Winter survival may also be improved by the addition of potassium. Phosphorus deficiency is difficult to recognize. Plants are stunted, and may appear bluish-green in colour. Under some soil conditions plants appear yellowish, similar to nitrogen or sulphur deficiency symptoms. Fertilize according to soil test results to improve yields.
Leaves are pale green or yellowish.
The yellowing may affect the new growth or the whole plant, while nitrogen deficiency tends to affect the older leaves first. Sulphur deficiency reduces nitrogen fixation and protein production. Alfalfa will grow poorly on soils when the pH is less than 5.9. Plants are light green, stunted and stands become thin. When alfalfa is grown on moderately-acid soil, yields and nitrogen content will be reduced.