 35 | 39 | 19 |
| Rice (Paddy) | 23 | 42 | 16.6 |
| Chickpea | 6 | 85 | 5.3 |
| Pigeonpea | 8 | 36 | 8.9 |
| Blackgram | 9 | 30 | 5.4 |
| Greengram | 6 | 40 | 3.3 |
| Groundnut | 29 | 34 | 13.3 (pods) |
| Mustard | 29 | 43 | 7.7 |
| Sunflower | 10 | 24 | 13 |
| Soybean | 8 | 36 | 9.4 |
| Linseed | 5 | 26 | 9.5 |
* Crops with 5 or more results included here
In other words, sulphur applications on sulphur deficient soils increased crop yield by:
| 32% in Groundnut | 25% in Soybean | 20% in Sunflower |
| 30% in Mustardt | 22% in Pigeonpea | 17% in Rice |
| 25% in Wheat | 20% in Greengram | 16% in Linseed |
Sulphur and Crop Quality
Sulphur improves crop quality in many ways:
- Increasing the oil content of seeds.
- Increasing protein percentage in plants and harvested produce.
- Improving nutritional quality of forages by providing a balanced N:S ratio.
- Improving starch content of tubers.
- Improving baking quality of wheat.
- Increasing sugar recovery in sugarcane.
- Enhancing marketability of copra (coconut kernel).
Sulphur and Fertilizer Use Efficiency
Sulphur interacts both synergistically and antagonistically with other nutrients. In most cases, sulphur acts synergistically with nitrogen, the most often applied nutrient. Both nitrogen and sulphur improve each other’s efficiency and their combined impact on yield and nutrient recovery by crops is bigger than the sum of their individual effects. The nature of interactions between sulphur and phosphorus depends on the rate of application which is a reflection of whether the two nutrients are balanced. The interaction of sulphur with magnesium and boron can be positive or negative but in the case of oil crops, it is more clearly evident in oil yield than in seed yield. Out of the total response of groundnut to sulphur and boron application, the synergistic effect contributed 22% to the increase in kernel yield but 43% to the increase in oil yield.