Nitrogen (N) ans sulphur (S) have synergistic interactions. The increase of N in soil increases the availability of S and vise versa. However, the appropriate proportion of these two elements should be known for better cultivation.
In crops of the cabbage family like canola the defensive system of the plant is based on glucosinolates with are high in sulfur. These crops are far more responsive to sulfur and have a higher requirement compared to crops like small grains. In areas that persist with coal fired electrical energy the sulfur emissions are able to supply most crop needs. But when these are controlled the need for sulfur will be more prevalent. Even in a high sulfur requirement crop 40 kg/ha would be sufficient to optimize production. Sulfur requirement in conventional fertilization strategy would usually focus on the use of ammonia sulfate and would need to balanced with liming in acid prone conditions.
The level of Sulfur most important is that in the leaf tissue. Taking just 20 leaves and drying them chemical analysis can give a very good idea of macro secondary and micro nutrients.
Sulfur can be used to adjust too alkaline soil conditions.
Aulakh et al., 1980 observed that the N:S ratio should be 7:1 in grains, above which deficiency of S can be observed. There is a strong relationship between S and N content in plants. The ratio of total N to total S and protein S determine the degree of availability of deficiency of S in protein.
It depends on crop species and soil structure.
Sulfur is part of an enzyme required for nitrogen uptake and lack of it can severely hamper nitrogen metabolism. Together with nitrogen, sulfur enables the formations of amino acids needed for protein synthesis. It is found in fatty acids and vitamins and has an important impact on the quality and taste or smell of crops.
Since S and N are needed for protein synthesis, the two nutrients are closely linked. Thus, correct N:S ratio result in improved crop yield.
N: S ratio for some crops is as under
Cotton- 12 :1
Corn 8:1
Soybean 18:1
Wheat 16:1
Alfalfa 9:1
Bermudagrass 12:1
Bromegrass 6:1
Canola 6:1.
The desired N:S ratio for optimum growth and development of plants has been found to be 15-16: 1 in legumes and 11-12:1 in cereals, whereas in case of soil it should 7:1.
Janzen and Bettany (1984) indicated the optimum ratio of available N to available S to be 7:1. Ratios below 7 gave the reduced seed yields.
https://www.yara.co.uk/crop-nutrition/agronomy-advice/dont-forget-about-sulphur/
Based on Fertilizer Association of India (FAI), the NPK ratio in the country has reached 6.5:2.9:1 in 2011-12. The ratio considered ideal stands at 4:2:1.
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